Collagen-based Biomaterials

Abstract

Collagen in tissues THE ROLE OF COLLAGENCollagen is the Inost abundant protein component of the extracellular matrix (ECM), and provides the insoluble fibres and microfibrils in this complex cOlnposite material.A key role for this collagenous network is to provide a scaffold for cell attachment and rnigration, as welI as providing specific Inechanical properties.The cOlnposition ofthe ECM varies substantially between different tissues due to different patterns of gene expression and due to variation in particular proteins where differential splicing effects may be present.The cOlnposition of the matrix can provide specific information to cells, and thus provides opportunity for developnlent of novel composite biolnaterials based on a collagen scaffold4 In addition, the topological arrangement of the matrix can provide information to cells and can lead to changes in cell morphology and phenotypic expression.An example of this effect is seen with cells froln cartilage which grow with a round, chondrocyte-like morphology in a three-dimensional nlatrix, such as a collagen gel, but becoIne flattened, like fibroblasts in a t\VO dilnensional monolayer culture.This importance of the collagen lattice is thus nnothcr feature which can be exploited in developnlcnl of collagen-based biomaterials. COLLAGEN DIVERSITYThe nanle 'collagen' is often used as a generic term to cover a wide range of protein rnolecules that all share the saine characteristic triple helical configuration as a nlajor structural motif (see below).Until 197 I, the wide variety of genetically distinct collagens in different tissues had not been realised (Miller, 1971).Subsequently, nunlerous distinct collagen types have been described.Thus, to date, at least 18 genetically distinct collagen types, cOlnprised of at least 32 individual genetically distinct polypeptide a . ..chains have now been identified (Table J).The amino acid sequence feature which is conllnon to, and defines, ul1 these collagens is the presence of a (Gly-X-Y)., repeat, \vhere X and Y could be any amino ,lcid, although these are frequently proline and hydroxyproline.