Phytotoxicity study of Ag@Fe2O3 nanocomposites based on O-carboxymethylchitosan on Cucumis sativus

The present study investigates the effects of Ag@Fe2O3 nanocomposites coated and uncoated with O-carboxymethylchitosan (OC) and synthesized with different reducing agents on Cucumis sativus seeds. The seeds were germinated and grown for 5 days in suspension at different concentrations of nanoparticles (0.1, 1, 10, 100 and 1000 mg L-1). The phytotoxic effects were studied using different parameters such as growth, germination index, uptake of Ag and Fe, chlorophyll contents, dry mass, mitochondrial activity, oxidative stress, cell death, metabolic activity, and electrolyte leakage. The nanoparticles at concentrations lower 100 mg L-1 did not affect the germination rate or plant growth and, the presence of magnetic nanoparticles promotes the stimulations in plant growth. Furthermore, electrolyte release and cell death percentage were not altered by the nanoparticle treatment. The total chlorophyll content was significantly reduced after exposure to CAg (O-carboxymehtylchitosan/gamma-Fe2O3/Ag without reducing agent) and CAgS (O-carboxymehtylchitosan/gamma-Fe2O3/Ag reduced with sucrose) nanoparticles. The catalase activities of seeds treated with CAg, OCM (O-carboxymehtylchitosan/gamma-Fe2O3), CAgS, and CAgN (O-carboxymehtylchitosan/gamma-Fe2O3/Ag reduced with NaBH4) were significantly increased relative to the controls, with a response that prevented oxidative damage. These preliminary results show that these silver nanocomposites are not phytotoxic, especially at concentrations lower than 100 mg L-1, suggesting that they could be useful for disinfecting water contaminated with bacteria.