Development of levofloxacin-loaded PLGA microspheres of suitable properties for sustained pulmonary release

Aerosol antibiotics are an interesting alternative to oral or intravenous therapy in Cystic Fibrosis lung infections. Levofloxacin (LVX) inhaled solution is already an effective option. In this study, the aim was the development of LVX-loaded PLGA microspheres (MS) for pulmonary administration as a dry powder. MS were prepared, for the first time, by a modified double emulsion solvent evaporation method with premix membrane homogenization. Aqueous phases were saturated with LVX and a fatty acid (lauric acid) was added to avoid the drug escaping from the organic phase. MS were characterized in terms of size, drug content, morphology and in vitro release properties. X-ray diffraction, Fourier-transform infrared spectroscopy, differential and gravimetric thermal analysis, and cytotoxicity analyses were performed. Results showed this new method increased the drug loading while maintaining an adequate (similar to 5 mu m) particle size and controlled release. Compared to a solution for inhalation, these properties combined with the dry-powder nature of these MS will improve patient compliance. The incorporation of lauric acid was not advantageous because the particle size was higher and no improvements concerning the sustained release occurred. LVX was molecularly dispersed in the matrix, or it was in amorphous state, as confirmed by the physico-chemical analyses. Calu-3 cell viability assays demonstrated no cytotoxicity for these MS, making them a promising system for LVX pulmonary delivery.