COMPARISON OF THE EFFECT OF DIFFERENT CHITOSAN SALTS AND N-TRIMETHYL CHITOSAN CHLORIDE ON THE PERMEABILITY OF INTESTINAL EPITHELIAL-CELLS (CACO-2)

A partially quaternized chitosan derivative, N-trimethyl chitosan chlo ride (TMC) (degree of quaternization 12.28%), was synthesized and the effects of this novel polymer on the permeability of intestinal epithe lial cells, using Caco-2 cell monolayers, were investigated and compar ed with those of chitosan hydrochloride and chitosan glutamate. Transe pithelial electrical resistance (TEER) measurements at pH 6.20 reveale d that all these polymers (0.25-1.5% w/v) caused an immediate and pron ounced lowering in TEER values in the order chitosan hydrochloride (84 % reduction after 2 h incubation) > chitosan glutamate (60% reduction) > TMC (24% reduction) at 0.25% w/v concentrations. At higher concentr ations (up to 2.5% w/v), TMC was able to decrease the TEER further. Si milar results were obtained in transport studies, using the hydrophili c radioactive markers, [C-14]-mannitol (MW 182.2) and [C-14]-polyethyl ene glycol 4000 (PEG-4000, MW 4000). Large increases in the permeation of these markers were found. The transport of [C-14]-mannitol was inc reased 34-fold (chitosan hydrochloride), 25-fold (chitosan glutamate) and Ii-fold (TMC) at 0.25% w/v concentrations. Further increases in th e permeation of both markers were found at higher concentrations of TM C. Due to its quaternary structure, TMC is better soluble than the oth er chitosan salts, and its higher solubility may compensate for its le sser effectivity at similar concentrations. It is also soluble at pH 7 .40, where the chitosan salts are insoluble and therefore ineffective. No deleterious effects to the cells could be demonstrated with trypan blue exclusion studies and confocal laser scanning microscopy (CLSM). CLSM confirmed that these polymers increase the transport of large hy drophilic compounds (using the fluorescent markers FD-4, MW 4400 and F D-20, MW 19600) through opening of tight junctions to allow for parace llular transport. It is concluded from this study that the charge, cha rge density and the structural features of chitosans and chitosan deri vatives are important factors determining their potential use as absor ption enhancers. (C) 1998 Elsevier Science B.V.