Nanoemulsion of Spiramycin against Tachyzoites of Toxoplasma gondii, RH Strain: Preparation, Toxicology, and Efficacy Studies

Background: Toxoplasma infection is caused by Toxoplasma gondii, which is an intracellular protozoan parasite. This infection consequently lead various congenital disabilities during pregnancy in patients. Spiramycin (Spi), a macrolide antibiotic, is typically recommended for T. gondii infection in pregnant women. We aimed to prepare the nanoemulsion of spiramycin (NE-Spi) and to evaluate the activity of this formulation in tachyzoites of T. gondii, RH strain. Methods: This study was conducted in 2019-2021 at the School of Public Health, Tehran University of Medical Sciences, Tehran, Iran. NE-Spi was prepared by spontaneous emulsification. The effects of this nanoemulsion on the viability of cultured cells were measured using MTT assay. To estimate the effects of NE-Spi on tachyzoites of T. gondii, RH strain, different concentrations of NE-Spi, S-Spi (suspension of spiramycin), and NE (nanoemulsion without any spiramycin) were added to tachyzoites and then stored for 30, 60, 90, 120 min and 24 h in 250 mu g/ml concentration at room temperature. Finally, Tachyzoites mortality rates were evaluated by trypan blue staining. Of note, flow cytometry was conducted to confirm the obtained results. Results: The final particle size of NE-Spi was calculated to be 11.3 nm by DLS and TEM. Thereafter, using MTT assay, in 62.5 mu g/ml concentration of NE-Spi, the Vero cells viability was obtained as 82%. The highest mortality rates of tachyzoites of T.gondii, RH strain were observed at 250 mu g/ml concentration and after 120 min of exposure, but it was not significantly different from 24 h of exposure. Conclusion: NE-Spi has lethal efficacy on T. gondii RH strain in- vitro.