Preparation of W/O/W microcapsule containing enzyme without alcohol

We proposed a novel method for the preparation of W/O/W type microcapsules containing enzymes. In this method, a gas phase was used in place of alcohol that has been conventionally used in solvent change processes for the preparation of W/O/W type microcapsules. As a model system for this study, we prepared glucose-oxidase encapsulated poly(l-lysine-alt-terephthalic acid) microcapsules whose volume can be decreased in the presence of glucose and evaluate the effect of glucose on the shrinking process. To estimate the relative concentration of enzyme in microcapsule, a simple model was proposed on assumption of linear dependence of the rate of change in the size and in the charge density of the microcapsule membrane. The diameters of the shrunk microcapsule observed were consistent with the theoretical value. By a fitting of the observed time course of the microcapsule size to the theoretical equations, two time constants were obtained, both related inversely to the relative enzyme concentration in the microcapsules. From the comparison of their constants for microcapsules prepared by the novel and conventional method, it became apparent that the glucose-oxidase containing microcapsule prepared by the novel method exhibited about 1.5 times higher enzyme activity of the case for the conventional method using ethanol in the solvent change processes.