Silica-Hydrogel Microcapsules for Controlled Release Applications

We present a methodology for the fabrication of silica-coated calcium alginate microcapsules (~ hydrogel core with permeable protective membrane). The microcapsules were synthesis in two steps. In the first step, alginate gel core were prepared by the drop-on-demand InkJet technology and in the second step the organo-silica shell has been formed by a sol-gel process using alkoxysilane precursors. Incorporation of nanoparticles or biomolecules inside the alginate core mimics the further encapsulation of active substances (drug) or immobilization of proteins. The resulting microcapsules have a mean diameter in the range of 40-80 µm and the silica surface layer thickness is in the range of a few µm’s.