Biogenic Zinc oxide nanoparticles from Celosia argentea: toward improved antioxidant, antibacterial, and anticancer activities

Abstract

Biogenic Zinc oxide (ZnO) nanoparticles (NPs) were synthesized from Celosia argentea (C. argentea) plant extract. Structural analysis confirms the successful synthesis of biogenic zinc oxide NPs from C. argentea extract. The biogenic ZnO NPs have an average particle size of 21.55 ± 4.73 nm, a semispherical shape, and a specific surface area of about 50 m²/g. The biogenic ZnO NPs have a powerful radical scavenging activity (Ic₅₀ = 91.24 mg/ml) comparable to ascorbic acid (ASC) as a standard (Ic₅₀ = 14.37 mg/ml). The antibacterial efficacy was tested against gram-positive and gram-negative bacteria using an agar disc diffusion method. Gram-positive strains with biogenic ZnO NPs have a greater bactericidal impact than gram-negative strains in a concentration-dependent manner. Anticancer activity against Liver hepatocellular cells (HepG2) and Human umbilical vein endothelial cells (HUVEC) was evaluated using a [3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide] (MTT) assay. The results reflect the concentration-dependent cytotoxic effect of biogenic ZnO NPs against HepG2 cells even at low concentrations (Ic₅₀ = 49.45 μg/ml) compared with doxorubicin (Ic₅₀ = 14.67 μg/ml) and C. argentea extract (Ic₅₀ = 112.24 μg/ml). The cell cycle and gene expression were analyzed to determine the potential anticancer mechanism. The flow cytometric analysis of the cell cycle revealed that biogenic ZnO NPs induce oxidative stress that activates the apoptotic genes NF-κB, CY-C, and P53, leading to cell death. The Celosia argentea improved the antioxidant, antibacterial, and anticancer activities of ZnO NPs without altering their structural properties. The effect of green synthesis on the bioactivity of biogenic ZnO NPs in vivo is recommended for future work.

Keywords: Celosia argentea; ZnO NPs; antibacterial; anticancer; antioxidant.

FIGURE 1

Schematic illustration of biogenic synthesis of ZnO NPs from C. argentea plant extract.

FIGURE 2

XRD pattern of C. argentea extract (A), and chemical and biogenic ZnO NPs (B).

FIGURE 3

The W-H plot for chemical ZnO NPs (A) and biogenic ZnO NPs (B).

FIGURE 4

HR-TEM image linked with particle size distribution for chemical ZnO NPs (A) and biogenic ZnO NPs as determined from HRTEM image (n = 100) (B).

FIGURE 5

Optical spectroscopy of C. argentea, chemical and biogenic ZnO NPs; FTIR spectrum (A) UV-vis spectrum (B), and band gap energy calculation (C).

FIGURE 6

Savaging activity of chemical and biogenic ZnO NPs from C. argentea, C. argentea aqueous extract of C. argentea, and Ascorbic acid as evaluated from DPPH assay.

FIGURE 7

Diameter of inhibition zone (mm) of biogenic ZnO NPs with different concentrations (100, 50, and 25 μg/ml), chemical ZnO Nps (100 μg/ml), C. argentea extract (20 μg/ml), and Gentamycin (20 μg/ml) against gram-positive bacteria (S. aureus and B. subtilis) and gram-negative bacteria (E. coli and Salmonella typhimurium).

FIGURE 8

The possible antibacterial mechanism of ZnO NPs.

FIGURE 9

Cytotoxicity as screened with MTT assay of C. argentena extract, doxorubicin as a positive control, and chemical and biogenic ZnO NPs against HepG2 cells (A) and HUVEC cells (B).

FIGURE 10

Flow cytometry. Cell cycle of HepG2 cells after treatment with biogenic ZnO NPs for 24 h. SubG1, S, and G2/M represented hepG2 cells in normal phases. In contrast, cells undergo apoptosis/necrosis represented in the G phase. (A) Analysis of necrosis and apoptosis percentage (Total, Early, and Late) of HepG2 cells before and after treatment with biogenic ZnO NPs (B). *Statistically significant difference as compared with the controls (P, 0.05 for each. HepG2).

FIGURE 11

(A) Flow cytometry for evaluation of cell cycle profile using PI and annexin V. stains on HepG2 cells. (B) Post-treatment with green ZnO NPs on HepG2 cells.

FIGURE 12

mRNA levels of proapoptotic and antiapoptotic genes HepG2 cells treated with biogenic ZnO NPs.