Crosslinking Of Self-Assembled Protein-Polymer Conjugates With Divanillin

Protein-based materials are widely used in biomedical applications. Often the proteins need to be crosslinked in order to be stable for application. Here, we explored the use of 5,5'-bisvanillin as a potentially non-toxic crosslinker that can react with lysine residues on proteins. To demonstrate the success of the crosslinking reaction, polymer-protein conjugates based on bovine serum albumin (BSA) and poly(N-isopropyl acrylamide) (PNIPAM) were employed. The BSA-PNIPAM conjugate is water soluble at room temperature, but heated above the cloud point, BSA-PNIPAM forms nanoparticles of around 70 nm that can again disassemble at lower temperatures. Reaction with 5,5'-bisvanillin prevented disassembly resulting in stable BSA nanoparticles of 50 nm in size. The formed nanoparticles were observed to be rather stable and were not easily cleaved in acidic conditions. The crosslinker 5,5'-bisvanillin was measured to have lower toxicity against A2780 lung cancer cell lines compared with the commonly applied crosslinker glutaraldehyde.