Non-covalent protein-based adhesives for transparent substrates – bovine serum albumin vs. recombinant spider silk

Protein-based adhesives could have several advantages over petroleum-derived alternatives, including substantially lower toxicity, smaller environmental footprint and renewable sourcing. Here, we report that non-covalently crosslinked bovine serum albumin (BSA) and recombinant spider silk proteins have high adhesive strength on glass (8.53 and 6.28 MPa, respectively) and other transparent substrates. Moreover, the adhesives have high visible transparency and showed no apparent degradation over a period of several months. The mechanism of adhesion was investigated and primarily attributed to dehydration-induced reorganisation of protein secondary structure, resulting in the supramolecular association of β-sheets into a densely hydrogen-bonded network.