Pure Collagen Research Articles

Primary Human Osteocyte Networks in Pure and Modified Collagen Gels.

Osteocytes play a key role in orchestrating bone homeostasis and turnover and, therefore, in vitro investigations with osteocytes are of high relevance for biomaterial and drug testing in future. In this study, collagen type I gels and collagen gels modified with biomimetically mineralized collagen were tested as three-dimensional (3D) environment for the maintenance of the osteocytic phenotype of primary human osteocytes. After cultivation in different collagen gels, cells were analyzed microscopically for the osteocytic phenotype and gene expression of osteocyte marker genes osteocalcin, podoplanin (PDPN)/E11, phosphate regulating endopeptidase homolog, X-linked (PHEX), matrix extracellular phosphoglycoprotein (MEPE), dentin matrix protein 1 (DMP-1), and sclerostin (SOST). Directly after isolation from bone tissue the cells expressed all examined osteocyte markers. After 7 days of 3D cultivation in collagen gels the osteocytic marker genes MEPE and SOST were upregulated and the other marker genes still expressed. Modification of collagen gels with biomimetically mineralized collagen and strontium-doped mineralized collagen prevented the cell-seeded gels from shrinking. Osteocyte morphology was not affected by the gel modification. However, the isolation of RNA from the mineralized gel variants was heavily impaired. Alternatively, the osteocytic differentiation of human osteoblasts in the different collagen gels was examined. Primary human osteoblasts were embedded into the gels and cultivated under osteogenic stimulation. After 14 days of cultivation, embedded osteoblasts showed osteocyte-like morphology and positive staining for DMP-1. Early osteocyte marker genes, such as PDPN/E11 and PHEX, were expressed while the expression of the osteoblast marker gene alkaline phosphatase (ALPL) increased. This ALPL upregulation was partly prevented by modification of collagen gels with mineralized collagen. Impact Statement This research focuses on the in vitro three-dimensional cultivation of primary human osteocytes instead of rodent osteocyte cell lines. Stable in vitro cultures of these regulating cells provide the opportunity to establish co- and triple cultures with osteoblasts and osteoclasts to analyze the cross talk between these cell species and to establish in vitro bone models for the testing of bioactive molecules, growth factors, drugs, and biomaterials.

Controlled degradable chitosan/collagen composite scaffolds for application in nerve tissue regeneration

The biodegradable materials have been widely used for fabricating various scaffolds in the application of peripheral nerve tissue engineering. The porous chitosan/collagen composite scaffolds with different tailored degradation ratio may be a candidate. In the present study, the porous chitosan/collagen composite scaffolds were prepared by controlled lyophylization and phase separation of corresponding composite solutions with different proportion of chitosan and collagen. The scaffolds were investigated via morphology, porosity, liquid uptake, swelling behavior, component, mechanical and In Vitro degradation testing. The cytotoxicity and cytocompatibility of the prepared composite scaffolds were evaluated using L929 fibroblasts, RSC96 cell lines and primary Schwann cells, respectively. The related molecular mechanism was further penetrated by RT-PCR and Western Blot. Finally, the In Vivo degradation behavior and inflammatory reaction were examined by subcutaneous implantation of rabbit. The results showed that the chitosan/collagen composite scaffolds possessed a surface fiber-like structure while inner porosity. Compared to a pure collagen scaffold, the addition of chitosan decreased the mean pore size, liquid uptake and degradation rate, while increased the mechanical property of the composite scaffolds. Physicochemical properties of scaffolds including porosity, swelling behavior and component were found satisfactory for intended application. The chitosan/collagen composite scaffolds showed good cytocompatibility without cytotoxicity. And our results also demonstrated that the chitosan/collagen composite scaffolds could promote the attachment, migration and proliferation of Schwann cells. The In Vivo implantation results indicated that the composites scaffolds showed obviously modulated degradation behavior without causing any inflammatory reaction. Taken together, the developed chitosan/collagen composite scaffolds here may have good potential promising application as scaffolds materials for peripheral nerve regeneration.

Dimension effect: Dendrimer functionalized carbon based nanomaterial mediated collagen scaffold for wound healing application

Carbon-based nanomaterials (CBNs) such as graphene oxide (GO, planar shape-2D), reduced graphene (rGR, planar shape-2D), carbon nanotube (CNT, tubular shape -1D) and fullerene (C60, sphere shape-0D) can offer higher mechanical strength and biocompatibility to scaffold employed in wound healing applications. It is important to understand the role of dimensional aspects of CBNs on the scaffold properties. To contribute to this understanding, this paper reports the effect of dimensional aspects of Triethoxysilane poly (amidoamine) dendrimer generation 3 (TES-PAMAM-G3 or G3) functionalized carbon nanomaterials were introduced in the self-assembly processes of collagen. The prepared CBNs-TES-PAMAM-G3 -collagen scaffolds were characterized through various spectroscopic techniques and used in-vivo wound healing application. Among the CBNs-TES-PAMAM-G3 -collagen scaffolds investigated, a CNT-TES-PAMAM-G3-collagen scaffold showed enhanced mechanical properties (46 times compared to pure collagen), better cell viability and accelerate wound healing process than other scaffolds. Such enhanced mechanical properties for CNT-TES-PAMAM-G3-collagen scaffold can be attributed to the inherent strength and possibilities of alignment of the nanostructure along the linear axis of the collagen through the use of 1D nanotube. These results suggested that the CNT-TES-PAMAM-G3-collagen scaffolds are promising materials for tissue engineering and wound healing application.

A crosslinked collagen membrane versus a non-crosslinked bilayer collagen membrane for supporting osteogenic functions of human bone marrow-multipotent stromal cells.

Barrier membranes are popularly used for guided bone regeneration (GBR). However, more knowledge is needed to assess how these membranes could be of therapeutic value when populated with native multipotent stromal cells (MSCs), particularly in the orthopaedic field. The present manuscript investigated the activities of human bone marrow-multipotent stromal cells (BM-MSCs) when loaded on to two differently structured pure collagen membranes. A crosslinked collagen membrane (CS) was tested versus a non-crosslinked bilayer collagen membrane, Bio-Gide® (BG). Following loading with BM aspirate containing native MSCs, cell attachment to the membranes was examined using electron microscopy and flow cytometry. Furthermore, alkaline phosphatase (ALP) expression and calcium deposition levels were investigated for these BM-aspirate-loaded membranes. Culture-expanded BM-MSCs were also used to load membranes and confirm the MSC functional data. All membranes supported BM-MSC attachment. However, larger numbers of attached BM-MSCs were detected for CS as compared to BG (p = 0.0010). In osteogenic medium, ALP activity was higher for CS than BG (p = 0.0312). Total calcium deposition (not normalised to cell count) was also higher for CS than BG (p = 0.0073). Consistently, the normalised secreted vascular endothelial growth factor A (VEGF-A) levels were higher in BM-MSCs loaded on CS relative to BG (p = 0.0302). Collectively, both collagen membranes supported the osteogenic functions of BM-MSCs. However, CS was found to be overall superior probably since it provided more BM-MSC attachment. These collagen membranes could potentially be used to improve GBR outcomes in orthopaedic applications.

Viscoll collagen solution as a novel bioink for direct 3D bioprinting.

Collagen is one of the most promising materials for 3D bioprinting because of its distinguished biocompatibility. Cell-laden constructs made of pure collagen with or without incorporated growth supplements support engineered constructs persistence in culture and are perfectly suitable for grafting. The limiting factor for direct 3D collagen printing was poor printability of collagen solutions, especially admixed with cells or tissue spheroids. In our study, we showed that concentrated solutions of native collagen branded Viscoll were effective as bioinks with high fidelity performance. Viscoll containing 20, 30, or 40 mg/ml collagen were used for direct extrusion 3D bioprinting to form scaffolds appropriate to support spatial arrangement of tissue spheroids into rigid patterns with resolution of 0.5 mm in details. Incorporated cells demonstrated sufficient viability. Associated rheological study showed that good printability of the collagen solutions correlates with their increased storage modulus value, notably exceeding the loss modulus value. The proper combination of these physical parameters could become technological criteria for manufacturing various collagen bioinks for 3D bioprinting.

Synergistic effect of bovine platelet lysate and various polysaccharides on the biological properties of collagen-based scaffolds for tissue engineering: Scaffold preparation, chemo-physical characterization, in vitro and ex ovo evaluation

Crosslinked 3D porous collagen-polysaccharide scaffolds, prepared by freeze-drying, were modified with bovine platelet lysate (BPL) and evaluated in terms of chemical, physical and biological properties. Natural antibacterial polysaccharides like chitosan, chitin/chitosan-glucan complex and calcium salt of oxidized cellulose (CaOC) incorporated in collagen scaffolds affected not only chemo-physical properties of the composite scaffolds but also improved their biological properties, especially when BPL was presented. Lipophilic BPL formed microspheres in porous scaffolds while reduced by half their swelling ratio. The resistance of collagen sponges to hydrolytic degradation in water depended strongly on chemical crosslinking varying from 60 min to more than one year. According to in-vitro tests, chemically crosslinked scaffolds exhibited a good cellular response, cell–matrix interactions, and biocompatibility of the material. The combination of collagen with natural polysaccharides confirmed a significant positive synergistic effect on cultivation of cells as determined by MTS assay and PicoGreen method, as well as on angiogenesis evaluated by ex ovo Chick Chorioallantoic Membrane (CAM) assay. Contrary, modification only by BLP of pure collagen scaffolds exhibited decreased biocompatibility in comparison to unmodified pure collagen scaffold. We propose that the newly developed crosslinked collagen sponges involving bioactive additives could be used as scaffold for growing cells in systems with low mechanical loading in tissue engineering, especially in dermis replacement, where neovascularization is a crucial parameter for successful skin regeneration.

Spectral fingerprinting of decellularized heart valve scaffolds.

Decellularized heart valves hold promise for their use as bioscaffolds in cardiovascular surgery. Quality assessment of heart valves after decellularization processing and/or storage is time consuming and destructive. Fourier transform infrared spectroscopy (FTIR) allows rapid non-invasive assessment of biomolecular structures in tissues. In this study, IR-spectra taken from different layers of the pulmonary artery trunk and leaflet tissues of decellularized porcine heart valves were compared with those of pure collagen and elastin, the main protein components in these tissues. In addition, spectral changes associated with aging and oxidative damage were investigated. Infrared absorbance spectra of the arteria intima and media layer were found to be very similar, whereas distinct differences were observed when compared with spectra of the externa layer. In the latter, the shape of the CH-stretching vibration region (3050-2800 cm-1) resembled that of pure collagen. Also, pronounced νCOOH and amide-II bands and a relatively high content of α-helical structures in the externa layer indicated the presence of collagen in this layer. The externa layer of the artery appeared to be sensitive to collagenase treatment, whereas the media and intima layer were particularly affected by elastase and not by collagenase treatment. Protein conformational changes after treatment with collagenase were observed in all three layers. Collagenase treatment completely degraded the leaflet tissue sections. Spectra were also collected from scaffolds after 2 and 12 weeks storage at 37 °C, and after induced oxidative damage. Spectral changes related to aging and oxidative damage were particularly evident in the CH-stretching region, whereas the shape of the amide-I band, reflecting the overall protein secondary structure, remained unaltered.

Screening of pathogenic strains of Pseudomonas aeruginosa in wound infections using a mushroom myco-model as a host - a novel approach

Introduction and Aim: The detection of pathogenic strains of Pseudomonas aeruginosa is usually carried out by antimicrobial susceptibility testing, molecular characterisation, selective isolation, 16S rRNA sequencing, immunological assays and through other methods. This study aimed to use mushroom as a host model for detecting pathogenic strains of P. aeruginosa in wound infection. Materials and Methods: The strains of P. aeruginosa from wound infection were isolated. The pathogenic, non- pathogenic and ATCC strains of P. aeruginosa as well as Escherichia coli were injected respectively into the cap region of the mushroom and incubated for the production of lesion. The collagen was extracted from mushroom by salt precipitation method and pure collagen was purchased commercially. The collagen degradation by all the above organisms was detected by performing UV spectrophotometric analysis. The organisms were allowed to grow on medium containing extracted collagen and pure collagen. Results: The lesions were found at the site of the injected region on mushroom cap when injected with pathogenic strain of P. aeruginosa while the rest of the strains failed to produce lesion. The collagen was degraded when infected with the pathogenic strain and the rest of the strains failed to degrade collagen. This is in accordance with the OD value. The medium containing collagen also showed growth only for pathogenic strain of P. aeruginosa. Conclusion: Thus, the study proved that mushroom can be used as a host model to differentiate the pathogenic and non-pathogenic strains of P. aeruginosa from wound infections. Keywords: Collagen; wound infection; mushroom; mycomodel; Pseudomonas aeruginosa.

Effect of mechanical properties on porous calcium phosphate scaffold

Abstract The effect of mechanical properties of porous calcium phosphate scaffold was examined. The scaffold is a temporary supporting structure into the patient's bone defect to enhance the development of new bones because of scaffolding declines. This study focuses on the effect of mechanical properties of porous calcium phosphate (CaP) scaffold using foam replication techniques. Sintering treatment treated at 1150°C and 1250°C were improved and the composite particles od porous calcium phosphate were homogeneously mixed and distributed. The specimen was analyzed under X-ray diffraction, SEM and compressive strength. The X-ray diffraction spectrum shows the presence of Ca10(PO4)6OH2 phases in sintered scaffolds. The formation of rod-like apatite was observed through SEM. An increase in the mechanical properties of scaffolds from 2.2MPa to up to 2.23MPa was found relative to pure collagen scaffold, while the porosity was decreased from 93.2% to 92%, indicating the potential of scaffold for bone tissue engineering or as a bone graft substitute

Synthesis of ultralong hydroxyapatite micro/nanoribbons and their application as reinforcement in collagen scaffolds for bone regeneration

Ultralong hydroxyapatite (HAp) micro/nanoribbons were successfully synthesized by a simple hydrothermal method without using any organic solvents and templates. The ultralong HAp micro/nanoribbons were up to several hundred micrometers in length and 100–400 nm in width. The growth process and mechanism of this micro/nanoribbons were also analyzed in this study. Moreover, the ultralong HAp micro/nanoribbons were used as reinforcement in collagen scaffolds and the HAp/collagen composite scaffolds were fabricated by freeze-drying process without cross-linking. The morphological results demonstrated homogeneous interconnected porous structure in 20 wt% and 35 wt% HAp reinforced scaffolds. The compressive modulus of the 35 wt% HAp/collagen composite was about 6 times that of the pure collagen scaffold. The ultralong HAp reinforced collagen scaffold possesses a porous structure, good flexibility as well as elasticity, and thus it is promising for used as bone repair material.

Investigation of the batch-to-batch inconsistencies of Collagen in PCL-Collagen nanofibers

The application of tissue engineered constructs is an approach in regenerative therapies to support regeneration of damaged muscular tissue. Therefore the development of highly aligned electrospun scaffolds based on polycaprolactone (PCL) and collagen enables a versatile development towards tailor made applications. However, the application of natural polymers like collagen brings the risk of batch-to-batch inconsistencies, which influence the reproducibility of the electrospinning process. Aligned PCL-Collagen nanofibers were fabricated via electrospinning using benign solvents. The spinnability of different collagen batches and polymer concentrations in diluted acetic acid as solvent was investigated. Furthermore spinning parameters and fiber morphology were investigated in order to determine the most stable spinning conditions and analyze the batch-to-batch variations. Finally the effect of the solution temperature and the time of pure collagen in solution were investigated, to complete the analysis of the influences on the spinning behavior.

Modulation of the Self-Assembly of Collagen by Phytic Acid: An In Vitro Study

Phytic acid, containing a myoinositol ring coupled with six phosphate groups, can react with the amino groups of collagen to regulate their self-assembly behavior. The aim of this research is to evaluate the effects of phytic acid on the selfassembly behavior of collagen, the structures and properties of the resulting fibrils and hydrogels. Turbidity and chloramine T assay suggested that phytic acid could improve the self-assembly kinetics and degree of collagen, and the optimal ratio of phytic acid/collagen was 1/1 (w/w). Scanning electron microscopy (SEM) analysis indicated that co-fibrils of collagen with phytic acid are more slender than that of pure collagen, and transmission electron microscopy (TEM) reveals that the characteristic D-periodicity of collagen fibrils is not affected by phytic acid. Besides, differential scanning calorimetry (DSC) and rheology revealed that the thermal stability of collagen fibrils and the viscoelasticity of collagen hydrogels could be improved by phytic acid and the optimal ratio of phytic acid/collagen is 1/1 (w/w).

The use of small angle light scattering in assessing strain induced collagen degradation in arterial tissue ex vivo

Collagen is the predominant load bearing component in many soft tissues including arterial tissue and is therefore critical in determining the mechanical integrity of such tissues. Degradation of collagen fibres is hypothesized to be a strain dependent process whereby the rate of degradation is affected by the magnitude of strain applied to the collagen fibres. The aim of this study is to investigate the ability of small angle light scattering (SALS) imaging to identify strain dependent degradation of collagen fibres in arterial tissue ex vivo, and determine whether a strain induced protection mechanism exists in arterial tissue as observed in pure collagen and other collagenous tissues. SALS was used in combination with histological and second harmonic generation (SHG) analysis to determine the collagen fibre architecture in arterial tissue subjected to strain directed degradation. SALS alignment analysis identified statistically significant differences in fibre alignment depending on the strain magnitude applied to the tissue. These results were also observed using histology and SHG. Our findings suggest a strain protection mechanism may exist for arterial collagen at intermediate strain magnitudes between 0% and 25%. These findings may have implications for the onset and progression of arterial disease where changes in the mechanical environment of arterial tissue may lead to changes in the collagen degradation rate.

Pure type-1 collagen application to third molar extraction socket reduces postoperative pain score and duration and promotes socket bone healing.

Extraction of the third molar may cause post-operative complications. This study assessed whether application of pure type-1 collagen to the third molar extraction socket can reduce post-operative pain score and duration and promote socket bone healing. Fourteen patients who underwent 20 bilateral and symmetric third molar extractions were included in this study. After two tooth extractions at two different occasions in the same patient, one socket was filled with pure type-1 collagen (experimental group, n=20) and the other socket received nothing but the blood clot (control group, n=20). The post-operative pain score and duration, mouth-opening limitation, and the bone density at the socket site were assessed at weeks 1, 2, 4, and 8 after tooth extraction. Patients in the experimental group had a significantly lower mean post-operative pain score (2.6±1.2) than patients in the control group (4.7±2.0), and had a significantly shorter post-operative pain duration (2.7±1.4 days) than patients in the control group (3.7±1.8 days). We also observed a significantly lower frequency of mouth-opening limitation in 20 experimental-group patients (45%) than in 20 control-group patients (90%, P=0.007). Moreover, a significantly higher mineralization ratio (10.2%) was found in the experimental socket site than in the control socket site. Application of pure type-1 collagen to the third molar extraction socket can reduce post-operative pain score and duration, decrease the frequency of mouth-opening limitation, and increase mineralization ratio at the extraction socket site.

Development of Young’s modulus for collagen thin films reinforced with ZnO nanorods probed by Atomic force microscopy

Zinc Oxide (ZnO) nanorods have been prepared and proposed for collagen Type I reinforcement. The insertion of ZnO has been confirmed by an x-ray Diffraction pattern. A nano-indentation technique implemented through an Atomic Force Microscopy has been effectively handled to probe a mechanical behavior of soft tissue like collagen. Measurements at different temperatures for collagen thin films filled with different amounts of ZnO reveals that ZnO significantly develops Young’s modulus from 9 GPa to 18 GPa. Without ZnO, the temperature increment leads to the dehydration of pure collagen while the reinforced ones were still elastic for cell growth. ZnO-reinforced collagen has, therefore, been improved both inherent rigidity and its stability against ambient temperature. The finding in this work suggests that nanoscale ZnO is good candidate for collagen reinforcement which is crucial for tissue engineering technology.

Fabrication of Stand-Alone Cell-Laden Collagen Vascular Network Scaffolds Using Fugitive Pattern-Based Printing-Then-Casting Approach.

Vascular networks are of great significance in tissue engineering and viewed as the first step to fabricate human tissues. Although various techniques have been investigated to create vascular and vascular-like networks, the fabrication of stand-alone pure collagen-based vascular constructs is still a challenge because of the poor extrudability, weak mechanical property, and long cross-linking time of pure collagen solutions. In this study, a fugitive pattern-based printing-then-casting approach is investigated. The proposed alginate-based fugitive ink has excellent mechanical strength (by adding Laponite nanoclay), printability (by adding Laponite nanoclay), and controllable gelation rate (by adding disodium hydrogen phosphate). Using this fugitive ink, complex vascular-like structures can be easily printed and cross-linked in Laponite EP bath as fugitive vascular tree patterns. Each fugitive vascular tree pattern is then embedded in a gelatin bath to make a gelatin mold with the tree patterns. With the help of sodium citrate, the fugitive vascular tree pattern is liquefied and removed to create the gelatin mold with vascular channels. Finally, a stand-alone collagen vascular network scaffold embedded with fibroblasts can be fabricated by casting the cell-laden collagen suspension into the gelatin mold and releasing it from the mold at 37 °C. The cell-related investigations indicate that the cells grow and spread well in the pure collagen vascular network scaffold. The proposed hybrid printing-then-casting approach also provides a feasible technology to fabricate with materials having low viscosity, long gelation time, and poor mechanical property.

Strain mediated enzymatic degradation of arterial tissue: Insights into the role of the non-collagenous tissue matrix and collagen crimp

Collagen fibre remodelling is a strain dependent process which is stimulated by the degradation of existing collagen. To date, literature has focussed on strain dependent degradation of pure collagen or structurally simple collagenous tissues, often overlooking degradation within more complex, heterogenous soft tissues. The aim of this study is to identify, for the first time, the strain dependent degradation behaviour and mechanical factors influencing collagen degradation in arterial tissue using a combined experimental and numerical approach.To achieve this, structural analysis was carried out using small angle light scattering to determine the fibre level response due to strain induced degradation. Next, strain dependent degradation rates were determined from stress relaxation experiments in the presence of crude and purified collagenase to determine the tissue level degradation response. Finally, a 1D theoretical model was developed, incorporating matrix stiffness and a gradient of collagen fibre crimp to decouple the mechanism behind strain dependent arterial degradation.SALS structural analysis identified a strain mediated degradation response in arterial tissue at the fibre level not dissimilar to that found in literature for pure collagen. Interestingly, two distinctly different strain mediated degradation responses were identified experimentally at the tissue level, not seen in other collagenous tissues. Our model was able to accurately predict these experimental findings, but only once the load bearing matrix, its degradation response and the gradient of collagen fibre crimp across the arterial wall were incorporated. These findings highlight the critical role that the various tissue constituents play in the degradation response of arterial tissue. Statement of SignificanceCollagen fibre architecture is the dominant load bearing component of arterial tissue. Remodelling of this architecture is a strain dependent process stimulated by the degradation of existing collagen. Despite this, degradation of arterial tissue and in particular, arterial collagen, is not fully understood or studied. In the current study, we identified for the first time, the strain dependent degradation response of arterial tissue, which has not been observed in other collagenous tissues in literature. We hypothesised that this unique degradation response was due to the complex structure observed in arterial tissue. Based on this hypothesis, we developed a novel numerical model capable of explaining this unique degradation response which may provide critical insights into disease development and aid in the design of interventional medical devices.

Effect of Multilaminate Small Intestinal Submucosa as a Barrier Membrane on Bone Formation in a Rabbit Mandible Defect Model.

A barrier membrane (BM) is essential for guided bone regeneration (GBR) procedures. Absorbable BMs based on collagen have been widely applied clinically due to their excellent biocompatibility. The extracellular matrix (ECM) provides certain advantages that can compensate for the rapid degradation and insufficient mechanical strength of pure collagen membrane due to the porous scaffold structure. Recently, small intestinal submucosa (SIS), one of the most widely used ECM materials, has drawn much attention in bone tissue engineering. In this study, we adopted multilaminate SIS (mSIS) as a BM and evaluated its in vivo and in vitro properties. mSIS exhibited a multilaminate structure with a smooth upper surface and a significantly coarser bottom layer according to microscopic observation. Tensile strength was 13.10 ± 2.56 MPa. In in vivo experiments, we selected a rabbit mandibular defect model and subcutaneous implantation to compare osteogenesis and biodegradation properties with one of the most commonly used commercial collagen membranes. mSIS was retained for up to 3 months and demonstrated longer biodegradation time than commercial collagen membrane. Quantification of bone regeneration revealed significant differences in each group. Micro-computed tomography (micro-CT) revealed that the quantity and maturity of bones in the mSIS group were significantly higher than those in the blank control group (P < 0.05) and were similar to those in a commercial collagen membrane group (P > 0.05) at 4 and 12 weeks after surgery. Hematoxylin and eosin staining revealed large amounts of mature lamellar bone at 12 weeks in mSIS and commercial collagen membrane groups. Therefore, we conclude that mSIS has potential as a future biocompatible BM in GBR procedures.

Preparation and characterization of novel poly (vinyl alcohol)/collagen double-network hydrogels

Hydrogels prepared by conventional methods show poor performance in many aspects. Many double network (DN) hydrogels prepared by crosslinking agents have disadvantages such as toxicity. In this work, we prepared novel DN hydrogels with fish-originated collagen (Col) and poly (vinyl alcohol) (PVA), in which self-assembly of collagen and self-crosslinking of PVA were achieved. Infrared spectra indicated the existence of double network with chemical interactions between Col and PVA. X-ray diffraction (XRD) patterns showed that characteristic peak of freeze-thaw PVA in DN hydrogel was retained. Scanning electron microscope (SEM) images before and after degradation and swelling property tests indicated that the morphology of the hydrogel was a compact meshwork, which is consistent with the high water-retention rate. The degradation rate of the DN hydrogels was controlled by the ratio of Col and PVA. Compared with a pure collagen hydrogels, the stress of DN hydrogels was greatly enhanced from 6 to 33 kPa at a strain of 40%. This study indicates that DN hydrogels prepared by Col and PVA are an ideal biomaterial for tissue engineering.

Elastic compliance of fibrillar assemblies in type I collagen

Fibrillary assemblies of Type I collagen find important applications in tissue engineering and as matrices for biophysical studies. The mechanical and structural properties of these structures are governed by factors such as protein concentration, temperature, pH and ionic strength. This study reports on an impedance based analysis of the elastic compliance of fibrillary assemblies of Type I collagen using quartz crystal microbalance with dissipation (QCM-D) at a fundamental frequency of 5 MHz and overtones (n = 3,5,7,9,11). Here, In situ partial fibrillation of the adsorbing collagen followed by its fibrillary assemblies on hydrophilic gold coated quartz surface have been crosslinked using Gallic acid (GA), Chromium (III) gallate (Cr-GA), Catechin (Cat), Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) and Oxazolidine (Ox). This approach allows direct comparison of how viscoelastic properties track the structural evolution of the fiber and network length scales. The collagen crosslinking shows significant positive impact on the protein's mechanical behaviour and on the type of crosslinking agents used. The elastic modulus increases as collagen <GA < THPS < Cr-GA < Cat < Ox. Atomic force microscopic studies on the adsorbed collagen after cross linking confirmed the presence of fibrous assemblies.The results indicate stabilization and reinforcement through strong physical entanglement between the molecules of collagen as well as chemical interaction between collagen matrix and fibrils during cross linking. The elastic compliance evaluated from ΔDissipation/Δfreq. from QCM-D showed that cross linking with GA, Cr-GA and Ox resulted in flexible fibrillary network while agents like THPS and Cat showed elastic moduli similar to that of pure collagen. Results suggest that optimal collagen-crosslinking agent ratio and degree of crosslinking of collagen can help tailor the mechanical properties for specific applications in design of bio-materials of these composites.