Green synthesis of Ni-doped ZnO nanoparticles using Salvia hispanica and their antibacterial, anticancer and anti-virulence activities

Researchers have devised a green method to synthesize nickel-doped zinc oxide (Ni–ZnO) nanoparticles using the extract from Salvia hispanica, a plant known for its antioxidant properties. Salvia hispanica extract serves as both a reducing agent and a capping material to create the nanoparticles. The study confirms that the extract contains phenolic and flavonoid compounds, which play a crucial role in the formation and stability of the nanoparticles.

Using a range of analytical techniques, including UV–Vis spectroscopy, FTIR analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), and zeta potential measurements, the researchers verified the successful creation of crystalline, predominantly spherical nanostructures with an average size of 72 nm. These nanoparticles have Ni ions evenly distributed throughout the ZnO crystal structure.

The biological evaluation of these Ni–ZnO nanoparticles demonstrated their multifunctional properties. They showed selective cytotoxicity, with an IC50 value of just 139.9 µg/mL against HNO97 cancer cells and 284.6 µg/mL against normal human endothelial cells (HOECs). Flow cytometry analysis revealed that the nanoparticles effectively induced apoptosis (with 50.0% early and 22.5% late apoptosis) and arrested cell cycle progression at the G2/M phase (70.6%).

In addition to their anticancer potential, the nanoparticles displayed impressive antibacterial activity, particularly against Staphylococcus aureus. The MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) analyses confirmed strong bactericidal effects. Moreover, the nanoparticles significantly inhibited biofilm formation, reducing it by up to 65%, and downregulated the expression of key virulence genes such as exoS, toxA, fimH, and papC.

While the Ni–ZnO nanoparticles exhibited moderate radical quenching efficiency, indicated by IC50 values of 359 µg/mL (DPPH) and 434 µg/mL (ABTS), these values were lower compared to ascorbic acid, suggesting that they may have good potential for use as antioxidants. The study highlights the promising biological performance of these green-synthesized Ni–ZnO nanoparticles, combining selective anticancer activity, broad-spectrum antibacterial efficacy, and anti-virulence properties.

The researchers acknowledge the support from Princess Nourah bint Abdulrahman University Researchers Supporting Project, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia, and the Deanship of Scientific Research at King Faisal University, Saudi Arabia.