Microfluidic fabrication and permeation behaviors of uniform zwitterionic hydrogel microparticles and shells.

This study introduces a flexible and straightforward method for generating monodisperse complex hydrogel microparticles. For this, a water-in-oil emulsion was generated in a microcapillary device and then the emulsion drops were photo-polymerized to transfer them to hydrogel particles. The hydrogel microparticles were made of poly (2-methacryloyloxyethyl phosphorylcholine) that has an enhanced biocompatibility due to the phosphatidyl choline moiety in the backbone. The average mesh size of the hydrogel network, which is 50Å, was estimated on the basis of the Peppas-Merrill equation. This mesh size was experimentally confirmed again by NMR cryoporometry analysis and permeation test for dextran probes. Furthermore, to diversify the applicability of microfluidic technology, an oil-in-water-in-oil double emulsion was also fabricated by using the co-axial jetting of three combined flows in the micro-channel. Then the aqueous shell was polymerized to give rise to hollow-structured hydrogel microparticles. Finally, we have shown that the microfluidic approach is useful for fabrication of complex hydrogel microparticles that have potential uses in drug immobilization and delivery.