Rapid gel formation and adhesion in photocurable and biodegradable block copolymers with high DOPA content

Marine mussels anchor to a variety of surfaces in turbulent intertidal zones through the use of adhesive plaques formed from hardened mussel adhesive proteins (MAPs). It is believed that 3,4-dihydroxyphenylalanine (DOPA) imparts both water-resistant adhesive characteristics and rapid curing ability to MAPs. In this paper, DOPA-modified triblock copolymers were synthesized and used to form adhesive hydrogels. Amphiphilic block copolymers with DOPA content as high as 10 wt % were prepared, and aqueous solutions of the polymers rapidly (< 1 min) formed hydrogels by photopolymerization of methacrylate end groups attached to the hydrophobic segments. Contact mechanics adhesion tests were performed on the photocured hydrogels, and it was shown that incorporating DOPA into the polymer structure significantly enhanced work of adhesion to titanium surfaces submerged in an aqueous medium. Work of adhesion values as high as 410 mJ/m ² were recorded for polymers containing 10 wt % DOPA, although the introduction of Lys in the form of a DOPA-Lys copolypeptide reduced the work of adhesion. Oxidation of DOPA was shown to reduce work of adhesion to Ti, confirming earlier studies suggesting that the catecholic form of DOPA is largely responsible for adhesion to metal oxide surfaces. The DOPA-containing block copolymers described in this study are candidates for use as adhesive biomaterials for medical applications.