Devices based on intelligent biopolymers for oral protein delivery.

The primary goal of bioadhesive controlled drug delivery is to localize a delivery device within the body to enhance the drug absorption process in a site-specific manner. An important contributor to good adhesion is the presence of molecular adhesion promoters such as polymer-tethered structure (e.g., poly(ethylene glycol) chains grafted to crosslinked networks) or even linear chains which are free to diffuse across the gel/gel interface. Recently, we have developed a very promising class of carriers for drug and especially protein delivery. Copolymer networks of poly(methacrylic acid) grafted with poly(ethylene glycol) exhibit reversible, pH-dependent swelling behavior due to the formation of interpolymer complexes between protonated pendant acid groups and the etheric groups on the graft chains. Gels containing equimolar amounts of MAA/EG exhibited the lowest degree of swelling at low pH increased complexation. The average network mesh size or correlation length was dramatically affected by the pH of the swelling solution. The in vitro release of insulin from P(MAA-g-EG) gels containing PEG grafts of molecular weight 1000 indicates a significant release of insulin as the gel decomplexes and insulin is freed through the structure. The results of additional in vitro studies have shown that insulin release rates can be controlled by appropriate adjustment of the structure of the gels.