Sustainable fabrication of dimorphic plant derived ZnO nanoparticles and exploration of their biomedical and environmental potentialities

Abstract

Although, different plant species were utilized for the fabrication of polymorphic, hexagonal, spherical, and nanoflower ZnO NPs with various diameters, few studies succeeded in synthesizing small diameter ZnO nanorods from plant extract at ambient temperature. This work sought to pioneer the ZnO NPs fabrication from the aqueous extract of a Mediterranean salt marsh plant species Limoniastrum monopetalum (L.) Boiss. and assess the role of temperature in the fabrication process. Various techniques have been used to evaluate the quality and physicochemical characteristics of ZnO NPs. Ultraviolet-visible spectroscopy (UV-VIS) was used as the primary test for formation confirmation. TEM analysis confirmed the formation of two different shapes of ZnO NPs, nano-rods and near hexagonal NPs at varying reaction temperatures. The nano-rods were about 25.3 and 297.9 nm in diameter and in length, respectively while hexagonal NPs were about 29.3 nm. The UV-VIS absorption spectra of the two forms of ZnO NPs produced were 370 and 365 nm for nano-rods and hexagonal NPs, respectively. FT-IR analysis showed Zn-O stretching at 642 cm^-1 and XRD confirmed the crystalline structure of the produced ZnO NPs. Thermogravimetric analysis; TGA was also used to confirm the thermal stability of ZnO NPs. The anti-tumor activities of the two prepared ZnO NPs forms were investigated by the MTT assay, which revealed an effective dose-dependent cytotoxic effect on A-431 cell lines. Both forms displayed considerable antioxidant potential, particularly the rod-shaped ZnO NPs, with an IC₅₀ of 148.43 µg mL^-1. The rod-shaped ZnO NPs were superior candidates for destroying skin cancer, with IC₅₀ of 93.88 ± 1 µg mL^-1 ZnO NPs. Thus, rod-shaped ZnO NPs are promising, highly biocompatible candidate for biological and biomedical applications. Furthermore, both shapes of phyto-synthesized NPs demonstrated effective antimicrobial activity against various pathogens. The outcomes highlight the potential of phyto-synthesized ZnO NPs as an eco-friendly alternative for water and wastewater disinfection.

Keywords: Anti-skin cancer; Antimicrobial; Antioxidants; Green synthesis; Halophyte; Mediterranean region.

Figure 1

Phytosynthesis of ZnO NPs using L. monopetalum aqueous extract.

Figure 2

(a, b) UV–Vis spectra of the phyto-synthesized ZnO NPs and (c) FT-IR spectra of L. monopetalum extract and the phyto-synthesized ZnO NPs.

Figure 3

GC spectrum of L. monopetalum extract.

Figure 4

TEM images of the phyto-synthesized ZnO NPs, (a) RT, (b) 70 °C and EDX spectrum (c) and (d).

Figure 5

XRD pattern of the phyto-synthesized ZnO NPs, (a) RT, (b) 70 °C.

Figure 6

TGA analysis of the phyto-synthesized ZnO NPs (a) RT, (b) 70 °C.

Figure 7

Cytotoxicity of the phyto-synthesized ZnO NPs against (a) A-431 cancer cell lines, (b) HFB4 normal cell lines. Data are expressed as mean ± SD, (n = 3).

Figure 8

Morphological changes of (a) A-431 cancer cell lines and (b) HFB4 normal cell lines at different ZnO NPs concentrations.

Figure 9

(a) The antioxidant activity of phytosynthesized ZnO NPs at RT and 70 °C. (b) The possible antioxidant mechanism of phyto-synthesized ZnO NPs. Data are expressed as mean ± SD (n = 3).