Collagen: Materials analysis and implant uses

Collagen is the oldest extracellular matrix component in the animal kingdom. Currently, 29 homo- and heterotrimers have been identified, all of which have in common the amino acid repeat [Gly-X-Y] _n that distinguishes their primary structure from other proteins and results in the signature quaternary structure, the triple helix. Collagens have been classified as fibrous, nonfibrous, filamentous, and fibril associated with interrupted triple helices. Collagen I is the most abundant collagen in mammals (70-90% of total body collagen) and its fibrils are the primary structural elements of all connective tissues, providing a structural scaffold and stabilized by lysyl oxidase cross-linking pathway. Since collagen I is associated with cell interaction, migration, attachment, differentiation, and organization, it is extensively used in tissue engineering. Mammalian-extracted collagen is almost exclusively used in the leather, food, biomaterial, cosmetic, and pharmaceutical industry. Concerns about interspecies transmission of disease have encouraged the development of synthetic and recombinant collagen technologies, which may hold some future in biomaterials applications. Numerous fabrication, stabilization, and functionalization strategies have been developed over the years in order to produce tissue facsimiles that will promote functional regeneration. A number of collagen-specific assays have also been developed to ensure reproducibility and full characterization of collagen preparations and collagen-based devices.