Influence of molecular weight on oral absorption of water soluble chitosans

Chitosan, a cationic polysaccharide, has been widely employed as dietary supplement and in pharmacological and biomedical applications. Although numerous studies have focused on its applications as pharmaceutical excipients or bioactive reagents, molecular weight (MW)-dependent pharmaceutical and bioactive properties remain unclear. As a preliminary study, we investigated the MW-dependent Caco-2 cell layer transport phenomena (in vitro) and intestinal absorption patterns after oral administration (in vivo) of water-soluble chitosans (WSCs). The absorption of chitosan was significantly influenced by its MW. As the MW increases, the absorption decreases. Compared to high-MW chitosan (WSC 230K, MW=230 kDa), absorption profiles were observed to increase more than 23 and 25 times with WSC 3.8K (MW=3.8 kDa) in both in vitro and in vivo transport experiments, respectively. Furthermore, the chitosans showed concentration- and MW-dependent cytotoxic effects, and the chitosan oligosaccharides (MW<10 kDa) showed negligible cytotoxic effect on the Caco-2 cells. In consideration with safety and absorption profiles, chitosan oligosaccharides may be considered as safe and potential candidates for pharmaceutical and biomedical applications.