Microcompartmentalized cell-free protein synthesis in semipermeable microcapsules composed of polyethylenimine-coated alginate.

We describe microcompartmentalized cell-free protein synthesis in semipermeable microcapsules prepared from water-in-oil-in-water droplets by a rupture-induced encapsulation method. An aqueous solution of template DNA coding for green fluorescent protein and enzymes for the cell-free protein synthesis was aliquoted into water-in-oil droplets using a microfluidic device, and the droplets were transformed into semipermeable microcapsules. Substrates for protein synthesis diffused into the microcapsules through their semipermeable polyion complex membranes composed of polyethylenimine-coated alginate. Cell-free protein synthesis was confirmed by detection of the fluorescence of the synthesized green fluorescence protein in the microcapsules. We also used this microcompartmentalized system to synthesize protein from a single molecule of template DNA encapsulated by limiting dilution.