Study On Preparation And Properties Of Collagen-Carboxymethyl Cellulose Composites

Tissue engineering scaffold material is one of the important research area in tissue engineering,which has received extensive attention.An ideal scaffold should serve as a tissue or organ temporarily and provide structural support for the repairing and regenerating tissue.At present,fabrication of an ideal scaffold with proper structure to a human tissue and matching performance,is still a difficult but important point.Collagen(Col)is the structural protein of extracellular matrix which is the most abundant protein in human body.Biomedical materials based on collagen have unlimited potential applications.Carboxymethyl cellulose(CMC)is a kind of cellulose ether that is non-toxic,renewable,biodegradable and highly salt-resistant with a great number of such reactive groups as hydroxyl and carboxyl groups.It has been used as a carrier for biological substrates,drug substrates,and biomedical products.Col and CMC were combined together to construct various composites.Based on Col-CMC(the protein-polysaccharide template),the effects of different fabrication methods on the structure and properties of composite scaffolds were studied.EDC/NHS biocross-linking,photocross-linking,and dual cross-linking were employed to modify the Col-CMC system.Organic/inorganic hybrid composites were fabricated by in-situ precipitation or biomimetic mineralization.By the methods mentioned,three-dimensional porous(3-D)scaffold materials with component-biomimetic or structure-biomimetic were fabricated,which had biodegradability and good biocompatibility.The main works are listed as follow:1.By EDC/NHS cross-linking,new covalent bonds between active carboxyl groups of CMC and amino groups of Col are formed.After emulsion freeze-drying,Col/CMC scaffolds were prepared.Effects of cross-linkers ratios and mass ratios of Col to CMC on the structure,swelling properties,mechanical properties,and degradation properties of scaffolds were investigated.Results showed that scaffolds crosslinked by EDC/NHS at the ratio of 2:1 possesse more regular porous structure and better compression strength than those of 1:1.Col/CMC scaffold reveales good swelling property and biocompatibility,and it can be gradually degraded,from 10 to 21 days.This porous scaffold is expected to find applications as a short-term tissue engineering material,such as vitrectomy.2.Mimicking the bone formation in extracellular matrix,collagen-carboxymethyl cellulose/calcium-deficient hydroxyapatite was fabricated by using Col-CMC(the protein-polysaccharide system)template via activization,in-situ deposition and freeze-drying route.The introduction of inorganic component decreases the swelling properties of scaffold and significantly improves the compression strength.The organic-inorganic scaffold reveales good biocompatibility and can be biodegraded in 8 weeks.This component-biomimetic scaffold is expected to be used as a dental prosthetic material.3.Based on photocross-linking,Col was modified with methacrylic acid to introduce double bonds.Besides,in order to increase the density of other reactive groups except acrylic double bonds in the system,two routes were studied.One was that the modified Col was further cross-linked with CMC by EDC/NHS cross-linker,then photocross-linking,namely dual cross-linking.The other one was that EDC-activated CMC molecules were grafted on Col macromolecules,then photocross-linked to form a gel.After freeze-drying,scaffolds were obtained.Results showed that both above scaffolds have similar structure and compression strength to spongy bone.And a good biocompatibility is found,when the ratio of methacrylic anhydride to Col solution is no more than 10%(v/v).The structure-biomimetic scaffold is potentially used as cell culture substrates and tissue engineering scaffolds.4.In order to mimic the bone formation in extracellular matrix and the organic/inorganic composition of nature bone,modified Col grafted CMC was used as a template and mineralized scaffolds were obtained.The results indicated that mineralization is uniform.The mineralized scaffolds are component-biomimetic and have similar compression strength to spongy bone.Besides,it shows better biodegradation performance.This mineralized scaffold has great potential application in the field of bone tissue engineering.