Understanding the potential of bio-fabricated non-oxidative silver nanoparticles to eradicate Leishmania and plant bacterial pathogens

Abstract: The present study was aimed to use an aqueous extract of Mentha arvensis L. to bio-fabricate silver nanoparticles (AgNPs) and evaluation of the potential of non-oxidative nanoparticles in photodynamic treatment of pathogens. Spectrophotometric analysis of colloidal AgNPs represented a characteristic SPR band at 485 nm of the light wavelength. Nanoparticles were structurally anisotropic and nearly spherical and observed between ~ 20 and 100 nm by using SEM and AFM images. The dynamic light scattering technique determined particle size between ~ 14 and 32 nm. Biological applications manifested that the AgNPs are highly biocompatible and caused rupturing of RBCs at an exceptionally high dose estimated as ~ 214 µg/ml, while 10 µg/ml of AgNPs killed nearly ~ 50% of Leishmania tropica. AgNPs were also found effective to curb the growth of various plant bacterial pathogens and the dose-dependent response was observed in between ~ 2 and 12 µg/ml and MIC was recorded at 12 µg/ml. ROS quantification revealed that the AgNPs are not potent to produce free radicles and did not report any quantum yield. The elemental composition analysis of AgNPs by EDX confirmed that these nanoparticles are non-oxidative. ROS quantification and photothermal activity evaluation showed that these nanoparticles cannot be used in photodynamic therapy. The experimental outcomes of this study clarify the use of biocompatible AgNPs into pharmaceutical formulations to treat Leishmaniasis and plant bacterial pathogens.