Catalytic and eco-toxicity investigations of bio-fabricated monometallic nanoparticles along with their anti-bacterial, anti-inflammatory, anti-diabetic, anti-oxidative and anti-cancer potentials

Abstract The present investigation highlights a unique, rapid, greener, economical and biological approach in the fabrication of gold (Au), copper (Cu), iron (Fe) and zinc (Zn) monometallic nanoparticles (MNPs) using Annona muricata aqueous leaf extract (AMLE) as a suitable reducing, capping and stabilizing agent. The bio-fabricated NPs were characterized using UV–Visible spectrophotometer and field emission scanning electron microscope with energy-dispersive x-ray spectroscopy (FESEM-EDX). Surface plasmon resonance (SPR) determined the formation of MNPs with maximum absorbance at 540, 570, 280 and 360 nm for Au, Cu, Fe and Zn-NPs respectively. Among all the bio-fabricated MNPs investigated CuNPs have showed superior activity for their anti-bacterial (against Escherichia coli), anti-inflammatory (egg albumin protein denaturation inhibition-51.46 ± 1.53 μg/mL), anti- diabetic (α-glucosidase activity inhibition-32.97 ± 2.51 μg/mL), anti-oxidative (DPPH free radical inhibition-63.44 ± 3.12 μg/mL) and anti-cancer (against K562 cancer cell line using MTT assay-53.34 ± 2.29 μg/mL) potentials. Whereas ZnNPs showed less-activity in anti-inflammatory and anti-oxidative (>100 μg/mL) and no activity was observed in anti-diabetic and anti-cancer assays compared to other investigated NPs. Both Cu- and Fe-NPs showed catalytic ability in the degradation of textile dyes in the presence of sodium borohydride (NaBH4). Cu and Fe-NPs degraded 94% of rhodamine-B (rh-B) under 35 and 90 min, whereas 94% of methyl orange (MO) under 25 and 70 min, respectively. Eco-toxicity studies carried out using Artemia nauplii have suggested that ZnNPs are less toxic (LC50 was >100 μg/mL after 24 h) compared to other investigated NPs.