Preparation and evaluation of physicochemical properties and anti-leishmanial activity of zirconium/tioxolone niosomes against Leishmania major

Due to the limitations of current chemotherapy for the treatment of leishmaniasis, there is an urgent requirement to search for new anti-leishmanial compounds and nano-drug delivery systems including niosomes. Therefore, the aim of this study was to prepare zirconium/tioxolone niosomes using the film hydration method and evaluate the physicochemical properties of the produced niosomes including morphology, size distribution, stability, and encapsulation efficiency. The best formulation was chosen as Span/Tween 40 (NZT₁) due to its physicochemical properties, and leishmanicidal activity against promastigotes and amastigotes was measured using both 3-(4,5-dimethylthiazol2yl)-2,5-diphenyltetrazolium bromide (MTT) and flow cytometry methods. In addition, to assess the mechanism of action of the prepared niosomes, apoptosis, levels of gene expression, reactive oxygen species (ROS) generation, superoxide dismutase (SOD) activity, and nitrite production were evaluated. The prepared formulation indicated log-normal particle size distribution curves, high encapsulation efficiency (more than 95.72 %), and good physical stability after one week, three months, and six months. Our findings demonstrated that amphotericin B was more effective than Zr/tioxolone niosomes (NZTs) due to the selectivity index (SI). However, the niosomal formulation of Zr/tioxolone showed no cytotoxic effect within the range of our experimental concentrations (CC₅₀ of 308.21 μg/mL). Moreover, the prepared niosomes increased the expression level of interleukin (IL)-12 and inducible nitric oxide synthase (iNOS) and significantly decreased the expression level of the IL-10 gene, which confirms the immunomodulatory role of NZTs. According to our findings in this study, the niosomal form of this combination can be considered for further therapeutic approaches against L. major in future planning.