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 μm 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.