Introduction, Theories and Mechanisms of Bioadhesion

Bioadhesion refers to adherence of macromolecules (synthetic and natural) to the mucosal layer of the body. The second generation bioadhesives, the biological mucoadhesives, have depicted specific interaction with biological cell surface as well as with the mucin. In this chapter, theories of bioadhesion which include wetting, diffusion, electronic, adsorption, and fracture theories have been described which are important for assessment of bioadhesion. These theories clearly explain the fundamental mechanisms of attachment and elaborate on the formation of bioadhesive bonds. This compilation also summarizes the mechanistic approach to bioadhesion which is a three-step phenomenon, namely: wetting and swelling of mucoadhesive polymer, interpenetration of polymer chains, and finally the formation of weak chemical bonds. Furthermore, various properties of mucoadhesive polymers, the mechanism(s) controlling bioadhesion, the factors affecting mucoadhesion, mucosal interaction, and biological mucoadhesives have also been elaborated.