Recombinant collagen hydrogels induced by disulfide bonds.

With the characteristics of low toxicity and biodegradability, recombinant collagen-like proteins have been chemically and genetically engineered as a scaffold for cell adhesion and proliferation. However, most of the existing hydrogels crosslinked with peptides or polymers are not pure collagen, limiting their utility as biomaterials. A major roadblock in the development of biomaterials is the need for high purity collagen that can self-assemble into hydrogels under mild conditions. In this work, we designed a recombinant protein, S-VCL-S, by introducing cysteine residues into the Streptococcus pyogenes collagen-like protein at both the N-and C-termini of the collagen with a trimerization domain (V) and a collagen domain (CL). The S-VCL-S protein was properly folded in complete triple helices and formed self-supporting hydrogels without polymer modifications. In addition, the introduction of cysteines was found to play a key role in the properties of the hydrogels, including their microstructure, pore size, mechanical properties, and drug release capability. Moreover, two/three-dimensional cell-culture assays showed that the hydrogels are noncytotoxic and can promote long-term cell viability. This study explored a crosslinking collagen hydrogel based on disulfide bonds and provides a design strategy for collagen-based biomaterials.