Preparation of Monodisperse ENX-Loaded PLGA Microspheres Using a Microfluidic Flow-Focusing Device

We present monodisperse enoxacin (ENX)-loaded poly(latic-co-glycolic acid) (PLGA) microspheres prepared by a microfluidic flow-focusing device (MFFD). Nowadays monodisperse biodegradable polymer spheres such as PLGA have gained great interest for drug delivery system (DDS) and bioassay. While a conventional emulsion method produces polydisperse microspheres, the MFFD allows a precise control of sphere size. In this study, monodisperse ENX-loaded PLGA microspheres were prepared using a MFFD with dichloromethane (DCM) and dimethyl carbonate (DMC) as a solvent of PLGA. The MFFD was fabricated by polydimethylsiloxane (PDMS) casting from SU-8 mold prepared by photolithography. The hydrophobic surface of PDMS channels in the MFFD was modified by poly(vinyl alcohol) (PVA) treatment to facilitate hydrophilicity. The PLGA solution was served as a dispersed phase while the PVA solution was used as a continuous phase in the device. The monodisperse microdroplets were generated in the narrow orifice where the dispersed phase is squeezed by a shear force of continuous phase. On the optimum conditions, the diameter of monodisperse PLGA microspheres was adjustable ranging from 30 to 70 mu m by controlling the flow rate of dispersed or continuous phase and concentration of PLGA. The morphology of PLGA microspheres was characterized by field emission scanning electron microscope (FE-SEM). The drug-loaded microspheres were prepared by adding 0.005 g ENX as a drug into PLGA solution that was sonicated to disperse undissolved ENX powder homogeneously. Drug release profiles from the drug-loaded PLGA microspheres were monitored by a UV-Vis spectroscopic method. The presented drug-loaded PLGA microspheres can be applicable to controlled DDS.