Mengmeng Yan

Gold nanoparticle–based colorimetric aptasensor for rapid detection of six organophosphorous pesticides

Fast immunoassay-based screening methods are unavailable for most small-molecule pesticides because of a lack of immunogenicity and the difficulty in obtaining antibodies by animal immunization. Aptamers are single-stranded DNA molecules selected through an in vitro process, which can bind to any target including nonimmunogenic small molecules with high affinity and specificity. Although various aptamer-based sensing methods have been developed for antibiotics, microorganisms, heavy metal ions, and biotoxins, there are few reports on aptamer-based methods for quick detection of organophosphorous pesticides. The gold (Au) nanoparticle (AuNP) colorimetric assay is a widely utilized rapid detection method because of properties such as easy operation and visualized results. In the present study, organophosphorous pesticide aptamers were adsorbed on the surface of AuNPs to stabilize the AuNP solution against high concentrations of salt to prevent AuNP aggregation. After the addition of targets, the aptamers binding to the targets are detached from the AuNPs, resulting in aggregation of AuNPs and a color change from red to purple-blue. The proposed method can detect 6 organophosphorous pesticides with good recoveries from 72% to 135% in environmental river water samples. The present study provides a new way for simple, rapid, and multiplex detection of organophosphorous pesticides.

AuNP‐based colorimetric aptasensor for rapid detection of six organophosphorus pesticides

Fast immunoassay-based screening methods are unavailable for most small-molecule pesticides because of a lack of immunogenicity and the difficulty in obtaining antibodies by animal immunization. Aptamers are single-stranded DNA molecules selected through an in vitro process, which can bind to any target including nonimmunogenic small molecules with high affinity and specificity. Although various aptamer-based sensing methods have been developed for antibiotics, microorganisms, heavy metal ions, and biotoxins, there are few reports on aptamer-based methods for quick detection of organophosphorous pesticides. The gold (Au) nanoparticle (AuNP) colorimetric assay is a widely utilized rapid detection method because of properties such as easy operation and visualized results. In the present study, organophosphorous pesticide aptamers were adsorbed on the surface of AuNPs to stabilize the AuNP solution against high concentrations of salt to prevent AuNP aggregation. After the addition of targets, the aptamers binding to the targets are detached from the AuNPs, resulting in aggregation of AuNPs and a color change from red to purple-blue. The proposed method can detect 6 organophosphorous pesticides with good recoveries from 72% to 135% in environmental river water samples. The present study provides a new way for simple, rapid, and multiplex detection of organophosphorous pesticides.

Visual colorimetric detection of cyromazine in river water using citrate-stabilized gold nanoparticles

In this paper, citrate-stabilized gold nanoparticles (AuNPs) were used to develop a method for rapidly and visually detecting cyromazine in river water. AuNPs could strongly interact with cyromazine, which causes an apparent color change observable by the naked eye, and their absorbance spectra could be measured by UV-vis spectroscopy. The citrate reduction method was used to synthesize different sizes of AuNPs and the optimized AuNP size for the visual detection sensor was determined to be 30 nm. The linear range of this method was from 0.1 to 1 mg L−1 and the limit of detection (LOD) was 0.1 mg L−1. The recoveries of cyromazine ranged from 83% to 117% with a good RSD of less than 6% for the river water samples spiked with three different concentrations of cyromazine. This method provided a simple and sensitive technique for screening environmental cyromazine contamination on site.

Highly sensitive and selective optical detection of lead(II) using a label-free fluorescent aptasensor

Lead (Pb) is a heavy metal that does great harm to human bodies through its accumulation in the food chain. It remains a challenge to use environment-friendly and biocompatible materials to sensitively detect lead in organisms and aquatic ecosystems. To achieve highly sensitive and selective Pb2+ detection, a sensor based on ultra-sensitive double-stranded DNA (dsDNA) specific dye PicoGreen and label-free oligonucleotides was reported. The principle of this method is that the Pb2+ induced a structural change of G-rich thrombin aptamer from random coil to G-quadruplex, which prevented its binding to its complementary sequences to form dsDNA and caused a fluorescence intensity decrease with PicoGreen. The results showed that this method satisfied the requirement of the maximum residue limit (MRL) of Pb2+ and could detect Pb2+ at a lowest concentration of 1 ng mL−1 within a dynamic range of six orders of magnitude. Since the aptamer was highly specific, this method showed high Pb2+ selectivity against eight other metals. Finally, the proposed assay was successfully validated by determining Pb2+ in water samples.