Sani_2020_J.Biomol.Struct.Dyn__1

Biosynthesis has emerged as an exciting interface for assembling multifunctional metal oxide nanoparticles for diverse medicinal applications. Herein, biogenic nickel oxide (NiO-NPs) is synthesized by using floral extracts of Callistemon viminalis (C. viminalis) as a low cost, ecofriendly reducing and stabilizing agent. NiO-NPs were annealed at 300 degrees C, 400 degrees C and 500 degrees C while their physiochemical properties were established by HR-SEM/TEM, UV, XRD, FTIR, EDS, SAED and SQUID techniques. Particle size of NiO-NPs decreased with increase in annealing temperatures. Magnetization curves indicated superparamagnetic behavior of the biogenic NiO-NPs at 300 K. Highly crystalline NiO-NPs obtained after annealing at 500 degrees C were used for biomedical applications. The anti-leishmanial activity on Leishmania tropica promastigotes (KMH-23) and anticancer activity on HepG2 (RCB1648) revealed excellent inhibition potential with IC50 of 37.21 microg/mL and 47 microg/mL, respectively. Significant antibacterial effect was observed against Klebsiella pneumonia and Proteus vulgaris with MIC's of 12.5 microg/mL each. Acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and alpha-glucosidase inhibitory potential were comparable with positive control drugs. Moderate antioxidant activities were observed. NiO-NPs were observed to be hemolytic (30%) at higher dose (1000 microg/mL). Overall, NiO-NPs revealed a multifunctional nature that can be explored for diverse biomedical applications.Communicated by Ramaswamy H. Sarma.