New smart thermosensitive biomaterials on the basis of collagen modified by ethylene glycol vinyl glycidyl ether for 4D bioprinting

Abstract

In this study, collagen reactive under UV radiation was obtained for the first time via the functionalization of the side amino groups of lysine moieties with unsaturated ethylene glycol vinyl glycidyl ether (Vinylox) containing, similarly to glycidyl methacrylate, an epoxy group. The presence of this group having a moderate reactivity provides selective grafting of the side amino groups of collagen in a neutral or weakly alkaline medium and excludes the formation of by-products in the Michael reaction and hydrolysis characteristic of the analog—glycidyl methacrylate. Photometry data indicate that with modification in a weakly basic aqueous solution at room temperature and a significant excess of Vinylox, a grafting degree of 23.4% can be achieved. For the first time, film-forming composites capable of photocuring were obtained by adding polyethylene glycol diacrylate and poly(N-isopropylacrylamide) to a weakly acidic aqueous solution of collagen. The presence of vinyl oxide groups provided satisfactory mechanical characteristics of films as the result of UV-initiated collagen cross-linking, while the presence of poly(N-isopropylacrylamide) ensured hydrophilic-hydrophobic smart sensitivity. The films have a well-developed fibrillar structure, and the size of voids enables the free movement of nutrients and other compounds. According to MTT assay data, the films release no cytotoxic components and maintain the metabolic activity of stem cells, providing sufficient density of stem cells on their surface. All of the factors mentioned above determine the prospects of using the films both as an artificial extracellular matrix scaffold and as smart thermosensitive scaffolds used to grow stem cells on their surfaces for subsequent laser transfer bioprinting.