Chitosan-alginate microparticles as a protein carrier

The oral administration of peptidic drugs requires their protection from de gradation in the gastric environment and the improvement of their absorptio n in the intestinal tract. For these requirements, a microsystem based on c ross-lined alginate as the carrier of bovine serum albumin (BSA), used as a model protein, was proposed. A spray-drying technique was applied to BSA/s odium alginate solutions to obtain spherical particles having a mean diamet er less than 10 mum. the microparticles were hardened using first a solutio n of calcium chloride and then a solution of chitosan (CS) to obtain stable microsystems. The cross-linking process was carried out at different CS co ncentrations and pH values of the cross-linking medium. The CS concentratio n affected the BSA loading in the micro particles prepared at a pH value le ss than the protein isoelectric point (pI). Moreover, the BSA loading at a pH value less than the pI was higher than that at a pH similar to the pI re gardless of the CS concentration. This finding could be attributable to the formation of a BSA/alginate complex. The evaluation of the interaction bet ween BSA and alginate at different pH values by means rheological measureme nts confirmed this hypothesis. This approach may represent a promising way to devise a microcarrier system with appropriate size for targeting the Pey er's patches, with appropriate immobilization capacity, and suitable for th e oral administration of peptidic drugs.