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Medical Device Applications for Collagen
This brochure provides a overview of the numerous collagen-based medical device applications that Collagen Solutions can support.
Medical Grade Soluble Collagen Benefits
This brochure summarizes the numerous soluble collagen applications and the benefits of working with a medical grade, highly purified collagen source. To order, click here.
Off-the-Shelf Collagen Products
This brochure describes all of the standard collagen products that are supplied by Collagen Solutions. To order, click here.
Regenerative Orthopaedic Solutions
This brochure highlights our experience and expertise in the development of orthobiologics, including bovine bone chips, Bone Graft Substitute, collagen scaffolds, decellularized ECM, collagen coatings, collagen particles, dressings & grafts, and flowable matrices.
Safe & Reliable Bovine Pericardium for Medical Devices
This brochure highlights our Quality and Logisitics standards and capabilities of our tissue procurement, processing, and delivery.
Collagen Function Technical Resources
3D Gel Formation Protocol
This video demonstrates the steps taken to form a 3D gel using our soluble collagen and titration buffer. To order, click here.
Atelo Soluble Collagen White Paper
This white paper provides atelo collagen specifications, storage requirements, and protocols for use. To order, click here.
Biomaterials to Progress Research to Clinic
This technical highlight summarizes the unique physical properties of collagen and the benefits of using medical grade collagen transition technologies into the clinic. To order, click here.
Bovine Tendon Long Fibre Powder White Paper
This white paper provides collagen specifications, storage requirements, and application details for long fibre milled powder from tendon.
Collagen for Cell Delivery
This review provides an overview of numerous applications where collagen has been investigated as delivery vehicle for cell therapies.
Collagen for Drug Delivery
This review provides an overview collagen carriers for a variety of drug delivery applications.
Exclusive IP position for a Unique Pericardium Biomaterial
This technical highlight summarizes the unique pericardium biomaterial properties and their advantages to percutaneous delivery devices for TAVR, TMVR & other transcatheter cardiovascular therapies.
Fibrillar Collagen White Paper
This white paper provides fibrillar collagen specifications, storage requirements, and protocols for use.
Lyophilized Polymeric Collagen White Paper
This white paper provides collagen specifications, storage requirements, and application details for neutral polymeric powder from tendon.
Support for Bovine Collagen in Medical Devices
This literature review addresses the advantages of using collagen in medical devices and clarifies the perceived risks associated with the use of bovine sources.
Collagen Resources Publications
A Methylcellulose and Collagen Based Temperature Responsive Hydrogel Promotes Encapsulated Stem Cell Viability and Proliferation In Vitro
With the number of stem cell-based therapies emerging on the increase, the need for novel and efficient delivery technologies to enable therapies to remain in damaged tissue and exert their therapeutic benefit for extended periods, has become a key requirement for their translation....read more
With the number of stem cell-based therapies emerging on the increase, the need for novel and efficient delivery technologies to enable therapies to remain in damaged tissue and exert their therapeutic benefit for extended periods, has become a key requirement for their translation. Hydrogels, and in particular, thermoresponsive hydrogels, have the potential to act as such delivery systems. Thermoresponsive hydrogels, which are polymer solutions that transform into a gel upon a temperature increase, have a number of applications in the biomedical field due to their tendency to maintain a liquid state at room temperature, thereby enabling minimally invasive administration and a subsequent ability to form a robust gel upon heating to physiological temperature. However, various hurdles must be overcome to increase the clinical translation of hydrogels as a stem cell delivery system, with barriers including their low tensile strength and their inadequate support of cell viability and attachment. In order to address these issues, a methylcellulose based hydrogel was formulated in combination with collagen and beta glycerophosphate, and key development issues such as injectability and sterilization processes were examined. The polymer solution underwent thermogelation at ~36 °C as determined by rheological analysis, and when gelled, was sufficiently robust to resist significant disintegration in the presence of phosphate buffered saline (PBS) while concomitantly allowing for diffusion of methylene blue dye solution into the gel. We demonstrate that human mesenchymal stem cells (hMSCs) encapsulated within the gel remained viable and showed raised levels of dsDNA at increasing time points, an indication of cell proliferation. Mechanical testing showed the “injectability”, i.e. force required for delivery of the polymer solution through devices such as a syringe, needle or catheter. Sterilization of the freeze-dried polymer wafer via gamma irradiation showed no adverse effects on the formed hydrogel characteristics. Taken together, these results indicate the potential of this gel as a clinically translatable delivery system for stem cells and therapeutic molecules in vivo.Read less
A Micro-Architecturally Biomimetic Collagen Template for Mesenchymal Condensation Based Cartilage Regeneration
The unique arcade-like orientation of collagen fibers enables cartilage to bear mechanical loads. In this study continuous-length aligned collagen threads were woven to emulate the interdigitated arcade structure of the cartilage....read more
The unique arcade-like orientation of collagen fibers enables cartilage to bear mechanical loads. In this study continuous-length aligned collagen threads were woven to emulate the interdigitated arcade structure of the cartilage. The weaving pattern provided a macropore network within which micromass cell pellets were seeded to take advantage of mesenchymal condensation driven chondrogenesis. Compression tests showed that the baseline scaffold had a modulus of 0.83 ± 0.39 MPa at a porosity of 80%. The modulus of pellet seeded scaffolds increased by 60% to 1.33 ± 0.37 MPa after 28 days of culture, converging to the modulus of the native cartilage. The scaffolds displayed duress under displacement controlled low-cycle fatigue at 15% strain amplitude such that load reduction stabilized at 8% after 4500 cycles of loading. The woven structure demonstrated a substantial elastic recoil where 40% mechanical strain was close to completely recovered following unloading. A robust chondrogenesis was observed as evidenced by positive staining for GAGs and type II collagen and aggrecan. Dimethyl methylene blue and sircol assays showed GAGs and collagen productions to increase from 3.36 ± 1.24 and 31.46 ± 3.22 at day 3 to 56.61 ± 12.12 and 136.70 ± 12.29 μg/μg of DNA at day 28 of culture. This woven collagen scaffold holds a significant potential for cartilage regeneration with shorter in vitro culture periods due to functionally sufficient mechanical robustness at the baseline. In conclusion, the mimicry of cartilage’s arcade architecture resulted in substantial improvement of mechanical function while enabling one of the first pellet delivery platforms enabled by a macroporous network.Read less
Acellular Hydroxyapatite-Collagen Scaffolds Support Angiogenesis and Osteogenic Gene Expression in an Ectopic Murine Model: Effects of Hydroxyapatite Volume Fraction
Acellular hydroxyapatite (HA) reinforced collagen scaffolds were previously reported to induce angiogenesis and osteogenesis after ectopic implantation but the effect of the HA volume fraction was not investigated....read more
Acellular hydroxyapatite (HA) reinforced collagen scaffolds were previously reported to induce angiogenesis and osteogenesis after ectopic implantation but the effect of the HA volume fraction was not investigated. Therefore, the objective of this study was to investigate the effect of HA volume fraction on in vivo angiogenesis and osteogenesis in acellular collagen scaffolds containing 0, 20, and 40 vol % HA after subcutaneous ectopic implantation for up to 12 weeks in mice. Endogenous cell populations were able to completely and uniformly infiltrate the entire scaffold within 6 weeks independent of the HA content, but the cell density was increased in scaffolds containing HA versus collagen alone. Angiogenesis, remodeling of the original scaffold matrix, mineralization, and osteogenic gene expression were evident in scaffolds containing HA, but were not observed in collagen scaffolds. Moreover, HA promoted a dose-dependent increase in measured vascular density, cell density, matrix deposition, and mineralization. Therefore, the results of this study suggest that HA promoted the recruitment and differentiation of endogenous cell populations to support angiogenic and osteogenic activity in collagen scaffolds after subcutaneous ectopic implantation.Read less
Age Dependent Differences in Collagen Alignment of Glutaraldehyde Fixed Bovine Pericardium
Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4–7 days old) is advantageously thinner and is considered as an alternative to that from adult animals....read more
Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4–7 days old) is advantageously thinner and is considered as an alternative to that from adult animals. Here, the structures of adult and neonatal bovine pericardium tissues fixed with glutaraldehyde are characterized by synchrotron-based small angle X-ray scattering (SAXS) and compared with the mechanical properties of these materials. Significant differences are observed between adult and neonatal tissue. The glutaraldehyde fixed neonatal tissue has a higher modulus of elasticity (83.7 MPa) than adult pericardium (33.5 MPa) and a higher normalized ultimate tensile strength (32.9 MPa) than adult pericardium (19.1 MPa). Measured edge on to the tissue, the collagen in neonatal pericardium is significantly more aligned (orientation index (OI) 0.78) than that in adult pericardium (OI 0.62). There is no difference in the fibril diameter between neonatal and adult pericardium. It is shown that high alignment in the plane of the tissue provides the mechanism for the increased strength of the neonatal material. The superior strength of neonatal compared with adult tissue supports the use of neonatal bovine pericardium in heterografts.Read less
Biologic and Synthetic Grafts in the Reconstruction of Large to Massive Rotator Cuff Tears
Rotator cuff injuries are common in both young and elderly patients. Despite improvements in instrumentation and surgical techniques, the failure rates following tendon reconstruction remain unacceptably high. To improve outcomes, graft patches have been developed to provide mechanical strength and to furnish a scaffold for biologic growth across the delicate tendon-bone junction....read more
Rotator cuff injuries are common in both young and elderly patients. Despite improvements in instrumentation and surgical techniques, the failure rates following tendon reconstruction remain unacceptably high. To improve outcomes, graft patches have been developed to provide mechanical strength and to furnish a scaffold for biologic growth across the delicate tendon-bone junction. Although no patch effectively re-creates the structured, highly organized system of prenatal tendon development, augmenting rotator cuff repair may help restore native tendon-to-bone attachment while reproducing the mechanical and biologic properties of native tendon. An understanding of biologically and synthetically derived grafts, along with knowledge of the preliminary data available regarding their combined use with growth factors and stem cells, is needed to improve management and treatment outcomes. The current literature has not been consistent in showing patch augmentation to be beneficial over traditional repair, but novel scaffolding materials may help facilitate rotator cuff tendon repair that is histologically and biomechanically comparable to native tendon.Read less
Bovine Pericardium Based Non-Cross Linked Collagen Matrix for Successful Root Coverage, a Clinical Study in Human
The aim of this study was to clinically assess the capacity of a novel bovine pericardium based, non-cross linked collagen matrix in root coverage. 62 gingival recessions of Miller class I or II were treated. The matrix was adapted underneath a coronal repositioned split thickness flap. Clinical values were assessed at baseline and after six months....read more
The aim of this study was to clinically assess the capacity of a novel bovine pericardium based, non-cross linked collagen matrix in root coverage. 62 gingival recessions of Miller class I or II were treated. The matrix was adapted underneath a coronal repositioned split thickness flap. Clinical values were assessed at baseline and after six months. The mean recession in each patient was 2.2 mm at baseline. 6 Months after surgery 86.7% of the exposed root surfaces were covered. On average 0,3 mm of recession remained. The clinical attachment level changed from 3.5 ± 1.3 mm to 1,8 ( ± 0,7) mm during the observational time period. No statistically significant difference was found in the difference of probing depth. An increase in the width of gingiva was significant. With a baseline value of 1.5 ± 0.9 mm an improvement of 2.4 ± 0.8 mm after six month could be observed. 40 out of 62 recessions were considered a thin biotype at baseline. After 6 months all 62 sites were assessed thick. The results demonstrate the capacity of the bovine pericardium based non-cross linked collagen matrix for successful root coverage. This material was able to enhance gingival thickness and the width of keratinized gingiva. The percentage of root coverage achieved thereby is comparable to existing techniques. This method might contribute to an increase of patient's comfort and an enhanced aesthetical outcome.Read less
Collagen as a Biological Glue for Cell Spraying in Wound Healing
In the US, about 6.5 million patients are treated for chronic wounds and burns, with a yearly financial burden of over $25 billion dollars. Worldwide, burns result in 265,000 deaths per year. Currently, the gold standard for wound therapy is the use of either split- or full-thickness autologous skin grafts....read more
In the US, about 6.5 million patients are treated for chronic wounds and burns, with a yearly financial burden of over $25 billion dollars. Worldwide, burns result in 265,000 deaths per year. Currently, the gold standard for wound therapy is the use of either split- or full-thickness autologous skin grafts. Although widely used with positive outcomes, there are still disadvantages, including lack of healthy donor sites, risk of donor site infection, and the challenge of handling such delicate scaffolds. A more recent approach that simplifies the wound healing procedure is the application of autologous cells via a spray device. Cell harvesting is considerably less invasive than skin harvesting, increasing the prospect of treating extensive wounds, even if donor sites are not available. The downside to cell spraying, however, is that cells have the tendency to fall off the wound site without a means to adhere. Collagen is a protein found naturally in the body, comprising about 75% of the skin. It is an essential component of the extracellular matrix and possesses wound-healing and hemostatic properties. Poly(ethylene) glycol (PEG) is used regularly in tissue engineering and has a “sticky” quality that can be used to enhance the adhesive property of collagen. This purpose of this work is to design a collagen/PEG formulation for adhering cells onto a wound site and investigate whether the forces of spraying affects the survival of embedded cells.Read less
Collagen Fibril Strain, Recruitment and Orientation for Pericardium Under Tension and the Effect of Cross Links
The structural response of collagen fibrils in pericardium and other tissues when subjected to strain and the effect of cross linking on those structural changes are not well understood. Specifically, there is uncertainty about whether natural cross links of glycosaminoglycan (GAG) and synthetic cross links of glutaraldehyde have a mechanical function....read more
The structural response of collagen fibrils in pericardium and other tissues when subjected to strain and the effect of cross linking on those structural changes are not well understood. Specifically, there is uncertainty about whether natural cross links of glycosaminoglycan (GAG) and synthetic cross links of glutaraldehyde have a mechanical function. Bovine pericardium was treated either with chondroitinase ABC to remove natural cross links or with glutaraldehyde to form synthetic cross links. The collagen fibril orientation index (OI) and D-spacing was measured on pericardium subjected to strain using synchrotron-based small angle X-ray scattering (SAXS). Under strain the collagen fibrils become much more oriented in the direction of the strain, with OI increasing from 0.25 to 0.89 in chondroitinase ABC-treated material, 0.22 to 0.93 in native material, and 0.22 to 0.77 in the glutaraldehyde-treated material. The proportion of fibrils that are recruited during stress varies from 36% in chondroitinase ABC-treated material, 12% in native material, to 45% in the glutaraldehyde-treated material. The increase in D-spacing shows the individual fibrils are strained in chondroitinase ABC-treated material by 2.4% on average or 4.6% for those in the direction of applied strain, in native material, 2.7% and 4.1%, respectively, and in the glutaraldehyde-treated material, 3.2% and 6.4%, respectively. Glutaraldehyde cross links are, therefore, shown to constrain the collagen fibrils and link them together mechanically. GAGs do not have such a marked mechanical effect; contrarily, the nature of internal structural responses to strain suggests that GAGs may have a lubricating rather than a binding effect.Read less
Collagen Substrate Stiffness Anisotropy Affects Cellular Elongation, Nuclear Shape, and Stem Cell Fate Toward Anisotropic Tissue Lineage
Rigidity of substrates plays an important role in stem cell fate. Studies are commonly carried out on isotropically stiff substrate or substrates with unidirectional stiffness gradients....read more
Rigidity of substrates plays an important role in stem cell fate. Studies are commonly carried out on isotropically stiff substrate or substrates with unidirectional stiffness gradients. However, many native tissues are anisotropically stiff and it is unknown whether controlled presentation of stiff and compliant material axes on the same substrate governs cytoskeletal and nuclear morphology, as well as stem cell differentiation. In this study, electrocompacted collagen sheets are stretched to varying degrees to tune the stiffness anisotropy (SA) in the range of 1 to 8, resulting in stiff and compliant material axes orthogonal to each other. The cytoskeletal aspect ratio increased with increasing SA by about fourfold. Such elongation was absent on cellulose acetate replicas of aligned collagen surfaces indicating that the elongation was not driven by surface topography. Mesenchymal stem cells (MSCs) seeded on varying anisotropy sheets displayed a dose-dependent upregulation of tendon-related markers such as Mohawk and Scleraxis. After 21 d of culture, highly anisotropic sheets induced greater levels of production of type-I, type-III collagen, and thrombospondin-4. Therefore, SA has direct effects on MSC differentiation. These findings may also have ramifications of stem cell fate on other anisotropically stiff tissues, such as skeletal/cardiac muscles, ligaments, and bone.Read less
Cross Linking and Fibril Alignment in Pericardium
The influence of natural cross linking by glycosaminoglycan (GAG) on the structure of collagen in animal tissue is not well understood. Neither is the effect of synthetic cross linking on collagen structure well understood in glutaraldehyde treated collagenous tissue for medical implants and commercial leather....read more
The influence of natural cross linking by glycosaminoglycan (GAG) on the structure of collagen in animal tissue is not well understood. Neither is the effect of synthetic cross linking on collagen structure well understood in glutaraldehyde treated collagenous tissue for medical implants and commercial leather. Bovine pericardium was treated with chondroitinase ABC to remove natural cross links or treated with glutaraldehyde to form synthetic cross links. The collagen fibril alignment was measured using synchrotron based small angle X-ray scattering (SAXS) and supported by atomic force microscopy (AFM) and histology. The alignment of the collagen fibrils is affected by the treatment. Untreated pericardium has an orientation index (OI) of 0.19 (0.06); the chondroitinase ABC treated material is similar with an OI of 0.21 (0.08); and the glutaraldehyde treated material is less aligned with an OI of 0.12 (0.05). This difference in alignment is also qualitatively observed in atomic force microscopy images. Crimp is not noticeably affected by treatment. It is proposed that glutaraldehyde cross linking functions to bind the collagen fibrils in a network of mixed orientation tending towards isotropic, whereas natural GAG cross links do not constrain the structure to quite such an extent.Read less
Ectopic Bone Formation in Rapidly Fabricated Acellular Injectable Dense Collagen-Bioglass Hybrid Scaffolds via Gel Aspiration-Ejection
Gel aspiration-ejection (GAE) has recently been introduced as an effective technique for the rapid production of injectable dense collagen (IDC) gel scaffolds with tunable collagen fibrillar densities (CFDs) and microstructures...read more
Gel aspiration-ejection (GAE) has recently been introduced as an effective technique for the rapid production of injectable dense collagen (IDC) gel scaffolds with tunable collagen fibrillar densities (CFDs) and microstructures. Herein, a GAE system was applied for the advanced production and delivery of IDC and IDC-Bioglass(®) (IDC-BG) hybrid gel scaffolds for potential bone tissue engineering applications. The efficacy of GAE in generating mineralizable IDC-BG gels (from an initial 75-25 collagen-BG ratio) produced through needle gauge numbers 8G (3.4 mm diameter and 6 wt% CFD) and 14G (1.6 mm diameter and 14 wt% CFD) was investigated. Second harmonic generation (SHG) imaging of as-made gels revealed an increase in collagen fibril alignment with needle gauge number. In vitro mineralization of IDC-BG gels was confirmed where carbonated hydroxyapatite was detected as early as day 1 in simulated body fluid, which progressively increased up to day 14. In vivo mineralization of, and host response to, acellular IDC and IDC-BG gel scaffolds were further investigated following subcutaneous injection in adult rats. Mineralization, neovascularization and cell infiltration into the scaffolds was enhanced by the addition of BG and at day 21 post injection, there was evidence of remodeling of granulation tissue into woven bone-like tissue in IDC-BG. SHG imaging of explanted scaffolds indicated collagen fibril remodeling through cell infiltration and mineralization over time. In sum, the results suggest that IDC-BG hybrid gels have osteoinductive properties and potentially offer a novel therapeutic approach for procedures requiring the injectable delivery of a malleable and dynamic bone graft that mineralizes under physiological conditions.Read less
Effect of Actuating Cell Source on Locomotion of Organic Living Machines with Electrocompacted Collagen Skeletons
In robotics, there is a need for small scale, compliant actuators for use in medical applications or minimally invasive environmental monitoring. Biohybrid devices offer one solution to this need by using muscle cells to actuate compliant scaffolds....read more
In robotics, there is a need for small scale, compliant actuators for use in medical applications or minimally invasive environmental monitoring. Biohybrid devices offer one solution to this need by using muscle cells to actuate compliant scaffolds. Such devices typically use biocompatible synthetic polymers as compliant scaffolds, which require additional processing steps to promote cellular alignment and attachment. Instead, electrocompacted and aligned collagen (ELAC) can be used as a completely organic scaffold, requiring no additional processing steps, with alignment being innately promoted by the topography. Locomotive living machines have been fabricated in this study using ELAC scaffolds. Devices have been produced using either primary cardiomyocytes or primary skeletal muscle cells isolated from chick embryos as actuators. When tested under the same conditions, skeletal muscle cell powered devices were approximately an order of magnitude faster, having a mean velocity of 77.6 ± 86.4 μm min–1, compared to 9.34 ± 6.69 μm min–1 for cardiomyocyte powered devices. In conclusion, completely organic living machines have been fabricated using electrocompacted collagen skeletons, and it was found that skeletal muscle powered devices were significantly faster than cardiomyocyte powered devices.Read less
Evaluation of a Collagen-Coated, Resporbable Fiber Scaffold Loaded with a Peptide Basic Fibroblast Growth Factor Mimetic in a Sheep Model of Rotator Cuff Repair
A new scaffold design combined with a peptide growth factor was tested prospectively for safety and for improved tendon healing in sheep. The infraspinatus tendon was detached and then surgically repaired to the humerus using sutures and anchors in 50 adult sheep....read more
A new scaffold design combined with a peptide growth factor was tested prospectively for safety and for improved tendon healing in sheep. The infraspinatus tendon was detached and then surgically repaired to the humerus using sutures and anchors in 50 adult sheep. The repairs in 40 of these sheep were reinforced with a scaffold containing F2A, a peptide mimetic of basic fibroblast growth factor. The sheep were examined after 8 or 26 weeks with magnetic resonance imaging, full necropsy, and histopathologic analysis. A second cohort of 30 sheep underwent surgical repair—20 with scaffolds containing F2A. The 30 shoulders were tested mechanically after 8 weeks. The scaffold and F2A showed no toxicity. Scaffold-repaired tendons were 31% thicker than surgically repaired controls (P = .037) at 8 weeks. There was more new bone formed at the tendon footprint in sheep treated with F2A. Surgically repaired tendons delaminated from the humerus across 14% of the footprint area. The extent of delamination decreased to 1.3% with increasing doses of F2A (P = .004). More of the repair tissue at the footprint was tendon-like in the peptide-treated sheep. On mechanical testing, only 7 shoulders tore at the repair site. The repairs in the other 23 shoulders were already stronger than the midsubstance tendon at 8 weeks. The new scaffold and peptide safely improved tendon healing.Read less
Evaluation of Fibroblast Behavior on a Collagen-Based Spray Adhesive
The ongoing search for a suitable surgical adhesive is fueled by deficiencies of current products such as mechanical properties, bonding strengths and curing times. An adhesive in a sprayable form has much appeal for ease of application. Collagen has shown great potential as an adhesive for its biocompatibility, blood absorption and hemostatic properties1....read more
The ongoing search for a suitable surgical adhesive is fueled by deficiencies of current products such as mechanical properties, bonding strengths and curing times. An adhesive in a sprayable form has much appeal for ease of application. Collagen has shown great potential as an adhesive for its biocompatibility, blood absorption and hemostatic properties1. The addition of an alcohol results in an esterification reaction with collagen carboxylic groups, producing methylated collagen, which is soluble, and therefore sprayable, at physiological pH. Introducing a multifunctional polymer such as polyethylene glycol (PEG) cross-links collagen, forming a bond between two surfaces. We aim to show the biocompatibility of a potential sprayable adhesive composed of gelled methylated collagen with succinimidyl glutarate (SG) and thiol (SH) PEGs by observing the proliferation and viability of fibroblast cells entrapped within the collagen/PEG matrix.Read less
Formulation of Poly(Ethylene Glycol) Hydrogens for Drug Delivery
Although described as a “bioinert” drug delivery platform, PEG hydrogels can also incorporate bioactive materials, such as extracellular matrix amino acid motifs or macromolecules such as collagen....read more
Although described as a “bioinert” drug delivery platform, PEG hydrogels can also incorporate bioactive materials, such as extracellular matrix amino acid motifs or macromolecules such as collagen. Incorporation of biological macromolecules facilitates integration into the native tissue environment due to cell-integrin recognition of extracellular matrix components such as laminin, fibronectin, collagen, and hyaluronic acid. This may be important for drug delivery applications where degradation of the hydrogel, and therefore drug release, should be mediated by the host microenvironment. Control of degradation is, therefore, critically dependent on the composition of the hydrogel and the sensitivity of the degradable sequences.Read less
Heparinized Collagen Sutures for Sustained Delivery of PDGF-BB: Delivery Profile and Effects on Tendon-Derived Cells In-Vitro
Suturing is the standard of repair for lacerated flexor tendons. Past studies focused on delivering growth factors to the repair site by incorporating growth factors to nylon sutures which are commonly used in the repair procedure. However, conjugation of growth factors to nylon or other synthetic sutures is not straightforward....read more
Suturing is the standard of repair for lacerated flexor tendons. Past studies focused on delivering growth factors to the repair site by incorporating growth factors to nylon sutures which are commonly used in the repair procedure. However, conjugation of growth factors to nylon or other synthetic sutures is not straightforward. Collagen holds promise as a suture material by way of providing chemical sites for conjugation of growth factors. On the other hand, collagen also needs to be reconstituted as a mechanically robust thread that can be sutured. In this study, we reconstituted collagen solutions as suturable collagen threads by using linear electrochemical compaction. Prolonged release of PDGF-BB (Platelet derived growth factor-BB) was achieved by covalent bonding of heparin to the collagen sutures. Tensile mechanical tests of collagen sutures before and after chemical modification indicated that the strength of sutures following chemical conjugation stages was not compromised. Strength of lacerated tendons sutured with epitendinous collagen sutures (11.2 ± 0.7 N) converged to that of the standard nylon suture (14.9 ± 2.9 N). Heparin conjugation of collagen sutures didn’t affect viability and proliferation of tendon-derived cells and prolonged the PDGF-BB release up to 15 days. Proliferation of cells seeded on PDGF-BB incorporated collagen sutures was about 50% greater than those seeded on plain collagen sutures. Collagen that is released to the media by the cells increased by 120% under the effects of PDGF-BB and collagen production by cells was detectable by histology as of day 21. Addition of PDGF-BB to collagen sutures resulted in a moderate decline in the expression of the tendon-associated markers scleraxis, collagen I, tenomodulin, and COMP; however, expression levels were still greater than the cells seeded on collagen gel. The data indicate that the effects of PDGF-BB on tendon-derived cells mainly occur through increased cell proliferation and that longer term studies are needed to confirm whether this proliferation is outweighs the moderate reduction in the expression of tendon-associated genes.Read less
Immediate Production of a Tubular Dense Collagen Construct with Bioinspired Mechanical Properties
The intrinsic complexity of tissues and organs demands tissue engineering approaches that extend beyond planar constructs currently in clinical use. However, the engineering of cylindrical or tubular tissue constructs with a hollow lumen presents significant challenges arising from geometrical and architectural considerations required to tailor biomaterials for tissue and organ repair....read more
The intrinsic complexity of tissues and organs demands tissue engineering approaches that extend beyond planar constructs currently in clinical use. However, the engineering of cylindrical or tubular tissue constructs with a hollow lumen presents significant challenges arising from geometrical and architectural considerations required to tailor biomaterials for tissue and organ repair. Type I collagen is an ideal scaffolding material due to its outstanding biocompatibility and high processability. However, the highly hydrated nature of collagen hydrogels results in their lack of mechanical properties and instability, as well as extensive cell-mediated contraction, which must be overcome to achieve process control. Herein, tubular dense collagen constructs (TDCCs) were produced simply and rapidly (in less than 1h) by circumferentially wrapping plastically compressed dense collagen gel sheets around a cylindrical support. The effects of collagen source, i.e. rat-tail tendon and bovine dermis-derived acid solubilized collagen, and concentration on TDCC properties were investigated through morphological, mechanical and chemical characterizations. Both tensile strength and apparent modulus correlated strongly with physiologically relevant collagen gel fibrillar densities. The clinical potential of TDCC as a tubular tissue substitute was demonstrated mechanically, through circumferential tensile properties, theoretical burst pressure, which ranged from 1225 to 1574 mm Hg, compliance values of between 8.3% to 14.2% per 100mm Hg and suture retention strength in the range of 116-151 grams-force, which were compatible with surgical procedures. Moreover, NIH/3T3 fibroblast viability and uniform distribution within the construct wall were confirmed up to day 7 in culture. TDCCs with fibrillar densities equivalent to native tissues can be readily engineered in various dimensions with tunable morphological and mechanical properties, which can be easily handled for use as tissue models and adapted to clinical needs.Read less
Influence of Telopeptides on the Structural and Physical Properties of Polymeric and Monomeric Acid-Soluble Type I Collagen
Currently two factors hinder the use of collagen as building block of regenerative devices: the limited mechanical strength in aqueous environment, and potential antigenicity. Polymeric collagen is naturally found in the cross-linked state and is mechanically tougher than the monomeric, acid-soluble collagen ex vivo....read more
Currently two factors hinder the use of collagen as building block of regenerative devices: the limited mechanical strength in aqueous environment, and potential antigenicity. Polymeric collagen is naturally found in the cross-linked state and is mechanically tougher than the monomeric, acid-soluble collagen ex vivo. The antigenicity of collagen, on the other hand, is mainly ascribed to inter-species variations in amino acid sequences of the non-helical terminal telopeptides. These telopeptides can be removed through enzymatic treatment to produce atelocollagen, although the effect of this cleavage on triple helix organization, amino acidic composition and thermal properties is often disregarded. Here, we compare the structural, chemical and physical properties of polymeric and monomeric type I collagen with and without telopeptides, in an effort to elucidate the influence of either mature covalent crosslinks or telopeptides. Circular dichroism (CD) was used to examine the triple helical conformation and quantify the denaturation temperature (Td) of both monomeric collagen (36.5 °C) and monomeric atelocollagen (35.5 °C). CD measurements were combined with differential scanning calorimetry (DSC) in order to gain insight into the triple helix-to-coil thermal transition and shrinkage temperature (Ts) of polymeric atelo collagen (44.8 °C), polymeric collagen (62.7 °C), monomeric atelo collagen (51.4 °C) and monomeric collagen (66.5 °C). Structural and thermal analysis was combined with high pressure liquid chromatography (HPLC) to determine the content of specific collagen amino acidic residues used as markers for the presence of telopeptides and mature crosslinks. Hydroxylamine was used as the marker for polymeric collagen, and had a total content of 9.66% for both polymeric and polymeric atelo collagen; tyrosine was used as the marker for telopeptide cleavage, was expressed as 0.526% of the content of polymeric collagen and the partially-reduced content of 0.39% for atelocollagen.Read less
Nerve Growth Factor Released from Collagen Scaffolds Protects Axotomized Cholinergic Neurons of the Basal Nucleus of Meynert in Organotypic Brain Slices
Background: Alzheimer´s disease is accompanied by cell death of cholinergic neurons, resulting in cognitive impairment and memory loss. Nerve growth factor (NGF) is the most potent protein to support survival of cholinergic neurons....read more
Background: Alzheimer´s disease is accompanied by cell death of cholinergic neurons, resulting in cognitive impairment and memory loss. Nerve growth factor (NGF) is the most potent protein to support survival of cholinergic neurons. New Method: Organotypic brain slices of the basal nucleus of Meynert (nBM) are a valuable tool to study cell death of axotomized cholinergic neurons, as well as protective effects of NGF added into the medium. The aim of the present study is to use collagen scaffolds crosslinked with polyethylineglycole and load with NGF to target delivery of NGF to organotypic nBM brain slices. Results: Collagen scaffolds (visualized by incorporating AlexaFluor 488 antibodies) slowly degraded when applied onto organotypic brain slices within 2 weeks in culture. GFAP reactive astrocytes and Iba1+ microglia became visible around the collagen scaffolds 7 days after incubation, showing reactive gliosis. Cholinergic neurons of the nBM survived (201±21, n=8) when incubated with 100 ng/ml NGF in the medium compared to NGF-free medium (69±12, n=7). Collagen scaffolds loaded with NGF (1 ng/2 μl scaffold) significantly rescued cholinergic cell death in the nBM brain slices (175±12, n=10), which was counteracted by an anti-NGF antibody (77±5, n=5). Comparison with existing Methods: The combination of coronal brain slices with biomaterial is a novel and potent tool to selectively study neuroprotective effects. Conclusions: Collagen scaffolds loaded with low amounts of a protein/drug of interest can be easily applied directly onto organotypic brain slices, allowing slow targeted release of a protective molecule. Such an approach is highly useful to optimize CollScaff for further in vivo applications.Read less
On-Demand Release of Hydrosoluble Drugs from a Paramagnetic Porous Collagen-Based Scaffold
The design of a collagen scaffold containing iron oxide nanostructures capped by a TiO2 (anatase) layer is reported....read more
The design of a collagen scaffold containing iron oxide nanostructures capped by a TiO2 (anatase) layer is reported. The TiO2 shell is proposed to perform a dual role: 1) as an innovative and biocompatible cross-linker agent, providing binding sites to the protein moiety, through the well-known TiO2 chemical affinity towards carboxyl groups, and 2) as a protective surface layer for the paramagnetic core against oxidation. Simultaneously, the presence of the nanostructures confers to the collagen gel sensitivity to an external stimulus; that is, the application of a magnetic field. The hybrid biomaterial was demonstrated to be nontoxic and is proposed as a smart scaffold for the release of bioactive compounds on demand. The tunable release of a model protein (myoglobin) upon application of a magnetic field was investigated. Myoglobin was loaded in the microporous material and discharge was induced by consecutive magnet applications, leading to release of the protein with high spatio–temporal and dosage control.Read less
Protease-Sensitive Atelocollagen Hydrogels Promote Healing in a Diabetic Wound Model
The design of exudate-managing wound dressings is an established route to accelerated healing, although such design remains a challenge from material and manufacturing standpoints....read more
The design of exudate-managing wound dressings is an established route to accelerated healing, although such design remains a challenge from material and manufacturing standpoints. Aiming towards the clinical translation of knowledge gained in vitro with highly-swollen rat tail collagen hydrogels, this study investigated the healing capability in a diabetic mouse wound model of telopeptide-free, protease-inhibiting collagen networks. 4-Vinylbenzylation and UV irradiation of type I atelocollagen (AC) led to hydrogel networks with chemical and macroscopic properties comparable to previous collagen analogues, attributable to similar lysine content and dichroic properties. After 4 days in vitro, hydrogels induced nearly 50 RFU% reduction in matrix metalloproteinase (MMP)-9 activity, whilst showing less than 20 wt% mass loss. After 20 days in vivo, dry networks promoted 99% closure of 10 × 10 mm full thickness wounds and accelerated neo-dermal tissue formation compared to Mepilex®. This collagen system can be equipped with multiple, customizable properties and functions key to personalized chronic wound care.Read less
Repair of Large Osteochondritis Dissecans Lesions Using a Novel Multilayered Tissue Engineered Construct in an Equine Athlete
Osteochondral lesions resulting from osteochondritis dissecans are problematic to treat and present a significant challenge for clinicians....read more
Osteochondral lesions resulting from osteochondritis dissecans are problematic to treat and present a significant challenge for clinicians. The aims of this study were to investigate the use of a scaffold-assisted microfracture approach, employing a novel, multilayered, collagen-based, osteochondral graft substitute in the treatment of severe osteochondritis dissecans of both lateral femoral trochlear ridges in an equine athlete, and to assess the potential of this novel scaffold to enhance repair of the osteochondral unit. A 15 month-old female filly presented with large osteochondritis dissecans lesions involving both femoral lateral trochlear ridges. After routine arthroscopic debridement and microfracture of the subchondral bone, multilayered osteochondral defect repair scaffolds were implanted into the fragmentation beds in both left and right femoropatellar joints via mini-arthrotomes. Exploratory arthroscopy 5 months postimplantation revealed smooth cartilaginous repair tissue, contiguous with the adjacent cartilage, covering the defect. At 22-month follow up, the filly had no signs of lameness and was exercising at her intended level. Radiographically, although still slightly flattened, the femoral trochlear ridges were smooth, with no evidence of osteoarthritis. Ultrasonographically, the defects were filled with bone and covered with an overlying cartilaginous layer, with the trochlear ridge contour almost entirely restored. This report demonstrates the effective clinical use of this novel, multilayered, osteochondral defect repair scaffold in the treatment of osteochondritis dissecans of an equine athlete. The successful repair achieved here using this novel scaffold in an equine patient with large bilateral lesions shows the potential for clinical translation in the treatment of human patients presenting with osteochondral defects.Read less
Synthesis and Fabrication of Nanocomposite Fibers of Collagen-Cellulose Nanocrystals by Coelectrocompaction
An electrochemical process has been used to compact cellulose nanocrystals (CNC) and access aligned micron-sized CNC fib...read more
An electrochemical process has been used to compact cellulose nanocrystals (CNC) and access aligned micron-sized CNC fibers. Placing a current across aqueous solutions of carboxylic acid functionalized CNCs (t-CNC–COOH) or carboxylic acid/primary amine functionalized CNCs (t-CNC–COOH-NH2) creates a pH gradient between the electrodes, which results in the migration and concentration of the CNC fibers at their isoelectric point. By matching the carboxylic acid/amine ratio of CNCs and collagen (ca. 30:70 carboxylic acid:amine ratio), it is possible to coelectrocompact both nanofibers and access aligned nanocomposite fibers. t-CNC–COOH-NH2/collagen fibers showed a maximum increase in mechanical properties at 5 wt % of t-CNC–COOH-NH2. Compared to collagen/CNC films which have no alignment in the plane of the films, the tensile properties of the aligned fibers show a significant enhancement in the wet mechanical properties (40 MPa vs 230 MPa) for the 5 wt % of t-CNC–COOH-NH2/collagen films and fiber, respectively.Read less
The Effect of Different Collagen Modifications for Titanium and Titanium Nitrite Surfaces on Functions of Gingival Fibroblasts
Targeted modifications of the bulk implant surfaces using bioactive agents provide a promising tool for improvement of the long-term bony and soft tissue integration of dental implants....read more
Targeted modifications of the bulk implant surfaces using bioactive agents provide a promising tool for improvement of the long-term bony and soft tissue integration of dental implants. In this study, we assessed the cellular responses of primary human gingival fibroblasts (HGF) to different surface modifications of titanium (Ti) and titanium nitride (TiN) alloys with type I collagen or cyclic-RGDfK-peptide in order to define a modification improving long-term implants in dental medicine.Read less
Translating the Role of Osteogenic-Angiogenic Coupling in Bone Formation: Highly Efficient Chitosan-pDNA Activated Scaffolds Can Accelerate Bone Regeneration in Critical-Sized Bone Defects
The clinical translation of bioactive scaffolds for the treatment of large segmental bone defects has remained a challenge due to safety and efficacy concerns as well as prohibitive costs....read more
The clinical translation of bioactive scaffolds for the treatment of large segmental bone defects has remained a challenge due to safety and efficacy concerns as well as prohibitive costs. The design of an implantable, biocompatible and resorbable device, which can fill the defect space, allow for cell infiltration, differentiation and neovascularisation, while also recapitulating the natural repair process and inducing cells to lay down new bone tissue, would alleviate the problems with existing treatments. We have developed a gene-activated scaffold platform using a bone-mimicking collagen hydroxyapatite scaffold loaded with chitosan nanoparticles carrying genes encoding osteogenic (BMP-2) and angiogenic (VEGF) proteins. With a single treatment, protein expression by mesenchymal stem cells (MSCs) seeded onto the scaffold is sustained for up to 28 days and is functional in inducing MSC osteogenesis. The in vivo safety and efficacy of this gene-activated scaffold platform was demonstrated resulting in the successful transfection of host cells, abrogating the requirement for multiple procedures to isolate cells or ex vivo cell culture. Furthermore, the level of bone formation at the exceptionally early time-point of 28 days was comparable to that achieved following recombinant BMP-2 protein delivery after 8 weeks in vivo, without the adverse side effects and at a fraction of the cost. This naturally derived cell-free geneactivated scaffold thus represents a new ‘off-the-shelf’ product capable of accelerating bone repair in critical-sized bone defects.Read less