Variation in Hydrogel Formation and Network Structure For Telo-, Atelo- and Methacrylated Collagens

As the most abundant protein in the extracellular matrix, collagen has become widely studied in the fields of tissue engineering and regenerative medicine. Of the various collagen types, collagen type I remains the most commonly utilised in laboratory studies. In tissues, collagen type I forms into fibrils that provide an extended fibrillar network. In tissue engineering and regenerative medicine, little emphasis has been placed on the nature of the network that is being formed. Various factors could affect the network structure, including the method used to extract collagen form the native tissue, since this may remove the telopeptides, and the nature and extent of any chemical modifications and crosslinking moieties. The structure of any fibril network impacts cellular proliferation and differentiation, as well as the overall modulus of hydrogels. In this study, the network forming properties of two distinct forms of collagen (telo- and atelo- collagen), and their methacrylated derivatives were compared. The presence of the telopeptides facilitated fibril formation for unmodified samples, but this benefit was substantially reduced by subsequent methacrylation, leading to a loss in the native self-assembly potential. Furthermore, the impact of methacrylation of the collagen which enables rapid crosslinking and makes it suitable for use in 3D printing was investigated. The crosslinking of the methacrylated samples (both telo- and atelo-) was seen to improve the fibril-like network compared to non-crosslinked samples. This contrasted with samples of methacrylated gelatin which showed little, if any, fibrillar or ordered network structure whether or not they were crosslinked.