Biological properties of itraconazole-SLN

Itraconazole (ITZ) belongs to azoles, an important family of antifungal drugs, and has been used for more than 30 years in clinical applications. These drugs inhibit lanosterol 1-4demethylase, the enzyme that converts lanosterol to ergosterol. As recently demonstrated, topical formulations of ITZ in solid lipid nanoparticles (SLN) and a coating layer of didodecyldimethylammonium bromide (DDAB) induce a decrease in cell viability for tumor cell lines SK-MEL-5 and A431. This potentiality of repurposing ITZ activity by using the combined nanoencapsulation strategy with the positively charged coating of DDAB prompted us to investigate such a feature versus other tumor cell lines, like malignant blood cells. The purpose of this in vitro study was to evaluate the antimycotic activity of neutral and cationic solid lipid nanoparticles (SLN and c-SLN, respectively), both unloaded and loaded with ITZ. Moreover, the cell viability after 24 h exposure of the histiocytic lymphoma cell line U937 was also investigated, with or without the addition of alpha-lipoic acid (ALA). Results highlighted the activity of ITZ-SLN; in particular, both neutral and cationic unloaded SLN, as well as neutral drug-loaded SLN, were found to be inactive. Improvements of the MIC50 value against Candida albicans strains were found for neutral ITZ-SLN (MIC50 was 0.006 μg/ml) and cationic ITZ-SLN (MIC50 equal to 0.004 μg/ml) (the MIC50 value for free ITZ was 0.015 μg/ml). Moreover, the SLN induced an anti-proliferative effect on lymphoma cells at 1 µg/ml. ALA did not modify the cellular proliferation of cells but its combination with the SLN showed, even with a certain improvement, that it was not able to recover the cellular vitality.