Fabrication of poly(lactic acid) microspheres with various micro-structure by microfluidic T-junction and gelatin pore-forming agent

Microporous-structured Poly(L-lactic acid) (PLLA) spheres were fabricated using a microfluidic shearing method. Poly(vinyl alcohol) (PVOH) solution is used as the continuous phase, and an emulsion containing matrix materials (PLLA), stabilizer (polysorbate 80) and pore-forming agents (gelatin) dissolved in dichloromethane (DCM) were emulsified to be dispersed phase for the generation of droplets, which were eventually transformed into microspheres. An ice water bath environment was shown to be necessary to produce stable microspheres. In addition, it was found that the mechanical stirring emulsification method was more conducive to microstructure construction than the ultrasonic emulsification. By regulating the amount of pore-forming agent (2.5 wt%, 5 wt%, and 7.5 wt% gelatin), three types of micro pores (small: 2.9±0.8 µm, middle: 46.9±14.9 µm, and large: 127.3±55.3 µm) on surface with different inner structure were obtained. Finally, it was demonstrated that the proposed method is general enough to prepare various other polymer microspheres such as PNAGA (Poly-N-acryloyl glycinamide) and PCL (Polycaprolactone).