Absorption and distribution of water-soluble hydroxypropyl chitosan in mice after oral administration

Two kinds of water-soluble hydroxypropyl chitosan (HPCS) samples with different weight-average molecular weights (Mw) (HHPCS for higher Mw, 1.43×105 Da; LHPCS for lower Mw, 5.71×103 Da) were used to investigate their absorption and distribution in mice by oral administration after being labeled by fluorescein isothiocyanate. The result of in vitro degradation showed that HPCS degraded more easily in the presence of lysozyme than in pepsin. After oral administration of HPCS, HPCS would undergo a series of degradation and absorption under the action of tissue cells and enzymes in the body. The absorption and distribution of HPCS in organ tissues was significantly influenced by its Mw. With the decrease of Mw, the absorption rate and amount of HPCS increased. In fact, only a small amount of HPCS and its catabolite with low Mw was absorbed by the tissues, and most HPCS was metabolized and excreted out of body rapidly. Additionally, there was some accumulation of HPCS in liver, and so HPCS content in liver and kidney was higher. The whole HPCS plasma concentration was lower instead, due to rapid plasma clearance. The absorbed HPCS molecules still maintained a relatively higher concentration even after 16 h in the tested tissues. The research results gave some valuable data for the application of water-soluble chitosan in food and biomedicine, especially as a potential candidate for drug delivery systems.