MUCOADHESIVE PROPERTIES OF THE MUSSEL ADHESIVE PROTEIN

The mucoadhesive properties of the mussel adhesive protein (MAP), a 13 0-kDa protein produced by the blue mussel (Mytilus edulis) to provide firm adhesion to underwater surfaces, were evaluated by measuring the maximum adhesive force of detachment for protein-coated cover glasses from porcine intestinal mucosa in a neutral physiological buffer using a modified tensiometer. In this simple test, air-dried films of MAP p erformed as good as analogously prepared films of polycarbophil, which is one of the best mucoadhesive polymers known so far and therefore w as chosen as reference. If MAP films were dried and stored in an N-2-a tmosphere, mucoadhesion was significantly improved by nearly doubling the force of detachment under otherwise the same experimental conditio ns. Apart from the presence of positively charged lysine residues and a high content of hydroxylated amino acids, the remarkably strong adhe sion of this protein to mucosal surfaces is probably due to the presen ce of o-dihydroxy-benzyl (carbachoyl) residues, as the molecule contai ns about 10-20% di-hydroxy-phenylalanine (Dopa). However, oxidation of carbachoyl residues to o-chinons under influence of air or appropriat e enzymes, which should allow for nucleophilic addition reactions with primary and secondary amines or mercaptans present in the substrate, did not ther with its favorable safety profile, MAP appears as an inte resting new compound for the development of mucoadhesive drug delivery systems, preferentially if these can be manufactured and stored under non-oxidative conditions.