Polyelectrolyte complex of carboxymethyl starch and chitosan as drug carrier for oral administration

A novel polyelectrolyte complex (PEC) of carboxymethyl starch (CMS) and chitosan was prepared, characterized and tested in vitro as a carrier for oral drug delivery. This PEC, containing 14% (w/w) of chitosan, showed a polymorphism with a lower order degree than those of CMS and of chitosan. Under conditions simulating the gastrointestinal transit, NMR imaging analysis showed slower fluid diffusion inside PEC monolithic tablets than inside CMS tablets. The PEC seems to be a more suitable drug carrier for colon targeting than CMS, since it can prolong acetaminophen release time from 8 h to 11 h and aspirin release time from 13 h to 30 h. In contrast, chitosan used as a coexcipient accelerated aspirin release from matrices based on a CMS:chitosan physical mixture.