Green Synthesis of Molybdenum Oxide Nanoparticles via Bacillus subtilis: Characterization, Optimization, Antimicrobial Activity and Cytotoxicity

Molybdenum oxide nanoparticles (MoNPs) have been widely studied and have gathered substantial amount of attention due to their fascinating characteristics. The current study aims at green-synthesis of MoNPs that is both safe and eco-friendly by employing bacteria (AJ7) after careful selection from 18 pure bacterial isolates. After inspection the bacterial isolate was identified as Bacillus subtilis (CP002905.1) based upon 16S rDNA sequence homology. Subsequently, optimization experiments were carried out and after assessment of different parameters, the optimum conditions attained were with temperature (37°C), pH 6, carbon source (glucose), nitrogen source (yeast), non-shaking with dark conditions. Also, the MoNPs were characterized and an average size of 202.8 nm was generated followed by polydispersity index (PDI) of 0.31 while zeta potential of MoNPs was recorded as –24.1 mV. UV-Vis spectrophotometer spectra exposed surface plasmon resonance (SPR) band between 250 to 290 nm validating the production of MoNPs whereas Fourier transform infrared (FTIR) investigation displayed the presence of some functional groups. Furthermore, Scanning Electron Microscopy (SEM) evaluation displayed irregular MoNPs between 140–260 nm whereas X-ray diffraction (XRD) revealed crystalline nature of the NPs whereas Energy Dispersive X-ray Spectroscopy (EDX) evaluated elements occurring within the nanoparticles i.e. Mo 33.08%. Additionally, antimicrobial activity assay with varying multidrug-resistant (MDR) bacterial strains with concentrations ranging from 10 to 200 mL was conducted. A minimum zone of inhibition (ZOI) at 9 mm ± 0.06c was obtained at 100 mL range against B. subtilis. Later on, cytotoxicity studies with MDA-MD-231 (MD Anderson) breast cancer cell lines displayed 67% viability against 100 µL MoNPs via MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results proved that MoNPs can be used in biomedical sector in future as they are safe, biocompatible, low-cost and sustainable.