Biogenesis of ZnO nanoparticles using Pandanus odorifer leaf extract: anticancer and antimicrobial activities

Abstract

The continuously increasing incidence rates of cancer and infectious diseases are open threats to the sustainable survival of animals and humans. In the last two decades, the demands of nanomaterials as modern therapeutic agents have increased. In this study, biogenic zinc oxide nanoparticles (ZnO NPs) were developed from aqueous Pandanus odorifer leaf extract (POLE) and characterized using modern methods and tools, such as electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy and UV-vis spectroscopy, which indicated the formation of very pure, spherical NPs approximately 90 nm in size. The anticancer activity of the ZnO NPs was evaluated by MTT and neutral red uptake (NRU) assays in MCF-7, HepG2 and A-549 cells at different doses (1, 2, 5, 10, 25, 50, 100 μg ml^-1). Moreover, the morphology of the treated cancer cells was examined by phase contrast microscopy. The results suggest that the synthesized ZnO NPs inhibited the growth of the cells when applied a concentration from 50-100 μg ml^-1. Moreover, the biogenic ZnO NPs were analysed as an antimicrobial agent against pathogenic bacteria. The highest antibacterial activity was observed against Gram-positive Bacillus subtilis (26 nm) and Gram-negative Escherichia coli (24 mm) at 50 μg per well. Complete bacterial growth (100%) vanished 100% upon treatment with ZnO NPs at 85 μg ml^-1. Overall, POLE mediated derived biogenic ZnO NPs could serve as a significant anticancer and antimicrobial agent and be used in the development of novel drugs and skin care products.

Fig. 1. (a) Typical X-ray diffraction (XRD) patterns of biogenic precursor and biogenic ZnO NPs after calcination at 400 °C and 600 °C. (b) UV-vis spectrum of biogenic ZnO NPs after calcination at 600 °C. (c) FTIR spectrum of biogenic ZnO NPs after calcination at 600 °C.

Fig. 2. Amorphous biogenic ZnO materials (a) FESEM image with high magnification (b) their corresponding EDX spectrum with elemental composition.

Fig. 3. Change in morphological structure of MCF-7, HepG-2 and A-549 cells following the exposure of variable dose of ZnO nanocrystals for 24 h. Images were captured under the phase contrast inverted microscope at 20× magnification. *p < 0.05, **p < 0.001 versus control.

Fig. 4. Cytotoxicity in MCF-7 cells; HepG2 cells; and A549 cell detection by MTT assay. Cells were exposed to different dose (1–100 μg ml⁻¹) ZnO for 24 h. Each data values are mean ± SE of three independent experiments. *p < 0.05, **p < 0.001 versus control.

Fig. 5. Cytotoxicity in MCF-7 cells; HepG2 cells; and A549 cells during neutral red uptake (NRU) assay. All the cells were exposed to different dose (1–100 μg ml⁻¹) of ZnO for 24 h. Values are mean ± SE of three independent experiments. *p < 0.05, **p < 0.001 versus control.

Fig. 6. The apoptotic effect of biosynthesized ZnO NPs at 100 μg ml⁻¹ concentration after 48 h incubation, using Annexin V-FITC/PI staining of tested MCF-7, HepG2, and A549 cancer cell line. Here dots represent cells as follows: lower right quadrant, early apoptotic cells (FITC⁺/PI⁻); lower left quadrant, normal cells (FITC⁻/PI⁻); upper right quadrant, late apoptotic cells (FITC⁺/PI⁺); upper left quadrant, necrotic cells (FITC⁻/PI⁺).

Fig. 7. (a) Effect of ZnO NPs on the growth of Gram-positive (B. subtilis) and Gram-negative (E. coli) bacteria. (b) Zone inhibition image of (i) B. subtilis and (ii) E. coli in the presence of biogenic ZnO loaded in the wells of medium plate.

Fig. 8. Scanning electron microscopy imaging at different resolution of partial damage and distorted cells of both bacterial cultures of E. coli at 2000× (a) 7000× (b) 15 000 (c) and B. subtilis at 2000× (d) 7000× (e) and 15 000× (f), treated with 75 μg ml⁻¹ ZnO NPs in growing media and after 8 h incubation at 37 °C.