Antimicrobial activity of β-lapachone encapsulated into liposomes against meticillin-resistant Staphylococcus aureus and Cryptococcus neoformans clinical strains

The aim of this study was to determine whether encapsulation of β-lapachone (β-lap) into liposomes interferes with its in vitro antimicrobial activity against meticillin-resistant Staphylococcus aureus (MRSA) and Cryptococcus neoformans clinical strains. Liposomes (β-lap:lipo or β-lap:HPβ-CD-lipo) were prepared using the hydration of thin lipid film method followed by sonication. The in vitro antimicrobial activities of β-lap-loaded liposomes against MRSA and C. neoformans were evaluated using the microdilution method according to the Clinical and Laboratory Standards Institute (CLSI). The liposomes presented a mean particle size ranging from 88.7 ± 1.5 nm to 112.4 ± 1.9 nm with a polydispersity index ranging from 0.255 to 0.340, zeta potential from −0.26 ± 0.01 mV to +0.25 ± 0.05 mV and drug encapsulation efficiency from 97.4 ± 0.3% to 98.9 ± 0.4%. β-Lap and β-lap:HPβ-CD had minimum inhibitory concentrations (MICs) ranging from 2 mg/L to 4 mg/L, whereas the MICs of β-lap-lipo or β-lap:HPβ-CD-lipo ranged from 4 mg/L to 16 mg/L for the MRSA strains tested. β-Lap and β-lap:HPβ-CD were able to inhibit fungal growth [MIC = 2-8 mg/L and minimum fungicidal concentration (MFC) = 4-8 mg/L]. However, β-lap-lipo and β-lap:HPβ-CD-lipo were more efficient, with MICs and MFCs of <4 mg/L. These findings suggest that the liposomal formulations tested do not interfere significantly with β-lap antibacterial activity against MRSA and improve its antifungal properties against C. neoformans.