Search

Adaptive drug release can combat coagulation and inflammation activation at the blood-material interface with minimized side effects. For that purpose, poly(styrene-alt-maleic-anhydride) copolymers were conjugated to heparin via coagulation-responsive linker peptides and shown to tightly adsorb onto poly(ethersulfone) (PES)-surfaces from aqueous solutions as monolayers. Coagulation-responsive release of unfractionated as well as low molecular weight heparins from the respective coatings was demonstrated to be functionally beneficial in human plasma and whole blood incubation with faster release kinetics resulting in stronger anticoagulant effects. Coated poly(ethersulfone)/poly(vinylpyrrolidone) (PES/PVP) flat membranes proved the technology to offer an easy, effective and robust anticoagulant interfacial functionalization of hemodialysis membranes. In perspective, the modularity of the adaptive release system will be used for inhibiting multiple activation processes., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Type 2 diabetes is characterized by hyperglycemia and a relative loss of β-cell function. Our research investigated the antidiabetic potential of betulin, a pentacyclic triterpenoid found primarily in birch bark and, intriguingly, in a few marine organisms. Betulin has been shown to possess diverse biological activities, including antioxidant and antidiabetic activities; however, no studies have fully explored the effects of betulin on the pancreas and pancreatic islets. In this study, we investigated the effect of betulin on streptozotocin-nicotinamide (STZ)-induced diabetes in female Wistar rats. Betulin was prepared as an emulsion, and intragastric treatments were administered at doses of 20 and 50 mg/kg for 28 days. The effect of treatment was assessed by analyzing glucose parameters such as fasting blood glucose, hemoglobin A1C, and glucose tolerance; hepatic and renal biomarkers; lipid peroxidation; antioxidant enzymes; immunohistochemical analysis; and hematological indices. Administration of betulin improved the glycemic response and decreased α-amylase activity in diabetic rats, although insulin levels and homeostatic model assessment for insulin resistance (HOMA-IR) scores remained unchanged. Furthermore, betulin lowered the levels of hepatic biomarkers (aspartate aminotransferase, alanine aminotransferase, and alpha-amylase activities) and renal biomarkers (urea and creatine), in addition to improving glutathione levels and preventing the elevation of lipid peroxidation in diabetic animals. We also found that betulin promoted the regeneration of β-cells in a dose-dependent manner but did not have toxic effects on the pancreas. In conclusion, betulin at a dose of 50 mg/kg exerts a pronounced protective effect against cytolysis, diabetic nephropathy, and damage to the acinar pancreas and may be a potential treatment option for diabetes.

We have designed and synthesized a series of bioinspired pyrano[2,3- f ]coumarin-based Calanolide A analogs with anti-HIV activity. The design of these new calanolide analogs involved incorporating nitrogen heterocycles or aromatic groups in lieu of ring C, effectively mimicking and preserving their bioactive properties. Three directions for the synthesis were explored: reaction of 5-hydroxy-2,2-dimethyl-10-propyl-2 H ,8 H -pyrano[2,3- f ]chromen-8-one with (i) 1,2,4-triazines, (ii) sulfonylation followed by Suzuki cross-coupling with (het)aryl boronic acids, and (iii) aminomethylation by Mannich reaction. Antiviral assay of the synthesized compounds showed that compound 4 has moderate activity against HIV-1 on enzymes and poor activity on the cell model. A molecular docking study demonstrates a good correlation between in silico and in vitro HIV-1 reverse transcriptase (RT) activity of the compounds when docked to the nonnucleoside RT inhibitor binding site, and alternative binding modes of the considered analogs of Calanolide A were established.

Betulin is a natural triterpene, usually from birch bark, known for its potential wound-healing properties. Despite having a wide range of pharmacological targets, no studies have proposed betulin as a multitarget compound. Betulin has protective effects against cardiovascular and liver diseases, cancer, diabetes, oxidative stress, and inflammation. It reduces postprandial hyperglycemia by inhibiting α-amylase and α-glucosidase activity, combats tumor cells by inducing apoptosis and inhibiting metastatic proteins, and modulates chronic inflammation by blocking the expression of proinflammatory cytokines via modulation of the NFκB and MAPKs pathways. Given its potential to influence diverse biological networks with high target specificity, it can be hypothesized that betulin may eventually become a new lead for drug development because it can modify a variety of pharmacological targets. The summarized research revealed that the diverse beneficial effects of betulin in various diseases can be attributed, at least in part, to its multitarget anti-inflammatory activity. This review focuses on the natural sources, pharmacokinetics, pharmacological activity of betulin, and the multi-target effects of betulin on signaling pathways such as MAPK, NF-κB, and Nrf2, which are important regulators of the response to oxidative stress and inflammation in the body.

This review summarizes and systematizes the literature on the anti-HIV activity of plant coumarins with emphasis on isolation and the mechanism of their antiviral action. This review summarizes the information on the anti-HIV properties of simple coumarins as well as annulated furano- and pyranocoumarins and shows that coumarins of plant origin can act by several mechanisms: inhibition of HIV reverse transcriptase and integrase, inhibition of cellular factors that regulate HIV-1 replication, and transmission of viral particles from infected macrophages to healthy ones. It is important to note that some pyranocoumarins are able to act through several mechanisms or bind to several sites, which ensures the resistance of these compounds to HIV mutations. Here we review the last two decades of research on the anti-HIV activity of naturally occurring coumarins.

Today's smallest energy storage devices for in-vivo applications are larger than 3 mm 3 and lack the ability to continuously drive the complex functions of smart dust electronic and microrobotic systems. Here, we create a tubular biosupercapacitor occupying a mere volume of 1/1000 mm 3 (=1 nanoliter), yet delivering up to 1.6 V in blood. The tubular geometry of this nano-biosupercapacitor provides efficient self-protection against external forces from pulsating blood or muscle contraction. Redox enzymes and living cells, naturally present in blood boost the performance of the device by 40% and help to solve the self-discharging problem persistently encountered by miniaturized supercapacitors. At full capacity, the nano-biosupercapacitors drive a complex integrated sensor system to measure the pH-value in blood. This demonstration opens up opportunities for next generation intravascular implants and microrobotic systems operating in hard-to-reach small spaces deep inside the human body., (© 2021. The Author(s).)

Computer vision (CV) algorithms are widely utilized in imaging processing for medical and personal electronics applications. In sensorics CV can provide a great potential to quantitate chemosensors' signals. Here we wish to describe a method for the CV-assisted spectrofluorometer-free detection of common nitro-explosive components, e.g. 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT), by using polyaromatic hydrocarbon (PAH, PAH = 1-pyrenyl or 9-anthracenyl) - based bola -type chemosensors. The PAH components of these chemical bolas are able to form stable, bright emissive in a visual wavelength region excimers, which allows their use as extended matrices of the RGB colors after imaging and digital processing. In non-polar solvents, the excimers have poor chemosensing properties, while in aqueous solutions, due to the possible micellar formation, these excimers provide "turn-off" fluorescence detection of DNT and TNT in the sub-nanomolar concentrations. A combination of these PAH-based fluorescent chemosensors with the proposed CV-assisted algorithm offers a fast and convenient approach for on-site, real-time, multi-thread analyte detection without the use of fluorometers. Although we focus on the analysis of nitro-explosives, the presented method is a conceptual work describing a general use of CV for quantitative fluorescence detection of various analytes as a simpler alternative to spectrofluorometer-assisted methods., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Glial-cell-line-derived neurotrophic factor (GDNF) is a protein that has therapeutic potential in the treatment of Parkinson's disease and other neurodegenerative diseases. The activity of GDNF is highly dependent on the interaction with sulfated glycans which bind at the N-terminus consisting of 19 residues. Herein, we studied the influence of different glycosaminoglycan (i.e., glycan; GAG) molecules on the conformation of a GDNF-derived peptide (GAG binding motif, sixteen amino acid residues at the N-terminus) using both experimental and theoretical studies. The GAG molecules employed in this study are heparin, heparan sulfate, hyaluronic acid, and sulfated hyaluronic acid. Circular dichroism spectroscopy was employed to detect conformational changes induced by the GAG molecules; molecular dynamics simulation studies were performed to support the experimental results. Our results revealed that the sulfated GAG molecules bind strongly with GDNF peptide and induce alpha-helical structure in the peptide to some extent., (Copyright © 2021. Published by Elsevier B.V.)

Chitin is the second most abundant biopolymer and functions as the main structural component in a variety of living organisms. In nature, chitin rarely occurs in a pure form, but rather as nanoorganized chitin-proteins, chitin-pigments, or chitin-mineral composite biomaterials. Although chitin has a long history of scientific studies, it is still extensively investigated for practical applications in medicine, biotechnology, and biomimetics. The complexity of chitin has required the development of highly sensitive analytical methods for its identification. These methods are crucial for furthering disease diagnostics as well as advancing modern chitin-related technologies. Here we provide a summary of chitin identification by spectroscopic (NEXAFS, FTIR, Raman, NMR, colorimetry), chromatographic (TLC, GC, HPLC), electrophoretic (HPCE), and diffraction methods (XRD, WAXS, SAXS, HRTEM-SAED). Biochemical and immunochemical (ELISA, immunostaining) methods are described with respect to their medical application. This review outlines the history as well as the current progress in the analytical methods for chitin identification., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Studies on the identification, properties and function of chitin in sponges (Porifera), which are recognized as the first multicellular organisms on Earth, continue to be of fundamental scientific interest. The occurrence of chitin has so far been reported in 21 marine sponge species and only in two inhabiting fresh water. In this study, we present the discovery of α-chitin in the endemic demosponge Ochridaspongia rotunda, found in Lake Ohrid, which dates from the Tertiary. The presence of chitin in this species was confirmed using special staining, a chitinase test, FTIR, Raman and NEXAFS spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). In contrast to the case of marine sponges, chitin in O. rotunda has been found only within its holdfast, suggesting a role of chitin in the attachment of the sponge to the hard substratum. Isolated fibrous matter strongly resemble the shape and size of the sponge holdfast with membrane-like structure., (Copyright © 2020 Elsevier B.V. All rights reserved.)

One of the major challenges of implantology is to design nanoscale modifications of titanium implant surfaces inducing osseointegration. The aim of this study was to investigate the behavior of rat osteoblasts cultured on anodized TiO 2 nanotubes of different crystallinity (amorphous and anatase phase) up to 24 days. TiO 2 nanotubes were fabricated on VT1-0 titanium foil via a two-step anodization at 20 V using NH 4 F as an electrolyte. Anatase-phase samples were prepared by heat treatment at 500 °C for 1 h. VT1-0 samples with flat surfaces were used as controls. Primary rat osteoblasts were seeded over experimental surfaces for several incubation times. Scanning electron microscopy (SEM) was used to analyze tested surfaces and cell morphology. Cell adhesion and proliferation were investigated by cell counting. Osteogenic differentiation of cells was evaluated by qPCR of runt-related transcription factor 2 (RUNX2), osteopontin (OPN), integrin binding sialoprotein (IBSP), alkaline phosphatase (ALP) and osteocalcin (OCN). Cell adhesion and proliferation, cell morphology and the expression of osteogenic markers were affected by TiO 2 nanotube layered substrates of amorphous and anatase crystallinity. In comparison with flat titanium, along with increased cell adhesion and cell growth a large portion of osteoblasts grown on the both nanostructured surfaces exhibited an osteocyte-like morphology as early as 48 h of culture. Moreover, the expression of all tested osteogenic markers in cells cultured on amorphous and anatase TiO 2 nanotubes was upregulated at least at one of the analyzed time points. To summarize, we demonstrated that amorphous and anodized TiO 2 layered substrates are highly biocompatible with rat osteoblasts and that the surface modification with about 1500 nm length nanotubes of 35 ± 4 (amorphous phase) and 41 ± 8 nm (anatase phase) in diameter is sufficient to induce their osteogenic differentiation. Such results are significant to the engineering of coating strategies for orthopedic implants aimed to establish a more efficient bone to implant contact and enhance bone repair., Competing Interests: The authors declare no conflict of interest.

Glycosaminoglycan (GAG)-based, biohybrid hydrogels offering far-reaching control over their physical and biomolecular signaling properties have been successfully used in various cell and tissue culture applications. To explore the suitability of the materials for in vivo use, we herein studied the host reaction to in situ-assembling star(PEG)-GAG hydrogel variants upon subcutaneous implantation in immunocompetent C57BL/6J mice for up to 28 days. Specifically, we investigated the immune reaction and the angiogenic response to hydrogels with systematically varied cytokine functionalizations, physical network (and mechanical) properties, cell adhesiveness, and enzymatic degradability. The GAG-based hydrogel elicited only minor foreign body reaction with low immune cell infiltration and collagen deposition compared to similarly implanted medical grade silicone. Adjusting of the physical properties, biofunctionalization, and degradability allowed to program the host response from nearly no degradation and infiltration to fast integration of the gel scaffolds into the tissue within days. The results demonstrate that foreign body reactions and starPEG-GAG hydrogel tissue integration can be effectively controlled by defined adjustments of the hydrogel system, suggesting the in situ-assembling materials as safe and effective for in vivo tissue engineering applications., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Multiphasic in vitro models with cross-scale heterogeneity in matrix properties and/or cellular composition can reflect the structural and compositional complexity of living tissues more faithfully, thereby creating new options for pathobiology and drug development studies. Herein, a new class of tunable microgel-in-gel materials is reported that build on a versatile platform of multifunctional poly(ethylene glycol)-heparin gel types and integrates monodisperse, cell-laden microgels within cell-laden bulk hydrogel matrices. A novel microfluidic approach was developed to enable the high-throughput fabrication of microgels of in situ adjustable diameters, stiffness, degradability and biomolecular functionalization. By choosing structure and composition of the microgel and the bulk gel compartments independently, our microgel-in-gel arrangements provide cross-scale control over tissue-mimetic features and pave the way for culture systems with designed mesoenvironmental characteristics. The potentialities of the introduced approach are exemplarily shown by creating a reductionistic in vitro model of vascularized prostate cancer tissue.

Medication-related osteonecrosis of the jaw (MRONJ) poses an ongoing challenge for clinicians and researchers. Currently, there is a lack of preventative measures available for at-risk patients undergoing tooth extractions, especially those with prior bisphosphonate treatment due to osteoporosis or bone metastasis diagnoses. Here, these issues are addressed using a preventative tissue engineering strategy against MRONJ development. This study evaluates the efficacy of a poly(ethylene glycol)-heparin hydrogel as a tool for the delivery of arginylglycylaspartic acid (RGD) and recombinant human bone morphogenic protein-2 (rhBMP-2). Three groups of skeletally mature rats each receive two doses of intravenous zoledronic acid prior to surgery and undergo extraction of the right first mandibular molar with gingival closure. Experimental groups either have the sockets left empty, filled with hydrogel minus rhBMP-2, or filled with hydrogel plus rhBMP-2. Eight weeks postoperatively specimens are analyzed using radiological, histological, and scanning electron microscopy (SEM) techniques. µCT analysis shows increased bone formation with hydrogel/rhBMP-2 delivery compared to the empty socket. Hydrogel-treated groups display increased presence of osteocytes and increased osteoclastic action compared to the empty sockets. These results represent the first step toward improved delivery of rhBMP-2 and a potential MRONJ preventative for patients undergoing bisphosphonate treatment., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Chitin, as a fundamental polysaccharide in invertebrate skeletons, continues to be actively investigated, especially with respect to new sources and the development of effective methods for its extraction. Recent attention has been focused on marine crustaceans and sponges; however, the potential of spiders (order Araneae) as an alternative source of tubular chitin has been overlooked. In this work, we focused our attention on chitin from up to 12 cm-large Theraphosidae spiders, popularly known as tarantulas or bird-eating spiders. These organisms "lose" large quantities of cuticles during their molting cycle. Here, we present for the first time a highly effective method for the isolation of chitin from Caribena versicolor spider molt cuticle, as well as its identification and characterization using modern analytical methods. We suggest that the tube-like molt cuticle of this spider can serve as a naturally prefabricated and renewable source of tubular chitin with high potential for application in technology and biomedicine., Competing Interests: The authors declare no conflict of interest.

Naturally occurring three-dimensional (3D) biopolymer-based matrices that can be used in different biomedical applications are sustainable alternatives to various artificial 3D materials. For this purpose, chitin-based structures from marine sponges are very promising substitutes. Marine sponges from the order Verongiida (class Demospongiae) are typical examples of demosponges with well-developed chitinous skeletons. In particular, species belonging to the family Ianthellidae possess chitinous, flat, fan-like fibrous skeletons with a unique, microporous 3D architecture that makes them particularly interesting for applications. In this work, we focus our attention on the demosponge Ianthella flabelliformis (Linnaeus, 1759) for simultaneous extraction of both naturally occurring ("ready-to-use") chitin scaffolds, and biologically active bromotyrosines which are recognized as potential antibiotic, antitumor, and marine antifouling substances. We show that selected bromotyrosines are located within pigmental cells which, however, are localized within chitinous skeletal fibers of I. flabelliformis . A two-step reaction provides two products: treatment with methanol extracts the bromotyrosine compounds bastadin 25 and araplysillin-I N20 sulfamate, and a subsequent treatment with acetic acid and sodium hydroxide exposes the 3D chitinous scaffold. This scaffold is a mesh-like structure, which retains its capillary network, and its use as a potential drug delivery biomaterial was examined for the first time. The results demonstrate that sponge-derived chitin scaffolds, impregnated with decamethoxine, effectively inhibit growth of the human pathogen Staphylococcus aureus in an agar diffusion assay.

Sponges are a valuable source of natural compounds and biomaterials for many biotechnological applications. Marine sponges belonging to the order Verongiida are known to contain both chitin and biologically active bromotyrosines. Aplysina archeri (Aplysineidae: Verongiida) is well known to contain bromotyrosines with relevant bioactivity against human and animal diseases. The aim of this study was to develop an express method for the production of naturally prefabricated 3D chitin and bromotyrosine-containing extracts simultaneously. This new method is based on microwave irradiation (MWI) together with stepwise treatment using 1% sodium hydroxide, 20% acetic acid, and 30% hydrogen peroxide. This approach, which takes up to 1 h, made it possible to isolate chitin from the tube-like skeleton of A. archeri and to demonstrate the presence of this biopolymer in this sponge for the first time. Additionally, this procedure does not deacetylate chitin to chitosan and enables the recovery of ready-to-use 3D chitin scaffolds without destruction of the unique tube-like fibrous interconnected structure of the isolated biomaterial. Furthermore, these mechanically stressed fibers still have the capacity for saturation with water, methylene blue dye, crude oil, and blood, which is necessary for the application of such renewable 3D chitinous centimeter-sized scaffolds in diverse technological and biomedical fields.

Among marine demosponges (Porifera: Demospongiae), only representatives of the order Verongiida have been recognized to synthetize both biologically active substances as well as scaffolds-like fibrous skeletons made of structural aminopolysaccharide chitin. The unique 3D architecture of such scaffolds open perspectives for their applications in waste treatment, biomimetics and tissue engineering. Here, we focus special attention to the demosponge Pseudoceratina purpurea collected in the coastal waters of Singapore. For the first time the detailed description of the isolation of chitin from the skeleton of this sponge and its identification using diverse bioanalytical tools were carried out. Calcofluor white staining, FTIR analysis, electrospray ionization mass spectrometry (ESI-MS), SEM, and fluorescence microscopy as well as a chitinase digestion assay were applied in order to confirm with strong evidence the finding of alpha-chitin in the skeleton of P. purpurea. We suggest that the discovery of chitin within representatives of Pseudoceratinidae family is a perspective step in evaluation of these verongiid sponges as novel renewable sources for both chitin and biologically active metabolites, which are of prospective use for marine oriented biomedicine and pharmacology, respectively., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Sponges (Porifera) are recognized as aquatic multicellular organisms which developed an effective biochemical pathway over millions of years of evolution to produce both biologically active secondary metabolites and biopolymer-based skeletal structures. Among marine demosponges, only representatives of the Verongiida order are known to synthetize biologically active substances as well as skeletons made of structural polysaccharide chitin. The unique three-dimensional (3D) architecture of such chitinous skeletons opens the widow for their recent applications as adsorbents, as well as scaffolds for tissue engineering and biomimetics. This study has the ambitious goal of monitoring other orders beyond Verongiida demosponges and finding alternative sources of naturally prestructured chitinous scaffolds; especially in those demosponge species which can be cultivated at large scales using marine farming conditions. Special attention has been paid to the demosponge Mycale euplectellioides (Heteroscleromorpha: Poecilosclerida: Mycalidae) collected in the Red Sea. For the first time, we present here a detailed study of the isolation of chitin from the skeleton of this sponge, as well as its identification using diverse bioanalytical tools. Calcofluor white staining, Fourier-transform Infrared Spcetcroscopy (FTIR), electrospray ionization mass spectrometry (ESI-MS), scanning electron microscopy (SEM), and fluorescence microscopy, as well as a chitinase digestion assay were applied in order to confirm with strong evidence the finding of a-chitin in the skeleton of M. euplectellioides . We suggest that the discovery of chitin within representatives of the Mycale genus is a promising step in their evaluation of these globally distributed sponges as new renewable sources for both biologically active metabolites and chitin, which are of prospective use for pharmacology and biomaterials oriented biomedicine, respectively., Competing Interests: The authors declare no conflict of interest.

Since the discovery of chitin in skeletal structures of sponges (Porifera) in 2007, studies on search of novel species which possess this structural aminopolysaccharide continue up today. The most potential source of chitin is suggested to be localized in the four families of sponges related to the order Verongida (Demospongiae) which nevertheless require further clarification. Here, we report for the first time the isolation and identification of α-chitin from the Suberea clavata demosponge (Aplysinidae: Verongida). Raman spectroscopy, Calcofluor White staining, chitinase test and ESI-MS techniques were used to identify chitin. We suggest that the presence of chitin within fibrous skeletons of diverse species of Verongida order, and, especially in all species of the Aplysinidae family, may be useful for the identification of novel, previously unidentified marine demosponges., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Two-photon excitation provides high spatial resolution in three dimensions of the corresponding chemical or physical processes, allowing submicrometer structuring in stereolithography and three-dimensional (3D) microfabrication. While studying two-photon structuring applications, we observed an undescribed phenomenon in photochemistry that dictates reactivity of maleimide groups in two-photon mode. A low-absorbance transition formerly ignored in classical photochemistry has been found for maleimides. This transition was assigned to symmetry-breaking donor-acceptor complex formation, which revealed a formally forbidden pathway in [2+2] cycloaddition reactions of maleimide moieties. This synthetic pathway allowed for the creation of hydrogel materials under physiological conditions at low laser excitation energy (0.1 J/cm 2 at 800 nm) without the use of photoinitiators, which makes it truly two-photon click chemistry.

Feedback-controlled anticoagulant hydrogels were formed by crosslinking the anticoagulant heparin with star-shaped poly(ethylene glycol) using peptide linkers, which are selectively cleaved by different activated blood coagulation factors acting as proteolytic enzymes. Various cleavable peptide units, differing either in their thrombin turnover rates or in their responsiveness to factors activated earlier in the course of blood coagulation, were used for the formation of the biohybrid materials. Release triggered by the early coagulation factors Xa (FXa) or FXIIa/kallikrein was shown to enhance the efficiency of the released anticoagulant. Furthermore, FXa-cleavable gels enabled a faster release of heparin, which was attributed to the lower affinity of the factor for heparin. Combining early and fast responses, FXa-cleavable gels were shown to provide anticoagulant protection of biomaterial surfaces at low levels of released heparin in human whole-blood incubation experiments. The results demonstrate the potential for employing biomolecular circuits in the design of functional biomaterials to tailor the adaptive delivery of bioactive molecules., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Dialysis or kidney transplantation is the only therapeutic option for end stage renal disease. Accordingly, there is a large unmet clinical need for new causative therapeutic treatments. Obtaining robust models that mimic the complex nature of the human kidney is a critical step in the development of new therapeutic strategies. Here we establish a synthetic in vitro human renal tubulogenesis model based on a tunable glycosaminoglycan-hydrogel platform. In this system, renal tubulogenesis can be modulated by the adjustment of hydrogel mechanics and degradability, growth factor signaling, and the presence of insoluble adhesion cues, potentially providing new insights for regenerative therapy. Different hydrogel properties were systematically investigated for their ability to regulate renal tubulogenesis. Hydrogels based on heparin and matrix metalloproteinase cleavable peptide linker units were found to induce the morphogenesis of single human proximal tubule epithelial cells into physiologically sized tubule structures. The generated tubules display polarization markers, extracellular matrix components, and organic anion transport functions of the in vivo renal proximal tubule and respond to nephrotoxins comparable to the human clinical response. The established hydrogel-based human renal tubulogenesis model is thus considered highly valuable for renal regenerative medicine and personalized nephrotoxicity studies., Statement of Significance: The only cure for end stage kidney disease is kidney transplantation. Hence, there is a huge need for reliable human kidney models to study renal regeneration and establish alternative treatments. Here we show the development and application of an in vitro human renal tubulogenesis model using heparin-based hydrogels. To the best of our knowledge, this is the first system where human renal tubulogenesis can be monitored from single cells to physiologically sized tubule structures in a tunable hydrogel system. To validate the efficacy of our model as a drug toxicity platform, a chemotherapy drug was incubated with the model, resulting in a drug response similar to human clinical pathology. The established model could have wide applications in the field of nephrotoxicity and renal regenerative medicine and offer a reliable alternative to animal models., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Tissue-derived fibrillated matrices can be instrumental for the in vitro reconstitution of multiphasic extracellular microenvironments. However, despite of several advantages, the obtained scaffolds so far offer a rather narrow range of materials characteristics only. In this work, we demonstrate how macromolecular crowding (MMC) - the supplementation of matrix reconstitution media with synthetic or natural macromolecules in ways to create excluded volume effects (EVE) - can be employed for tailoring important structural and biophysical characteristics of kidney-derived fibrillated matrices. Porcine kidneys were decellularized, ground and the obtained extracellular matrix (ECM) preparations were reconstituted under varied MMC conditions. We show that MMC strongly influences the fibrillogenesis kinetics and impacts the architecture and the elastic modulus of the reconstituted matrices, with diameters and relative alignment of fibrils increasing at elevated concentrations of the crowding agent Ficoll400, a nonionic synthetic polymer of sucrose. Furthermore, we demonstrate how MMC modulates the distribution of key ECM molecules within the reconstituted matrix scaffolds. As a proof of concept, we compared different variants of kidney-derived fibrillated matrices in cell culture experiments referring to specific requirements of kidney tissue engineering approaches. The results revealed that MMC-tailored matrices support the morphogenesis of human umbilical vein endothelial cells (HUVECs) into capillary networks and of murine kidney stem cells (KSCs) into highly branched aggregates. The established methodology is concluded to provide generally applicable new options for tailoring tissue-specific multiphasic matrices in vitro., Statement of Significance: Tissue-derived fibrillated matrices can be instrumental for the in vitro reconstitution of multiphasic extracellular microenvironments. However, despite of several advantages, the obtained scaffolds so far offer a rather narrow range of materials characteristics only. Using the kidney matrix as a model, we herein report a new approach for tailoring tissue-derived fibrillated matrices by means of macromolecular crowding (MMC), the supplementation of reconstitution media with synthetic or natural macromolecules. MMC-modulation of matrix reconstitution is demonstrated to allow for the adjustment of fibrillation kinetics and nano-architecture, fiber diameter, alignment, and matrix elasticity. Primary human umbilical vein endothelial cells (HUVEC) and murine kidney stem cells (KSC) were cultured within different variants of fibrillated kidney matrix scaffolds. The results showed that MMC-tailored matrices were superior in supporting desired morphogenesis phenomena of both cell types., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Polymer hydrogels can be readily modulated with regard to their physical properties and functionalized to recapitulate molecular cues of the extracellular matrix (ECM). However, they remain structurally different from the hierarchical supramolecular assemblies of natural ECM. Accordingly, we herein report a set of hydrogel composite materials made from starPEG-peptide conjugates, maleimide-functionalized heparin and collagen type I that combine semisynthetic and ECM-derived components. Collagen fibrillogenesis was controlled by temperature and collagen concentration to form collagen microstructures which were then homogeneously distributed within the 3D composite matrix during hydrogel formation. The collagen-laden hydrogel materials showed a heterogeneous local variation of the stiffness and adhesion ligand density. Composite gels functionalized with growth factors and cell adhesive peptides (RGDSP) supported the growth of embedded human umbilical cord vein endothelial cells (HUVECs) and induced the alignment of embedded bone marrow-derived human mesenchymal stem cells (MSCs) to the collagen microstructures in vitro. The introduced composite hydrogel material is concluded to faithfully mimic cell-instructive features of the ECM., Statement of Significance: Cell-instructive materials play an important role in the generation of both regenerative therapies and advanced tissue and disease models. For that purpose, biofunctional polymer hydrogels recapitulating molecular cues of the extracellular matrix (ECM) were successfully applied in various different studies. However, hydrogels generally lack the hierarchical supramolecular structure of natural ECM. We have therefore developed a hydrogel composite material made from starPEG-peptide conjugates, maleimide-functionalized heparin and collagen type I fibrils. The collagen-laden scaffolds showed a heterogeneous local variation in the stiffness of the material. The composite gels were successfully tested in culture experiments with human umbilical cord vein endothelial cells and bone marrow-derived human mesenchymal stem cells. It was concluded that the composite scaffold was able to faithfully mimic important cell-instructive features of the ECM., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Matrix systems used to study complex three-dimensional (3D) cellular processes like mammary epithelial tissue morphogenesis and tumorigenesis ex vivo often require ill-defined biological components, which lead to poor reproducibility and a lack of control over physical parameters. In this study, a well-defined, tunable synthetic biohybrid hydrogel composed of the glycosaminoglycan heparin, star-shaped poly(ethylene glycol) (starPEG), and matrix metalloproteinase- (MMP-) cleavable crosslinkers was applied to dissect the biophysical and biochemical signals promoting human mammary epithelial cell (MEC) morphogenesis. We show that compliant starPEG-heparin matrices promote the development of polarized MEC acini. Both the presence of heparin and MMP-cleavable crosslinks are essential in facilitating MEC morphogenesis without supplementation of exogenous adhesion ligands. In this system, MECs secrete and organize laminin in basement membrane-like assemblies to promote integrin signaling and drive acinar development. Therefore, starPEG-heparin hydrogels provide a versatile platform to study mammary epithelial tissue morphogenesis in a chemically defined and precisely tunable 3D in vitro microenvironment. The system allows investigation of biophysical and biochemical aspects of mammary gland biology and potentially a variety of other organoid culture studies., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Creating hydrogel systems to mimic the extracellular matrix is often limited by their static nature. The use of a two-photon [2+2] cycloaddition of maleimide groups to structure surfaces, to create hydrogels, and add 3D modifications with sub-micrometer precision is reported. The absence of photoinitiators and usage of near-infrared light is promising for future in vivo studies., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

While vascular endothelial growth factor (VEGF) has been shown to be one of the key players in wound healing by promoting angiogenesis current clinical applications of this growth factor to the wound environment are poorly controlled and not sustainable. Hydrogels made of sulfated glycosaminoglycans (GAG) allow for the sustained release of growth factors since GAGs engage in electrostatic complexation of biomolecules. In here, we explore a set of hydrogels formed of selectively desulfated heparin derivatives and star-shaped poly(ethylene glycol) with respect to VEGF binding and release and anticoagulant activity. As a proof of concept, supportive effects on migration and tube formation of human umbilical vein endothelial cells were studied in vitro and the promotion of wound healing was followed in genetically diabetic (db/db) mice. Our data demonstrate that the release of VEGF from the hydrogels is modulated in dependence on the GAG sulfation pattern. Hydrogels with low sulfate content (11% of initial heparin) were found to be superior in efficacy of VEGF administration, low anticoagulant activity and promotion of angiogenesis.

Matrix-metalloproteinase and photosensitive peptide units are combined with heparin and poly(ethylene glycol) into a light-sensitive multicomponent hydrogel material. Localized degradation of the hydrogel matrix allows the creation of defined spatial constraints and adhesive patterning for cells grown in culture. Using this matrix system, it is demonstrated that the degree of confinement determines the fate of neural precursor cells in vitro., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report a novel, noncovalent hydrogel system crosslinked solely by receptor-ligand interactions between biotin and avidin. The simple hydrogel synthesis and functionalization together with the widespread use of biotinylated ligands in biosciences make this versatile system suitable for many applications. The gels possess a range of tunable physical properties, including stiffness, lifetime, and swelling. The erosion rates, unexpectedly fast compared to the kinetic parameters for biotin-avidin, are explored in terms of stretching tensions on the polymers, a concept well-known on the single-molecule level, but largely unexplored in supramolecular systems. As proof of utility, the gels were functionalized with different peptide sequences to control human mesenchymal stromal cell morphology in 3D culture., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Sulfation patterns of glycosaminoglycans (GAG) govern the electrostatic complexation of biomolecules and thus allow for modulating the release profiles of growth factors from GAG-based hydrogels. To explore options related to this, selectively desulfated heparin derivatives were prepared, thoroughly characterized, and covalently converted with star-shaped poly(ethylene glycol) into binary polymer networks. The impact of the GAG sulfation pattern on the network characteristics of the obtained hydrogels was theoretically evaluated by mean field methods and experimentally analyzed by rheometry and swelling measurements. Sulfation-dependent differences of reactivity and miscibility of the heparin derivatives were shown to determine network formation. A theory-based design concept for customizing growth factor affinity and physical characteristics was introduced and validated by quantifying the release of fibroblast growth factor 2 from a set of biohybrid gels. The resulting new class of cell-instructive polymer matrices with tunable GAG sulfation will be instrumental for multiple applications in biotechnology and medicine.

Glycosaminoglycan (GAG)-based hydrogels gain increasing interest in regenerative therapies. To support specific applications, the biomolecular functionality of gel matrices needs to be customized via conjugation of peptide sequences that mediate cell adhesion, expansion and differentiation. Herein, we present an orthogonal strategy for the formation and chemoselective functionalization of starPEG-GAG hydrogels, utilizing the uniform and specific conjugation of peptides and GAGs for customizing the resulting materials. The introduced approach was applied for the incorporation of three different types of RGD peptides to analyze the influence of peptide sequence and conformation on adhesion and morphogenesis of endothelial cells (ECs) grown on the peptide-containing starPEG-GAG hydrogels. The strongest cellular response was observed for hydrogels functionalized with cycloRGD followed by linear forms of RGDSP and RGD, showing that morphogenesis and growth rate of ECs is controlled by both type and quantity of the conjugated peptides.

Angiogenesis, the outgrowth of blood vessels, is crucial in development, disease and regeneration. Studying angiogenesis in vitro remains challenging because the capillary morphogenesis of endothelial cells (ECs) is controlled by multiple exogenous signals. Therefore, a set of in situ-forming starPEG-heparin hydrogels was used to identify matrix parameters and cellular interactions that best support EC morphogenesis. We showed that a particular type of soft, matrix metalloproteinase-degradable hydrogel containing covalently bound integrin ligands and reversibly conjugated pro-angiogenic growth factors could boost the development of highly branched, interconnected, and lumenized endothelial capillary networks. Using these effective matrix conditions, 3D heterocellular interactions of ECs with different mural cells were demonstrated that enabled EC network modulation and maintenance of stable vascular capillaries over periods of about one month in vitro. The approach was also shown to permit in vitro tumor vascularization experiments with unprecedented levels of control over both ECs and tumor cells. In total, the introduced 3D hydrogel co-culture system could offer unique options for dissecting and adjusting biochemical, biophysical, and cell-cell triggers in tissue-related vascularization models.

Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of the early evolution of metazoans. Here, we present the discovery of 505-million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.

The recent discovery of chitin within skeletons of numerous marine and freshwater sponges (Porifera) stimulates further experiments to identify this structural aminopolysaccharide in new species of these aquatical animals. Aplysina fistularis (Verongida: Demospongiae: Porifera) is well known to produce biologically active bromotyrosines. Here, we present a detailed study of the structural and physico-chemical properties of the three-dimensional skeletal scaffolds of this sponge. Calcofluor white staining, Raman and IR spectroscopy, ESI-MS as well as chitinase digestion test were applied in order to unequivocally prove the first discovery of α-chitin in skeleton of A. fistularis., (Copyright © 2013 Elsevier B.V. All rights reserved.)

This work demonstrates that chitin is an important structural component within the skeletal fibers of the freshwater sponge Spongilla lacustris. Using a variety of analytical techniques ((13)C solid state NMR, FT-IR, Raman, NEXAFS, ESI-MS, Morgan-Elson assay and Calcofluor White Staining); we show that this sponge chitin is much closer to α-chitin, known to be present in other animals, than to β-chitin. Genetic analysis confirmed the presence of chitin synthases, which are described for the first time in a sponge. The presence of chitin in both marine (demosponges and hexactinellids) and freshwater sponges indicates that this important structural biopolymer was already present in their common ancestor., (Copyright © 2013 Elsevier Inc. All rights reserved.)

A holdfast is a root- or basal plate-like structure of principal importance that anchors aquatic sessile organisms, including sponges, to hard substrates. There is to date little information about the nature and origin of sponges' holdfasts in both marine and freshwater environments. This work, to our knowledge, demonstrates for the first time that chitin is an important structural component within holdfasts of the endemic freshwater demosponge Lubomirskia baicalensis. Using a variety of techniques (near-edge X-ray absorption fine structure, Raman, electrospray ionization mas spectrometry, Morgan-Elson assay and Calcofluor White staining), we show that chitin from the sponge holdfast is much closer to α-chitin than to β-chitin. Most of the three-dimensional fibrous skeleton of this sponge consists of spicule-containing proteinaceous spongin. Intriguingly, the chitinous holdfast is not spongin-based, and is ontogenetically the oldest part of the sponge body. Sequencing revealed the presence of four previously undescribed genes encoding chitin synthases in the L. baicalensis sponge. This discovery of chitin within freshwater sponge holdfasts highlights the novel and specific functions of this biopolymer within these ancient sessile invertebrates.

Poly(ethylene glycol)-peptide- and glycosaminoglycan-peptide conjugates obtained by a regio-selective amino acid protection strategy are converted into cell-instructive hydrogel matrices capable of inducing morphogenesis in embedded human vascular endothelial cells and dorsal root ganglia., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Local delivery of growth factors (GFs) can accelerate regeneration of injured tissue, but for many medical applications, injectable GF delivery systems are required for clinical success. Viscoelastic, injectable aggregates of micrometer-sized hydrogel particles made of multiarmed polyethylene glycol (starPEG) and heparin were prepared and tested for site-specific paracrine stimulation of tissue regeneration. Heparin was used as it binds, protects and releases numerous GFs. Hydrogel based delivery of basic fibroblast growth factor (bFGF) and murine epidermal growth factor (EGF) was monitored utilizing enzyme-linked immunosorbent assay (ELISA). bFGF was released slowly because of its high affinity to the heparin while the significantly higher release of the non-specific binding EGF was controlled by diffusion only. To investigate GF delivery in vivo, a hydrogel loaded with murine EGF or bFGF was injected subcapsularly into the left kidney of mice with experimental acute kidney injury caused by glycerol induced rhabdomyolysis. Visual examination confirmed sustained stability of the injected gel aggregates during the timescale of the experiment. The number of proliferating kidney tubular epithelial cells was quantified both in the injected kidney and the non-injected contralateral kidney. bFGF delivery from hydrogels induced a significant increase in cell proliferation in the injected kidney, although small effects were also seen in the non-injected kidney due to a systemic effect. EGF delivery strongly increased cell proliferation for both kidneys, but also showed a local effect on the injected kidney. The hydrogel without loaded GFs was used as a control and showed no increase in cell proliferation. Our results suggest that this novel starPEG-heparin hydrogel system can be an effective approach to deliver GFs locally., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Bio-responsive polymer architectures can empower medical therapies by engaging molecular feedback-response mechanisms resembling the homeostatic adaptation of living tissues to varying environmental constraints. Here we show that a blood coagulation-responsive hydrogel system can deliver heparin in amounts triggered by the environmental levels of thrombin, the key enzyme of the coagulation cascade, which--in turn--becomes inactivated due to released heparin. The bio-responsive hydrogel quantitatively quenches blood coagulation over several hours in the presence of pro-coagulant stimuli and during repeated incubation with fresh, non-anticoagulated blood. These features enable the introduced material to provide sustainable, autoregulated anticoagulation, addressing a key challenge of many medical therapies. Beyond that, the explored concept may facilitate the development of materials that allow the effective and controlled application of drugs and biomolecules.

Cell-responsive degradation of biofunctional scaffold materials is required in many tissue engineering strategies and commonly achieved by the incorporation of protease-sensitive oligopeptide units. In extension of this approach, we combined protease-sensitive and -insensitive cleavage sites for the far-reaching control over degradation rates of starPEG-heparin hydrogel networks with orthogonally modulated elasticity, RGD presentation and VEGF delivery. Enzymatic cleavage was massively accelerated when the accessibility of the gels for proteases was increased through non-enzymatic cleavage of ester bonds. The impact of gel susceptibility to degradation was explored for the 3-dimensional ingrowth of human endothelial cells. Gels with accelerated degradation and VEGF release resulted in strongly enhanced endothelial cell invasion in vitro as well as blood vessel density in the chicken chorioallantoic membrane assay in vivo. Thus, combination of protease-sensitive and -insensitive cleavage sites can amplify the degradation of bioresponsive gel materials in ways that boost endothelial cell morphogenesis., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Cell responsive materials are instrumental to regenerative therapies. Here, we report about a novel biohybrid hydrogel that consists of heparin and peptide-conjugated star-shaped poly(ethylene glycol), crosslinked by peptide units that combine matrix metalloproteinase (MMP) sensitivity and cell adhesive modules. Taking advantage of the high affinity of vascular endothelial growth factor to heparin, we illustrate the applicability of our hydrogels as a novel system that is supportive of cellular remodeling and three-dimensional migration of human endothelial cells., (Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new class of biodegradable materials was prepared by combining polyethylene glycol, heparin, and a matrix metalloproteinase-cleavable peptide sequence into a well-defined hydrogel network which mimics native extracellular matrices in its ability to provide mechanical support and chemical signals as well as elicit a dynamic reciprocal response.

Two amphipathic polypeptides were coordinated to the cis positions of a square planar Pt(II) complex in order to provide the metal center with two noncovalent oligomerization domains. This resulted in the formation of new metal-peptide nanoassemblies which are shown to exist as nanometer-sized spheres and fibrils. Construction of these assemblies was based on the 30-residue polypeptide AQ-Pal14 which was designed for its ability to self-assemble into the common protein oligomerization motif of a noncovalent coiled-coil, and modified to contain a metal-binding 4-pyridylalanine residue at its surface. When AQ-Pal14 was reacted with Pt(en)(NO 3) 2, a new metal-peptide complex was formed in which two AQ-Pal14 peptides were coordinated to a single metal center as determined by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electrospray ionization mass spectrometry (ESI-MS). When the reaction mixture was analyzed under nondenaturing conditions by high performance size exclusion chromatography (HPSEC), it was found that all species present eluted at the column void volume, indicating the formation of very large metal-peptide assemblies. This was verified by multiangle light scattering (MALS) which showed that the metal-peptide assemblies have a weight-averaged molecular mass and z-average root-mean-square radius of Mw = (7 +/- 4) x 10 (6) g/mol and Rz = 18 +/- 4 nm, respectively. The presence of such nanometer scale assemblies was confirmed by transmission electron microscopy and atomic force microscopy which showed the existence of both spherical and fibrillar nanostructures.

Metal coordination is used to alter the oligomerization state of a designed peptide structure. The 30-residue polypeptide AQ-Pal14Pal21contains two metal-binding 4-pyridylalanine (Pal) residues on its solvent-exposed surface and exists as a very stable two-stranded alpha-helical coiled-coil. Upon the addition of Pt(en)(NO3)2, a significant conformational change to a metal-bridged, four-helix bundle is seen.

A new class of metal-peptide nanoassemblies has been prepared by combining the principles of supramolecular coordination chemistry with those of de novo protein design., (Copyright 2004 The Royal Society of Chemistry)

Some features of the formation, expression and inheritance of basic genetic and androgen programs of the level of unusual estrogen-binding protein (UEBP) in mature female rat hepatocytes under experimental conditions were investigated. Liver regeneration after partial (2/3) hepatectomy of mature rats was used for generation of a new population of differentiated hepatocytes. The UEBP content was determined by radioligand technique in control liver and at 2, 4, 14 days of liver regeneration and related to the total DNA content as an indicator of cell proliferative activity. It was revealed that the basic genetic program of low UEBP level of hepatocytes of ovariectomized females was fully transferred to daughter cell during cell proliferation and characterized by a temporary elevation of its expression during initial steps of liver regeneration. It was shown that the androgen program of a high UEBP level was completely and stably formed after androgen action in hepatocytes of ovariectomized females and was fully transferred to daughter cells during hepatocyte proliferation. However experimentally formed androgen program of a high UEBP level in female hepatocytes was completely revealed only during early steps of liver regeneration (the 4th day), its expression was essentially declined after regeneration process was over.