Gold and silver nanoparticles functionalized with 4',7-dihydroxyflavone exhibit activity against Leishmania donovani

Leishmaniasis is a neglected tropical disease that has been burdening the world for over a century. Though there are drugs to treat leishmaniasis, the repertoire suffers several drawbacks like toxicity and low therapeutic value. Therefore, there is a rising concern to develop new anti-leishmanial strategies. In this study, we report, for the first time, the one-pot synthesis method and functionalization of gold and silver nanoparticles with 4',7-dihydroxyflavone (Au-47DHF and Ag-47DHF)) and their anti-leishmanial activity. Oval and spherical-shaped Au-47DHF nanoparticles were obtained with an average size of 5.8 ± 0.1 nm and while synthesized dodecahedron-shaped Ag-47DHF had an average size of 25.1 ± 1 nm. The zeta potential of Au-47DHF and Ag-47DHF were measured to be stable with values of 40 mV and 60 mV, respectively. The functionalization of nanoparticles with 4',7-dihydroxyflavone was confirmed by FTIR spectra. Both Au-47DHF and Ag-47DHF exhibited promising anti-leishmanial activity against the promastigote forms with IC₅₀ values of 0.1226 ± 0.02 µg/ml and 0.8483 ± 0.14 µg/ml, respectively. The nanoparticles were also capable of anti-intracellular amastigote activity with 0.121 ± 0.36 µg/ml and 0.215 ± 0.85 µg/ml for Au-47DHF and Ag-47DHF, respectively. Interestingly, the treatment with Au-47DHF and Ag-47DHF nanoparticles generated high ROS concentrations in the parasites suggesting a ROS-mediated anti-leishmanial activity of Au-47DHF and Ag-47DHF. Concluding from the results, we present here a novel synthesis method of Au-47DHF and Ag-47DHF nanoparticles that have immense potential to be anti-leishmanial agents.