Attomolar Determination of Coumaphos by Electrochemical Displacement Immunoassay Coupled with Oligonucleotide Sensing

Coumaphos, an organophosphorus pesticide (OP) used worldwide, has raised serious public concerns due to its positive association with major types of cancer. Herein, a novel method for attomolar coumaphos detection was developed on the basis of an electrochemical displacement immunoassay coupled with oligonucleotide sensing. An optimized displacement immunoassay was constructed to improve the binding efficiency of an antigen–antibody pair, and a guanine-rich single-strand DNA label, in combination with oligonucleotide sensing, was used to amplify the detection signal with “direct” relationship to the analyte. As a result, coumaphos was sensitively determined from the enhanced catalytic cycle of guanine-Ru­(bpy)₃²⁺ by chronoamperometry. The limit of detection (LOD) was down to 0.18 ng L^–1 (S/N = 3), which is equal to 49.6 amol in a sample solution of 100 μL. In comparison with conventional methods, the proposed method has the lowest LOD and better accessibility to high-throughput sensing systems. Besides, it can complete the whole analysis process in under 50 min and exhibits good performance of excellent selectivity to the OPs. With regard to the advantages of rapidity, convenience, low cost, and ease of operation, the proposed method has provided a promising platform capable of fast and in-field OP detection, which may make the system promising for potential applications in the detection of other small molecules

Novel haptens synthesis and development of a monoclonal antibody-based enzyme-linked immunosorbent assay for leuco-malachite green in fish

<p>To produce specific antibodies against leuco-malachite green (LMG), 15 haptens were synthesized and characterized, and conjugated to carrier protein for immunization. One antigen with excellent reactogenicity and immunogenicity was discovered. Specific monoclonal antibody with high sensitivity for LMG in competitive indirect enzyme-linked immunosorbent assay (ciELISA) was screened and selected. After the screening of a series of heterologous coating antigen and optimization of working conditions, the proposed ciELISA showed the 50% inhibition value (IC₅₀) of 1.16 ng mL⁻¹ and the limit of detection of 0.06 ng mL⁻¹ for LMG. The average recoveries of LMG from spiked fish samples ranged from 78.0% to 101.0%, with coefficients of variation below 15%. Good correlation (<i>R</i>² = 0.9977) was obtained between the results of ciELISA analysis and those of standard liquid chromatography–tandem mass spectrometry analysis. The proposed ciELISA is ideal for the rapid and sensitive detection of LMG with a low cost and high throughput.</p

Low-Temperature-Initiated Cracking of Hydrocarbons to Produce Olefins: Simulation and Comparison of Different Initiators

Low-temperature-initiated cracking technology has significant potential to develop new hydrocarbon pyrolysis with better atomic economy and higher yields of light olefins. The impacts of three representative initiators, triethylamine (TEA), nitromethane (NM), and di-tert-butyl peroxide (DTBP), were compared. Sufficiently detailed co-cracking reaction networks of three initiators with n-hexane were obtained through an automatic reaction network generator RMG, and the corresponding steam cracking tubular reactor simulation was performed. The results showed that the initiator with a lower cracking temperature brought about a more noticeable decrease in the cracking temperature of n-hexane. Both TEA and NM increased the carbon atom conversion from n-hexane to ethylene and propylene, especially propylene. NM was more significant, while DTBP was almost ineffective. Through kinetic parameter analysis, it was found that the temperature dependence of the key reaction caused different initiator performance. NM completely cracked at an appropriate temperature where the rate constants of the hydrogen abstraction and ethylene generation had reached a high level, and the released free radicals were effective. Visual reaction network analysis revealed that NM had a strong ability to release free radicals, and these free radicals significantly adjusted the competitive reaction path to produce ethylene and propylene, resulting in the most obvious effect on improving the conversion of n-hexane and the yield of propylene. The action laws of NM described above under hydrocarbon pyrolysis conditions indicate that NM may be the most suitable initiator for low-temperature-initiated cracking of hydrocarbons among these three initiator types

Facile Fabrication of Highly Quantum Dot/AuNP-Loaded Tags for a Dual-Modal Colorimetric/Reversed Ratiometric Fluorescence Immunochromatographic Assay

Developing an easily-prepared, sensitive, and accurate point-of-need immunochromatographic assay (ICA) is significant in food safety screening, clinical diagnosis, and environmental monitoring. However, the current single-modal ICAs are limited in certain instinct drawbacks that restrict analytical performances. Herein, we introduce an ultrasensitive dual-modal colorimetric/reversed ratiometric fluorescence ICA based on facilely prepared immunoprobes with a high loading capacity of red quantum dots and AuNPs. By smartly integrating these red-colored/fluorescent signal probes with an immobilized green quantum dot antigen on the test lines, discrete “turn-on” visual inspection and reversed ratiometric quantification via a portable smartphone-based analyzer were accomplished. As an application, this method was employed to detect 11 phosphodiesterase-5 inhibitors in health foods with ultralow detection limits (0.0028–0.045 ng/mL), high repeatability (coefficient of variations of 0.3–1.91%), and reasonable accuracy (recoveries of 86.6–107%). The proposed method was further validated by the authorized liquid chromatography with tandem mass spectrometry method in actual sample detection. This new assay format can be extended to ultrasensitive flexible detection of other food contaminants, environmental pollutants, or tumor biomarkers within minutes, and it just requires simply prepared signal reporters, easy-to-operate procedures, and a low-cost miniaturized analyzer