Nannorrhops ritchiana Leaf-Based Biomolecular Extract-Mediated Silver Nanoparticles as a Platform for Mercury(II) Sensing, Antimicrobial Activity, and DNA Interaction

Heavy metal-based pollutants are one of the most alarming health hazards causing multiple diseases including cancer, hepatotoxicity, brain hemorrhage, kidney and heart failures, etc. In this study, we report an ecofriendly, low cost, and simple synthesis of silver nanoparticles (AgNPs) mediated by Nannorrhops ritchiana leaf-based biomolecular extract as a key biosensor for the mercury(II) heavy metal. The formation of AgNPs was confirmed by using different characterization techniques including UV–visible spectroscopy, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The synthesized AgNPs are yellowish-brown and exhibit the surface plasmon resonance around 435 nm. The various functional groups responsible for reduction of Ag+ to Ag0 and capping agents present in the leaf extract were confirmed by infrared spectroscopy. Energy-dispersive X-ray and scanning electron microscopic analysis were used to confirm the presence of silver and surface morphology of the nanoparticles, respectively. X-ray diffraction data suggested crystalline nature of the prepared nanoparticles. The AgNPs were successfully applied as a sensitive and selective platform for sensing of mercury(II) ions. Various parameters including nanoparticles loading, concentration of Hg+2, pH, and reaction time were optimized. The platform demonstrates a low limit of detection (4.8 × 10–7 M) and limit of quantification (4.8 × 10–7 M) with an R2 value of 0.999. The SS-DNA interaction with the AgNPs, studied by UV–Vis spectroscopy revealed intercalative mode of binding with a binding constant of 1.04 × 104 units. Importantly, this AgNPs platform also demonstrated good antibacterial efficacy against Proteus mirabilis, Shigella flexneria, Escherichia coli, and Staphylococcus aureus.