A Simple and Efficient Method to Improve Mechanical Properties of Collagen Scaffolds by UV Irradiation

Collagen is the major protein component of cartilage, bone, skin and connective tissue and constitutes the major part of the extracellular matrix. Collagen type I has complex structural hierarchy, which consists of treepolypeptide α-chains wound together in a rod-like helical structure. Collagen is an important biomaterial, finding many applications in the field of tissue engineering. It has been processed into various shapes, such as, gel, film, sponge and fiber. It is commonly used as the scaffolding material for tissue engineering due to its many superior properties including low antigenicity and high growth promotion. Unfortunately, poor mechanical properties and rapid degradation rates of collagen scaffolds can cause instability and difficulty in handling. By crosslinking, the structural stability of the collagen and its rate of resorption can be adapted with respect to its demanding requirements. The strength, resorption rate, and biocompatibility of collagenous biomaterials are profoundly influenced by the method and extent of crosslinking. In thisstudy, the effect of UV irradiation on collagen scaffolds has been carried out.Collagen scaffolds were fabricated using freeze drying method with freezing temperature of -80oC, then exposed to UV irradiation. Mean pore size of the scaffolds was obtained as 98.52±14.51 μm using scanning electron microscopy. Collagen scaffolds exposed to UV Irradiation (254 nm) for 15 min showed the highest tensile strain (17.37±0.98 %), modulus (1.67±0.15 MPa) and maximum load (24.47±2.38 cN) values. As partial loss of the native collagen structure may influence attachment, migration, and proliferation of cells on collagen scaffolds, we detected no intact α-chains after SDS-Page chromatography. We demonstrate that UV irradiation is a rapid and easily controlled means of increasing the mechanical strength of collagen scaffolds without any molecular fracture

Behaviour of Human Induced Pluripotent Stem Cell-Derived Neural Progenitors on Collagen Scaffolds Varied in Freezing Temperature and Laminin Concentration Citation: Seeding hiPSC-NPs on Collagen Scaffolds

Abstract Objective: Biomaterial technology, when combined with emerging human induced pluripotent stem cell (hiPSC) technology, provides a promising strategy for patient-specific tissue engineering. In this study, we have evaluated the physical effects of collagen scaffolds fabricated at various freezing temperatures on the behavior of hiPSC-derived neural progenitors (hiPSC-NPs). In addition, the coating of scaffolds using different concentrations of laminin was examined on the cells. Materials and Methods: Initially, in this experimental study, the collagen scaffolds fabricated from different collagen concentrations and freezing temperatures were characterized by determining the pore size, porosity, swelling ratio, and mechanical properties. Effects of cross-linking on free amine groups, volume shrinkage and mass retention was also assessed. Then, hiPSC-NPs were seeded onto the most stable three-dimensional collagen scaffolds and we evaluated the effect of pore structure. Additionally, the different concentrations of laminin coating of the scaffolds on hiPSC-NPs behavior were assessed. Results: Scanning electron micrographs of the scaffolds showed a pore diameter in the range of 23-232 μm for the scaffolds prepared with different fabrication parameters. Also porosity of all scaffolds was >98% with more than 94% swelling ratio. hiPSC-NPs were subsequently seeded onto the scaffolds that were made by different freezing temperatures in order to assess for physical effects of the scaffolds. We observed similar proliferation, but more cell infiltration in scaffolds prepared at lower freezing temperatures. The laminin coating of the scaffolds improved NPs proliferation and infiltration in a dose-dependent manner. Immunofluorescence staining and scanning electron microscopy confirmed the compatibility of undifferentiated and differentiated hiPSC-NPs on these scaffolds. Conclusion: The results have suggested that the pore structure and laminin coating of collagen scaffolds significantly impact cell behavior. These biocompatible three-dimensional laminin-coated collagen scaffolds are good candidates for future hiPSC-NPs biomedical nerve tissue engineering applications

Critical-sized bone defects regeneration using a bone-inspired 3D bilayer collagen membrane in combination with leukocyte and platelet-rich fibrin membrane (L-PRF): An in vivo study

Objectives: We aim to develop a 3D-bilayer collagen (COL) membrane reinforced with nano beta-tricalcium-phosphate (nβ-TCP) particles and to evaluate its bone regeneration in combination with leukocyte-platelet-rich fibrin (L-PRF) in vivo. Background data: L-PRF has exhibited promising results as a cell carrier in bone regeneration in a number of clinical studies, however there are some studies that did not confirm the positive results of L-PRF application. Methods: Mechanical & physiochemical characteristics of the COL/nβ-TCP membrane (1/2 & 1/4) were tested. Proliferation and osteogenic differentiation of seeded cells on bilayer collagen/nβ-TCP thick membrane was examined. Then, critical-sized calvarial defects in 8 white New Zealand rabbits were filled with either Col, Col/nβ-TCP, Col/nβ-TCP combined with L-PRF membrane, or left empty. New bone formation (NBF) was measured histomorphometrically 4 & 8 weeks postoperatively. Results: Compressive modulus increases while porosity decreases with higher β-TCP concentrations. Mechanical properties improve, with 89 porosity (pore size �100 μm) in the bilayer-collagen/nβ-TCP membrane. The bilayer design also enhances the proliferation and ALP activity. In vivo study shows no significant difference among test groups at 4 weeks, but Col/nβ-TCP + L-PRF demonstrates more NBF compared to others (P < 0.05) after 8 weeks. Conclusion: The bilayer-collagen/nβ-TCP thick membrane shows promising physiochemical in vitro results and significant NBF, as ¾ of the defect is filled with lamellar bone when combined with L-PRF membrane. © 201