BIOADHESIVE DRUG DELIVERY

Bioadhesive drug delivery systems adhere to the mucin-network and/or underlying epithelial layer of mucosal surfaces. Mucus is a continuous network of cross-linked glycoproteins which, at physiological pH, carries a substantial negative charge due to the presence of sialic acid and sulfonic acid residues. The glycocalyx (polysaccharide-containing structures) on the external surface of cells is partly responsible for the adhesive properties of the cell and carries a net negative charge as well. Bioadhesion begins with establishment of intimate contact between the polymer and substrate. This is followed by bond formation and interpenetration/interdiffusion of polymer and substrate. Any increase in contact area and establishment of physical entanglement at the interface strengthens the force of bioadhesion. Thus, factors that favor intimacy of contact, increased bond formation and enhanced physical entanglement will potentially increase bioadhesive strength. Bioadhesive polymers can be used in drug delivery to localize delivery systems at specific sites for either local treatment or for prolonged delivery of drug in a route of administration that would otherwise cause rapid removal of the system.