Developments in the area of bioadhesive drug delivery systems

This paper aims to review the current progress in bioadhesion for drug delivery applications as well as new techniques related to this field. Research started with mucoadhesive polymers that had already been in use as excipients and were rapidly used in new formulations. Their major drawback was found in their unspecific binding, as they adhere to almost any mucosal surface. As some of the polymers showed additional properties such as enzyme inhibition and permeation enhancement, however, they remain interesting as multifunctional excipients. In contrast to mucoadhesion, the concept of specific bioadhesion by use of lectins and other adhesion molecules is now gaining increasing attention as these substances bind directly to receptors on the cell surface rather than to the mucus gel layer. Since specific binding to the cell surface is often followed by uptake and intracellular transport, new chances for drug delivery evolved. Bioadhesion may, thus, enable researchers to deliver macromolecular drugs directly to specific target cells and has implications also relevant to other fields of science, such as tissue engineering, gene delivery and nanotechnology.