A photopolymerizable, methacrylated alginate was synthesized by conjugating methacryloyl groups to the side chains of alginate. Cell-enclosing microcapsules were subsequently prepared by the photopolymerization of cell-suspending methacrylated alginate droplets triggered by irradiation with visible light. Cells enclosed by this method remained alive in the microcapsules for at least 2 weeks. (C) 2009, The Society for Biotechnology. Japan. All rights reserved.