Silica-coated alginate beads for in vitro protein synthesis via transcription/translation machinery encapsulation.

Silica-coated alginate beads successfully encapsulate transcriptional and translational machinery for the prolonged cell-free synthesis of functional protein. The silica coating, identified by optical microscope and energy-dispersive spectroscopy, made the beads more resistant-than bare or chitosan-coated beads-to an alginate-dissolving environment. The permeation of small molecules through the silica coat was confirmed by the efficient intake of small fluorescent molecules. Macromolecules such as enhanced green fluorescent protein (EGFP) and fluorescence-labeled antibody were retained much longer in the silica-coated beads than in other beads. These characteristics of silica-coated beads have found utility in cell-free protein synthesis, which was verified by the successful synthesis of EGFP in the beads including DNAs and protein synthesis machinery. The productivity of the target protein increased by two-fold in the silica-coated beads over the bare alginate beads, and the activity of the protein synthesis machinery was elongated by five-fold and three-fold over bare and chitosan-coated beads, respectively. The individual protein synthesis units of silica-coated alginate beads can be utilized for the parallel synthesis of diverse functional proteins in designed combinations, which may lead to the development of artificial cells in the future.