Ionotropic alginate beads for controlled intestinal protein delivery: Effect of chitosan and barium counter-ions on entrapment and release

Alginate beads containing the model protein haemoglobin (Hb) were prepared by coagulation with various counter-ions to improve the controlled release of the protein. The effect of Ba2+ and Ca2+ ions and of the polycationic polysaccharide chitosan was investigated. Coagulation with Ba2+, Ca2+ and/or chitosan showed differences in the swelling index of the beads, in the encapsulation efficiency of Hb entrapment and in the release of the entrapped protein. Chitosan in the coagulation fluid markedly enhanced the encapsulation efficiency of the Hb. Release studies were conducted in simulated gastric fluid (SGF pH congruent to 1.2) and subsequently in simulated intestinal fluid (SIF pH congruent to 1.2) at 37 degrees C. Beads were stable in the gastric fluid but released their protein upon transfer to intestinal fluid. The release coincides with the burst and disintegration of beads. Rate of protein release from the beads was affected by the Ba2+ and chitosan concentration in coagulation fluid.