One-step fabrication of pH-responsive microcapsules with aqueous cargo using aqueous two-phase system

A new approach was developed to generate the pH-responsive poly(polyethylene glycol-co-acrylic acid) poly (PEG-co-AA) microcapsules by in-situ photopolymerization of the water–in–water–in–oil (W/W/O) double emulsion droplets (DEDs) in the microfluidic channel. The two immiscible W solutions used in the microfluidic preparation of the W/W/O DED were prepared with two phase-separated aqueous phases obtained from the so-called aqueous two-phase system (ATPS) by adding (NH4)2SO4 salts to the aqueous PEG diacrylate/AA mixture solution. The waterborne cargo could be directly loaded into the water phase at the core of the W/W/O DED during the microfluidic production. The produced microcapsules were shown to be smartly responsive to pH change and recyclable, and their in-situ and ex-situ cargo loading and releasing properties were demonstrated using fluorescein isothiocyanate dextrans with different molecular weights. This new one-step microfluidic fabrication method of pH-responsive microcapsules can be used to load other valuable waterborne cargos at the core of the pH-responsive microcapsule.