Release profile of insulin entrapped on mesoporous materials by freeze–thaw method

Adsorption profiles of insulin on porous materials and release profiles of insulin entrapped on folded-sheet mesoporous silica (FSM) were studied. Three types of FSM with different pore sizes (3.0, 6.1, and 9.2 nm) were used as candidates. A simple technique of repeated freezing and thawing resulted in effective adsorption of insulin on mesoporous structures. The amount of adsorbed insulin, estimated by protein assay, increased with an increase in the pore sizes of FSM used. Nitrogen sorption analysis showed that the specific surface area and pore volume decreased according to the insulin adsorption. On the release profile of insulin, the smallest pore size of FSM (3.0) was found to be a suitable material for a fast release of insulin, whereas the medium-pore FSM (6.1) held the insulin inside the pores for a longer time. Consequently, the desired release of insulin could be achieved by selecting the appropriate pore size of FSM.