Synchrotron Verification of TiO₂ Accumulation in Cucumber Fruit: A Possible Pathway of TiO₂ Nanoparticle Transfer from Soil into the Food Chain

Abstract

The transfer of nanoparticles (NPs) into the food chain through edible plants is of great concern. Cucumis sativus L. is a freshly consumed garden vegetable that could be in contact with NPs through biosolids and direct agrichemical application. In this research, cucumber plants were cultivated for 150 days in sandy loam soil treated with 0 to 750 mg TiO2 NPs kg(-1). Fruits were analyzed using synchrotron μ-XRF and μ-XANES, ICP-OES, and biochemical assays. Results showed that catalase in leaves increased (U mg(-1) protein) from 58.8 in control to 78.8 in 750 mg kg(-1) treatment; while ascorbate peroxidase decreased from 21.9 to 14.1 in 500 mg kg(-1) treatment. Moreover, total chlorophyll content in leaves increased in the 750 mg kg(-1) treatment. Compared to control, FTIR spectra of fruit from TiO2 NP treated plants showed significant differences (p ≤ 0.05) in band areas of amide, lignin, and carbohydrates, suggesting macromolecule modification of cucumber fruit. In addition, compared with control, plants treated with 500 mg kg(-1) had 35% more potassium and 34% more phosphorus. For the first time, μ-XRF and μ-XANES showed root-to-fruit translocation of TiO2 in cucumber without biotransformation. This suggests TiO2 could be introduced into the food chain with unknown consequences.

Random amplified polymorphic DNA reveals that TiO2 nanoparticles are genotoxic to Cucurbita pepo

“…TiO 2 NPs have also been reported to be toxic to plants. Servin et al (2013) reported that TiO 2 NPs induced macromolecular changes in cucumber fruit. In addition, there is evidence that TiO 2 in the nano-anatase form increases antioxidant stress in spinach chloroplasts (Zheng et al, 2008).…”

“…The selected plants were hydroponically grown in modified Hoagland nutrient solution for 7 d in an environmental growth chamber (Environmental Growth Chamber, Chagrin Falls, OH) with a 14-h photoperiod, illumination of 340 µmol/(m 2 ·s), 25 °C/ 20 °C day/night temperature, and 65% relative humidity. Cultivation was performed as previously described by Servin et al (2013).…”

Interaction of Nanomaterials with Plants: What Do We Need for Real Applications in Agriculture?

“…Typically, nanoparticles will accumulate in certain tissues and organs, in the same way it happens with animals (Varna et al, 2012). As commented above, plant organs acting as strong sinks for sap and nutrients are likely to accumulate nanomaterials traveling through the vascular system, mainly fruits (Servin et al, 2013), grains (Lin et al, 2009), flowers, and young leaves (Cifuentes et al, 2010;Koo et al, 2015). That is something to be used in our advantage when deciding the role of the nanomaterial we want to test.…”

Effect of TiO2 Nanoparticles on Antioxidant Enzymes Activity and Biochemical Biomarkers in Pinto Bean (Phaseolus vulgaris L.)

“…Malondialdehyde content serves as an indicator of the extent of lipid peroxidation and an indirect reflection of the extent of cell damage (Wang et al, 2011). Servin et al (2013) reported an increase in CAT activity (250-750 mg/kg) but a decrease in APX (500 mg/kg) when cucumber plants were exposed to nano TiO 2 . Also, Laware and Raskar (2014) reported that CAT and GPX activities can be enhanced in the presence of 10-30 μgml -1…”

“…In this regard, it is reported that metal oxide nanoparticles exposure can induce the generation of ROS, consequently causing oxidative stress and activating plant responses for detoxification such as enzymatic activity (Ma et al, 2015). Similarly, Servin et al (2013), Hong et al (2005) and Song et al (2013) reported an increase in the activities of SOD, CAT, POD and decreased accumulation of ROS when plants were exposed to TiO 2 nanoparticle.…”