60 results on '"Molly S. Shoichet"'
Search Results
2. Chemically and mechanically defined hyaluronan hydrogels emulate the extracellular matrix for unbiased in vivo and in vitro organoid formation and drug testing in cancer
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Alexander E.G. Baker, Laura C. Bahlmann, Chang Xue, Yung Hsiang (John) Lu, Allysia A. Chin, Jennifer Cruickshank, David W. Cescon, and Molly S. Shoichet
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Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
3. Hydrogel assisted photoreceptor delivery inhibits material transfer
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Margaret T. Ho, Arturo Ortin-Martinez, Nicole E. Yan, Lacrimioara Comanita, Akshay Gurdita, Victor Pham Truong, Hong Cui, Valerie A. Wallace, and Molly S. Shoichet
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Biomaterials ,Mechanics of Materials ,Biophysics ,Ceramics and Composites ,Bioengineering - Published
- 2023
4. Targeting tumour-associated macrophages in hodgkin lymphoma using engineered extracellular matrix-mimicking cryogels
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Laura C. Bahlmann, Chang Xue, Allysia A. Chin, Arianna Skirzynska, Joy Lu, Brigitte Thériault, David Uehling, Yulia Yerofeyeva, Rachel Peters, Kela Liu, Jianan Chen, Anne L. Martel, Martin Yaffe, Rima Al-awar, Rashmi S. Goswami, Jarkko Ylanko, David W. Andrews, John Kuruvilla, Rob C. Laister, and Molly S. Shoichet
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Biomaterials ,Mechanics of Materials ,Biophysics ,Ceramics and Composites ,Bioengineering - Published
- 2023
5. Local delivery of FK506 to injured peripheral nerve enhances axon regeneration after surgical nerve repair in rats
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Molly S. Shoichet, Katelyn Chan, Kasra Tajdaran, Tessa Gordon, and Gregory H. Borschel
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Nervous system ,0206 medical engineering ,Biomedical Engineering ,02 engineering and technology ,Biochemistry ,Tacrolimus ,Fibrin ,Rats, Sprague-Dawley ,Biomaterials ,Drug detection ,Drug Delivery Systems ,Peripheral Nerve Injuries ,polycyclic compounds ,medicine ,Animals ,Tissue Distribution ,Nerve Tissue ,Axon ,Molecular Biology ,Surgical repair ,biology ,business.industry ,organic chemicals ,Regeneration (biology) ,Body Weight ,General Medicine ,Nerve injury ,021001 nanoscience & nanotechnology ,020601 biomedical engineering ,Axons ,Microspheres ,Nerve Regeneration ,3. Good health ,medicine.anatomical_structure ,Anesthesia ,cardiovascular system ,biology.protein ,Female ,Sciatic nerve ,medicine.symptom ,0210 nano-technology ,business ,Biotechnology - Abstract
Administration of FK506, an FDA approved immunosuppressant, has been shown to enhance nerve regeneration following peripheral nerve injuries. However, the severe side effects of the systemically delivered FK506 has prevented clinicians from the routine use of the drug. In this study, we analyzed the effectiveness of our fibrin gel-based FK506 delivery system to promote axon regeneration in a rat peripheral nerve transection and immediate surgical repair model. In addition, biodistribution of FK506 from the local delivery system to the surrounding tissues was analyzed in vivo. Rats in the negative control groups either did not receive any delivery system treatment or received fibrin gel with empty microspheres. The experimental groups included rats treated with fibrin gel loaded with solubilized, particulate, and poly(lactic-co-glycolic) acid microspheres-encapsulated FK506. Rats in experimental groups receiving FK506 microspheres and the particulate FK506 regenerated the highest number of motor and sensory neurons. Histomorphometric analysis also demonstrated greater numbers of myelinated axons following particulate FK506 and FK506 microspheres treatment compared to the negative control groups. In biodistribution studies, FK506 was found at the nerve repair site, the sciatic nerve, and spinal cord, with little to no drug detection in other vital organs. Hence, the local application of FK506 via our delivery systems enhanced axon regeneration whilst avoiding the toxicity of systemic FK506. This local delivery strategy represents a new opportunity for clinicians to use for cases of peripheral nerve injuries. STATEMENT OF SIGNIFICANCE: This work for the first time investigated the influence of locally administered FK506 to the site of nerve injury and immediate repair directly on the number of motor and sensory neurons that regenerated their axons. Furthermore, using the immediate nerve repair model, we obtained valuable information about the biodistribution of FK506 within the nervous system following its release from the delivery system implanted at the site of nerve injury and repair. The strategy of local FK506 delivery holds a great promise in the clinical translation, as the localized delivery circumvents the main limitation of the systemic delivery of FK506, that of immunosuppression and toxicity.
- Published
- 2019
6. Influencing neuroplasticity in stroke treatment with advanced biomaterials-based approaches
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Eric C.H. Ho, Aileen Gracias, Molly S. Shoichet, and Jaclyn M. Obermeyer
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0303 health sciences ,Neuronal Plasticity ,Biocompatibility ,business.industry ,Pharmaceutical Science ,Biocompatible Materials ,02 engineering and technology ,021001 nanoscience & nanotechnology ,medicine.disease ,Stroke ,Stroke treatment ,03 medical and health sciences ,Drug Delivery Systems ,Neuroprotective Agents ,Neuroplasticity ,medicine ,Humans ,Treatment strategy ,0210 nano-technology ,business ,Neuroscience ,030304 developmental biology - Abstract
Since the early 1990s, we have known that the adult brain is not static and has the capacity to repair itself. The delivery of various therapeutic factors and cells have resulted in some exciting pre-clinical and clinical outcomes in stroke models by targeting post-injury plasticity to enhance recovery. Developing a deeper understanding of the pathways that modulate plasticity will enable us to optimize delivery strategies for therapeutics and achieve more robust effects. Biomaterials are a key tool for the optimization of these potential treatments, owing to their biocompatibility and tunability. In this review, we identify factors and targets that impact plastic processes known to contribute to recovery, discuss the role of biomaterials in enhancing the efficacy of treatment strategies, and suggest combinatorial approaches based on the stage of injury progression.
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- 2019
7. Cationic block amphiphiles show anti-mitochondrial activity in multi-drug resistant breast cancer cells
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Vianney Delplace, Petro Czupiel, and Molly S. Shoichet
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alpha-Tocopherol ,Cell ,Pharmaceutical Science ,Antineoplastic Agents ,Apoptosis ,Breast Neoplasms ,Peptide ,02 engineering and technology ,Mitochondrion ,Surface-Active Agents ,03 medical and health sciences ,medicine ,Humans ,030304 developmental biology ,chemistry.chemical_classification ,0303 health sciences ,Cationic polymerization ,Cancer ,Transfection ,021001 nanoscience & nanotechnology ,medicine.disease ,Lipids ,Drug Resistance, Multiple ,Mitochondria ,3. Good health ,medicine.anatomical_structure ,Biochemistry ,chemistry ,Drug Resistance, Neoplasm ,Cancer cell ,Female ,Efflux ,0210 nano-technology ,Oligopeptides - Abstract
Currently, there are limited treatment options for multi-drug resistant breast cancer. Lipid-modified cationic peptides have the potential to reach the mitochondria, which are attractive targets for the treatment of multi-drug resistant (MDR) breast cancer; yet, little is known about their mitochondrial targeting and anti-cancer activity. Interestingly, lipid-modified cationic peptides, typically used as gene transfection agents, exhibit similar structural features to mitochondrial targeted peptides. Using octahistidine-octaarginine (H8R8) as a model cationic peptide for cell penetration and endosomal escape, we explored the anti-cancer potential of lipid-modified cationic peptides as a function of amphiphilicity, biodegradability and lipid structure. We found that cationic peptides modified with a lipid that is at least 12 carbons in length exhibit potent anti-cancer activity in the low micromolar range in both EMT6/P and EMT6/AR-1 breast cancer cells. Comparing degradable and non-degradable linkers, as well as L- and D-amino acid sequences, we found that the anti-cancer activity is mostly independent of the biodegradation of the lipid-modified cationic peptides. Two candidates, stearyl-H8R8 (Str-H8R8) and vitamin E succinate-H8R8 (VES-H8R8) were cytotoxic to cancer cells by mitochondria depolarization. We observed increased reactive oxygen species (ROS) production, reduced cell bioenergetics and drug efflux, triggering apoptosis and G1 cell cycle arrest. Compared to Str-H8R8, VES-H8R8 showed enhanced cancer cell selectivity and drug efflux inhibition, thereby serving as a potential novel therapeutic agent. This study deepens our understanding of lipid-modified cationic peptides and uncovers their potential in multi-drug resistant breast cancer.
- Published
- 2019
8. A hyaluronan/methylcellulose-based hydrogel for local cell and biomolecule delivery to the central nervous system
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Molly S. Shoichet, Carter J. Teal, and Margaret T. Ho
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Central Nervous System ,0301 basic medicine ,Cell Survival ,Cell ,Central nervous system ,Biocompatible Materials ,Methylcellulose ,Cell fate determination ,Regenerative medicine ,Neuroprotection ,Retina ,03 medical and health sciences ,Drug Delivery Systems ,0302 clinical medicine ,medicine ,Animals ,Humans ,Hyaluronic Acid ,Spinal Cord Injuries ,chemistry.chemical_classification ,Chemistry ,Stem Cells ,General Neuroscience ,Biomolecule ,Brain ,Hydrogels ,Controlled release ,3. Good health ,Cell biology ,030104 developmental biology ,medicine.anatomical_structure ,Spinal Cord ,Drug delivery ,030217 neurology & neurosurgery - Abstract
Regenerative medicine strategies rely on exogenous cell transplantation and/or endogenous cell stimulation. Biomaterials can help to increase the regenerative potential of cells and biomolecules by controlling transplanted cell fate and provide a local, sustained release of biomolecules. In this review, we describe the use of a hyaluronan/methylcellulose (HAMC)-based hydrogel as a delivery vehicle to the brain, spinal cord, and retina to promote cellular survival and tissue repair. We discuss various controlled release strategies to prolong the delivery of factors for neuroprotection. The versatility of this hydrogel for a diversity of applications highlights its potential to enhance cell- and biomolecule-based treatment strategies.
- Published
- 2019
9. Initial cell maturity changes following transplantation in a hyaluronan-based hydrogel and impacts therapeutic success in the stroke-injured rodent brain
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Jaclyn M. Obermeyer, Molly S. Shoichet, Carter J. Teal, Andras Nagy, Balazs V. Varga, Samantha L. Payne, Anup Tuladhar, and Cindi M. Morshead
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Male ,Neurogenesis ,Cellular differentiation ,Cell ,Population ,Neuroepithelial Cells ,Biophysics ,Bioengineering ,02 engineering and technology ,Biology ,Rats, Sprague-Dawley ,Biomaterials ,03 medical and health sciences ,Neural Stem Cells ,medicine ,Animals ,Humans ,Hyaluronic Acid ,Progenitor cell ,education ,Cells, Cultured ,030304 developmental biology ,0303 health sciences ,education.field_of_study ,Tissue Scaffolds ,Regeneration (biology) ,Hydrogels ,Recovery of Function ,021001 nanoscience & nanotechnology ,Rats ,Cell biology ,Stroke ,Neuroepithelial cell ,Transplantation ,medicine.anatomical_structure ,Mechanics of Materials ,Ceramics and Composites ,Stem cell ,0210 nano-technology - Abstract
Ischemic stroke results in a loss of neurons for which there are no available clinical strategies to stimulate regeneration. While preclinical studies have demonstrated that functional recovery can be obtained by transplanting an exogenous source of neural progenitors into the brain, it remains unknown at which stage of neuronal maturity cells will provide the most benefit. We investigated the role of neuronal maturity on cell survival, differentiation, and long-term sensorimotor recovery in stroke-injured rats using a population of human cortically-specified neuroepithelial progenitor cells (cNEPs) delivered in a biocompatible, bioresorbable hyaluronan/methylcellulose hydrogel. We demonstrate that transplantation of immature cNEPs result in the greatest tissue and functional repair, relative to transplantation of more mature neurons. The transplantation process itself resulted in the least cell death and phenotypic changes in the immature cNEPs, and the greatest acute cell death in the mature cells. The latter negatively impacted host tissue and negated any potential positive effects associated with cell maturity and the hydrogel vehicle, which itself showed some functional and tissue benefit. Moreover, we show that more mature cell populations are drastically altered during the transplantation process itself. The phenotype of the cells before and after transplantation had an enormous impact on their survival and the consequent tissue and behavioral response, emphasizing the importance of characterizing injected cells in transplantation studies more broadly.
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- 2019
10. Controlled release strategy designed for intravitreal protein delivery to the retina
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En Leh Samuel Tsai, Valerie A. Wallace, Molly S. Shoichet, Alan N. Amin, Arturo Ortín-Martínez, and Vianney Delplace
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Male ,STAT3 Transcription Factor ,Retinal degeneration ,genetic structures ,Pharmaceutical Science ,Peptide binding ,02 engineering and technology ,Methylcellulose ,Ciliary neurotrophic factor ,Pharmacology ,Retina ,03 medical and health sciences ,Downregulation and upregulation ,medicine ,Animals ,Ciliary Neurotrophic Factor ,Hyaluronic Acid ,030304 developmental biology ,0303 health sciences ,biology ,Chemistry ,Hydrogels ,Models, Theoretical ,021001 nanoscience & nanotechnology ,medicine.disease ,Controlled release ,Fusion protein ,Mice, Inbred C57BL ,STAT1 Transcription Factor ,Rhodopsin ,Delayed-Action Preparations ,Intravitreal Injections ,Drug delivery ,biology.protein ,Female ,sense organs ,0210 nano-technology - Abstract
Therapeutic protein delivery directly to the eye is a promising strategy to treat retinal degeneration; yet, the high risks of local drug overdose and cataracts associated with bolus injection have limited progress, requiring the development of sustained protein delivery strategies. Since the vitreous humor itself is a gel, hydrogel-based release systems are a sensible solution for sustained intravitreal protein delivery. Using ciliary neurotrophic factor (CNTF) as a model protein for ocular treatment, we investigated the use of an intravitreal, affinity-based release system for protein delivery. To sustain CNTF release, we took advantage of the affinity between Src homology 3 (SH3) and its peptide binding partners: CNTF was expressed as a fusion protein with SH3, and a thermogel of hyaluronan and methylcellulose (HAMC) was modified with SH3 binding peptides. Using a mathematical model, the hydrogel composition was successfully designed to release CNTF-SH3 over 7 days. The stability and bioactivity of the released protein were similar to those of commercial CNTF. Intravitreal injections of the bioengineered thermogel showed successful delivery of CNTF-SH3 to the mouse retina, with expected transient downregulation of phototransduction genes (e.g., rhodopsin, S-opsin, M-opsin, Gnat 1 and 2), upregulation of STAT1 and STAT3 expression, and upregulation of STAT3 phosphorylation. This constitutes the first demonstration of intravitreal protein release from a hydrogel. Immunohistochemical analysis of the retinal tissues of injected eyes confirmed the biocompatibility of the delivery vehicle, paving the way towards new intravitreal protein delivery strategies.
- Published
- 2019
11. Induction of rod versus cone photoreceptor-specific progenitors from retinal precursor cells
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Gilbert Bernier, Brenda L. K. Coles, Gary D. Bader, Valerie A. Wallace, Molly S. Shoichet, Jeff C. Liu, Brian G. Ballios, Saeed Khalili, Justin Belair-Hickey, Tahani Baakdhah, Kenneth Grise, Derek van der Kooy, and Laura Donaldson
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0301 basic medicine ,genetic structures ,Retinal precursor cells ,Retinoic acid ,Biology ,Retina ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,Retinal Rod Photoreceptor Cells ,medicine ,Animals ,Progenitor cell ,lcsh:QH301-705.5 ,Progenitor ,Stem Cells ,Gene Expression Regulation, Developmental ,Cell Differentiation ,Retinal ,Cell Biology ,General Medicine ,Embryonic stem cell ,Cell biology ,030104 developmental biology ,medicine.anatomical_structure ,lcsh:Biology (General) ,chemistry ,Retinal Cone Photoreceptor Cells ,sense organs ,Stem cell ,Developmental Biology - Abstract
During development, multipotent progenitors undergo temporally-restricted differentiation into post-mitotic retinal cells; however, the mechanisms of progenitor division that occurs during retinogenesis remain controversial. Using clonal analyses (lineage tracing and single cell cultures), we identify rod versus cone lineage-specific progenitors derived from both adult retinal stem cells and embryonic neural retinal precursors. Taurine and retinoic acid are shown to act in an instructive and lineage-restricted manner early in the progenitor lineage hierarchy to produce rod-restricted progenitors from stem cell progeny. We also identify an instructive, but lineage-independent, mechanism for the specification of cone-restricted progenitors through the suppression of multiple differentiation signaling pathways. These data indicate that exogenous signals play critical roles in directing lineage decisions and resulting in fate-restricted rod or cone photoreceptor progenitors in culture. Additional factors may be involved in governing photoreceptor fates in vivo. Keywords: Stem cell, Retina, Rod photoreceptor, Cone photoreceptor, Progenitors
- Published
- 2018
12. Photo-immobilized EGF chemical gradients differentially impact breast cancer cell invasion and drug response in defined 3D hydrogels
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Ana Fokina, M. Mohsen Mahmoodi, Mark D. Distefano, Roger Y. Tam, Stephanie A. Fisher, and Molly S. Shoichet
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0301 basic medicine ,Light ,medicine.medical_treatment ,Biophysics ,Breast Neoplasms ,Bioengineering ,Matrix metalloproteinase ,Article ,Biomaterials ,03 medical and health sciences ,In vivo ,Epidermal growth factor ,medicine ,Humans ,Neoplasm Invasiveness ,Hyaluronic Acid ,Furans ,skin and connective tissue diseases ,Receptor ,EGFR inhibitors ,Tumor microenvironment ,Epidermal Growth Factor ,Cetuximab ,Chemistry ,Growth factor ,Hydrogels ,Immobilized Proteins ,030104 developmental biology ,Mechanics of Materials ,MCF-7 Cells ,Ceramics and Composites ,Cancer research ,Female ,medicine.drug - Abstract
Breast cancer cell invasion is influenced by growth factor concentration gradients in the tumor microenvironment. However, studying the influence of growth factor gradients on breast cancer cell invasion is challenging due to both the complexities of in vivo models and the difficulties in recapitulating the tumor microenvironment with defined gradients using in vitro models. A defined hyaluronic acid (HA)-based hydrogel crosslinked with matrix metalloproteinase (MMP) cleavable peptides and modified with multiphoton labile nitrodibenzofuran (NDBF) was synthesized to photochemically immobilize epidermal growth factor (EGF) gradients. We demonstrate that EGF gradients can differentially influence breast cancer cell invasion and drug response in cell lines with different EGF receptor (EGFR) expression levels. Photopatterned EGF gradients increase the invasion of moderate EGFR expressing MDA-MB-231 cells, reduce invasion of high EGFR expressing MDA-MB-468 cells, and have no effect on invasion of low EGFR-expressing MCF-7 cells. We evaluate MDA-MB-231 and MDA-MB-468 cell response to the clinically tested EGFR inhibitor, cetuximab. Interestingly, the cellular response to cetuximab is completely different on the EGF gradient hydrogels: cetuximab decreases MDA-MB-231 cell invasion but increases MDA-MB-468 cell invasion and cell number, thus demonstrating the importance of including cell-microenvironment interactions when evaluating drug targets.
- Published
- 2018
13. Antibody-Antisense Oligonucleotide Conjugate Downregulates a Key Gene in Glioblastoma Stem Cells
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Molly S. Shoichet, Masad J. Damha, Amy E. Arnold, Saúl Martínez-Montero, Kevin Petrecca, Elise Malek-Adamian, Phuong Uyen Le, and Anika Meng
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0301 basic medicine ,endocrine system ,Genetic enhancement ,Article ,03 medical and health sciences ,Antigen ,Cancer stem cell ,Drug Discovery ,FAM107A ,Nuclease ,glioblastoma stem cells ,biology ,Chemistry ,Oligonucleotide ,lcsh:RM1-950 ,fungi ,CD44 ,gene therapy ,targeted therapies ,3. Good health ,lcsh:Therapeutics. Pharmacology ,030104 developmental biology ,antibody conjugates ,Cancer research ,biology.protein ,Molecular Medicine ,antisense oligonucleotides ,Antibody ,Stem cell - Abstract
Glioblastoma stem cells (GSCs) are invasive, treatment-resistant brain cancer cells that express downregulated in renal cell carcinoma (DRR), also called FAM107A, a genetic driver of GSC invasion. We developed antibody-antisense oligonucleotide (AON) conjugates to target and reduce DRR/FAM107A expression. Specifically, we used antibodies against antigens expressed on the GSCs, such as CD44 and EphA2, conjugated to chemically modified AONs against DRR/FAM107A, which were designed as chimeras of DNA and 2′-deoxy-2′-fluoro-beta-D-arabinonucleic acid (FANA) for increased nuclease stability and mRNA affinity. We demonstrate that these therapeutic conjugates successfully internalize, accumulate, and reduce DRR/FAM107A expression in patient-derived GSCs. This is the first example of an antibody-antisense strategy against cancer stem cells.
- Published
- 2018
14. Effect of hyaluronic acid hydrogels containing astrocyte-derived extracellular matrix and/or V2a interneurons on histologic outcomes following spinal cord injury
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Shelly E. Sakiyama-Elbert, Molly S. Shoichet, Lindsay Crawford, Laura Smith, Peter Kenny, Russell E. Thompson, and Jennifer Pardieck
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0301 basic medicine ,Biophysics ,Bioengineering ,Article ,Glial scar ,Biomaterials ,Lesion ,Extracellular matrix ,Mice ,03 medical and health sciences ,Interneurons ,medicine ,Animals ,Hyaluronic Acid ,Axon ,Embryonic Stem Cells ,Spinal Cord Injuries ,Tissue Engineering ,Microglia ,Chemistry ,Hydrogels ,Extracellular Matrix ,Nerve Regeneration ,Rats ,Cell biology ,Transplantation ,030104 developmental biology ,medicine.anatomical_structure ,Mechanics of Materials ,Astrocytes ,Self-healing hydrogels ,Ceramics and Composites ,medicine.symptom ,Astrocyte - Abstract
One reason for the lack of regeneration, and poor clinical outcomes, following central nervous system (CNS) injury is the formation of a glial scar that inhibits new axon growth. In addition to forming the glial scar, astrocytes have been shown to be important for spontaneous SCI recovery in rodents, suggesting some astrocyte populations are pro-regenerative, while others are inhibitory following injury. In this work, the effect of implanting hyaluronic acid (HA) hydrogels containing extracellular matrix (ECM) harvested from mouse embryonic stem cell (mESC)-derived astrocytes on histologic outcomes following SCI in rats was explored. In addition, the ability of HA hydrogels with and without ECM to support the transplantation of mESC-derived V2a interneurons was tested. The incorporation of ECM harvested from protoplasmic (grey matter) astrocytes, but not ECM harvested from fibrous (white matter) astrocytes, into hydrogels was found to reduce the size of the glial scar, increase axon penetration into the lesion, and reduce macrophage/microglia staining two weeks after implantation. HA hydrogels were also found to support transplantation of V2a interneurons and the presence of these cells caused an increase in neuronal processes both within the lesion and in the 500 μm surrounding the lesion. Overall, protoplasmic mESC-derived astrocyte ECM showed potential to treat CNS injury. In addition, ECM:HA hydrogels represent a novel scaffold with beneficial effects on histologic outcomes after SCI both with and without cells.
- Published
- 2018
15. Recent advances in regenerative medicine approaches for spinal cord injuries
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Molly S. Shoichet, Marian H. Hettiaratchi, and Tobias Führmann
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0301 basic medicine ,Pathology ,medicine.medical_specialty ,business.industry ,Cell ,Biomedical Engineering ,Medicine (miscellaneous) ,Bioengineering ,Endogeny ,medicine.disease ,Spinal cord ,Inhibitory postsynaptic potential ,Regenerative medicine ,Biomaterials ,03 medical and health sciences ,030104 developmental biology ,medicine.anatomical_structure ,Traumatic injury ,Drug delivery ,Medicine ,business ,Spinal cord injury ,Neuroscience - Abstract
Traumatic injury to the spinal cord leads to a loss of motor and sensory function below the level of injury. The lack of growth-associated proteins, local expression of inhibitory factors, and scar and cyst formation create an inhibitory environment in the spinal cord, which limits the regenerative capacity of endogenous or transplanted cells. Cell and drug delivery strategies, either alone or in combination, can induce changes in the local microenvironment at and around the lesion site to promote transplanted cell survival, integration, and/or endogenous repair. New biomaterial strategies also provide a platform for sustained delivery of otherwise unstable drugs.
- Published
- 2017
16. Engineered safe and immune-tolerant ‘designer’ rpe cells towards the treatment of age-related macular degeneration
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Valerie A. Wallace, Molly S. Shoichet, Peter J. Kertes, J. Tang, T. Oussenko, P. Yan, M. Ho, Sabiha Hacibekiroglu, Andras Nagy, and E. Jong
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Cancer Research ,Transplantation ,business.industry ,Immunology ,Cell Biology ,Macular degeneration ,medicine.disease ,Immune system ,Oncology ,Age related ,medicine ,Immunology and Allergy ,business ,Genetics (clinical) - Published
- 2021
17. Local delivery of chondroitinase ABC with or without stromal cell-derived factor 1α promotes functional repair in the injured rat spinal cord
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Charles H. Tator, Malgosia M. Pakulska, and Molly S. Shoichet
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0301 basic medicine ,Stromal cell ,Biophysics ,Enzyme-Linked Immunosorbent Assay ,Bioengineering ,Chondroitin ABC Lyase ,Methylcellulose ,Pharmacology ,Hydrogel, Polyethylene Glycol Dimethacrylate ,Glial scar ,Rats, Sprague-Dawley ,Biomaterials ,03 medical and health sciences ,chemistry.chemical_compound ,Neural Stem Cells ,Precursor cell ,medicine ,Animals ,Distribution (pharmacology) ,Spinal cord injury ,Spinal Cord Injuries ,business.industry ,medicine.disease ,Spinal cord ,Immunohistochemistry ,Chemokine CXCL12 ,Rats ,3. Good health ,030104 developmental biology ,medicine.anatomical_structure ,Chondroitin Sulfate Proteoglycans ,chemistry ,Mechanics of Materials ,Chondroitin sulfate proteoglycan ,Drug delivery ,Ceramics and Composites ,Female ,business ,Biomedical engineering - Abstract
Traumatic spinal cord injury (SCI) is a devastating event for which functional recovery remains elusive. Due to the complex nature of SCI pathology, a combination treatment strategy will likely be required for success. We hypothesized that tissue and functional repair would be achieved in a rat model of impact-compression SCI by combining degradation of the glial scar, using chondroitinase ABC (ChABC), with recruitment of endogenous neural precursor cells (NPCs), using stromal cell-derived factor 1α (SDF). To test this hypothesis, we designed a crosslinked methylcellulose hydrogel (XMC) for minimally invasive, localized, and sustained intrathecal drug delivery. ChABC was released from XMC using protein-peptide affinity interactions while SDF was delivered by electrostatic affinity interactions from polymeric nanoparticles embedded in XMC. Rats with SCI were treated acutely with a combination of SDF and ChABC, SDF alone, ChABC alone, or vehicle alone, and compared to injury only. Treatment with ChABC, both alone and in combination with SDF, resulted in faster and more sustained behavioural improvement over time than other groups. The significantly reduced chondroitin sulfate proteoglycan levels and greater distribution of NPCs throughout the spinal cord tissue with ChABC delivery, both alone and in combination with SDF, may explain the improved locomotor function. Treatment with SDF alone had no apparent effect on NPC number or distribution nor synergistic effect with ChABC delivery. Thus, in this model of SCI, tissue and functional repair is attributed to ChABC.
- Published
- 2017
18. Preclinical evaluation of taxane-binding peptide-modified polymeric micelles loaded with docetaxel in an orthotopic breast cancer mouse model
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Rima Al-awar, Ahil N. Ganesh, Jennifer Logie, Ahmed Aman, and Molly S. Shoichet
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Drug ,Polymers ,media_common.quotation_subject ,Drug Evaluation, Preclinical ,Biophysics ,Antineoplastic Agents ,Breast Neoplasms ,Bioengineering ,Docetaxel ,02 engineering and technology ,Pharmacology ,010402 general chemistry ,01 natural sciences ,Biomaterials ,Mice ,Therapeutic index ,Nanocapsules ,Pharmacokinetics ,Cell Line, Tumor ,medicine ,Animals ,Distribution (pharmacology) ,Micelles ,media_common ,Taxane ,business.industry ,021001 nanoscience & nanotechnology ,3. Good health ,0104 chemical sciences ,Treatment Outcome ,Targeted drug delivery ,Mechanics of Materials ,Ceramics and Composites ,Nanomedicine ,Emulsions ,Female ,Taxoids ,Peptides ,0210 nano-technology ,business ,Protein Binding ,medicine.drug - Abstract
We developed a novel taxane-binding peptide (TBP) modified, biodegradable polymeric micelle that overcomes limitations of drug loading and poor serum stability typically seen with particle delivery, leading to enhanced pharmacokinetics and tumor distribution of docetaxel (DTX). The use of the taxane-binding peptide to increase docetaxel loading is particularly compelling as it takes advantage of a known intracellular binding mechanism in a new way. Docetaxel is a potent chemotherapeutic with a therapeutic index often limited by the toxicity of the excipients that are necessary to enhance its solubility for intravenous delivery. Our polymeric micelle has terminal furan groups that enable facile antibody Fab conjugation by Diels-Alder chemistry for targeted delivery. Compared to the conventional ethanolic polysorbate 80 formulation (Free DTX), our nanoparticle (NP DTX) formulation exhibited a two-fold increase in exposure and tumor accumulation. Notably, the reduced toxicity of the NP DTX formulation increased the therapeutic index and allowed for higher dosing regimens, with a maximum tolerated dose (MTD) 1.6-fold higher than that of the Free DTX formulation, which is significant and similar to enhancements observed in clinical products for docetaxel and other drugs. These improved properties led to enhanced mouse survival in an orthotopic model of breast cancer; however, the targeted formulation of Fab-NP DTX did not further improve efficacy. Together, these results clearly demonstrate the benefits of the TBP-modified polymeric micelles as promising carriers for docetaxel.
- Published
- 2017
19. Circumventing the blood–brain barrier: Local delivery of cyclosporin A stimulates stem cells in stroke-injured rat brain
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Cindi M. Morshead, Molly S. Shoichet, and Anup Tuladhar
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Brain Infarction ,Male ,Drug Compounding ,Central nervous system ,Pharmaceutical Science ,Cell Count ,Stimulation ,Methylcellulose ,Pharmacology ,Blood–brain barrier ,Drug Delivery Systems ,Polylactic Acid-Polyglycolic Acid Copolymer ,In vivo ,Lateral Ventricles ,Cyclosporin a ,Animals ,Medicine ,Rats, Long-Evans ,Lactic Acid ,Hyaluronic Acid ,Progenitor cell ,business.industry ,Stem Cells ,Hydrogels ,Rats ,Stroke ,medicine.anatomical_structure ,Blood-Brain Barrier ,Drug delivery ,Cyclosporine ,Stem cell ,business ,Immunosuppressive Agents ,Polyglycolic Acid - Abstract
Drug delivery to the central nervous system is limited by the blood-brain barrier, which can be circumvented by local delivery. In applications of stroke therapy, for example, stimulation of endogenous neural stem/progenitor cells (NSPCs) by cyclosporin A (CsA) is promising. However, current strategies rely on high systemic drug doses to achieve small amounts of CsA in the brain tissue, resulting in systemic toxicity and undesirable global immunosuppression. Herein we describe the efficacy of local CsA delivery to the stroke-injured rat brain using an epi-cortically injected hydrogel composed of hyaluronan and methylcellulose (HAMC). CsA was encapsulated in poly(lactic-co-glycolic acid) microparticles dispersed in HAMC, allowing for its sustained release over 14days in vivo. Tissue penetration was sufficient to provide sustained CsA delivery to the sub-cortical NSPC niche. In comparison to systemic delivery using an osmotic minipump, HAMC achieved higher CsA concentrations in the brain while significantly reducing drug exposure in other organs. HAMC alone was beneficial in the stroke-injured rat brain, significantly reducing the stroke infarct volume relative to untreated stroke-injured controls. The combination of HAMC and local CsA release increased the number of proliferating cells in the lateral ventricles - the NSPC niche in the adult brain. Thus, we demonstrate a superior method of drug delivery to the rat brain that provides dual benefits of tissue protection and endogenous NSPC stimulation after stroke.
- Published
- 2015
20. Controlled release of bioactive PDGF-AA from a hydrogel/nanoparticle composite
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Irja Elliott Donaghue and Molly S. Shoichet
- Subjects
Male ,Materials science ,Cell Survival ,medicine.medical_treatment ,Population ,Biomedical Engineering ,Enzyme-Linked Immunosorbent Assay ,Biochemistry ,Hydrogel, Polyethylene Glycol Dimethacrylate ,Polyethylene Glycols ,Biomaterials ,chemistry.chemical_compound ,Drug Delivery Systems ,Neural Stem Cells ,PEG ratio ,medicine ,Animals ,Rats, Wistar ,education ,Molecular Biology ,Platelet-Derived Growth Factor ,education.field_of_study ,Multipotent Stem Cells ,Growth factor ,Oligodendrocyte differentiation ,General Medicine ,Controlled release ,Molecular biology ,PLGA ,chemistry ,Delayed-Action Preparations ,Drug delivery ,Biophysics ,Nanoparticles ,Ethylene glycol ,Biotechnology - Abstract
Polymer excipients, such as low molar mass poly(ethylene glycol) (PEG), have shown contradictory effects on protein stability when co-encapsulated in polymeric nanoparticles. To gain further insight into these effects, platelet-derived growth factor (PDGF-AA) was encapsulated in polymeric nanoparticles with vs. without PEG. PDGF-AA is a particularly compelling protein, as it has been demonstrated to promote cell survival and induce the oligodendrocyte differentiation of neural stem/progenitor cells (NSPCs) both in vitro and in vivo . Here we show, for the first time, the controlled release of bioactive PDGF-AA from an injectable nanoparticle/hydrogel drug delivery system (DDS). PDGF-AA was encapsulated, with high efficiency, in poly(lactide-co-glycolide) nanoparticles, and its release from the drug delivery system was followed over 21 d. Interestingly, the co-encapsulation of low molecular weight poly(ethylene glycol) increased the PDGF-AA loading but, unexpectedly, accelerated the aggregation of PDGF-AA, resulting in reduced activity and detection by enzyme-linked immunosorbent assay (ELISA). In the absence of PEG, released PDGF-AA remained bioactive as demonstrated with NSPC oligodendrocyte differentiation, similar to positive controls, and significantly different from untreated controls. This work presents a novel delivery method for differentiation factors, such as PDGF-AA, and provides insights into the contradictory effects reported in the literature of excipients, such as PEG, on the loading and release of proteins from polymeric nanoparticles. Statement of Significance Previously, the polymer poly(ethylene glycol) (PEG) has been used in many biomaterials applications, from surface coatings to the encapsulation of proteins. In this work, we demonstrate that, unexpectedly, low molecular weight PEG has a deleterious effect on the release of the encapsulated protein platelet-derived growth factor AA (PDGF-AA). We also demonstrate release of bioactive PDGF-AA (in the absence of PEG). Specifically, we demonstrate the differentiation of neural stem and progenitor cells to oligodendrocytes, similar to what is observed with the addition of fresh PDGFAA. A differentiated oligodendrocyte population is a key strategy in central nervous system regeneration. This work is the first demonstration of controlled PDGF-AA release, and also brings new insights to the broader field of protein encapsulation.
- Published
- 2015
21. Click-crosslinked injectable hyaluronic acid hydrogel is safe and biocompatible in the intrathecal space for ultimate use in regenerative strategies of the injured spinal cord
- Author
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Jaclyn M. Obermeyer, Charles H. Tator, Molly S. Shoichet, and Tobias Führmann
- Subjects
Intrathecal space ,Central nervous system ,Biocompatible Materials ,Regenerative Medicine ,General Biochemistry, Genetics and Molecular Biology ,Rats, Sprague-Dawley ,chemistry.chemical_compound ,Drug Delivery Systems ,Polylactic Acid-Polyglycolic Acid Copolymer ,Materials Testing ,Hyaluronic acid ,medicine ,Animals ,Humans ,Lactic Acid ,Hyaluronic Acid ,Molecular Biology ,Spinal cord injury ,Injections, Spinal ,Spinal Cord Injuries ,Brain-derived neurotrophic factor ,business.industry ,Brain-Derived Neurotrophic Factor ,Hydrogels ,Spinal cord ,Biocompatible material ,medicine.disease ,Rats ,Cross-Linking Reagents ,medicine.anatomical_structure ,chemistry ,Delayed-Action Preparations ,Drug delivery ,Nanoparticles ,Click Chemistry ,Female ,business ,Polyglycolic Acid ,Biomedical engineering - Abstract
Traumatic spinal cord injury (SCI) causes damage and degeneration at and around the lesion site resulting in a loss of function. SCI presents a complex regenerative problem due to the multiple aspects of growth inhibition and the heterogeneity in size, shape and extent of injury. Currently, there is no widely accepted treatment strategy available and delivering biomolecules to the central nervous system remains a challenge. With a view towards achieving local release, we designed a hydrogel that can be injected into the intrathecal space. Here we describe the synthesis and characterization of a click-crosslinked hyaluronic acid hydrogel and demonstrate controlled in vitro release of bioactive brain derived neurotrophic factor. Importantly, we demonstrate that this new hydrogel is both biocompatible in the intrathecal space based on immunohistochemistry of the host tissue response and safe based on behavioral analysis of locomotor function.
- Published
- 2015
22. A Hyaluronan-Based Injectable Hydrogel Improves the Survival and Integration of Stem Cell Progeny following Transplantation
- Author
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Molly S. Shoichet, Laura Donaldson, Derek van der Kooy, Cindi M. Morshead, Brian G. Ballios, Michael J. Cooke, and Brenda L. K. Coles
- Subjects
Rhodopsin ,Cell type ,Cell Survival ,Cell ,Methylcellulose ,Blindness ,Real-Time Polymerase Chain Reaction ,Biochemistry ,Hydrogel, Polyethylene Glycol Dimethacrylate ,Retina ,Article ,Mice ,chemistry.chemical_compound ,Retinal Rod Photoreceptor Cells ,Hyaluronic acid ,Genetics ,medicine ,Animals ,Distribution (pharmacology) ,Hyaluronic Acid ,Progenitor cell ,lcsh:QH301-705.5 ,Mice, Knockout ,lcsh:R5-920 ,biology ,Stem Cells ,CD44 ,Cell Biology ,Anatomy ,Immunohistochemistry ,3. Good health ,Cell biology ,Mice, Inbred C57BL ,Stroke ,Transplantation ,Hyaluronan Receptors ,medicine.anatomical_structure ,lcsh:Biology (General) ,chemistry ,biology.protein ,Stem cell ,lcsh:Medicine (General) ,Stem Cell Transplantation ,Developmental Biology - Abstract
Summary The utility of stem cells and their progeny in adult transplantation models has been limited by poor survival and integration. We designed an injectable and bioresorbable hydrogel blend of hyaluronan and methylcellulose (HAMC) and tested it with two cell types in two animal models, thereby gaining an understanding of its general applicability for enhanced cell distribution, survival, integration, and functional repair relative to conventional cell delivery in saline. HAMC improves cell survival and integration of retinal stem cell (RSC)-derived rods in the retina. The pro-survival mechanism of HAMC is ascribed to the interaction of the CD44 receptor with HA. Transient disruption of the retinal outer limiting membrane, combined with HAMC delivery, results in significantly improved rod survival and visual function. HAMC also improves the distribution, viability, and functional repair of neural stem and progenitor cells (NSCs). The HAMC delivery system improves cell transplantation efficacy in two CNS models, suggesting broad applicability., Highlights • An injectable biomaterial improves rod survival/integration into adult retina • The same material improves neural stem cell distribution/survival into adult brain • Functional repair is demonstrated after cell transplantation in both retina and brain • Hyaluronan-CD44 interaction is implicated in the pro-survival effect on stem cell progeny, Shoicet, van der Kooy, and colleagues demonstrate how an injectable biomaterial delivery system enhances survival and functional integration of stem cell progeny delivered to both adult retina and brain in animal models of disease. The mechanism underlying the direct pro-survival effect of HAMC on cells is elucidated.
- Published
- 2015
23. Mathematical model accurately predicts protein release from an affinity-based delivery system
- Author
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Malgosia M. Pakulska, Molly S. Shoichet, Arun Ramachandran, Rohit Sonthalia, and Katarina Vulic
- Subjects
Asymptotic analysis ,Chemistry ,Recombinant Fusion Proteins ,Diffusion ,Kinetics ,Analytical chemistry ,Pharmaceutical Science ,Hydrogels ,Chondroitin ABC Lyase ,Models, Theoretical ,Ligand (biochemistry) ,Controlled release ,Small molecule ,Dissociation (chemistry) ,Receptor–ligand kinetics ,src Homology Domains ,Drug Delivery Systems ,Biophysics ,Fibroblast Growth Factor 2 - Abstract
Affinity-based controlled release modulates the delivery of protein or small molecule therapeutics through transient dissociation/association. To understand which parameters can be used to tune release, we used a mathematical model based on simple binding kinetics. A comprehensive asymptotic analysis revealed three characteristic regimes for therapeutic release from affinity-based systems. These regimes can be controlled by diffusion or unbinding kinetics, and can exhibit release over either a single stage or two stages. This analysis fundamentally changes the way we think of controlling release from affinity-based systems and thereby explains some of the discrepancies in the literature on which parameters influence affinity-based release. The rate of protein release from affinity-based systems is determined by the balance of diffusion of the therapeutic agent through the hydrogel and the dissociation kinetics of the affinity pair. Equations for tuning protein release rate by altering the strength (KD) of the affinity interaction, the concentration of binding ligand in the system, the rate of dissociation (koff) of the complex, and the hydrogel size and geometry, are provided. We validated our model by collapsing the model simulations and the experimental data from a recently described affinity release system, to a single master curve. Importantly, this mathematical analysis can be applied to any single species affinity-based system to determine the parameters required for a desired release profile.
- Published
- 2015
24. Click conjugated polymeric immuno-nanoparticles for targeted siRNA and antisense oligonucleotide delivery
- Author
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Shawn C. Owen, Masad J. Damha, Glen F. Deleavey, Dianna P.Y. Chan, and Molly S. Shoichet
- Subjects
Small interfering RNA ,Materials science ,Polymers ,Genetic enhancement ,Biophysics ,Bioengineering ,02 engineering and technology ,Biomaterials ,03 medical and health sciences ,Cell Line, Tumor ,Humans ,Gene silencing ,RNA, Small Interfering ,Micelles ,030304 developmental biology ,0303 health sciences ,Nuclease ,biology ,Oligonucleotide ,Transfection ,Oligonucleotides, Antisense ,021001 nanoscience & nanotechnology ,Combinatorial chemistry ,Mechanics of Materials ,Lipofectamine ,Ceramics and Composites ,biology.protein ,Nucleic acid ,Nanoparticles ,0210 nano-technology - Abstract
Efficient and targeted cellular delivery of small interfering RNAs (siRNAs) and antisense oligonucleotides (AONs) is a major challenge facing oligonucleotide-based therapeutics. The majority of current delivery strategies employ either conjugated ligands or oligonucleotide encapsulation within delivery vehicles to facilitate cellular uptake. Chemical modification of the oligonucleotides (ONs) can improve potency and duration of activity, usually as a result of improved nuclease resistance. Here we take advantage of innovations in both polymeric delivery vehicles and ON stabilization to achieve receptor-mediated targeted delivery of siRNAs or AONs for gene silencing. Polymeric nanoparticles comprised of poly(lactide-co-2-methyl, 2-carboxytrimethylene carbonate)-g-polyethylene glycol-furan/azide are click-modified with both anti-HER2 antibodies and nucleic acids on the exterior PEG corona. Phosphorothioate (PS), 2'F-ANA, and 2'F-RNA backbone chemical modifications improve siRNA and AON potency and duration of activity. Importantly, delivery of these nucleic acids on the exterior of the polymeric immuno-nanoparticles are as efficient in gene silencing as lipofectamine transfection without the associated potential toxicity of the latter.
- Published
- 2013
25. A hydrogel composite system for sustained epi-cortical delivery of Cyclosporin A to the brain for treatment of stroke
- Author
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Molly S. Shoichet, Matthew J. Caicco, Yuanfei Wang, Michael J. Cooke, Cindi M. Morshead, and Anup Tuladhar
- Subjects
Drug ,Time Factors ,Surface Properties ,media_common.quotation_subject ,Pharmaceutical Science ,Stimulation ,macromolecular substances ,Methylcellulose ,Pharmacology ,Models, Biological ,Mice ,chemistry.chemical_compound ,Drug Delivery Systems ,Neural Stem Cells ,Polylactic Acid-Polyglycolic Acid Copolymer ,Tandem Mass Spectrometry ,In vivo ,Cyclosporin a ,Neurosphere ,Animals ,Lactic Acid ,Hyaluronic Acid ,Particle Size ,Progenitor cell ,media_common ,Chemistry ,technology, industry, and agriculture ,Brain ,Hydrogels ,Microspheres ,Mice, Inbred C57BL ,Stroke ,PLGA ,Solubility ,Delayed-Action Preparations ,Drug delivery ,Cyclosporine ,Microscopy, Electron, Scanning ,Polyglycolic Acid ,Chromatography, Liquid - Abstract
Stimulation of endogenous neural stem/progenitor cells (NSPCs) with therapeutic factors holds potential for the treatment of stroke. Cyclosporin A (CsA) is a particularly promising candidate molecule because it has been shown to act as a survival factor for these cells over a period of weeks both in vitro and in vivo; however, systemically-delivered CsA compromises the entire immune system, necessitating sustained localized delivery. Herein we describe a local delivery strategy for CsA using an epi-cortical hydrogel of hyaluronan-methylcellulose (HAMC) as the drug reservoir. Three methods of incorporating the drug into the hydrogel (solubilized, particulate, and poly(lactic-co-glycolic) acid (PLGA) microsphere-encapsulated) resulted in tunable release, spanning a period of hours to weeks. Importantly, PLGA-encapsulated CsA released from the hydrogel had equivalent bioactivity to fresh drug as measured by the neurosphere assay. Moreover, when CsA was released from the PLGA/HAMC composite that was injected on the cortex of adult mice, CsA was detected in the NSPC niche at a constant concentration for at least 24days post-implant. Thus this hydrogel composite system may be promising for the treatment of stroke.
- Published
- 2013
26. Design considerations of polymeric nanoparticle micelles for chemotherapeutic delivery
- Author
-
Karyn Ho and Molly S. Shoichet
- Subjects
Drug ,General Energy ,Targeted drug delivery ,Chemistry ,media_common.quotation_subject ,Tissue level ,Nanoparticle ,Nanotechnology ,Conjugated system ,Polymeric nanoparticles ,Micelle ,Targeting ligands ,media_common - Abstract
To improve safety and efficacy of anti-cancer therapy, drug-loaded polymeric nanoparticle micelle systems have been designed to target tumour pathophysiology. To accomplish this, nanoparticles take advantage of enhanced permeability and retention (EPR) of macromolecules to target tumours on a tissue level (passive targeting) while conjugated targeting ligands bind cancer surface markers and promote nanoparticle uptake (active targeting). Composition, size, shape, drug loading, and ligand density are all tunable design parameters that impact nanoparticle targeting. Understanding the complex interplay between these parameters and the resulting effects on drug targeting rationalizes adjustments to nanoparticle formulations.
- Published
- 2013
27. The effects of intrathecal injection of a hyaluronan-based hydrogel on inflammation, scarring and neurobehavioural outcomes in a rat model of severe spinal cord injury associated with arachnoiditis
- Author
-
Lisa DiDiodato, Greg J. Stanisz, Kajana Satkunendrarajah, Molly S. Shoichet, James W. Austin, Jefferson R. Wilson, Michael G. Fehlings, Catherine E. Kang, and M. Douglas Baumann
- Subjects
Biophysics ,Enzyme-Linked Immunosorbent Assay ,Bioengineering ,Inflammation ,Hydrogel, Polyethylene Glycol Dimethacrylate ,Biomaterials ,Lesion ,Fibrosis ,medicine ,Animals ,Hyaluronic Acid ,Rats, Wistar ,Spinal cord injury ,Injections, Spinal ,Spinal Cord Injuries ,business.industry ,medicine.disease ,Spinal cord ,Immunohistochemistry ,Magnetic Resonance Imaging ,Rats ,Electrophysiology ,medicine.anatomical_structure ,Arachnoiditis ,Mechanics of Materials ,Anesthesia ,Ceramics and Composites ,Female ,medicine.symptom ,Subarachnoid space ,business ,Syringomyelia - Abstract
Traumatic spinal cord injury (SCI) comprises a heterogeneous condition caused by a complex array of mechanical forces that damage the spinal cord – making each case somewhat unique. In addition to parenchymal injury, a subset of patients experience severe inflammation in the subarachnoid space or arachnoiditis, which can lead to the development of fluid-filled cavities/syringes, a condition called post-traumatic syringomyelia (PTS). Currently, there are no therapeutic means to address this devastating complication in patients and furthermore once PTS is diagnosed, treatment is often prone to failure. We hypothesized that reducing subarachnoid inflammation using a novel bioengineered strategy would improve outcome in a rodent model of PTS. A hydrogel of hyaluronan and methyl cellulose (HAMC) was injected into the subarachnoid space 24 h post PTS injury in rats. Intrathecal injection of HAMC reduced the extent of fibrosis and inflammation in the subarachnoid space. Furthermore, HAMC promoted improved neurobehavioural recovery, enhanced axonal conduction and reduced the extent of the lesion as assessed by MRI and histomorphometric assessment. These findings were additionally associated with a reduction in the post-traumatic parenchymal fibrous scar formation as evidenced by reduced CSPG deposition and reduced IL-1α cytokine levels. Our data suggest that HAMC is capable of modulating inflammation and scarring events, leading to improved functional recovery following severe SCI associated with arachnoiditis.
- Published
- 2012
28. Polymers used to influence cell fate in 3D geometry: New trends
- Author
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Yukie Aizawa, Shawn C. Owen, and Molly S. Shoichet
- Subjects
chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Cell adhesion molecule ,Organic Chemistry ,technology, industry, and agriculture ,Nanotechnology ,Surfaces and Interfaces ,Polymer ,Cell fate determination ,Extracellular matrix ,Tissue engineering ,chemistry ,Self-healing hydrogels ,Materials Chemistry ,Ceramics and Composites ,3d geometry ,Function (biology) - Abstract
The extracellular matrix (ECM) is a hydrogel-like structure comprised of several different biopolymers, encompassing a wide range of biological, chemical, and mechanical properties. The composition, organization, and assembly of the ECM play a critical role in cell function. Cellular behavior is guided by interactions that occur between cells and their local microenvironment, and this interrelationship plays a significant role in determining physiological functions. Bioengineering approaches have been developed to mimic native tissue microenvironments by fabricating novel bioactive hydrogel scaffolds. This review explores material designs and fabrication approaches that are guiding the design of hydrogels as tissue engineered scaffolds. As the fundamental biology of the cellular microenvironment is often the inspiration for material design, the review focuses on modifications to control bioactive cues such as adhesion molecules and growth factors, and summarizes the current applications of biomimetic scaffolds that have been used in vitro as well as in vivo .
- Published
- 2012
29. Targeting the amyloid-β antibody in the brain tissue of a mouse model of Alzheimer's disease
- Author
-
Peter St George-Hyslop, Daniel McLean, Molly S. Shoichet, Yuanfei Wang, Michael J. Cooke, and Paul E. Fraser
- Subjects
Diagnostic Imaging ,Gene isoform ,Pathology ,medicine.medical_specialty ,medicine.drug_class ,Transgene ,Pharmaceutical Science ,Mice, Transgenic ,Plaque, Amyloid ,Biology ,Monoclonal antibody ,Models, Biological ,Mice ,Alzheimer Disease ,In vivo ,Parenchyma ,medicine ,Extracellular ,Animals ,Tissue Distribution ,Amyloid beta-Peptides ,Antibodies, Monoclonal ,Brain ,Disease Models, Animal ,Microscopy, Fluorescence ,biology.protein ,Molecular imaging ,Antibody - Abstract
Alzheimer's disease is a neurodegenerative disease characterized pathologically by amyloid-β (Aβ) aggregates in the brain. Notwithstanding many promising therapeutics that are under development, early diagnosis of Alzheimer's disease is limited. By targeting the Aβ aggregates, diagnosis can be improved and disease progression reduced. Molecular imaging using monoclonal antibodies to target specific isoforms of Aβ aggregates offer increased specificity in comparison to conventional imaging tracers; however, antibodies that are widely used in histology do not necessarily show similar binding in a dynamic in vivo environment. In this study, the diffusion and binding were studied of a classical monoclonal antibody, 6E10, in the brain of the TgCRND8 mouse model of AD. After intracranial injection of fluorescent 6E10, we observed broad and rapid labelling of Aβ deposits in the cortex and corpus callosum within 4h. Aβ plaques were detected up to 2.5mm away from the injection site in TgCRND8 mice and not in wild type mice at all, demonstrating specificity of binding. The apparent diffusivity and elimination constant of the anti-Aβ antibody were found to be independent of both the age of the animal and the accumulation of Aβ in the extracellular space, suggesting broad applicability of this targeting molecule. Mathematical modelling of the diffusion profiles of the anti-Aβ antibody in the brain parenchyma provides insights into the utility of antibodies as molecular imaging tools and targeted therapeutics.
- Published
- 2012
30. Polymeric micelle stability
- Author
-
Dianna P.Y. Chan, Molly S. Shoichet, and Shawn C. Owen
- Subjects
chemistry.chemical_classification ,Aqueous solution ,Polymeric micelles ,Materials science ,Polymer composition ,Biomedical Engineering ,Pharmaceutical Science ,Nanoparticle ,Bioengineering ,Nanotechnology ,Polymer ,Micelle ,Systemic toxicity ,chemistry ,Drug delivery ,General Materials Science ,Biotechnology - Abstract
Summary Polymeric micelles provide a platform that can be carefully tuned for drug delivery. The nano-scale aggregates form spontaneously in aqueous solution and can be used to overcome drug insolubility and increase circulation half life. Self-assembled polymeric micelles are dynamic in nature; thermodynamics defines how the system acts as micelles approach equilibrium, while kinetics characterizes the system's behavior over time. In this review, we discuss factors that affect the stability of self-assembled polymeric micelle systems for drug delivery and methods used to study stability. Considerations of polymer composition, drug encapsulation, and environmental conditions influence polymeric micelle stability. Ultimately, we emphasize the importance of investigating micelle systems in physiologically relevant media to improve therapeutic efficacy and reduce systemic toxicity in clinical applications.
- Published
- 2012
31. Creating permissive microenvironments for stem cell transplantation into the central nervous system
- Author
-
Michael J. Cooke, Molly S. Shoichet, and Howard Kim
- Subjects
Adult ,Cell Survival ,medicine.medical_treatment ,Central nervous system ,Biocompatible Materials ,Bioengineering ,Biology ,Neural Stem Cells ,Tissue engineering ,medicine ,Humans ,Progenitor cell ,Permissive ,Growth factor ,Graft Survival ,Cell Differentiation ,Cell biology ,Transplantation ,medicine.anatomical_structure ,Traumatic injury ,Cellular Microenvironment ,Brain Injuries ,Immunology ,Intercellular Signaling Peptides and Proteins ,Stem cell ,Stem Cell Transplantation ,Biotechnology - Abstract
Traumatic injury to the central nervous system (CNS) is highly debilitating, with the clinical need for regenerative therapies apparent. Neural stem/progenitor cells (NSPCs) are promising because they can repopulate lost or damaged cells and tissues. However, the adult CNS does not provide an optimal milieu for exogenous NSPCs to survive, engraft, differentiate, and integrate with host tissues. This review provides an overview of tissue engineering strategies to improve stem cell therapies by providing a defined microenvironment during transplantation. The use of biomaterials for physical support, growth factor delivery, and cellular co-transplantation are discussed. Providing the proper environment for stem cell survival and host tissue integration is crucial in realizing the full potential of these cells in CNS repair strategies.
- Published
- 2012
32. Controlled epi-cortical delivery of epidermal growth factor for the stimulation of endogenous neural stem cell proliferation in stroke-injured brain
- Author
-
Cindi M. Morshead, Yuanfei Wang, Michael J. Cooke, and Molly S. Shoichet
- Subjects
Central nervous system ,Biophysics ,Subventricular zone ,Bioengineering ,Stimulation ,Endogeny ,Biology ,Models, Biological ,Polyethylene Glycols ,Biomaterials ,Mice ,Neural Stem Cells ,Epidermal growth factor ,medicine ,Animals ,Hyaluronic Acid ,Progenitor cell ,Cell Proliferation ,Mice, Inbred BALB C ,Epidermal Growth Factor ,Brain ,Neural stem cell ,Cell biology ,Stroke ,medicine.anatomical_structure ,Mechanics of Materials ,Drug delivery ,Immunology ,Ceramics and Composites ,Peptide Hydrolases - Abstract
One of the challenges in treating central nervous system (CNS) disorders with biomolecules is achieving local delivery while minimizing invasiveness. For the treatment of stroke, stimulation of endogenous neural stem/progenitor cells (NSPCs) by growth factors is a promising strategy for tissue regeneration. Epidermal growth factor (EGF) enhances proliferation of endogenous NSPCs in the subventricular zone (SVZ) when delivered directly to the ventricles of the brain; however, this strategy is highly invasive. We designed a biomaterials-based strategy to deliver molecules directly to the brain without tissue damage. EGF or poly(ethylene glycol)-modified EGF (PEG-EGF) was dispersed in a hyaluronan and methylcellulose (HAMC) hydrogel and placed epi-cortically on both uninjured and stroke-injured mouse brains. PEG-modification decreased the rate of EGF degradation by proteases, leading to a significant increase in protein accumulation at greater tissue depths than previously shown. Consequently, EGF and PEG-EGF increased NSPC proliferation in uninjured and stroke-injured brains; and in stroke-injured brains, PEG-EGF significantly increased NSPC stimulation. Our epi-cortical delivery system is a minimally-invasive method for local delivery to the brain, providing a new paradigm for local delivery to the brain.
- Published
- 2011
33. Endothelial cells guided by immobilized gradients of vascular endothelial growth factor on porous collagen scaffolds
- Author
-
Milica Radisic, Molly S. Shoichet, Loraine L.Y. Chiu, and Devang Odedra
- Subjects
Vascular Endothelial Growth Factor A ,Scaffold ,Materials science ,VEGF receptors ,Biomedical Engineering ,Biochemistry ,Cell Line ,Biomaterials ,Mice ,chemistry.chemical_compound ,Tissue engineering ,In vivo ,Animals ,Porosity ,Molecular Biology ,Carbodiimide ,Tissue Scaffolds ,biology ,Endothelial Cells ,General Medicine ,Vascular endothelial growth factor ,Immobilized Proteins ,chemistry ,Cell culture ,biology.protein ,Collagen ,Biotechnology ,Biomedical engineering - Abstract
A key challenge in tissue engineering is overcoming cell death in the scaffold interior due to the limited diffusion of oxygen and nutrients therein. We here hypothesize that immobilizing a gradient of a growth/survival factor from the periphery to the center of a porous scaffold would guide endothelial cells into the interior of the scaffold, thus overcoming a necrotic core. Proteins were immobilized by one of three methods on porous collagen scaffolds for cardiovascular tissue engineering. The proteins were first activated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/sulfo N-hydroxysuccinimide and then applied to the scaffold by one of three methods to establish the gradient: perfusion (the flow method), use of a source and a sink (the source-sink method) or by injecting 5 μl of the solution at the center of the scaffold (point source method). Due to the high reproducibility and ease of application of the point source method it was further used for VEGF-165 gradient formation, where an ~2 ng ml(-1) mm(-1) gradient was formed in a radial direction across a scaffold, 12 mm in diameter and 2.5mm thick. More endothelial cells were guided by the VEGF-165 gradient deep into the center of the scaffold compared with both uniformly immobilized VEGF-165 (with the same total VEGF concentration) and VEGF-free controls. All scaffolds (including the controls) yielded the same number of cells, but notably the VEGF-165 gradient scaffolds demonstrated a higher cell density in the centre. Thus we concluded that the VEGF-165 gradient promoted the migration, but not proliferation, of cells into the scaffold. These gradient scaffolds provide the foundation for future in vivo tissue engineering studies.
- Published
- 2011
34. Transport of epidermal growth factor in the stroke-injured brain
- Author
-
Yuanfei Wang, Michael J. Cooke, Molly S. Shoichet, Nadia Sachewsky, Yakov Lapitsky, Dale Corbett, Cindi M. Morshead, and Ryan G. Wylie
- Subjects
Pathology ,medicine.medical_specialty ,Epidermal Growth Factor ,business.industry ,Brain ,Pharmaceutical Science ,Subventricular zone ,Endogeny ,Pharmacology ,medicine.disease ,Polyethylene Glycols ,Stroke ,Central nervous system disease ,Mice ,Protein Transport ,medicine.anatomical_structure ,In vivo ,Epidermal growth factor ,Precursor cell ,Extracellular ,medicine ,Animals ,Humans ,business - Abstract
Stroke is a neurological disorder that currently has no cure. Intrathecal delivery of growth factors, specifically recombinant human epidermal growth factor (rhEGF), stimulates endogenous neural precursor cells in the subventricular zone (SVZ) and promotes tissue regeneration in animal models of stroke. In this model, rhEGF is delivered with an invasive minipump/catheter system, which causes trauma to the brain. A less invasive strategy is to deliver rhEGF from the brain cortex; however, this requires the protein to diffuse through the brain, from the site of injection to the SVZ. Although this method of delivery has great potential, diffusion is limited by rapid removal from the extracellular space and hence for successful translation into the clinic strategies are needed to increase the diffusion distance. Using integrative optical imaging we investigate diffusion of rhEGF vs. poly(ethylene glycol)-modified rhEGF (PEG-rhEGF) in brain slices of both uninjured and stroke-injured animals. For the first time, we quantitatively show that PEG modification reduces the rate of growth factor elimination by over an order of magnitude. For rhEGF this corresponds to a two to threefold increase in predicted brain penetration distance, which we confirm with in vivo data.
- Published
- 2011
35. Combined cell and gene therapy towards the treatment of age-related macular degeneration and diabetic retinopathy
- Author
-
Iacovos P. Michael, D van der Kooy, Brian G. Ballios, Martin Friedlander, Nikolaos Mitrousis, Andras Nagy, Peter D. Westenskow, Sabiha Hacibekiroglu, Molly S. Shoichet, M. Massumi, H. Yang, and R. Vawda
- Subjects
Cancer Research ,Transplantation ,medicine.medical_specialty ,business.industry ,Genetic enhancement ,Immunology ,Cell ,Cell Biology ,Diabetic retinopathy ,Macular degeneration ,medicine.disease ,medicine.anatomical_structure ,Oncology ,Ophthalmology ,Age related ,Immunology and Allergy ,Medicine ,business ,Genetics (clinical) - Published
- 2018
36. Accelerated release of a sparingly soluble drug from an injectable hyaluronan–methylcellulose hydrogel
- Author
-
Yuanfei Wang, Molly S. Shoichet, Yakov Lapitsky, and Catherine E. Kang
- Subjects
Drug ,Surface Properties ,media_common.quotation_subject ,Pharmaceutical Science ,Excipient ,Methylcellulose ,Pharmacology ,Dosage form ,chemistry.chemical_compound ,Hyaluronic acid ,medicine ,Hyaluronic Acid ,Solubility ,Nimodipine ,media_common ,Chemistry ,Hydrogels ,Calcium Channel Blockers ,Kinetics ,Delayed-Action Preparations ,Drug delivery ,Biophysics ,Liberation ,Algorithms ,medicine.drug - Abstract
An injectable hydrogel, comprised of hyaluronan and methylcellulose (HAMC), shows promise for localized, sustained delivery of growth factors for treatment of spinal cord injury (SCI). To better understand its potential for the delivery of small molecules, the release of sparingly soluble neuroprotectant, nimodipine, was investigated experimentally and via continuum modeling. This revealed that the MC in HAMC increased the solubility of sparingly soluble drug by over an order of magnitude, and enabled highly tunable release rates to be achieved by varying the method by which the drug was introduced into the scaffold. When nimodipine was introduced into HAMC in solubilized form, it was rapidly released from the scaffold within 8 h. Conversely, when nimodipine was blended into HAMC in particulate form, the release rates were greatly reduced, giving rise to complete release over 2–3 days for small, sub-micron particles, and longer times for large, 100 μm particles. The nimodipine particle-loaded gels yielded particle size-dependent, biphasic release profiles, which reflected rapid release of the solubilized drug followed by the slow, dissolution-limited release of solid nimodipine. This suggests that injectable hydrogel matrices can act as polymeric excipients that accelerate the delivery of poorly soluble drugs and yield highly tunable release rates.
- Published
- 2009
37. The effect of substrate stiffness on adult neural stem cell behavior
- Author
-
Molly S. Shoichet and Nic D. Leipzig
- Subjects
Adult ,Cell signaling ,Population ,Cell Culture Techniques ,Biophysics ,Biocompatible Materials ,Bioengineering ,Biology ,Myelin oligodendrocyte glycoprotein ,Biomaterials ,Astrocyte differentiation ,Elastic Modulus ,Materials Testing ,medicine ,Animals ,Humans ,RNA, Messenger ,Progenitor cell ,education ,Cells, Cultured ,Neurons ,Acrylamides ,Chitosan ,education.field_of_study ,Cell Differentiation ,Hydrogels ,Neural stem cell ,Oligodendrocyte ,Rats ,Cell biology ,Adult Stem Cells ,Oligodendroglia ,medicine.anatomical_structure ,Mechanics of Materials ,Immunology ,Ceramics and Composites ,biology.protein ,Female ,Stress, Mechanical ,Biomarkers ,Adult stem cell - Abstract
Adult stem cells reside in unique niches that provide vital cues for their survival, self-renewal and differentiation. In order to better understand the contribution of substrate stiffness to neural stem/progenitor cell (NSPC) differentiation and proliferation, a photopolymerizable methacrylamide chitosan (MAC) biomaterial was developed. Photopolymerizable MAC is particularly compelling for the study of the central nervous system stem cell niche because Young's elastic modulus (E(Y)) can be tuned from less than 1 kPa to greater than 30 kPa. Additionally, the numerous free amine functional groups enable inclusion of biochemical signaling molecules that, together with the mechanical environment, influence cell behavior. Herein, NSPCs proliferated on MAC substrates with Young's elastic moduli below 10 kPa and exhibited maximal proliferation on 3.5 kPa surfaces. Neuronal differentiation was favored on the soft est surfaces with E(Y)1 kPa as confirmed by both immunohistochemistry and qRT-PCR. Oligodendrocyte differentiation was favored on stiffer scaffolds (7 kPa); however, myelin oligodendrocyte glycoprotein (MOG) gene expression suggested that oligodendrocyte maturation and myelination was best on1 kPa scaffolds where more mature neurons were present. Astrocyte differentiation was only observed on1 and 3.5 kPa surfaces and represented less than 2% of the total cell population. This work demonstrates the importance of substrate stiffness to the proliferation and differentiation of adult NSPCs and highlights the importance of mechanical properties to the success of scaffolds designed to engineer central nervous system tissue.
- Published
- 2009
38. A quantitative ELISA for bioactive anti-Nogo-A, a promising regenerative molecule for spinal cord injury repair
- Author
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M. Douglas Baumann, Michael G. Fehlings, Molly S. Shoichet, and James W. Austin
- Subjects
Analyte ,Neurite ,medicine.drug_class ,Nogo Proteins ,Cell ,Enzyme-Linked Immunosorbent Assay ,Monoclonal antibody ,PC12 Cells ,General Biochemistry, Genetics and Molecular Biology ,chemistry.chemical_compound ,mental disorders ,Neurites ,medicine ,Animals ,Molecular Biology ,Peptide sequence ,Spinal Cord Injuries ,Chemistry ,Antibodies, Monoclonal ,Neuroregeneration ,Rats ,medicine.anatomical_structure ,Biochemistry ,Cell culture ,Growth inhibition ,Myelin Proteins ,psychological phenomena and processes - Abstract
The detection and quantification of bioactive anti-Nogo-A mAbs, which is of interest for the treatment of spinal cord injury, has previously been accomplished using cellular or indirect immunoassays. In one such assay the presence of Nogo-A inhibits neurite outgrowth from the PC12 neuronal cell line: pre-treatment with anti-Nogo-A overcomes this inhibition and the concentration of anti-Nogo-A is correlated with the reduction in growth inhibition. In the current work we demonstrate the first anti-Nogo-A sandwich ELISA utilizing a Nogo-A fragment in the role of capture agent and the anti-Nogo-A mAb 11c7 as the soluble analyte. Because the Nogo-A fragment contains the amino acid sequence against which 11c7 was raised, we postulate this combination reproduces the native binding mechanism and results in the detection of bioactive anti-Nogo-A. In support of this hypothesis, we have found good agreement between the inhibitory action of the Nogo-A fragment and myelin proteins used in existing PC12 cell assays. Importantly, unlike the several days required for cellular assays the ELISA is a fast and easy to use method for the detection and quantification of bioactive 11c7 in the range of 500–6000 pg/mL.
- Published
- 2009
39. The effect of immobilized platelet derived growth factor AA on neural stem/progenitor cell differentiation on cell-adhesive hydrogels
- Author
-
Nic D. Leipzig, Tasneem Zahir, Molly S. Shoichet, and Yukie Aizawa
- Subjects
Male ,Cell type ,Cell ,Biophysics ,Bioengineering ,Biology ,Regenerative medicine ,Myelin oligodendrocyte glycoprotein ,Biomaterials ,Gene expression ,Cell Adhesion ,medicine ,Animals ,Nerve Tissue ,Rats, Wistar ,Progenitor cell ,Platelet-Derived Growth Factor ,Stem Cells ,Cell Differentiation ,Hydrogels ,Molecular biology ,Rats ,Oligodendroglia ,medicine.anatomical_structure ,Mechanics of Materials ,Ceramics and Composites ,biology.protein ,Immunohistochemistry ,Multipotentiality - Abstract
Neural stem/progenitor cells (NSPCs) hold great promise in regenerative medicine; however, controlling their differentiation to a desired phenotype within a defined matrix is challenging. To guide the differentiation of NSPCs, we first created a cell-adhesive matrix of agarose modified with glycine– arginine–glycine–aspartic acid–serine (GRGDS) and then demonstrated the multipotentiality of NSPCs to differentiate to the three primary cell types of the central nervous system on this matrix: neurons, oligodendrocytes and astrocytes. We then examined whether immobilized platelet derived growth factor AA (PDGF-AA) would promote differentiation similarly to the same soluble factor and found similar percentages of NSPCs differentiated to oligodendrocytes as determined by immunohistochemistry (IHC) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Interestingly, the gene expression of the differentiated oligodendrocytes was similar for 2 0 ,3 0-cyclic nucleotide 30-phosphodiesterase (CNPase) but different for myelin oligodendrocyte glycoprotein (MOG) in the presence of soluble PDGF-AA vs. immobilized PDGF-AA. These results demonstrate for the first time, that it is possible to control the differentiation of NSPCs, and specifically to oligodendrocytes, in cell-adhesive matrices with immobilized PDGF-AA.
- Published
- 2008
40. Promoting neuron adhesion and growth
- Author
-
Nic D. Leipzig, Laura M.Y. Yu, and Molly S. Shoichet
- Subjects
Nervous system ,Materials science ,Neurite ,Mechanical Engineering ,Regeneration (biology) ,Cell ,Nanotechnology ,Condensed Matter Physics ,Neural tissue engineering ,Cell biology ,Extracellular matrix ,medicine.anatomical_structure ,Materials Science(all) ,Mechanics of Materials ,medicine ,General Materials Science ,Neuron adhesion ,Cell adhesion - Abstract
During nervous system development, the extracellular matrix (ECM) plays a pivotal role offering anchorage points to maturing neurons and neurites, as well as a permissive environment for tissue formation. Thus enhancement of cell adhesion is often an important criterion when designing biomaterials for neural tissue engineering. In addition to functionalizing biomaterials with ECM-derived cell adhesive molecules, there is emerging evidence that indicates the surface topography, stiffness, and electrical properties play an important role in neuron adhesion and neurite outgrowth. We describe recent developments in biomaterials modification for simulating the microenvironment in order to promote neuron adhesion and growth, as well as to encourage nerve regeneration after injury or disease.
- Published
- 2008
41. Synthesis and thermal stability of hybrid fluorosilicone polymers
- Author
-
Molly S. Shoichet and Michael P. C. Conrad
- Subjects
chemistry.chemical_classification ,Polymers and Plastics ,Anomeric effect ,Organic Chemistry ,Condensation ,chemistry.chemical_element ,Polymer ,Oxygen ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Thermal stability ,Benzene ,Bond cleavage - Abstract
Aromatic hybrid fluorosilicones, such as perfluorocyclobutane aromatic polyethers, have higher thermal stability than typical polysiloxanes. While these polyethers decompose by homolytic cleavage of the oxygeneperfluorocyclobutane bond, the enhanced thermal stability of the polyethers may, in part, arise from this oxygen through the anomeric effect. To determine the effect of the ether oxygen on thermal stability, two perfluorocyclobutane aromatic units, one with and one without the oxygen, were modeled. To confirm the results experimentally, a series of hybrid fluorosilicones based on the latter were synthesized by thermocyclodimerization of 1-bromo-4-(trifluorovinyl)benzene, metalehalogen exchange, and condensation with one of 1,3-dichlorotetramethyldisiloxane; 1,7-dichlorooctamethyltetrasiloxane; or chlorine-terminated poly(dimethylsiloxane). The degradation temperature (T1%) was lower (w240 � C) than the comparable polyethers (w430 � C). These results demonstrate the importance of the ether oxygen to the stability of perfluorocyclobutane aromatic polyethers through a number of effects including the anomeric effect and enhancing the strength of the silicon-aromatic bond. 2007 Elsevier Ltd. All rights reserved.
- Published
- 2007
42. Synthesis of cell-adhesive dextran hydrogels and macroporous scaffolds
- Author
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Molly S. Shoichet and Stéphane G. Lévesque
- Subjects
Materials science ,Biophysics ,Tissue Adhesions ,Bioengineering ,Peptide ,Chick Embryo ,Biomaterials ,chemistry.chemical_compound ,Tissue engineering ,Adhesives ,Ganglia, Spinal ,Polymer chemistry ,Cell Adhesion ,Ethylamines ,Neurites ,Copolymer ,Animals ,Cell adhesion ,Cells, Cultured ,chemistry.chemical_classification ,Peptide modification ,Tissue Engineering ,Dextrans ,Hydrogels ,Dextran ,chemistry ,Mechanics of Materials ,Drug delivery ,Self-healing hydrogels ,Ceramics and Composites ,Methacrylates ,Oligopeptides ,Porosity - Abstract
Dextran hydrogels have been previously investigated as drug delivery vehicles and more recently as macroporous scaffolds; however, the non-cell-adhesive nature of dextran has limited its utility for tissue engineering. To overcome this limitation, macroporous scaffolds of methacrylated dextran (Dex-MA) copolymerized with aminoethyl methacrylate (AEMA) were synthesized, thereby introducing primary amine groups for covalent immobilization of extracellular-matrix-derived peptides. The amino group density for hydrogels copolymerized with 0.5 wt% AEMA was found to be 36.1±0.4 μmol/cm 3 by elemental analysis. To further enhance cellular interaction, poly(Dex-MA -co- AEMA) hydrogels were modified with either C RGD S or a mixture of CDPG YIGSR and CQAAS IKVAV (1:1, v/v) using sulfo-( N -maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC). The immobilized peptide concentration was determined using amino acid analysis at: 2.6±0.9 μmol/cm 3 for C RGD S-derived hydrogels and 2.2±0.3 μmol/cm 3 plus 1.9±0.2 μmol/cm 3 for CDPG YIGSR plus CQAAS IKVAV -derived hydrogels, respectively. Cellular interactions of primary embryonic chick dorsal root ganglia (DRGs) were compared on the hydrogels. Cell adhesion and neurite outgrowth on poly(Dex-MA) increased with copolymerization of AEMA and further improved with peptide modification and significantly for CDPG YIGSR /CQAAS IKVAV -derived poly(Dex-MA -co- AEMA) hydrogels. Moreover, DRGs penetrated within the first 600 μm of the scaffolds, thereby demonstrating the potential of this scaffold for guided cell and axonal regeneration in vivo.
- Published
- 2006
43. Incorporation of protein-eluting microspheres into biodegradable nerve guidance channels for controlled release
- Author
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Vanessa I. ScangaV.I. Scanga, Molly S. Shoichet, Cindi M. Morshead, and Alex Goraltchouk
- Subjects
Polymers ,Drug Compounding ,Pharmaceutical Science ,Chitin ,macromolecular substances ,Dosage form ,Chitosan ,chemistry.chemical_compound ,Drug Delivery Systems ,Polylactic Acid-Polyglycolic Acid Copolymer ,Lactic Acid ,Particle Size ,Microparticle ,Epidermal Growth Factor ,Regeneration (biology) ,Proteins ,Serum Albumin, Bovine ,Anatomy ,Controlled release ,Microspheres ,Recombinant Proteins ,Nerve Regeneration ,PLGA ,chemistry ,Delayed-Action Preparations ,Drug delivery ,Biophysics ,Algorithms ,Polyglycolic Acid - Abstract
Nerve guidance channels (NGCs) promote axonal regeneration after transection injury of the peripheral nerve or spinal cord, yet this regeneration is limited. To enhance regeneration further, we hypothesize that localized delivery of therapeutic molecules combined with the NGC is required. In an attempt to achieve such an NGC, we designed and synthesized a novel NGC in which protein-encapsulated microspheres were stably incorporated into the tube wall. Specifically, poly(lactide-co-glycolide) (PLGA 50/50) microspheres were physically entrapped in the annulus between two concentric tubes, consisting of a chitosan inner tube and a chitin outer tube. Taking advantage of the extensive shrinking that the outer chitin tube undergoes with drying, >15 mg of microspheres were loaded within the tube walls. Using BSA-encapsulated microspheres as the model drug delivery system, BSA was released from microsphere loaded tubes (MLTs) for 84 days, and from freely suspended PLGA microspheres for 70 days. An initial burst release was observed for both MLTs and free microspheres, followed by a degradation-controlled release profile that resulted in a higher release rate from MLTs initially, which was then attenuated likely due to the buffering effect of chitin and chitosan tubes. Epidermal growth factor (EGF), co-encapsulated with BSA in PLGA 50/50 microspheres in MLTs, was released for 56 days with a similar profile to that of BSA. Released EGF was found to be bioactive for at least 14 days as assessed by a neurosphere forming bioassay.
- Published
- 2006
44. Macroporous interconnected dextran scaffolds of controlled porosity for tissue-engineering applications
- Author
-
Molly S. Shoichet, Stéphane G. Lévesque, and Ryan M. Lim
- Subjects
Materials science ,Surface Properties ,Biophysics ,Biocompatible Materials ,Bioengineering ,Methacrylate ,Phase Transition ,Polyethylene Glycols ,Diffusion ,Biomaterials ,chemistry.chemical_compound ,Tissue engineering ,Materials Testing ,Polymer chemistry ,PEG ratio ,Molar mass ,Tissue Engineering ,Water ,Dextrans ,Hydrogels ,Serum Albumin, Bovine ,Microporous material ,Microspheres ,Dextran ,Acrylates ,chemistry ,Chemical engineering ,Mechanics of Materials ,Self-healing hydrogels ,Ceramics and Composites ,Porosity ,Ethylene glycol - Abstract
Dextran hydrogels have been studied as drug delivery vehicles but not as scaffolds for tissue-engineering likely because previously synthesized dextran hydrogels had pores too small for cell penetration. Our goal was to create macroporous, interconnected dextran scaffolds. To this end, we took advantage of the liquid-liquid immiscibility of poly(ethylene glycol) and methacrylated dextran during radical crosslinking of the methacrylated moieties. By controlling the degree of methacrylate substitution on dextran, dextran molar mass and PEG concentration, macroporous hydrogels were created. The presence of PEG in solution had a significant effect on the final morphology of the dextran hydrogel leading to the formation of different types of structures, from microporous gel to macroporous gel-wall to a macroporous interconnected-beaded structure. A series of formulation diagrams were prepared which allowed us to determine which conditions led to the formation of macroporous interconnected-beaded scaffolds. Dextran macroporous interconnected-beaded gels had a high water content, between 89% and 94%, a homogeneous morphology, determined by scanning electron microscopy, with interconnected macroporous pores, as determined by protein diffusivity where the effective diffusion coefficients of BSA were calculated to be 3.1 x 10(-7)cm2/s for Dex-MA 40 kDa DS 5 and 1 x 10(-7)cm2/s for Dex-MA 6 kDa DS10, which are similar to that of BSA in water, 5.9 x 10(-7)cm2/s. Mercury intrusion porosimetry showed that the macroporous interconnected-beaded scaffolds had a bimodal distribution of macropores, with a median diameter of 41 microm, interconnected by throats, which had a median diameter of 11 microm. Together, these data suggest that the dextran scaffolds will be advantageous in applications that require an interconnected macroporous geometry, such as those of tissue engineering where cell penetration and nutrient diffusion are necessary for tissue regeneration.
- Published
- 2005
45. Chitin-based tubes for tissue engineering in the nervous system
- Author
-
Molly S. Shoichet, Hui Shan Koh, Rivelino Montenegro, and Thomas Freier
- Subjects
Materials science ,Biophysics ,Chitin ,Bioengineering ,macromolecular substances ,Polysaccharide ,Biomaterials ,Chitosan ,Hydrolysis ,chemistry.chemical_compound ,Tissue engineering ,Ganglia, Spinal ,Animals ,Composite material ,Alkaline hydrolysis ,Cells, Cultured ,chemistry.chemical_classification ,Tissue Engineering ,technology, industry, and agriculture ,Adhesion ,carbohydrates (lipids) ,Compressive strength ,chemistry ,Chemical engineering ,Mechanics of Materials ,Ceramics and Composites ,Chickens - Abstract
The purpose of this study was to investigate chitin and chitosan as potential materials for biodegradable nerve guides. Transparent chitin hydrogel tubes were synthesized, for the first time, from chitosan solutions using acylation chemistry and mold casting techniques. Alkaline hydrolysis of chitin tubes resulted in chitosan tubes, with the extent of hydrolysis controlling the resulting amine content. This, in turn, impacted compressive strength and cell adhesion. Chitosan tubes were mechanically stronger than their chitin origins, as measured by the transverse compressive test, where tubes having degrees of acetylation of 1%, 3%, 18% (i.e. chitosan) and 94% (i.e. chitin) supported loads at a 30% displacement of 40.6 +/- 4.3, 25.3 +/- 4.5, 10.6 +/- 0.8, and 8.7 +/- 0.4 g, respectively. However, the chitin processing methodology could be optimized for compressive strength, by either incorporating reinforcing coils in the tube wall, or air-drying the hydrogel tubes. Chitin and chitosan supported adhesion and differentiation of primary chick dorsal root ganglion neurons in vitro. Chitosan films showed significantly enhanced neurite outgrowth relative to chitin films, reflecting the dependence of nerve cell affinity on the amine content in the polysaccharide: neurites extended 1794.7 +/- 392.0 microm/mm(2) on chitosan films vs. 140.5 +/- 41.6 microm/mm(2) on chitin films after 2 days of culture. This implies that cell adhesion and neurite extension can be adjusted by amine content, which is important for tissue engineering in the nervous system. The methods for easy processing and modification of chitin and chitosan described herein, allow the mechanical properties and cyto-compatibility to be controlled and provide a means for a broader investigation into their use in biomedical applications.
- Published
- 2005
46. Injectable intrathecal delivery system for localized administration of EGF and FGF-2 to the injured rat spinal cord
- Author
-
Molly S. Shoichet, Charles H. Tator, and Maria C. Jimenez Hamann
- Subjects
Pathology ,medicine.medical_specialty ,Ependymal Cell ,Microinjections ,Basic fibroblast growth factor ,Central nervous system ,PC12 Cells ,Subarachnoid Space ,Rats, Sprague-Dawley ,Lesion ,Mice ,chemistry.chemical_compound ,Developmental Neuroscience ,Epidermal growth factor ,Ependyma ,Neural Pathways ,medicine ,Animals ,Spinal cord injury ,Injections, Spinal ,Spinal Cord Injuries ,Cell Proliferation ,Epidermal Growth Factor ,business.industry ,Drug Administration Routes ,Recovery of Function ,medicine.disease ,Spinal cord ,Nerve Regeneration ,Rats ,Disease Models, Animal ,Treatment Outcome ,medicine.anatomical_structure ,Spinal Cord ,Neurology ,chemistry ,Anesthesia ,Nerve Degeneration ,NIH 3T3 Cells ,Female ,Fibroblast Growth Factor 2 ,medicine.symptom ,business - Abstract
The administration of growth factors (GFs) for treatment of experimental spinal cord injury (SCI) has shown limited benefits. One reason may be the mode of delivery to the injury site. We have developed a minimally invasive and safe drug delivery system (DDS) consisting of a highly concentrated collagen solution that can be injected intrathecally at the site of injury providing localized delivery of GFs. Using the injectable DDS, epidermal growth factor (EGF) and basic fibroblast growth factor (FGF-2) were co-delivered in the subarachnoid space of Sprague-Dawley rats. The in vivo distribution of EGF and FGF-2 in both injured and uninjured animals was monitored by immunohistochemistry. Although significant differences in the distribution of EGF and FGF-2 in the spinal cord were evident, localized delivery of the GFs resulted in significantly less cavitation at the lesion epicenter and for at least 720 mum caudal to it compared to control animals without the DDS. There was also significantly more white matter sparing at the lesion epicenter in animals receiving the GFs compared to control animals. Moreover, at 14 days post-injection, delivery of the GFs resulted in significantly greater ependymal cell proliferation in the central canal immediately rostral and caudal to the lesion edge compared to controls. These results demonstrate that the injectable DDS provides a new paradigm for localized delivery of bioactive therapeutic agents to the injured spinal cord.
- Published
- 2005
47. Long-term in vivo biomechanical properties and biocompatibility of poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) nerve conduits
- Author
-
Catherine A. Munro, Molly S. Shoichet, Rajiv Midha, Jason S. Belkas, and Miles G. Johnston
- Subjects
Male ,Materials science ,Biocompatibility ,Biophysics ,Nerve guidance conduit ,Biocompatible Materials ,Bioengineering ,Methacrylate ,2-Hydroxyethyl Methacrylate ,Biomaterials ,Implants, Experimental ,In vivo ,Materials Testing ,medicine ,Animals ,Longitudinal Studies ,Polyhydroxyethyl Methacrylate ,Tissue Engineering ,Foreign-Body Reaction ,medicine.disease ,Elasticity ,Biomechanical Phenomena ,Nerve Regeneration ,Rats ,Treatment Outcome ,Rats, Inbred Lew ,Mechanics of Materials ,Ceramics and Composites ,Methacrylates ,Sciatic nerve ,Sciatic Neuropathy ,Epineurial repair ,Calcification ,Biomedical engineering - Abstract
Artificial grafts are promising alternatives to nerve grafts for peripheral nerve repair because they obviate the complications and disadvantages associated with autografting such as donor site morbidity and limited tissue availability. We have synthesized poly(2-hydroxyethyl methacrylate-co-methyl methacrylate) (PHEMA-MMA) porous tubes and studied their efficacy in vivo. Specifically, we studied the short- and long-term stability and biocompatibility of 12 mm long tubes for the repair of surgically created 10 mm nerve gaps in rat sciatic nerves. Prior to implantation, tubes were analyzed in vitro using a micro-mechanical tester to measure displacement achieved with load applied. These results served as a calibration curve, y =6.8105×−0.0073 ( R 2 =0.9750, n =28), for in vivo morphometric tube compression measurements. In vivo, most of the PHEMA-MMA conduits maintained their structural integrity up to 8 weeks, but 29% (4/14) of them collapsed by 16 weeks. Interestingly, the tube wall area of collapsed 16-week tubes was significantly lower than those of patent tubes. Tubes were largely biocompatible; however, a small subset of 16-week tubes displayed signs of chronic inflammation characterized by “finger-like” tissue extensions invading the inner tube aspect, inflammatory cells (some of which were ED1+macrophages) and giant cells. Tubes also demonstrated signs of calcification, which increased from 8 to 16 weeks. To overcome these issues, future nerve conduits will be re-designed to be more robust and biocompatible.
- Published
- 2005
48. Axonal guidance channels in peripheral nerve regeneration
- Author
-
Jason S. Belkas, Molly S. Shoichet, and Rajiv Midha
- Subjects
business.industry ,Anatomy ,Nerve injury ,Tissue engineering ,Peripheral nerve ,medicine ,Regenerating axons ,Exogenous growth ,Orthopedics and Sports Medicine ,Surgery ,Guidance channel ,medicine.symptom ,business ,Neuroscience - Abstract
In recent times, tissue engineering researchers have been attempting to provide the scientific and medical communities with improvements in the repair of peripheral nerve injuries using synthetic grafts. Although the nerve autograft still remains the clinical gold standard in bridging nerve injury gaps, many advances on several fronts have been made in developing a more effective nerve tubular construct to guide regenerating axons across the lesion. This review discusses several strategies that have been employed to enhance the regenerative effectiveness of artificial nerve guidance channels. These strategies include the use of scaffolds, the integration of contact-mediated cues within the tubular construct, and incorporation or delivery of exogenous growth factors into the conduit lumen uniformly or in a gradient form. Animal and clinical studies are reviewed to explain some of the ideas involved in developing a guidance channel of the future.
- Published
- 2004
49. Fiber templating of poly(2-hydroxyethyl methacrylate) for neural tissue engineering
- Author
-
Paul D. Dalton, Lauren E. Flynn, and Molly S. Shoichet
- Subjects
Materials science ,Polymers ,Polyesters ,Sonication ,Composite number ,Biophysics ,Biocompatible Materials ,Bioengineering ,Methacrylate ,Hydrogel, Polyethylene Glycol Dimethacrylate ,Neural tissue engineering ,2-Hydroxyethyl Methacrylate ,Acetone ,Biomaterials ,chemistry.chemical_compound ,Tensile Strength ,Materials Testing ,Regeneration ,Fiber ,Composite material ,Polyhydroxyethyl Methacrylate ,Neurons ,technology, industry, and agriculture ,Water ,Hydrogels ,Axons ,Spinal Cord ,chemistry ,Mechanics of Materials ,Self-healing hydrogels ,Polycaprolactone ,Ceramics and Composites ,Methacrylates ,Biomedical engineering - Abstract
We have developed a method to create longitudinally oriented channels within poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels for neural tissue engineering applications. Incorporated into an entubulation strategy, these scaffolds have the potential to enhance nerve regeneration after transection injuries of either the spinal cord or the peripheral nerve by increasing the available surface area and providing guidance to extending axons and invading cells. The fabrication process is straightforward and the resultant scaffolds are highly reproducible. Polycaprolactone (PCL) fibers were extruded and embedded in transparent, crosslinked pHEMA gels. Sonication of the pHEMA/PCL composite in acetone resulted in the complete dissolution of the PCL, leaving longitudinally oriented, fiber-free channels in the pHEMA gel. Regulating the size and quantity of the PCL fibers allowed us to control the diameter and number of channels. Small and large channel scaffolds were fabricated and thoroughly characterized. The small channel scaffolds had 142+/-7 channels, with approximately 75% of the channels in the 100-200 micro m size range. The large channel scaffolds had 37+/-1 channels, with approximately 77% of the channels in the 300-400 micro m range. The equilibrium water content (EWC), porosity and compressive modulus were measured for each of the structures. Small and large channel scaffolds had, respectively, EWCs of 55.0+/-1.2% and 56.2+/-2.9%, porosities of 35+/-1% and 40+/-1% and compressive moduli of 191+/-7 and 182+/-4kPa.
- Published
- 2003
50. Novel intrathecal delivery system for treatment of spinal cord injury
- Author
-
Charles H. Tator, Eve C. Tsai, Maria C. Jimenez Hamann, and Molly S. Shoichet
- Subjects
Models, Neurological ,Subarachnoid Space ,Central nervous system disease ,Cerebrospinal fluid ,Implants, Experimental ,Developmental Neuroscience ,In vivo ,Absorbable Implants ,medicine ,Animals ,Spinal canal ,Spinal cord injury ,Injections, Spinal ,Spinal Cord Injuries ,Behavior, Animal ,business.industry ,Spinal cord ,medicine.disease ,Immunohistochemistry ,Rats ,medicine.anatomical_structure ,Spinal Cord ,Neurology ,Anesthesia ,Drug delivery ,Female ,Collagen ,Safety ,Subarachnoid space ,business ,Spinal Canal - Abstract
A novel, localized method for potential delivery of therapeutic agents to the injured spinal cord was investigated. The strategy consists of a polymeric drug solution that gels after injection into the subarachnoid space (SAS). By dispersing therapeutic agents in the polymeric solution, a method is provided for localized delivery to the spinal cord. To determine whether intrathecal injection of this drug delivery system (DDS) would affect cerebrospinal fluid (CSF) flow, a spinal canal model was built using dimensional analysis. Blocking up to 52% of the modeled subarachnoid space of the spinal canal caused minimal pressure differences (9.22 +/- 1.45 Pa), suggesting that implantation of a DDS would not subject the spinal cord to increased pressure. The safety of the DDS was also assessed in vivo by injecting collagen into the SAS of Sprague Dawley rats. Controls received injections of artificial CSF (aCSF). Collagen or aCSF was injected at the T2-T3 spinal level of both uninjured rats and rats injured with a 20g compression clip. The injected collagen persisted in the SAS for at least 8 weeks post-implantation and did not elicit an inflammatory reaction in either uninjured or injured animals. Long-term functional behavior was evaluated with the Basso, Beattie, and Bresnahan (BBB) scale weekly for 8 weeks. Functional behavior was similar in the collagen and aCSF groups, also indicating that the DDS was safe. This minimally invasive DDS may provide an alternative, safe method to deliver therapeutic agents intrathecally.
- Published
- 2003
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