Green Synthesis of Zinc Oxide Nanoparticles (ZnO-NPs) Using Arthrospira platensis (Class: Cyanophyceae) and Evaluation of their Biomedical Activities

Abstract

In this study, zinc oxide nanoparticles (ZnO-NPs) were successfully fabricated through the harnessing of metabolites present in the cell filtrate of a newly isolated and identified microalga <i>Arthrospira platensis</i> (Class: Cyanophyceae). The formed ZnO-NPs were characterized by UV-Vis spectroscopy, Fourier transform infrared (FT-IR)<b>,</b> transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Data showed the efficacy of cyanobacterial metabolites in fabricating spherical, crystallographic ZnO-NPs with a size ≈30.0 to 55.0 nm at a wavelength of 370 nm. Moreover, FT-IR analysis showed varied absorption peaks related to nanoparticle formation. XPS analysis confirms the presence of Zn(II)O at different varied bending energies. Data analyses exhibit that the activities of biosynthesized ZnO-NPs were dose-dependent. Their application as an antimicrobial agent was examined and formed clear zones, 24.1 ± 0.3, 21.1 ± 0.06, 19.1 ± 0.3, 19.9 ± 0.1, and 21.6 ± 0.6 mm, at 200 ppm against <i>Bacillus subtilis</i>, <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, and <i>Candida albicans</i>, respectively, and these activities were reduced as the NPs concentration decreased. The minimum inhibitory concentration (MIC) values were determined as 50 ppm for <i>S. aureus,</i> 25 ppm for <i>P. aeruginosa</i>, and 12.5 ppm for <i>B. subtilis</i>, <i>E. coli</i>, and <i>C. albicans.</i> More interestingly, ZnO-NPs exhibit high in vitro cytotoxic efficacy against cancerous (Caco-2) (IC₅₀ = 9.95 ppm) as compared with normal (WI38) cell line (IC₅₀ = 53.34 ppm).