Konjac glucomannan-graft-acrylic acid hydrogels containing azo crosslinker for colon-specific delivery

In this article, the synthesis and characterization of novel hydrogel systems designed for colon-targeting drug delivery are reported. The gels were composed of konjac glucomannan, copolymerized with acrylic acid, and crosslinked by the aromatic azo agent bis(methacryloylamino)-azobenzene. The influence of various parameters on the dynamic and equilibrium swelling ratios (SRs) of the hydrogels was investigated. It is shown that the SR was inversely proportional to the grafting degree of acrylic acid and the content of bis(methacryloylamino)-azobenzene. The dependence of SR on the pH indicates that obtained hydrogels are potential for drug delivery to colon. It was possible to modulate the degree of swelling and the pH sensitivity of the gels by changing crosslinking density of the polymer. The main chain of hydrogels can be degraded by P-glycosidase which is abundant in colon. They can be in vitro degraded for 73% in a month by Cereflo(R) and 86% in 20 days by Mannaway25L. We have also prepared the hydrogels that loaded with bovine serum albumin about 1.5%, 3%, 9%, and 20% by weight. In vitro release of model drug bovine serum albumin was studied in the presence of Mannaway25L or Fungamyl(R)800L in pH 7.4 phosphate buffer at 37 degreesC. The drug release can be controlled by the biodegradation of the hydrogels. (C) 2004 Wiley Periodicals, Inc.