The role of tyrosine in protein-dopamine based bioinspired adhesives: the stoichiometry that maximizes bonding strength

Nature has evolved adhesive materials adaptive for several different environments by using versatile chemistry that largely relies on two simple components: catechols and polypeptides. Herein, using dopamine as a catechol compound and several model proteins, we show how the adhesive properties can be tuned by controlling the ratio between catechol units and the tyrosine amino acid residue in the protein components. We found that the best bonding strength performance is obtained using a dopamine molar excess to tyrosine of 8.6 ± 2.9. Our study points out a general design criterion and process to obtain high-performance adhesives (>2 MPa) starting from cheap, commercially available, and sustainable raw materials.