Alteration of the Nonsystemic Behavior of the Pesticide Ferbam on Tea Leaves by Engineered Gold Nanoparticles

A model system consisting of a nonsystemic pesticide (ferbam), engineered gold nanoparticles (AuNPs) and a plant tissue (tea leaves) was investigated using surface enhanced Raman spectroscopy (SERS). Ferbam has no ability by itself to penetrate into tea leaves. When AuNPs were placed with ferbam onto the surface of tea leaves, however, the SERS signal of the ferbam-AuNPs complex was observed inside of the tea leaves. Within 1 h, the ferbam-AuNPs complex rapidly penetrated into the leaf to a depth of approximately 190 μm, about ¹/₃ to ¹/₂ of the leaf’s thickness. The rate of penetration was dependent on the size of AuNPs, with 30 nm AuNPs-ferbam penetrating more rapidly when compared with complexes made with the 50 and 69 nm AuNPs. These results clearly demonstrated an alteration of the nonsystemic behavior of ferbam in the combined presence with AuNPs. This finding might lead to the development of some new pesticide formulations. Conversely, new toxicity issues may arise as the behaviors and fate of pesticides are altered significantly upon interaction with engineered NPs in the pesticide formulation or environment

Uptake, Translocation, Metabolism, and Distribution of Glyphosate in Nontarget Tea Plant (<i>Camellia sinensis</i> L.)

The uptake, translocation, metabolism, and distribution behavior of glyphosate in nontarget tea plant were investigated. The negative effects appeared to grown tea saplings when the nutrient solution contained glyphosate above 200 mg L^–1. Glyphosate was highest in the roots of the tea plant, where it was also metabolized to aminomethyl phosphonic acid (AMPA). The glyphosate and AMPA in the roots were transported through the xylem or phloem to the stems and leaves. The amount of AMPA in the entire tea plant was less than 6.0% of the amount of glyphosate. The glyphosate level in fresh tea shoots was less than that in mature leaves at each day. These results indicated that free glyphosate in the soil can be continuously absorbed by, metabolized in, and transported from the roots of the tea tree into edible leaves, and therefore, free glyphosate residues in the soil should be controlled to produce teas free of glyphosate

Real-Time and <i>in Situ</i> Monitoring of Pesticide Penetration in Edible Leaves by Surface-Enhanced Raman Scattering Mapping

Understanding of the penetration behaviors of pesticides in fresh produce is of great significance for effectively applying pesticides and minimizing pesticide residues in food. There is lack, however, of an effective method that can measure pesticide penetration. Herein, we developed a novel method for real-time and <i>in situ</i> monitoring of pesticide penetration behaviors in spinach leaves based on surface-enhanced Raman scattering (SERS) mapping. Taking advantage of penetrative gold nanoparticles (AuNPs) as probes to enhance the internalized pesticide signals <i>in situ</i>, we have successfully obtained the internal signals from thiabendazole, a systemic pesticide, following its penetration into spinach leaves after removing surface pesticide residues. Comparatively, ferbam, a nonsystemic pesticide, did not show internal signals after removing surface pesticide residues, demonstrating its nonsystemic behavior. In both cases, if the surface pesticides were not removed, copenetration of both AuNPs and pesticides was observed. These results demonstrate a successful application of SERS as an effective method for measuring pesticides penetration in fresh produce <i>in situ</i>. The information obtained could provide useful guidance for effective and safe applications of pesticides on plants

Migration kinetics of four photo-initiators from paper food packaging to solid food simulants

<p>The migration behaviour of four photo-initiators (BP, EHA, MBP and Irgacure 907) was studied by ‘printing’ onto four different food-packaging materials (Kraft paper, white cardboard, Polyethylene (PE)-coated paper and composite paper) and tracking movement into the food simulant: Tenax-TA (porous polymer 2,6-diphenyl furan resin). The results indicated that the migration of the photo-initiators was related to the molecular weight and log <i>K</i>_o/w of each photo-initiator. At different temperatures, the migration rates of the photo-initiators were different in papers with different thicknesses. The amount of each photo-initiator found in the food was closely related to the food matrix. The Weibull model was used to predict the migration load into the food simulants by calculating the parameters <i>τ</i> and <i>β</i> and determining the relationship of the two parameters with temperature and paper thickness. The established Weibull model was then used to predict the migration of each photo-initiator with respect to different foods. A two-parameter Weibull model fitted the actual situation, with some deviation from the actual migration amount.</p

Comparison of the Metabolic Behaviors of Six Systemic Insecticides in a Newly Established Cell Suspension Culture Derived from Tea (<i>Camellia sinensis</i> L.) Leaves

The use of an <i>in vitro</i> cell suspension to study insecticide metabolism is a simpler strategy compared to using intact plants, especially for a difficult matrix such as tea. In this study, a sterile tea leaf callus was inoculated into B₅ liquid media with 2,4-dichlorophenoxyacetic acid (2,4-D, 1.0 mg L^–1) and Kinetin (KT, 0.1 mg L^–1). After 3–4 subcultures (28 days each), a good cell suspension was established. Utilizing these cultures, the metabolic behaviors of six insecticides, including two organophosphates (dimethoate, omethoate) and four neonicotinoids (thiamethoxam, imidacloprid, acetamiprid, and imidaclothiz) were compared. The results showed that thiamethoxam, dimethoate, and omethoate were easily metabolized by tea cells, with degradation ratios after 75 days of 55.3%, 90.4%, and 100%, respectively. Seven metabolites of thiamethoxan and two metabolites of dimethoate were found in treated cell cultures using mass-spectrometry, compared to only two metabolites for thiamethoxam and one for dimethoate in treated intact plants