Green biosynthesis of magnetic iron oxide (Fe₃O₄) nanoparticles using the aqueous extracts of food processing wastes under photo-catalyzed condition and investigation of their antimicrobial and antioxidant activity

In this study, a simple, rapid, and eco-friendly green method was introduced to synthesize magnetite iron oxide nanoparticles (Fe₃O₄ NPs) using the aqueous extracts of two food processing wastes, namely silky hairs of corn (Zea mays L.) and outer leaves of Chinese cabbage (Brassica rapa L. subsp. pekinensis). The boiled solutions of silky hairs (MH) and outer leaves of Chinese cabbage (CCP) were used to synthesize Fe₃O₄ NPs under photo exposed condition. The MH-FeNPs and CCP-FeNPs synthesized via green route were characterized by UV–Vis spectroscopy, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), differential thermogravimetric (TG/DTG) analysis, and vibrating sample magnetometer (VSM) analysis. The UV–Visible spectra displayed two absorption bands at 325 nm and 375 mm for the MH-FeNPs, and 325 mm and 365 mm for the CCP-FeNPs, respectively. The estimated absolute crystallite sizes of the MH-FeNPs and CCP-FeNPs were calculated to be 84.81 and 48.91 nm, respectively. VSM analysis revealed that both FeNPs were superparamagnetic in nature. Both FeNPs mixed with kanamycin and rifampicin displayed positive synergistic antibacterial activity against pathogenic foodborne bacteria (9.36–24.42 mm inhibition zones), and those mixed with amphotericin b also exerted synergistic anticandidal activity against five different pathogenic Candida species (9.81–17.68 mm inhibition zones). Both FeNPs exhibited strong antioxidant activities; therefore, all the properties of the green synthesized MH-FeNPs and CCP-FeNPs using food processing wastes could be beneficial for their potential applications in various fields such as drug delivery, antibacterial and anticandidal drugs, and biomedical fields.