Development of polymer-based nanoparticles in combination with Pheroid® technology to improve therapy for Mycobacterium avium complex

Abstract

The difficulties associated with conventional therapy for Mycobacterium avium complex (MAC) treatment provide opportunities for drug delivery platforms. In this research investigation, the results obtained for the development of a hybrid system of poly (lactic-co-glycolic acid) (PLGA) nanoparticles encapsulated into a Pheroid® vesicle are reported. Ethambutol (ETB) and clarithromycin (CLR) together with mycolic acids (MA) were encapsulated into PLGA NPs by using a double emulsion solvent evaporation technique. The particles displayed an average size of 305—397 nm with an average zeta potential of -26.5 to -29.8 mV. Liquid chromatography mass spectrometry (LCMS) drug quantification revealed that PLGA/ETB/MA and PLGA/CLR/MA NPs had a drug encapsulation efficiency (EE) of 96.6 and 94.3%, respectively. The drug loaded particles were subjected to a cytotoxicity screening towards the HeLa cell line and THP-1 macrophages. The cytotoxicity evaluation revealed that PLGA, MA, and ETB displayed no cytotoxic effect after 24-hour exposure to the particles. PLGA-CLR NP's on the other hand had a much more prominent effect on the survival of the treated cells when compared to the DF and ETB NP's treated cells. In vitro tests indicated that the CLR incorporated in the PLGA NP's had a lower cytotoxic effect compare to the pure drug alone. Successful cellular uptake of all particles (Drug Free (DF), CLR and ETB, with and without MA) was observed into THP-1 macrophages thus suggesting that targeted delivery to the site of infection may be possible. The nanoparticles containing the drug and/or the MA, were encapsulated into Pheroid® vesicles via a post mix approach. DF and ETB-loaded PLGA NPs were successfully encapsulated into Pheroid® vesicles, however the same fate was not observed for CLR-loaded PLGA-MA NPs. Furthermore, the cytotoxicity assay results indicated that Pheroid® vesicles were cytotoxic to HeLa cells at concentration ? 2% (v/v). Further evaluation indicated that Pheroid® vesicles were non-cytotoxic at low concentration when exposed to THP-1 macrophages after 24 hours of incubation. The in vitro uptake studies revealed that PLGA NPs were observed at a greater density in close proximity within THP-1 macrophages after 1 hour of incubation when compared to the control of PLGA NP formulations without Pheroid® vesicles, however further investigation is warranted for further conclusions to be drawn. In summary, the PLGA NP-Pheroid® vesicle hybrid system may have potential to be considered as an attractive and promising approach to enhance the current conventional therapy for MAC.