Physicochemical properties and controlled drug release of microcapsules prepared by simple coacervation

Ternary phase diagrams of gelatin–water–methanol, gelatin–water–ethanol, and gelatin–water–propanol systems were prepared to evaluate optimal coacervation. The results of their evaluation suggested that the optimal coacervation region expands with the hydrophobicity of the added poor solvent (methanol, ethanol, 1-propanol, and 2-propanol).Microcapsules prepared based on the optimal coacervation region differed in controlled drug release among poor solvents used even when the concentration of gelatin, a membrane component, is the same. Compared with microcapsules prepared using the gelatin–water–ethanol system, those prepared using the gelatin–water–propanol system showed a 34% decrease in the drug release rate 24 h after the initiation of the drug release test. These results suggested that microcapsules prepared using gelatin–water–various lower alcohol systems can readily control drug release and can be a useful drug delivery system (DDS).

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► Ternary phase diagrams were prepared to evaluate optimal coacervation.
► The optimal coacervation region expands with the hydrophobicity of poor solvent.
► Gelatin microcapsules were prepared based on the optimal coacervation region.
► Drug release from microcapsules could be controlled by various poor solvents.