Construction And Evaluation Of Collagen Based Hydrogel For Tissue Repair Application

Tissue engineering is a discipline which combines materials science with biology to simulate human tissues or organs.With the development of bionics in recent years,the microimplant with biological activity can be constructed to repair tissue defects by understanding the structure and function of human extracellular matrix.Collagen is a very important extracellular matrix protein in animals,which is closely related to cell adhesion,growth and expression.It was used to prepare hydrogels due to its unique low immunogenicity,biocompatibility and biodegradability,which had attracted extensive attention in the field of tissue engineering.However,pure collagen hydrogels have some problems,such as poor mechanical properties and poor plasticity.Based on the conditions of different crosslinking agents,self-assembly and covalent bonding,the collagen-based composite polymer gel was prepared by combining with other polymer materials.This could not only endow the gel with new functional properties,but also overcome the defects of collagen.The self-assembly of collagen and the chemical cross-linking between collagen and polypyrrole were used to form the interpenetrating network structure to realize the layered supramolecular structure.SCPN gel presented uniform internal structure of pores,good thermodynamic performance and better swelling performance,and the material could undergo degradation for nearly a month.Physical properties indicated that the chemical interaction between gel materials and the self-assembly of collagen could significantly improve the mechanical strength of SCPN hydrogel.In vitro biological properties showed that PC12 cells had good growth and proliferation ability on SCPN hydrogel,while differentiating into longer synapses under the action of electrical stimulation.Polypyrrole/heparin/collagen composite double network film for peripheral nerve regeneration were fabricated by crosslinking the mixture of collagen and polypyrrole modified by heparin.Physical stability of composite film can be verified by various characterization including physical characterizations and biological methods.The results show that composite film composing of 10% pyrrole has the densest inner structure.The conductivity reached 0.336 S/cm.Combined with the promotion results of cell growth of PC12 cell,this composite film modified with heparin is promising in the application of tissue regeneration.As the main material,collagen and polyethylene glycol were used to prepare the pH responsive self-healing hydrogel with forming poly-dopamine in situ.The concentration of collagen,the molecular weight of polyethylene glycol,collagen amino and polyethylene glycol aldehyde content proportion,polydopamine concentration and polymerization time were varied to investigate the preparation of polydopamine/collagen/polyethylene glycol gel.The results show that,under the conditions of 3% collagen concentration,polyethylene glycol(6000 Da),the collagen and polyethylene glycol content ratio(1.2),1 mg/mL polydopamine concentration and polymerization time within six hours,the gel structure was relatively uniform,and had with good mechanical properties,adhesion affinity and thermodynamic stability.Gel surface had better antibacterial performance at the same time.