Azocross-linked poly(acrylic acid) for colonic delivery and adhesion specificity: synthesis and characterisation.

A new synthetic pathway to 4,4'-divinylazobenzene is presented together with a procedure for the copolymerisation of this compound with acrylic acid. The chemical structure of the synthesised series of copolymers is examined in the light of infrared spectroscopy results and nuclear magnetic resonance data. The thermal properties of the materials are assessed using a combination of thermal analysis techniques and their swelling behaviour is evaluated at physiologically relevant buffers designed to mimic the gastrointestinal environment.

Azocrosslinked poly(acrylic acid) for colonic delivery and adhesion specificity: in vitro degradation and preliminary ex vivo bioadhesion studies.

This study reports on the performance of a novel polymeric material that is capable of providing site specificity in active agent delivery and the development of mucoadhesive interactions. Azo-networks, based on an acrylic backbone crosslinked with 4,4'-divinylazobenzene, were subjected to in vitro degradation and mucoadhesion (before and after degradation) testing in order to model their performance in the gastrointestinal tract. Advanced surface characterisation techniques (SEM, AFM, FTIR microscopy) were used to examine the network morphology prior to, and after degradation. The data obtained from these studies indicate that there is an optimum crosslinking density to allow non-adhesive particles to reach the colon. Within the colonic environment, the azo network degrades to produce a structure capable of developing mucoadhesive interactions with the colonic mucosa.