Synthesis of 3,4-dihydroxyphenylalanine (DOPA) containing monomers and their co-polymerization with PEG-diacrylate to form hydrogels

L-3,4-Dihydroxyphenylalanine (DOPA) is an unusual amino acid found in mussel adhesive proteins (MAPs) that is believed to lend adhesive characteristics to these proteins. Most previous efforts to incorporate DOPA into hydrogels have utilized oxidative cross-linking, which is hypothesized to reduce the adhesive properties of DOPA and requires reagents that are harmful to biological tissues. In this paper, we describe the synthesis of N-methacrylated DOPA monomers and their copolymerization with poly(ethylene glycol) diacrylate (PEG-DA) using either ultraviolet (UV) or visible light. The effect of DOPA containing monomers on gelation time, gel conversion and elastic modulus of the photocured hydrogels was investigated. Despite a retarding effect of DOPA on photopolymerization, DOPA was successfully incorporated into hydrogels with elastic moduli suitable for many biomedical applications. The incorporation of DOPA into hydrogels by photopolymerization may lead to new adhesive hydrogels for medical applications.