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There is an enormous demand for bone graft biomaterials to treat developmental and acquired bony defects arising from infections, trauma, tumor, and other conditions. Polycaprolactone (PCL) has been extensively utilized for bone tissue engineering but limited cellular interaction and tissue integration are the primary concerns. PCL-based composites with different biomaterials have been attempted to improve the mechanical and biological response. Interestingly, a few studies have tried to blend PCL with aqueous silk fibroin solution, but the structures prepared with the blend were mechanically weak due to phase mismatch. As a result, silk microparticle-based PCL composites have been prepared, but the microfibers-reinforced composites could be superior to them due to significant fiber-matrix interaction. This study aims at developing a unique composite by incorporating 100-150 μm long (aspect ratio; 8:1-5:1) silk-fibroin microfibers into the PCL matrix for superior biological and mechanical properties. Two silk variants were used, that is, Bombyx mori and a wild variant, Antheraea mylitta, reported to have cell recognizable Arginine-Glycine-Aspartic acid (RGD) sequences. A. mylitta silk fibroin microfibers were produced, and composites were made with PCL for the first time. The morphological, tensile, thermal, biodegradation, and biological properties of the composites were evaluated. Importantly, we tried to optimize the silk concentration within the composite to strike a balance among the cellular response, biodegradation, and mechanical strength of the composites. The results indicate that the PCL-silk fibroin microfiber composite could be an efficient biomaterial for bone tissue engineering.

Biocompatibility, mechanical strength, and osteogenesis properties of three-dimensional scaffolds are critical for bone tissue engineering. In addition, reactive oxygen species accumulate around bone defects and limit the activities of surrounding cells and bone formation. Therefore, the presence of an antioxidant in a bone tissue scaffold is also essential to address this issue. This study aimed to evaluate a composite nanofibrous scaffold similar to the natural extracellular matrix with antioxidant and osteogenic properties. To this end, polylactic acid (PLA)/organophilic montmorillonite (OMMT)/resveratrol (RSV) nanofibers were fabricated using the electrospinning method and characterized. RSV was used as an antioxidant, which promotes osteogenic differentiation, and OMMT was used as a mineral phase to increase the mechanical strength and control the release of RSV. The scaffolds' antioxidant activity was measured using DPPH assay and found 83.75% for PLA/OMMT/RSV nanofibers. The mechanical strength was increased by adding OMMT to the neat PLA. The biocompatibility of the scaffolds was investigated using an MTT assay, and the results did not show any toxic effects on human adipose mesenchymal stem cells (hASCs). Moreover, the Live/Dead assay indicated the appropriate distribution of live cells after 5 days. Cell culture results displayed that hASCs could adhere and spread on the surface of composite nanofibers. Meanwhile, the level of alkaline phosphatase, osteocalcin, and osteopontin was increased for hASCs cultured on the PLA/OMMT/RSV nanofibrous scaffold. Therefore, this study concludes that the RSV-loaded composite nanofibers with antioxidant and osteogenesis properties and appropriate mechanical strength can be introduced for bone tissue regeneration applications.

In this study, the effect of coated hydrogel layer on characteristics of the whole gelatin/silver nanoparticles multi-coated polycaprolactone membrane (PCLGelAg) was investigated through systematic and typical wound dressing characterizations to select the optimal number of layers for practical applications. Scanning electron microscopy, free swell absorptive capacity and tensile test in both wet and dry conditions were conducted to characterize all fabricated membranes of six coating times. In vitro cytotoxicity and agar diffusion evaluation were also carried out to assess the biocompatibility and antibacterial activity of the membranes. The findings illustrated that as the coated layers increase, the absorptive capacity, and degradation rate were higher, the membranes were stiffer in dry state while the tensile strength in wet state, elongation, and cell viability were significantly decreased. PCLGelAg3 was chosen to be the best fit for wound healing since it maintained quite sufficient maximum buffer uptake, elasticity, cell viability along with inducing abnormalities in bacterial morphology and preventing biofilm formation.

Long-term in vivo observation in large animal model is critical for evaluating the potential of small diameter tissue engineering vascular graft (SDTEVG) in clinical application, but is rarely reported. In this study, a SDTEVG is fabricated by the electrospinning of poly(ε-caprolactone) and subsequent heparin modification. SDTEVG is implanted into canine's abdominal aorta for 511 days in order to investigate its clinical feasibility. An active and robust remodeling process was characterized by a confluent endothelium, macrophage infiltrate, extracellular matrix deposition and remodeling on the explanted graft. The immunohistochemical and immunofluorescence analysis further exhibit the regeneration of endothelium and smooth muscle layer on tunica intima and tunica media, respectively. Thus, long-term follow-up reveals viable neovessel formation beyond graft degradation. Furthermore, the von Kossa staining exhibits no occurrence of calcification. However, although no TEVG failure or rupture happens during the follow-up, the aneurysm is found by both Doppler ultrasonic and gross observation. Consequently, as-prepared TEVG shows promising potential in vascular tissue engineering if it can be appropriately strengthened to prevent the occurrence of aneurysm.

A main problem in the design of blood-contacting biomaterials has been the deficiency of a systematic understanding of blood-biomaterial interactions and the strategy to modulate blood responses. In this work, different functional groups including carboxyl (COOH), hydroxyl (OH) and zwitterionic sulfobetaine group (⊕N((CH3 )2 )(CH2 )3 SO3-○- , SMDB) were grafted on the poly (butylene terephthalate) (PBT) film to study how the functional groups modulate blood responses and in terms of interaction with the coagulation system, the complement system, and platelets. The results showed protein absorption and platelet adhesion was stronger on the PBT bearing COOH group than PBT films bearing OH and zwitterionic sulfobetaine groups (total protein (μg/cm2 ): 32.92 ± 5.89 vs. 22.02 ± 1.44 vs. 19.09 ± 1.59; platelet adhesion (/mm2 ): 1,626.7 ± 120.1 vs. 1,395.6 ± 363.3 vs. 1,102.2 ± 373.7), which had a rougher and negatively charged surface, and the coagulation system was inhibited by binding fibrinogen (Fg) and coagulation factors. Meanwhile, PBT-PSMDB showed anticoagulant property and induced platelet activation. As a result, complement formation on these two films were less than PBT bearing OH groups by inhibiting the coagulation system (C3a (ng/ml): 3,745.4 ± 143.9 vs. 3,290.9 ± 249.7 vs. 4,887.9 ± 88.9; C5a (ng/ml): 22.1 ± 2.6 vs. 22.3 ± 1.8 vs. 27.9 ± 2.0). On the other hand, PBT bearing OH groups did not facilitate remarkable platelet adhesion and activation, and had no influence on platelet aggregation, hypotonic shock response, and coagulation system. The above results showed that the blood responses were highly interlinked, and could be modulated by grafting with different functional groups on the biomaterial surfaces. These findings may help identify a strategy to design materials with better hemocompatibility for blood contact, filtration, and purification applications.

Fabrication of scaffolds using polymers and then cell seeding is a routine protocol of tissue engineering applications. Synthetic polymers have adequate mechanical properties to substitute for some bone tissue, but they are generally hydrophobic and have no specific cell recognition sites, which leads to poor cell affinity and adhesion. Some natural polymers, have high cell affinity but are mechanically weak and do not have the strength required as a bone supporting material. In the present study, 3D printed hybrid scaffolds were fabricated using PCL and GelMA carrying dental pulp stem cells (DPSCs), which is printed in the gaps between the PCL struts. This cell loaded GelMA was shown to support osteoinductivity, while the PCL provided mechanical strength needed to mimic the bone tissue. 3D printed PCL/GelMA and GelMA scaffolds were highly stable during 21 days of incubation in PBS. The compressive moduli of the hybrid scaffolds were in the range of the compressive moduli of trabecular bone. DPSCs were homogeneously distributed throughout the entire hydrogel component and exhibited high cell viability in both scaffolds during 21 days of incubation. Upon osteogenic differentiation DPSCs expressed two key matrix proteins, osteopontin and osteocalcin. Alizarin red staining showed mineralized nodules, which demonstrates osteogenic differentiation of DPSCs within GelMA. This construct yielded a very high cell viability, osteogenic differentiation and mineralization comparable to cell culture without compromising mechanical strength suitable for bone tissue engineering applications. Thus, 3D printed, cell loaded PCL/GelMA hybrid scaffolds have a great potential for use in bone tissue engineering applications.

Engineering osteoinductive, self-fitting scaffolds offers a potential treatment modality to repair irregularly shaped craniomaxillofacial bone defects. Recently, we innovated on osteoinductive poly(ε-caprolactone)-diacrylate (PCL-DA) shape memory polymers (SMPs) to incorporate poly-L-lactic acid (PLLA) into the PCL-DA network, forming a semi-interpenetrating network (semi-IPN). Scaffolds formed from these PCL-DA/PLLA semi-IPNs display stiffnesses within the range of trabecular bone and accelerated degradation relative to scaffolds formed from slowly degrading PCL-DA SMPs. Herein, we demonstrate for the first time that PCL-DA/PLLA semi-IPN SMP scaffolds show increased intrinsic osteoinductivity relative to PCL-DA. We also confirm that application of a bioinspired polydopamine (PD) coating further improves the osteoinductive capacity of these PCL-DA/PLLA semi-IPN SMPs. In the absence of osteogenic supplements, protein level assessment of human mesenchymal stem cells (h-MSCs) cultured in PCL-DA/PLLA scaffolds revealed an increase in expression of osteogenic markers osterix, bone morphogenetic protein-4 (BMP-4), and collagen 1 alpha 1 (COL1A1), relative to PCL-DA scaffolds and osteogenic medium controls. Likewise, the expression of runt-related transcription factor 2 (RUNX2) and BMP-4 was elevated in the presence of PD-coating. In contrast, the chondrogenic and adipogenic responses associated with the scaffolds matched or were reduced relative to osteogenic medium controls, indicating that the scaffolds display intrinsic osteoinductivity.

Whereas synthetic biodegradable polymers have been successfully applied for the delivery of biologics in other tissues, the anatomical complexity, poor blood supply, and reduced clearance of degradation byproducts in the rotator cuff create unique design challenges for implantable biomaterials. Here, we investigated lower molecular weight poly-lactic acid co-epsilon-caprolactone (PLA-CL) formulations with varying molecular weight and film casting concentrations as potential matrices for the therapeutic delivery of biologics in the rotator cuff. Matrices were fabricated with target footprint dimensions to facilitate controlled and protected release of model biologic (Bovine Serum Albumin), and anatomically-unhindered implantation under the acromion in a rodent model of acute rotator cuff repair. The matrix obtained from the highest polymeric-film casting concentration showed a controlled release of model biologics payload. The tested matrices rapidly degraded during the initial 4 weeks due to preferential hydrolysis of the lactide-rich regions within the polymer, and subsequently maintained a stable molecular weight due to the emergence of highly-crystalline caprolactone-rich regions. pH evaluation in the interior of the matrix showed minimal change signifying lesser accumulation of acidic degradation byproducts than seen in other bulk-degrading polymers, and maintenance of conformational stability of the model biologic payload. The context-dependent biocompatibility evaluation in a rodent model of acute rotator cuff repair showed matrix remodeling without eliciting excessive inflammatory reaction and is anticipated to completely degrade within 6 months. The engineered PLA-CL matrices offer unique advantages in controlled and protected biologic delivery, non-toxic biodegradation, and biocompatibility overcoming several limitations of commonly-used biodegradable polyesters.

Congenital heart defects (CHDs) are the leading cause of death in live-born infants. Currently, patches used in the repair of CHDs are exclusively inert and non-degradable, which increases the risk of arrhythmia, follow-up surgeries, and sudden cardiac death. In this preliminary study, we sought to fabricate biodegradable scaffolds that can support cardiac regeneration in the repair of CHDs. We electrospun biodegradable scaffolds using various blends of polyurethane (PU) and polycaprolactone (PCL) with and without sacrificial poly(ethylene oxide) (PEO) particles and assessed the mechanical properties, cell infiltration levels, and inflammatory response in vitro (surface cell seeding) and in vivo (subcutaneous mouse implant). We hypothesized that a blend of the two polymers would preserve the low stiffness of PU as well as the high cell infiltration observed in PCL scaffolds. The inclusion of PU in the blends, even as low as 10%, decreased cell infiltration both in vitro and in vivo. The inclusion of sacrificial PEO increased pore sizes, reduced Young’s moduli, and reduced the inflammatory response in all scaffold types. Collectively, we have concluded that a PCL patch electrospun with sacrificial PEO particles is the most promising scaffold for further assessment as in our heart defect model.

In this study, a light cross-linkable biocomposite scaffold based on a photo-cross-linkable poly (propylene fumarate) (PPF)-co-polycaprolactone (PCL) tri-block copolymer was synthesized and characterized. The developed biodegradable scaffold was further modified with β-tricalcium phosphate (β-TCP) bioceramic for bone tissue engineering applications. The developed biocomposite was characterized using H nuclear magnetic resonance and Fourier transform infrared spectroscopy. Moreover, the bioceramic particle size distribution and morphology were evaluated using Brunauer-Emmett-Teller method, X-ray diffraction, and scanning electron microscopy. The mechanical properties and biodegradation of the scaffolds were also evaluated. Cytotoxicity and mineralization assays were performed to analyze the biocompatibility and bioactivity capacity of the developed biocomposite. The characterization data confirmed the development of a biodegradable and photo-cross-linkable PCL-based biocomposite reinforced with β-TCP bioceramic. In vitro analyses demonstrated the biocompatibility and mineralization potential of the synthesized bioceramic. Altogether, the results of the present study suggest that the photo-cross-linkable PCL-PPF-PCL tri-block copolymer reinforced with β-TCP is a promising biocomposite for bone tissue engineering applications. According to the results, this newly synthesized material has a proper chemical composition for further clinically-relevant studies in tissue engineering.

One of the main challenges in treating osteochondral lesions via tissue engineering approach is providing scaffolds with unique characteristics to mimic the complexity. It has led to application of heterogeneous scaffolds as a potential candidate for engineering of osteochondral tissues, in which graded multilayered-structure should promote bone and cartilage growth. By designing three-dimensional (3D)-nanofibrous scaffolds mimicking the native extracellular matrix's nanoscale structure, cells can grow in controlled conditions and regenerate the damaged tissue. In this study, novel 3D-functionality graded nanofibrous scaffolds composed of five layers based on different compositions containing polycaprolactone(PCL)/gelatin(Gel)/nanohydroxyapatite (nHA) for osteoregeneration and chitosan(Cs)/polyvinylalcohol(PVA) for chondral regeneration are introduced. This scaffold is fabricated by electrospinning technique using spring as collector to create 3D-nanofibrous scaffolds. Fourier-transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, mechanical compression test, porosimetry, and water uptake studies were applied to study each layer's physicochemical properties and whole functionally graded scaffold. Besides, biodegradation and biological studies were done to investigate biological performance of scaffold. Results showed that each layer has a fibrous structure with continuous nanofibers with improved pore size and porosity of novel 3D scaffold (6-13 μm and 90%) compared with two-dimensional (2D) mat (2.2 μm and 19.3%) with higher water uptake capacity (about 100 times of 2D mat). Compression modulus of electrospun scaffold was increased to 78 MPa by adding nHA. The biological studies revealed that the layer designed for osteoregeneration could improve cell proliferation rate in comparison to the layer designed for chondral regeneration. These results showed such structure possesses a promising potential for the treatment of osteochondral defects.

Recombinant human bone morphogenetic protein 2 (rhBMP‐2) has been widely used in bone tissue engineering to enhance bone regeneration because of its osteogenic inductivity. However, clinical outcomes can vary depending on the scaffold materials used to deliver rhBMP‐2. In this study, 3D‐printed scaffolds with a ratio of 1:1 polycaprolactone and beta‐tricalcium phosphate (PCL/T50) were applied as carriers for rhBMP‐2 in mandibular bone defect models in dog models. Before in vivo application, in vitro experiments were conducted. Preosteoblast proliferation was not significantly different between scaffolds made of PCL/T50 and polycaprolactone alone (PCL/T0) regardless of rhBMP‐2 delivery. However, PCL/T50 showed an increased level of the alkaline phosphatase activity and mineralization assay when rhBMP‐2 was delivered. In in vivo, the newly formed bone volume of the PCL/T50 group was significantly increased compared with that of the PCL/T0 scaffolds regardless of rhBMP‐2 delivery. Histological examination showed that PCL/T50 with rhBMP‐2 produced significantly greater amounts of newly bone formation than PCL/T0 with rhBMP‐2. The quantities of scaffold remaining were lower in the PCL/T50 group than in the PCL/T0 group, although it was not significantly different. In conclusion, PCL/T50 scaffolds were advantageous for rhBMP‐2 delivery as well as for maintaining space for bone formation in mandibular bone defects.

Reactive oxygen species (ROS) play an important role in cellular metabolism and many oxidative stress related diseases. Oxidative stress results from toxic effects of ROS and plays a critical role in the pathogenesis of a variety of diseases like cancers and many important biological processes. It is known that the unique feature of high intracellular ROS level in cancer cells can be considered as target and utilized as a useful cancer-related stimulus to mediate intracellular drug delivery. Therefore, biomaterials responsive to excess level of ROS are of great importance in biomedical applications. In this study, a novel ROS-responsive polymer based on L-methionine poly(ester amide) (Met-PEA-PEG) was designed, synthesized, characterized and self-assembled into nano-micellar-type nanoparticles (NP). The Met-PEA-PEG NP exhibited responsiveness to an oxidative environment. The size and morphology of the nanoparticle changed rapidly in the presence of H2 O2 . The Nile Red dye was loaded into the Met-PEA-PEG NP to demonstrate a H2 O2 concentration induced time-dependent release behavior. The Met-PEA-PEG NP was sensitive to high intracellular ROS level of PC3 prostate cancer cells. Furthermore, the Met-PEA-PEG NP was investigated as a carrier of a Chinese medicine-based anticancer component, gambogic acid (GA). Compared to free GA, the GA-loaded nanocomplex (GA-NP) showed enhanced cytotoxicity toward PC3 and HeLa cells. The GA-NP also induced a higher level of apoptosis and mitochondrial depolarization in PC3 cells than free GA. The Met-PEA-PEG NP improved the therapeutic effect of GA and may serve as a potential carrier for anticancer drug delivery.

Replacement of peripheral nerve autografts with tissue engineered nerve grafts will potentially resolve the lack of nerve tissue especially in patients with severe concomitant soft tissue injuries. This study attempted to fabricate a tissue engineered nerve graft composed of electrospun PCL conduit filled with collagen-hyaluronic acid (COL-HA) sponge with different COL-HA weight ratios including 100:0, 98:2, 95:5 and 90:10. The effect of HA addition on the sponge porosity, mechanical properties, water absorption and degradation rate was assessed. A good cohesion between the electrospun PCL nanofibers and COL-HA sponges were seen in all sponges with different HA contents. Mechanical properties of PCL nanofibrous layer were similar to the rat sciatic nerve; the ultimate tensile strength was 2.23 ± 0.35 MPa at the elongation of 35%. Additionally, Schwann cell proliferation and morphology on three dimensional (3D) composite scaffold were evaluated by using MTT and SEM assays, respectively. Rising the HA content resulted in higher water absorption as well as greater pore size and porosity, while a decrease in Schwann cell proliferation compared to pure collagen sponge, although reduction in cell proliferation was not statistically significant. The lower Schwann cell proliferation on the COL-HA was attributed to the greater degradation rate and pore size of the COL-HA sponges. Also, dorsal root ganglion assay showed that the engineered 3D construct significantly increases axon growth. Taken together, these results suggest that the fabricated 3D composite scaffold provide a permissive environment for Schwann cells proliferation and maturation and can encourage axon growth.

Inconsistencies in graft osteoconduction and osteoinduction present a clinical challenge in regeneration of large bone defects. Deposition of decellularized extracellular matrix (dECM) on tissue engineered scaffolds offers an alternative approach that can enhance these properties by mimicking bone's molecular complexity and direct infiltrating cells to repair damaged bone. However, dECMs derived from homogenous cell populations do not adequately simulate the heterogeneous and vascularized microenvironment of the bone. In this study, successive culture and decellularization of fibroblasts and endothelial cells (ECs) grown on polycaprolactone microfibers was used to develop a bioactive scaffold with heterogeneous dECM mimicking endothelial basement membrane. These scaffolds had greater amount of protein and minimally increased nucleic acid content than scaffolds with homogenous culture dECM. Coomassie Blue and antibody staining revealed extensive tube formation by ECs on fibroblast dECM. Fibroblast/endothelial dECM significantly enhanced osteoblast attachment, alkaline phosphatase activity, and osteocalcin- and osteopontin-positive extracellular mineral deposits. We demonstrated that the osteoconduction of dECMs can be tailored with the appropriate combination of cells to accelerate osteoblast mineral secretion. The overall concept can be expanded to generate increasingly more complex tissue constructs for regeneration of bone defects and other vascularized tissues.

Alveolar bone loss is always a big challenge for oral implant placement. Guided bone regeneration (GBR) is one of the solutions to fix this problem. Among all the factors, the barrier membrane plays a key role in this technology. At present, lack of the osteoinductivity remains the biggest weakness for clinical application. Focusing on this, we tried to fabricate an osteoinductive three-dimensional (3D) nanofiber membrane with drug releasing system by introducing parathyroid hormone (PTH)-Fc into the poly(lactic acid-co-caprolactone) PLCL/SF solution for electrospinning. The characteristics were determined by scanning electron microscopy, X-ray diffraction, contact angle measurement, and mechanical strength. According to the optimum parameters tested, we proceed to the in vitro experiments. Drug release and matrix degradation profiles of electrospinning fibers were investigated. Cell morphology was observed and cell proliferation was analyzed after bone marrow mesenchymal stem cells (BMMSCs) were seeded. The results showed favorable physical and chemical properties and good biocompatibility of these 3D nanofibers. The effect on the BMMSCs suggested the drug releasing promoted osteogenic differentiation of cells stably. This study exhibited a promising method of GBR oeteoinductive membrane fabrication. The bone reconstruction will be benefited from the osteogenic differentiation positive drug releasing system.

International audience; Layer-by-layer (LBL) BioAssembly method was developed to enhance the control of cell distribution within 3D scaffolds for tissue engineering applications. The objective of this study was to evaluate in vivo the development of blood vessels within LBL bioassembled membranes seeded with human primary cells, and to compare it to cellularized massive scaffolds. Poly(lactic) acid (PLA) membranes fabricated by fused deposition modeling were seeded with monocultures of human bone marrow stromal cells or with cocultures of these cells and endothelial progenitor cells. Then, four cellularized membranes were assembled in LBL constructs. Early osteoblastic and endothelial cell differentiation markers, alkaline phosphatase, and von Willebrand's factor, were expressed in all layers of assemblies in homogenous manner. The same kind of LBL assemblies as well as cellularized massive scaffolds was implanted subcutaneously in mice. Human cells were observed in all scaffolds seeded with cells, but not in the inner parts of massive scaffolds. There were significantly more blood vessels observed in LBL bioassemblies seeded with cocultures compared to all other samples. LBL bioassembly of PLA membranes seeded with a coculture of human cells is an efficient method to obtain homogenous cell distribution and blood vessel formation within the entire volume of a 3D composite scaffold.

Long-chain branched poly (lactic acid) (LCB-PLA) with antimicrobial functional group was fabricated through a two-step ring-opening reactive processing for improving antimicrobial properties and broadening the PLA processing window. A combination of linear viscoelasticity and the branch-on-branch (BOB) model predicted probable compositions and chain topologies of the products. It is also explored the antimicrobial properties of LCB-PLA to provide a theoretical basis for broadening the possible applications.

It is already known that cells respond strongly to topography and chemistry of 2D surfaces. In this work we study cell-material interactions; in particular, we investigated the attachment and alignment of SH-SY5Y cells of neuronal origin on grooved-patterns made from Silicon (Si) and Gold (Au). The Au-Si groove-pattern stimulated 93% of SH-SY5Y cells to differentiate into neuroblast-like type (N-type) in 2 days and outgrown neurites exhibited strong anisotropy along the grooves with 90% of cells having one or two neurites. In comparison, random distribution of morphology type, neurite number, and alignment were observed on control flat surfaces (Si and Au). We further show that designed Au-Si groove-patterns can be used to form reversed groove patterns on polycarolactone surface via soft lithography approach. Sixty-nine percentage of SH-SY5Y cells aligned along the obtained reversed groove patterns of the same dimensional characteristics to Si-Au grooves. In particular, this work demonstrated that the Au-Si grooves pattern stimulates neurite polarity, elongation, and morphological differentiation of neuroblastoma cells without any exogenous supply of growth factors or stimulants in just 2 days, which can lead to selective procedure of obtaining homologous population of neuron-like cells for future nerve regeneration therapies.

One of the central challenges in the field of vaccine delivery is to develop a delivery method that maintains antigen stability while also enabling control over the system's release kinetics. Addressing these challenges would not only allow for expanded access to vaccines worldwide but would also help significantly reduce mortality rates in developing countries. In this article, we report the development of single-injection vaccine depots for achieving novel delayed burst release. Synthesized poly(ε-caprolactone) and poly(ε-caprolactone) triacrylate were used to form stationary bubbles within an aqueous solution of 10% carboxymethylcellulose. These polymeric bubbles (referred to as "polybubbles") can then be injected with an aqueous solution of cargo, resulting in the formation of a polymeric shell. The puncture resulting from cargo injection self-heals prior to ultraviolet (UV) curing. UV curing and lyophilization were shown to enhance the stability of the polybubbles. BSA- CF 488 and HIV1 gp120/41 were used as the antigen in the study as a proof-of-concept. Further endeavors to automate the production of polybubbles are underway.

Scaffolds composed of synthetic polymers such as poly(caprolactone) (PCL) are widely used for the support and repair of tissues in biomedicine. Pores are common features in scaffolds as they facilitate cell penetration. Various surface modifications can be performed to promote key biological responses to these scaffolds. However, verifying the chemistry of these materials post surface modification is problematic due to the combination of three-dimensional (3D) topography and surface sensitivity. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is commonly used to correlate surface chemistry with cell response. In this study, 3D imaging mass spectrometry analysis of surface modified synthetic polymer scaffolds is demonstrated using PCL porous scaffold, a pore filling polymer sample preparation, and 3D imaging ToF-SIMS. We apply a simple sample preparation procedure, filling the scaffold pores with a poly(vinyl alcohol)/glycerol mixture to remove topographic influence on image quality. This filling method allows the scaffold (PCL) and filler secondary ions to be reconstructed into a 3D chemical image of the pore. Furthermore, we show that surface modifications in the pores of synthetic polymer scaffolds can be mapped in 3D. Imaging of "dry" and "wet" surface modifications is demonstrated as well as a comparison of surface modifications with relatively strong ToF-SIMS peaks (fluorocarbon films [FC]) and to more biologically relevant surface modification of a protein (bovine serum albumin [BSA]). We demonstrate that surface modifications can be imaged in 3D showing that characteristic secondary ions associated with FC and BSA are associated with C3 F8 plasma treatment and BSA, respectively within the pore.

Hydrogels for biomedical applications were limited toward bone tissue engineering due to the poor mechanical performance. Tough hydrogels with strong and elastic features have received extensive attention, the application of which, however, was limited by their degradation. The present study introduced an approach to enhance mechanical properties of hydrogel while ensuring its degradation. Carboxyl dextran (Dex) was grafting modified by poly (e-caprolactone) (PCL), sequentially followed by being cross-linked through polyethyleneglycol 400 (PEG400) to yield a gel with covalent cross-linking units in DMSO. The gel was underwent solvent displacement in H2 O to induce hydrophobic association of PCL to form non-covalent cross-linking units. The tough Dex-g-PCL hydrogel showed maximum strain of Dex-g-PCL hydrogel was 90% ± 6%, with the corresponding stress of 2.7 ± 0.2 MPa, which was significantly enhanced when comparing to dextran hydrogel (maximum strain 65% ± 5%, with the corresponding stress of 0.225 ± 0.06 MPa). Most hydrogel degraded after 12 w in vivo with only a little residues. Adipose-derived stem cells (ASCs) proliferated well after being seeded in hydrogel to form micro-mass at 14 days post-seeding. In vitro and in vivo angiogenesis, as well as in vitro osteogenesis illustrated the potential of the Dex-g-PCL hydrogel carrying ASCs toward vascularized bone tissue engineering. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1120-1131, 2019.

PCL (poly-caprolactone) nanofibers have good biocompatibility and high porosity, which are usually utilized for application in wound dressings. However, wound healing could be hindered by the overproduction of reactive oxygen species (ROS) and different factors. Pure nanofibers cannot satisfy these requirements of wound healing. N-acetylcysteine (NAC), as an antioxidant, meets the requirements for wound healing by resisting the overproduction of ROS and by promoting angiogenesis and maturation of the epidermis. In this study, we prepared a sandwich structured PCL-Col/NAC scaffold using the molding method, which consisted of PCL nanofibers at the core and NAC-loaded collagen on both sides. The hydroscopicity and tensile modulus of PCL-Col/NAC scaffolds showed best performance of these properties among groups. Meanwhile, the drug release profiles of PCL-Col/NAC scaffolds were investigated using the HPLC method and the results suggested a sustained drug release of NAC for PCL-Col/NAC scaffolds. In addition, PCL-Col/NAC scaffolds presented better properties than the control groups in cell migration and proliferation. The in vivo wound healing therapy effect was studied using an oval (2 × 1 cm) full-thickness skin defect wound model for SD rats. After 21 days, gross view and histological analysis showed a favorable beneficial therapeutic effect as well as better epidermal maturation compared with the control groups. CD31 immunohistology results revealed relatively more new vessels in the PCL-Col/NAC group than the control groups. This study developed novel PCL-Col/NAC scaffolds with an excellent hydroscopicity, tensile modulus and the ability to promote epidermal maturation and angiogenesis, demonstrating its promising potential in wound healing treatment. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

In this study, submicron, monodispersed, spherical bioactive glass (BG) particles with a mean diameter of 720 ± 80 nm were produced through sol-gel process. The prepared BG particles were successfully incorporated into 70/30 (W/W) ratio of polycaprolactone/gelatin (PCL/GT) nanofibrous mats (250 ± 60 nm) through electrospinning to obtain a unique architectural structure for the first time. To enhance biodegradation and stability of the scaffolds, crosslinking using gluteraldehyde was applied. The structure, wettability, hydroxyapatite (HA) formation, cell adhesion, cell viability and osteogenic potential of the fibrous mats were evaluated. A continuous, uniform and hydrophilic structure of PCL/GT/BG was obtained. The fibers were found to be bioactive as they formed HA on their surface after immersion in simulated body fluid. The unique structure significantly reduced HA formation time to 5 days. For in vitro investigations, human dental pulp stem cells (hDPSCs) were cultured on PCL/GT and PCL/GT/BG fibrous mats. Results demonstrated good cell attachment after 4 and 24 h with no significant levels of cytotoxicity during 10 days of culture. Alizarin red staining was applied to quantitatively analyze the potential of PCL/GT/BG in osteogenic differentiation of hDPSCs. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2019.

Advancements in tissue engineering and biomaterial development have the potential to provide a scalable solution to the problem of large-volume skeletal muscle defects. Previous research on the development of scaffolds for skeletal muscle regeneration has focused on strategies for increasing conductivity, which has improved satellite cell attachment and differentiation. However, these strategies usually increase scaffold stiffness, which some studies suggest may be detrimental to myoblast development. In this study, the polymers polypyrrole (PPy) and polycaprolactone (PCL) were synthesized together into a copolymer (PPy-PCL) designed to increase scaffold conductivity without significantly influencing stiffness. Different scaffold groups were fabricated via electrospinning, characterized, and assessed for their suitability for myoblast proliferation and differentiation. The groups included an aligned and random iteration of pure PCL, 10% PPy-PCL, 20% PPy-PCL, and 40% PPy-PCL. Only the 40% PPy-PCL group had a measureable conductivity, and the addition of PPy-PCL had no significant effect on the stiffness of the scaffolds. The PPy-PCL copolymer significantly increased the attachment of C2C12 myoblasts as compared to pure PCL scaffolds, but the concentration of PPy-PCL did not significantly alter cell attachment. In addition, scaffolds with PPy-PCL promoted myoblast differentiation to a greater extent than scaffolds made of PCL as measured by fusion index and number of nuclei per myotube. Aligned scaffolds were superior to random scaffolds in almost all measures. These results suggest that conductivity may not be the key factor in improving skeletal muscle scaffolds. Instead, cell attachment and aligned guidance cues may have a greater impact on myoblast differentiation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 220-231, 2019.

To enhance anticancer efficacy and decrease side effects, the synergistic multi-agent therapy has now increasingly gotten great attention. Herein, the flexible polycaprolactone had been modified by histidine and formed assembles with PEGylated metallo-porphyrin via metal-coordinated supramolecular interaction. This supramolecular assembles showed excellent acid sensitivity. At neutral environment, the hydrophobic anticancer drug could be effectively co-encapsulated with photosensitizer Fe-TPP to improve the water solubility. While at the intracellular microenvironment, the changed acid environment would trigger the drug and Fe-TPP release due to the reduction of metal-coordinated interaction between histidine and metallo-porphyrin leading to the disintegration of assembles. The in vivo anticancer experiments toward HeLa and MCF-7 cells disclosed that this co-delivery system of anticancer drug and photosensitizer showed enhanced anticancer efficacy, implying that the synergistic chemo-photodynamic therapy could improve cellular proliferation inhibition. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2955-2962, 2018.

Bacterial infection of implanted biomaterials is a serious problem that increases health care costs and negatively affects a considerable fraction of orthopedic procedures. In this field, magnesium oxide nanoparticles (MgO NPs) have emerged as a promising material to combat bacterial infection while maintaining or improving bone cell functions. Here, MgO NPs were electrophoretically deposited onto poly-L-lactic acid (PLLA) sheets to achieve a coating of highly exposed MgO NPs that directly influenced cell-substrate interactions at short time scales. Samples were characterized for their surface chemistry, crystal structure, roughness, wettability, degradation characteristics, and their ability to support the growth of human fibroblasts and osteoblasts, as well as their resistance to colonization by Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. In general, increasing the applied voltage during deposition increased the surface coverage of the coating and significantly decreased the colonization of all three bacterial strains (up to a 90% reduction). Furthermore, S. aureus cells that did attach onto substrates prepared at high voltages exhibited trademark signs of membrane damage and cell death. Importantly, MTS cell viability assays indicated that osteoblast adhesion increased with increasing deposition voltage, while fibroblast adhesion exhibited the opposite trend. Thus, although requiring more studies, this research provides the first evidence that MgO NP coatings prepared at relatively high voltages (120-150 V) may have the ability to resist bacterial colonization, promote bone cell attachment, and curb fibrous capsule formation. Therefore, it is recommended that this technology be further investigated and developed for numerous orthopedic applications. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3136-3147, 2017.

The presence of inorganic bioactive minerals with polymers can accelerate and promote several processes including: bone cell joining, proliferation, differentiation, and expression of osteogenic proteins. In this study, zinc (Zn), copper (Cu), and imidazole metal-organic framework (MOF) nanoparticles were synthesized and coated over poly-l-lactic acid (PLLA) nanofibrous scaffolds for bone tissue engineering application. The surface and bioactive features of the scaffolds were characterized. The osteogenic potential of the scaffolds on human adipose tissue-derived mesenchymal stem cells (MSCs) was evaluated. Zn-Cu imidazole MOF coated PLLA scaffolds (PLLA@MOF) showed a comparable rate of MSC proliferation with the pure PLLA scaffolds and tissue culture plate (TCP). However, the PLLA@MOF potential of osteogenic differentiation was significantly greater than either pristine PLLA scaffolds or TCP. Hence, coating Zn-Cu imidazole MOF has a significant effect on the osteogenesis of MSC. Therefore, PLLA@MOF is novel scaffolds with bioactive components which are crucial for osteoconductivity and also able to provoke the osteogenesis and angiogenesis.

Effects of varied bioactive fillers on the biological behavior of porous polymer/inorganic composite scaffolds are lack of comprehensive comparison and remain elusive. Moreover, composite scaffolds with high porosity suffer from inferior mechanical performance. Herein, high-pressure molding and salt leaching were employed to prepare poly(ε-caprolactone) (PCL) composite porous scaffolds loaded with hydroxyapatite (HA) and bioactive glass (BG), respectively. Structural analysis indicated all the porous scaffolds presented interconnected open-pore structure with the porosity of ~87% and pore size of ~180 μm, hinging on the amounts and size of porogen. Compared to PCL/HA scaffolds, PCL/BG scaffolds showed ~2.3-fold augment in the water absorption. Attributing to the compact framework, the PCL/HA and PCL/BG porous scaffolds exhibited outstanding compressive modulus, which was notably higher than other PCL composite porous scaffolds reported in literatures. Cells culture results demonstrated that PCL/BG scaffolds displayed higher expression of osteogenic differentiation than PCL and PCL/HA scaffolds. Furthermore, in vivo results showed that more mature bone was formed within PCL/BG scaffolds than PCL/HA scaffolds, manifesting that the introduction of BG accelerated cranial bone regeneration to obtain complete bone healing within a short time. Therefore, these data indicate that PCL/BG scaffolds are more competitive for bone tissue engineering application. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 654-662, 2019.

Research on the neuromuscular junction (NMJ) and its function and development spans over a century. However, researchers are limited in their ability to conduct experimentation on this highly specialized synapse between motor neurons and muscle fibers, as NMJs are not easily accessible outside the body. The aim of this work is to provide a reliable and reproducible muscle sheet model for in vitro NMJ study. A novel culture system was designed by engineering a method for the directional growth of myofiber sheets, using muscle progenitor cells cultured on electrospun fiber networks. Myoblastic C2C12 cells cultured on suspended aligned fibers were found to maintain directionality, with alignment angle standard deviations approximately two-thirds lower on fibers than on regular culture surfaces. Morphological studies found nuclei and cytoskeleton aspect ratios to be elongated by 20 and 150%, respectively. Furthermore, neurons were shown to form innervation patterns parallel to suspended fibers when co-cultured on developed muscle sheets, with alignment angle standard deviations three times lower compared with those on typical surfaces. The effect of agrin on samples was quantified through the slow release of agrin medium, encapsulated in alginate pellets and imbedded within culture chambers. Samples exposed to agrin showed significantly increased percentage of AChR-covered area. The developed model has potential to serve as the basis for synaptogenesis and NMJ studies, providing a novel approach to bio-artificial muscle alignment and setting the groundwork for further investigations in innervation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1165-1176, 2018.

Differentiation of mesenchymal stem cells (MSCs) into neuron cells has great potential in therapy of damaged nerve tissue. It has been shown that three-dimensional biomaterials have great ability to up regulate the expression of neuronal proteins. In this study, O-2 plasma technology was used to enhance hydrophilicity of poly (epsilon-caprolactone) (PCL) toward selective differentiation of MSCs into neural cells. Random and aligned PCL nanofibers scaffolds were fabricated by electrospinning method and their physicochemical and mechanical properties were carried out by scanning electron microscope (SEM), contact angle, and tensile measurements. Contact angle studies of PCL and plasma treated PCL (p-PCL) nanofibers revealed significant change on the surface properties PCL nanofibers from the view point of hydrophilicity. Physiochemical studies revealed that p-PCL nanofibers were extremely hydrophilic compared with untreated PCL nanofibers which were highly hydrophobic and nonabsorbent to water. Differentiation of MSCs were carried out by inducing growth factors including basic fibroblast growth factor, nerve growth factor, and brain derived growth factor, NT3, 3-isobutyl-1-methylxanthine (IBMX) in Dulbecco's modified Eagle's medium/F12 media. Differentiated MSCs on nanofibrous scaffold were examined by immunofluorescence assay and was found to express the neuronal proteins; -tubulin III and Map2, on day 15 after cell culture. The real-time polymerase chain reaction (RT-PCR) analysis showed that p-PCL nanofibrous scaffold could upregulate expression of Map-2 and downregulate expression of Nestin genes in nerve cells differentiated from MSCs. This study indicates that mesenchymal stem cell cultured on nanofibrous scaffold have potential differentiation to neuronal cells on and could apply in nerve tissue repair. (c) 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 1875-1881, 2015.

The success of tissue engineered vascular grafts depends greatly on the synthetic tubular scaffold, which can mimic the architecture, mechanical, and anticoagulation properties of native blood vessels. In this study, small-diameter tubular scaffolds were fabricated with different weight ratios of poly(l-lactic acid) (PLLA) and poly(l-lactide-co-ɛ-caprolactone) (PLCL) by means of thermally induced phase separation technique. To improve the anticoagulation property of materials, heparin was covalently linked to the tubular scaffolds by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide coupling chemistry. The as-prepared PLLA/PLCL scaffolds retained microporous nanofibrous structure as observed in the neat PLLA scaffolds, and their structural and mechanical properties can be fine-tuned by changing the ratio of two components. The scaffold containing 60% PLCL content was found to be the most promising scaffold for engineering small-diameter blood vessel in terms of elastic properties and structural integrity. The heparinized scaffolds showed higher hydrophilicity, lower protein adsorption ability, and better in vitro anticoagulation property than their untreated counterparts. Pig iliac endothelial cells seeded on the heparinized scaffold showed good cellular attachment, spreading, proliferation, and phenotypic maintenance. Furthermore, the heparinized scaffolds exhibited neovascularization after subcutaneous implantation into the New Zealand white rabbits for 1 and 2 months. Taken together, the heparinized PLLA/PLCL nanofibrous scaffolds have the great potential for vascular tissue engineering application.

Adipose tissue is an easily accessible source of stem cells for use in tissue regenerative medicine. In the literature, different methods have been used to stimulate acquisition of neuronal characteristics by adipose-derived stem cells (ADSC). Herein we study the growth and neuronal differentiation potential of ADSC seeded onto a porous polycaprolactone (PCL) scaffold. The objective of this study is to demonstrate that PCL can be used as a scaffold to support reconstruction of new nervous tissue using adipose stem cells. We have previously shown that undifferentiated ADSC adhere and grow on PCL. Herein we show that, after culture on PCL in neuronal differentiation medium, ADSC expressed molecular markers characteristic of neuronal cells (β-tubulin-III, Neuron-Specific Enolase (NSE), Nestin) and secrete brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF). This study suggests that PCL can be used as a scaffold to generate nervous tissue in vitro. PLC has excellent mechanical properties and a slow degradation rate. Moreover, on the basis of our results, we propose that PCL could be used for to make in vitro, scaffold coated with neuronal cells derived from Adipose stem cells (ADSC). Neuronal cells-coated PCL could find several applications to replace damaged area of ​​the body; for example, a possible use could be the generation of nerves. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014. Adipose tissue is an easily accessible source of stem cells for use in tissue regenerative medicine. In the literature, different methods have been used to stimulate acquisition of neuronal characteristics by adipose-derived stem cells (ADSC). Herein we study the growth and neuronal differentiation potential of ADSC seeded onto a porous polycaprolactone (PCL) scaffold. The objective of this study is to demonstrate that PCL can be used as a scaffold to support reconstruction of new nervous tissue using adipose stem cells. We have previously shown that undifferentiated ADSC adhere and grow on PCL. Herein we show that, after culture on PCL in neuronal differentiation medium, ADSC expressed molecular markers characteristic of neuronal cells (β-tubulin-III, Neuron-Specific Enolase (NSE), Nestin) and secrete brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF). This study suggests that PCL can be used as a scaffold to generate nervous tissue in vitro. PLC has excellent mechanical properties and a slow degradation rate. Moreover, on the basis of our results, we propose that PCL could be used for to make in vitro, scaffold coated with neuronal cells derived from Adipose stem cells (ADSC). Neuronal cells-coated PCL could find several applications to replace damaged area of the body; for example, a possible use could be the generation of nerves.

The objective of this study is to compare the effects of the two calcium phosphate composite scaffolds on the attachment, proliferation, and osteogenic differentiation of rabbit dental pulp stem cells (DPSCs). One nano-hydroxyapatite/collagen/poly (l-lactide) (nHAC/PLA), imitating the composition and the micro-structure characteristics of the natural bone, was made by Beijing Allgens Medical Science & Technology Co., Ltd. (China). The other beta-tricalcium phosphate (β-TCP), being fully interoperability globular pore structure, was provided by Shanghai Bio-lu Biomaterials Co, Ltd. (China). We compared the absorption water rate and the protein adsorption rate of two scaffolds and the characterization of DPSCs cultured on the culture plate and both scaffolds under osteogenic differentiation media (ODM) treatment. The constructs were then implanted subcutaneously into the back of severely combined immunodeficient (SCID) mice for 8 and 12 weeks to compare their bone formation capacity. The results showed that the ODM-treated DPSCs expressed osteocalcin (OCN), bone sialoprotein (BSP), type I collagen (COLI) and osteopontin (OPN) by immunofluorescence staining. Positive alkaline phosphatase (ALP) staining, calcium deposition and calcium nodules were also observed on the ODM-treated DPSCs. The absorption water rate and protein adsorption rate of nHAC/PLA was significantly higher than β-TCP. The initial attachment of DPSCs seeded onto nHAC/PLA was significantly higher than that onto β-TCP; and the proliferation rate of the cells was also significantly higher than that of β-TCP on 1, 3, and 7 days of cell culture. The ALP activity, calcium/phosphorus content and mineral formation of DPSCs + β-TCP were significantly higher than DPSCs + nHAC/LA. When implanted into the back of SCID mice, nHAC/PLA alone had no new bone formation, newly formed mature bone and osteoid were only observed in β-TCP alone, DPSCs + nHAC/PLA and DPSCs + β-TCP, and this three groups displayed increased bone formation over the 12-week period. The percentage of total bone formation area had no difference between DPSCs + β-TCP and DPSCs + nHAC/PLA at each time point, but the percentage of mature bone formation area of DPSCs + β-TCP was significantly higher than that of DPSCs + nHAC/PLA. Our results demonstrated that the DPSCs on nHAC/PLA had a better proliferation, and that the DPSCs on β-TCP had a more mineralization in vitro, much more newly formed mature bones in vivo were presented in DPSCs + β-TCP group. These findings have provided a further knowledge that scaffold architecture has different influence on the attachment, proliferation and differentiation of cells. This study may provide insight into the clinical periodontal bone tissue repair with DPSCs + β-TCP construct. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part: 103A: 1732–1745, 2015.

Scaffolds made of polycaprolactone and nanocrystalline silicon-substituted hydroxyapatite have been fabricated by 3D printing rapid prototyping technique. To asses that the scaffolds fulfill the requirements to be considered for bone grafting applications, they were implanted in New Zealand rabbits. Histological and radiological studies have demonstrated that the scaffolds implanted in bone exhibited an excellent osteointegration without the interposition of fibrous tissue between bone and implants and without immune response after 4 months of implantation. In addition, we have evaluated the possibility of improving the scaffolds efficiency by incorporating demineralized bone matrix during the preparation by 3D printing. When demineralized bone matrix (DBM) is incorporated, the efficacy of the scaffolds is enhanced, as new bone formation occurs not only in the peripheral portions of the scaffolds but also within its pores after 4 months of implantation. This enhanced performance can be explained in terms of the osteoinductive properties of the DBM in the scaffolds, which have been assessed through the new bone tissue formation when the scaffolds are ectopically implanted. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.

Previously, we used 2D films to identify an annealed PCL-PDLLA phase-separated blend morphology which provided nanoscale surface texture and patterning that stimulated osteoblast differentiation. In order to translate these 2D surface nanopatterning effects to the walls of 3D salt-leached scaffolds, the blend phase morphology of scaffold walls must be characterized. For salt-leached scaffolds, NaCl is used as a porogen, which may affect phase separation in PCL-PDLLA blends. However, it is not possible to characterize the surface blend morphology of 3D scaffold walls using standard approaches such as AFM or optical microscopy, since scaffolds are too rough for AFM and do not transmit light for optical microscopy. We introduce a 2.5D approach that mimics the processing conditions of 3D salt-leached scaffolds, but has a geometry amenable to surface characterization by AFM and optical microscopy. For the 2.5D approach, PCL-PDLLA blend films were covered with NaCl crystals prior to annealing. The presence of NaCl significantly influenced blend morphology in PCL-PDLLA 2.5D constructs causing increased surface roughness, higher percent PCL area on the surface and a smaller PCL domain size. During cell culture on 2.5D constructs, osteoblast (MC3T3-E1) and dermal endothelial cell (MDEC) adhesion were enhanced on PCL-PDLLA blends that were annealed with NaCl while chondrogenic cell (ATDC5) adhesion was diminished. This work introduces a 2.5D approach that mimicked 3D salt-leached scaffold processing, but enabled characterization of scaffold surface properties by AFM and light microscopy, to demonstrate that the presence of NaCl during annealing strongly influenced polymer blend surface morphology and cell adhesion.

The functionalization of degradable polymeric scaffolds with therapeutic molecules such as vascular endothelial growth factor (VEGF) is a key strategy to gain better regenerative ability of damaged bone tissue by stimulating vascularization and tissue perfusion. Here, we combined VEGF with poly(lactic acid) (PLA) porous scaffold, after modifying the PLA surface with calcium phosphate (CaP) mineral. The mineralized PLA scaffold (mPLA) showed more effective loading capacity of VEGF than the PLA without mineralization as well as profiled sustainable release of VEGF for up to a couple of weeks. The VEGF-loaded mPLA scaffold presented significantly improved proliferation of primary endothelial cells for up to 7 days, with respect to the scaffold without the VEGF loading. The performance of the engineered scaffold was assessed after subcutaneous implantation in rats for 4 weeks. Histological results showed favorable tissue compatibility of both the mPLA scaffolds (with and without VEGF loading), as characterized by infiltration of inflammatory cells, formation of fibrous capsule, and ingrowth of fibroblasts into the matrices. Immunohistochemical staining of the von Willebrand Factor revealed significantly improved formation of neo-capillaries in the VEGF-loaded mPLA. Based on this study, the strategy of VEGF loading onto mineralized PLA scaffold is considered beneficial for gaining improved vascularization of the polymeric scaffolds, suggesting potential applications for bone tissue engineering.