Rapid preparation of polymersomes by a water addition/solvent evaporation method

In this article we demonstrate a rapid water addition/solvent evaporation method to produce polymersomes with controllable sizes. For this method a solution of an amphiphilic block copolymer in THF is quickly mixed with an aqueous solution, followed by organic solvent evaporation under reduced pressure using a rotary evaporator. The parameters that influence the formation, size, and stability of the polymersomes are easily controlled, and the entire process can take less than five minutes. The method was initially tested with a series of rod-rod peptidic block copolymers, where the hydrophilic block is a charged designed peptide, and the hydrophobic block is poly(gamma-benzyl L-glutamate) with varying degrees of polymerization (35-250 monomers), and the polymersome formation was monitored and confirmed with dynamic light scattering, optical microscopy, and transmission electron microscopy. The widespread applicability of the technique was also proven with more traditional charged and non-charged coil-coil block copolymers of varying length. The method was found to be very robust with regards to salt concentration and initial mixing, and the polymersome size could be precisely adjusted over a wide range, with the same block copolymer forming polymersomes ranging from similar to 200 nm to similar to 2 mu m in diameter. Given its simplicity, versatility, and speed, the water addition/solvent evaporation method described here is a very practical tool for polymersome preparation.