Production and Properties of Photoactive Collagen-Based Wet Spun Fibres

The excellent biocompatibility of collagen-based biomaterials make them highly relevant in the field of medical textiles. The manufacture of continuous filaments and staple fibres permits their incorporation into textiles with more easily controllable properties than other material structures such as sponges, electrospun meshes, and hydrogels. However collagen-based biomaterial spinning has thus far presented a challenge with issues such as wet instability, triple helix denaturation, rapid in vivo biodegradation and poor mechanical properties, particularly for gelatin fibres. Herein, to address these challenges alternative crosslinking strategies have been developed to stabilise the protein structure, without the need for chemical treatments post-spinning that carry the risk of residual cytotoxic effects. To provide a novel approach, selected photo-active crosslinking moieties are grafted onto the collagen-based material before spinning and then crosslinked in the presence of a light source and a specific water-soluble photoinitiator. The vinybenzylation approach enables unreacted reagents to be washed away in the precipitation stage following functionalisation of the collagen-based material minimising potential for adverse reactions when the material is in vivo. Preparation of gelatin-4 vinyl benzyl chloride (Gel-4VBC) materials was studied, including the feasibility of spinning, effects of varying wet-spinning coagulants, and comparisons between the spinning of gelatin-4VBC and methacrylated gelatin, another photoactive material widely used in the biomaterials industry. Results showed the vinylbenzylated material had a better combination of mechanical (UTS= 74 ± 3 MPa) and swelling index (SI= 260 ± 24 a%), was more readily wet spun into room temperature, using aqueous coagulants, and was significantly more biocompatible than gelatin-methacrylate (Gel-MA) after 7 days of incubation. Collagen-4VBC staple fibres were also prepared and wet spun and characterised with factors such as coagulant type, extrusion and collection rate, and spinneret dimensions’ influence upon collagen triple helix denaturation, swelling, and enzymatic, tensile, and thermal resistance observed. A triple helix retention of 82% was measured using circular dichroism, indicating low levels of denaturation during the functionalisation and spinning processes. Increased stretching of the fibre during spinning was shown to increase fibre strength as compared to increasing shear stress induced by higher extrusion rates. Reducing the needle aperture was shown to increase fibre tensile strength and modulus by a factor of 2.3 and 2.9 respectively. The staple fibres had high ultimate tensile strength (UTS) and modulus, comparable to native collagen reported in the literature with a UTS of 286 ± 38 MPa and modulus of 4 ± 0.5 GPa recorded. The feasibility of converting the staple fibres into nonwoven and braided textile structures was then confirmed. The prototypes were tested with respect to morphological, swelling, collagenase degradation and cell tolerance characteristics showing suitable properties for use in medical devices. Overall this work demonstrates that 4VBC functionalisation of collagen-based materials followed by UV-crosslinking is a promising route for manufacture of biocompatible wet spun staple fibres relevant to applications in healthcare.