Evaluation and validation of commercially available enzyme-linked immunosorbent assays (ELISAs) specific for atrazine, chlorpyrifos, and diazinon in aqueous phase

Simplified validation of the ELISA kit determination of Microcystins in surface water

The enzyme-linked immunosorbent assay (ELISA), as a universal method for the determination of Microcystins, is of great significance for the rapid detection of Microcystins pollution. This study aimed to propose a simplified validation method for Microcystins ELISA kit by summarizing related documents and guidelines. After summarizing and clarifying from 20 validation parameters, 11 parameters were selected to simplify the validation of Microcystins ELISA kit. In addition, the acceptable range and validation details of each parameter were analyzed. The results indicated that the coefficient of determination of the Microcystin-LR standard curve was higher than 0.99. The concentration of quality control samples was within control limits. The accuracy of spiked and proficient samples was within 70%-130%. The variability of intra-assay, inter-assay, and reproducibility was less than 11, 15 and 21%, respectively. The LOD and LLOQ were 0.002 μg/L and 0.05 μg/L, respectively. When the concentration of Microcystins exceeded 5 μg/L, it was recommended to dilute the samples to the working range before detection. The specificity was estimated with seven Microcystin analogues and three amino acids, indicating that the cross-reactivity was less than 30%. These results revealed that the ELISA kit was satisfactory for detecting Microcystins in water.

Immunoassay-based approaches for development of screening of chlorpyrifos

Chlorpyrifos (CPF) is an extensively used organophosphate pesticide for crop protection. However, there are concerns of it contaminating the environment and human health with estimated three lakh deaths annually. Detection of CPF in blood samples holds significance to avoid severe health outcomes due to continuous exposure. The most common techniques for CPF detection are Gas chromatography (GC) and high-performance liquid chromatography (HPLC). However, these techniques might not be feasible at the community healthcare level due to high-cost instrumentation, time-consuming sample preparation protocol and skilled analysts. Therefore, rapid, effective and economical methods such as immunoassay would be imperative for CPF detection in biological samples. The vital step in immunoassay development is the design of a potent immunogen from non-immunogenic molecules. The molecular modelling protocol could assist in redesigning known CPF linkers and inserting them at different substitutable positions of CPF to get distinctive CPF derivatives. Molecular docking and binding free energy analysis can be used to identify the CPF derivatives having a better binding affinity with carrier protein compared to CPF. The top-ranked CPF derivatives based on docking score and binding energy could be ideal for synthesis and immunogen development. The present review will comprehend technological trends in immunoassay kits for detecting chlorpyrifos from biological samples.

Impacts of climate-induced changes on the distribution of pesticides residues in water and sediment of Lake Naivasha, Kenya

This study reports evidence of increased chlorpyrifos contamination in sediment and water in Lake Naivasha following its intensive application in the horticultural farms in the catchment area. Analytical results show that levels of chlorpyrifos residues were influenced by climate-induced rainfall pattern with higher levels reported during period of heavy precipitation with significant decrease during low rainfall. On average, the levels ranged between 14.8 and 32.8 ng g(-1) in sediment during rainy season compared to a range of 8.5-16.6 ng g(-1) in the dry season. Additionally, the mean concentration of chlorpyrifos in water ranged between 8.61 and 22.4 μg L(-1) during rainy season and below detection limit (bdl) -13.6 μg L(-1) in dry season as quantified by enzyme-linked immunosorbent assay. Meanwhile, independent t test analysis indicated that there was significant difference in concentration at p ≤ 0.05 between the seasons with respect to sediment and water samples. This demonstrated that climate-induced variations had considerable influence on contamination. While diazinon and carbofuran were equally applied intensively, their levels were below the detection limit in the all the samples analyzed. ELISA results were validated by the capillary-HPLC photodiode-array detector instrument analysis, and statistical comparison showed no significant difference between them. It was evident that chlorpyrifos residues determination in water and sediment by ELISA can be a useful strategy in environmental management and monitoring program, and a complimentary analytical tool to high performance liquid chromatography. Levels of chlorpyrifos detected in sediment and water were found to exceed recommended criteria for protection of aquatic life and preservation of water quality and may be hazardous if not regularly monitored.

Functionality of Photosynthetic Reaction Centers in Polyelectrolyte Multilayers: Toward an Herbicide Biosensor

The bacterial reaction center (RC), a membrane photosynthetic protein, has been adsorbed onto a glass surface by alternating deposition with the cationic polymer poly(dimethyldiallylammonium chloride) (PDDA) obtaining as an end result an ordinate polyelectrolyte multilayer (PEM) where the protein retains its integrity and photoactivity over a period of several months. Such a system has been characterized from the functional point of view by checking the protein photoactivity at different hydration conditions, from extensive drought to full hydration. The kinetic analysis of charge recombination indicates that incorporation of RCs into dehydrated PEM hinders the conformational dynamics gating QA- to QB electron-transfer leaving unchanged the protein relaxation that stabilizes the primary charge separated state P+QA-. The herbicide-induced inhibition of the QB activity was studied in some detail. By dipping the PEM in herbicide solutions for short times, kinetics of herbicide binding and release have been determined; binding isotherms have been studied using PEM immersed in herbicide solution. QB functionality of RC has been restored by rinsing the PEM with water, thus allowing the reuse of the same sample. This last point has been exploited to design a simple optical biosensor for herbicides. A suitable kinetic model has been proposed to describe the interplay between forward and back electron-transfer processes upon continuous illumination, and the use of the PDDA-RC multilayers in herbicide bioassays was successfully tested.

Diazinon in surface waters before and after a federally-mandated ban

Samples collected from rural and urban streams in the City of Denton, Texas, USA were analyzed for the organophosphorus pesticide diazinon during the years preceding and following a United States Environmental Protection Agency ban on many diazinon uses. A network of 70 monitoring stations, based mainly on topography and hydrological considerations, were established within the three main watersheds of Denton. Monitoring stations were sampled monthly from March through August during periods of normal flow (baseflow), resulting in a total of 1243 samples collected during the years of 2001-2004. Pesticide concentrations were determined using commercially available enzyme-linked immunosorbent assays (ELISAs) specific for diazinon. Results from this temporally and spatially dense monitoring effort illustrated the impacts of a decrease in diazinon production during 2002, followed by a ban on most outdoor, non-agricultural diazinon retail sales imposed during 2003. The total number of samples exhibiting diazinon concentrations above the lower limits of detection (LLD) significantly decreased between 2001 through 2004 (Mantel-Haenszel Chi-Square test, p<0.0001, n=1243) and decreased significantly during the four monitoring years (Cochran-Armitage Trend test, z=-17.94, p<0.0001, n=1243). The total number of stations exhibiting at least one sample above the LLD during the four monitoring years showed similar patterns (Mantel-Haenszel Chi-Square test, p<0.0001; Cochran-Armitage Trend test, z=-3.21, p=0.0007; n=276). Results indicate that the phased reduction of outdoor, non-agricultural diazinon uses led to a highly significant decrease in surface water occurrences of this pesticide.