Chitosan based water-resistant adhesive. Analogy to mussel glue

Using analogies from nature, we investigated the possibility that tyrosinas e-catalyzed reactions of 3,4-dihydroxyphenethylamine (dopamine) could confe r water-resistant adhesive properties to semidilute solutions of the polysa ccharide chitosan. Rheological measurements showed that the tyrosinase-cata lyzed, and subsequent uncatalyzed, reactions lead to substantial increases in the viscosity of the chitosan solutions. Samples from these high-viscosi ty modified-chitosans were spread onto dry glass slides, the slides were la pped and clipped together either in air or after being submerged in water, and the bound slides were held under water for several hours. Adhesive shea r strengths of over 400 kPa were observed for these modified chitosan sampl es, while control chitosan solutions conferred no adhesive strength (i.e., the glass slides separated in the absence of measurable forces). High visco sities and water-resistant adhesive strengths were also observed when semid ilute chitosan solutions were treated with the known cross-linking agent, g lutaraldehyde, Further studies indicate a relationship between the increase d viscosities and water-resistant adhesion. These results demonstrate that the renewable biopolymer chitosan can be converted into a water-resistant a dhesive.