Competing two enzymatic reactions realizing one-step preparation of cell-enclosing duplex microcapsules.

The usefulness of cell-enclosing microcapsules in biomedical and biopharmaceutical fields is widely recognized. In this study, we developed a method enabling the preparation of microcapsules with a liquid core in one step using two enzymatic reactions, both of which consume H2 O2 competitively. The microcapsule membrane prepared in this study is composed of the hydrogel obtained from an alginate derivative possessing phenolic hydroxyl moieties (Alg-Ph). The cell-enclosing microcapsules with a hollow core were obtained by extruding an aqueous solution of Alg-Ph containing horseradish peroxidase (HRP), catalase, and cells into a co-flowing stream of liquid paraffin containing H2 O2 . Formation of the microcapsule membrane progressed from the surface of the droplets through HRP-catalyzed cross-linking of Ph moieties by consuming H2 O2 supplied from the ambient liquid paraffin. A hollow core structure was induced by catalase-catalyzed decomposition of H2 O2 resulting in the center region being at an insufficient level of H2 O2 . The viability of HeLa cells was 93.1% immediately after encapsulation in the microcapsules with about 250 µm diameter obtained from an aqueous solution of 2.5% (w/v) Alg-Ph, 100 units mL(-1) HRP, 9.1 × 10(4) units mL(-1) catalase. The enclosed cells grew much faster than those in the microparticles with a solid core. In addition, the thickness of microcapsule membrane could be controlled by changing the concentrations of HRP and catalase in the range of 13-48 µm. The proposed method could be versatile for preparing the microcapsules from the other polymer derivatives of carboxymetylcellulose and gelatin.