Influence of glutaraldehyde on drug release and mucoadhesive properties of chitosan microspheres

Among bioadhesive drug delivery systems, chitosan microspheres can be considered useful formulations for mucosal administration of drugs. The feasibility of modulating drug release from chitosan microparticles is due to polymer cross-linking, i.e. by glutaraldehyde. The aim of this work was to develop a new simple ‘in vitro’ technique based on electron microscopy in order to study the effect of polymer crosslinking density on mucoadhesive properties of the chitosan microspheres. This technique consists of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations on morphological changes of chitosan microspheres with various cross-linking densities in contact with mucin solution. The results of SEM and TEM analyses have permitted to confirm the high affinity for mucin of uncross-linked chitosan microspheres and thus their bioadhesive properties. Moreover, bioadhesive characteristics of the microparticulate drug delivery systems were depressed for glutaraldehyde cross-linked chitosan microspheres.