Carboxymethyl high amylose starch: Chitosan self-stabilized matrix for probiotic colon delivery

A new hydrophilic tablet dosage system based on an ionic self-stabilization of a carboxylated (carboxymethyl high amylose starch, CM-HAS) and an amino (Chitosan) excipient was proposed for probiotic colon delivery. CM-HAS (protonated and compacted in acidic medium) ensures gastro-protection and Chitosan (low soluble in intestinal media) prevents early release of Lactobacillus rhamnosus bacteria. Thus, in CM-HAS:Chitosan monolithic tablets, increasing percentage and molecular weight (MW) of Chitosan generated a decrease of bacteria release rate, bacteria being the most effectively retarded by the highest MW of Chitosan (2.2 x 10(6) g/mol). The monolithic formulations containing high percentages of CM-HAS (80%) delivered bacteria after 2 h of incubation in gastrointestinal conditions for all the Chitosan MWs used. A combined mechanism of bacteria release is proposed for CM-HAS:Chitosan monolithic tablets, involving the swelling of the tablets (due to the Chitosan), followed by the erosion and dissolution of CM-HAS. In addition, a gel-forming barrier of Chitosan in acidic conditions also contributed to the delay of the bacteria delivery. The CM-HAS dry-coated monolithic tablets changed the effect of Chitosan molecular weight on bacteria liberation and improved the percentage of delivered bacteria in simulated intestinal conditions. (C) 2008 Elsevier B.V. All rights reserved.