Green Synthesis of Nickel Nanoparticles Using Salvadora persica and Their Application in Antimicrobial Activity against Oral Microbes

The current study evaluated the biogenic synthesis of nickel oxide nanoparticles (SP-NiONPs) from the root extract of (Salvadora persica) S. persica and their biological properties. The nanoparticles were characterized using spectroscopic and microscopic techniques and then evaluated for their antimicrobial properties against 10 oral pathogens. The ultraviolet-visible (UV–Vis) spectra exhibited a distinctive resonance spectrum at 334 nm for the SP-NiONPs produced from S. persica. The fourier transform infrared (FTIR) analysis revealed the presence of functional groups of biomolecules of S. persica that served as reducing and capping agents of the SP-NiONPs. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyses showed that the nanoparticles were spherical-shaped, tightly packed, and ranged in size from 18.20 nm to 45.12 nm. The energy dispersive x-ray (EDX) analysis confirmed 69.9% of the nickel (Ni) content by weight, and the X-ray diffraction (XRD) results showed the face-centered cubic (FCC) crystalline structure of the formed SP-NiONPs. The antioxidant activity of the SP-NiONPs exhibited a dose-dependent profile with an IC50 value of 51.45 ± 0.65 and a 54.13 ± 0.98 DPPH• and ABTS•+ radical scavenging activity, respectively. The SP-NiONPs showed an antibacterial activity against all the test strains; however, E. cloacae was found to be the most sensitive strain, with an inhibition zone of 31 ± 0.50 mm. The SEM image of the E. cloacae cells treated with SP-NiONPs showed irregular shapes and ruptured, destroyed cell membranes. Our findings revealed that SP-NiONPs could be used as excellent antibacterial agents against oral pathogens.