Beta cyclodextrin-insulin-encapsulated chitosan/alginate matrix: Oral delivery system

Cyclodextrins (CD) form inclusion complexes with many drug molecules. The c omplexed drugs have increased bioabsorption in in vivo system. We have atte mpted to complex insulin with P-Cyclodextrin (BCD) and encapsulate in the c hitosan/ calcium alginate matrix. For drug release studies insulin complexe d with BCD for 20 min and that complexed with BCD for 150 min have been use d for encapsulation in the chitosan/calcium alginate matrix. The two matric es seem to have different drug release profiles in simulated intestinal med ium (pH 7.4) It appears that drug release from the 20-min BCD complexed sys tem encapsulated in the chitosan/calcium alginate matrix begins only after an hour, where, being released from the 150-min BCD complexed system it beg ins in the first hour itself. Also, aggregation of the insulin molecules se ems to be reduced by the complexation of the drug with BCD. Another noticea ble fact is the change in the loading character, which is found to be inver sely related to the concentration of BCD when it is above the stoichiometri c equivalent of the drug. In an attempt to increase the payload of the drug in the matrix, the pH of the processing medium consisting of calcium chlor ide and chitosan is varied. It is found that the encapsulation efficiency i ncreases as the pH is decreased from 6.0 to 4.0. Another way of increasing the loading is studied by decreasing the concentration gradient of insulin in the processing alginate solution and the crosslinking medium consisting of chitosan/calcium chloride. Preliminary animal studies on rabbits seem to be promising. (C) 2000 John Wiley & Sons, Inc.