Phyto-mechanochemical synthesis of iron oxide nanoparticles using Polygonum paronychioides and their pesticidal and antimicrobial applications

Abstract

New developments in nanotechnology have provided an effective method for addressing insect pest problems that affect critical commodities. This research represents the first report on the phyto-mechanochemical synthesis of iron oxide (Fe₃O₄) nanoparticles (NPs) using Polygonum paronychioides (PP) extract to determine their pesticidal potential against two crop pests, Tribolium castaneum (TC) and Oryzaephilus surinamensis (OS). The PP extract was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS) to determine the presence of phytochemicals that act as reducing agents. The influence of parameters such as salt concentration, stirring time, temperature, and pH was optimized using the central composite design (CCD) of response surface methodology (RSM). The PP/Fe₃O₄ NPs were characterized by UV-visible spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), zeta sizing, and X-ray diffraction (XRD) techniques. The PP/Fe₃O₄ NPs show an absorbance peak at 237 nm in the UV-visible spectrum, with an average size of 87.43 nm in a Zetasizer. The FTIR spectra also showed the existence of phenolic compounds in PP leaf extract and bond stretching of Fe–O, O–H, N–H, CN, and CO. The Ames test revealed that the PP/Fe₃O₄ NPs were not cytotoxic. The pesticidal potential of PP/Fe₃O₄ NPs was determined using the mortality rates of two crop pests, TC and OS. Results were obtained after 24, 48, and 72 hours. Maximum results were obtained for OS (88 ± 4) rather than TC (80 ± 4). The pesticide activity was enhanced by enhancing the concentration of PP extract and the Fe₃O₄ NPs. The PP/Fe₃O₄ NPs were also tested against multiple bacteria and fungi. The antibacterial activity of PP/Fe₃O₄ NPs was tested against two bacterial strains Pseudomonas syringae and Clavibacter michiganensis. The inhibition zone of Clavibacter michiganensis (34.4 ± 0.2) is more significant than that of Pseudomonas syringae (32.2 ± 0.1). The antifungal test of PP/Fe₃O₄ NPs was assessed against two fungal strains Alternaria alternata and Aspergillus niger. The zone of inhibition of Aspergillus niger (28 ± 0.1) is more significant than that of Alternaria alternata (27 ± 0.5). Results revealed that PP/Fe₃O₄ NPs could be used against pathogens. To our knowledge, PP extract has never been used for the phyto-mechanochemical synthesis of Fe₃O₄ NPs.