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 × 106 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.