Calcium pectinate gel bead intended for oral protein delivery: preparation improvement and formulation development

Calcium pectinate gel (CPG) micrometer-sized beads (microbeads) containing insulin, as a model amphoteric protein, were prepared by ionotropic gelation technique together with an air compressor. The influences of phosphate buffer, pH as well as calcium and pectin concentrations of cross-linking solution on the characteristics and release profiles of microbeads were investigated. With the aid of compressed air flow, the mean diameters of beads were successfully decreased to micron-sized. The results showed that all the factors investigated greatly affected the entrapment efficiencies and release profiles of the microbeads. Suitable formulation concentrations should be considered and great care should be taken to maintain the pH of working solutions at or close to isoelectric point of protein loaded during the whole preparation process. Hence, CPG microbeads of perfect spherical shape, uniform sizes, enhanced mechanical strength, good entrapment efficiencies and delayed release profiles were prepared for a load of amphoteric protein and peptide drugs, without any use of organic solvents or harsh ingredients. Therefore, CPG microbeads could be a promising carrier for oral controlled-release systems of amphoteric protein and peptide drugs.