Immersion coating of pellet cores consisting of chitosan and calcium intended for colon drug delivery.

Biopolymers such as pectin, alginate, and chitosan have a great potential in colon drug delivery. The aim of this study was to produce pellets with calcium and chitosan in the core and then by an interfacial complexation reaction coat the cores with pectin or alginate in combination with calcium or chitosan. Pellets with calcium in the core acted as a reference. The drug release was investigated in environments mimicking the stomach and the small intestine. The morphology of the coatings indicated a more wrinkled and irregular structure for coatings composed of pectin or alginate in combination with chitosan compared to the coat consisting of alginate in combination with calcium. The results from the drug release experiments showed that all the investigated coatings, especially with alginate, slowed down the drug release compared to the uncoated cores. The release from the chitosan-containing pellets was higher than the reference. The swelling studies revealed a high degree of swelling of the core consisting of chitosan. This probably explains the higher drug release from the coated chitosan pellets.