Due to the crucial role of amino acids in life sciences and pharmaceutics, identification of optical amino acid molecules is of great significance. In this study, the two materials (CNT and PANI) were combined together to obtain the magnification of electrochemical signal by substrate material (CNT/PANI). Then a self‐assembled multiwalled carbon nanotubes/polyaniline/sodium alginate (CNT/PANI/SA) nanocomposite with chiral sites and conductive material was synthesized as the electrochemical sensing interface. Next, a novel electrochemical sensing interface was fabricated via modifying the as‐prepared chiral material on a polished glassy carbon electrode (CNT/PANI/SA/GCE) for precisely, efficiently, and rapidly differentiation of tryptophan (Trp) enantiomers. It was observed that CNT/PANI/SA/GCE showed desirable stereoselective recognition effect in the variety of signal strength to peak current (Ip) to the different optical activity of Trp enantiomers. In the case of optimal conditions, the peak current ratio in the solution of l‐Trp and d‐Trp (ID/IL) was observed to be 2.1 at CNT/PANI/SA/GCE by differential pulse voltammogram (DPV). UV–visible spectroscopy further showed that CNT/PANI/SA had a greater binding energy to l‐Trp. Also different factors affecting the enantioselectivity of CNT/PANI/SA/GCE, such as the incubation time, pH, and dropcoating volume of CNT/PANI/SA were optimized. Moreover, the proposed CNT/PANI/SA/GCE showed excellent specific stereoselectivity and anti‐interference ability. Besides, the proposed chiral sensing platform can be effectively applied in real samples to detect Trp enantiomers sensitively. This work inspires us a new path for the preparation of substrate material with excellent electrical conductivity, as well as extend its application potential in chiral recognition.
Acetamiprid (ACE) is widely used in various vegetables to control pests, resulting in residues and posing a threat to human health. For the rapid detection of ACE residues in vegetables, an indirect competitive chemiluminescence enzyme immunoassay (ic-CLEIA) was established. The optimized experimental parameters were as follows: the concentrations of coating antigen (ACE-BSA) and anti-ACE monoclonal antibody were 0.4 and 0.6 µg/mL, respectively; the pre-incubation time of anti-ACE monoclonal antibody and ACE (sample) solution was 30 min; the dilution ratio of goat anti-mouse-HRP antibody was 1:2500; and the reaction time of chemiluminescence was 20 min. The half-maximum inhibition concentration (IC50), the detection range (IC10–IC90), and the detection limit (LOD, IC10) of the ic-CLEIA were 10.24, 0.70–96.31, and 0.70 ng/mL, respectively. The cross-reactivity rates of four neonicotinoid structural analogues (nitenpyram, thiacloprid, thiamethoxam, and clothianidin) were all less than 10%, showing good specificity. The average recovery rates in Chinese cabbage and cucumber were 82.7–112.2%, with the coefficient of variation (CV) lower than 9.19%, which was highly correlated with the results of high-performance liquid chromatography (HPLC). The established ic-CLEIA has the advantages of simple pretreatment and detection process, good sensitivity and accuracy, and can meet the needs of rapid screening of ACE residues in vegetables.
Chlorpyrifos is an organophosphorus insecticide, which can be used to control a variety of chewing and piercing mouthparts pests in agricultural production. It can destroy the normal nerve impulse conduction by inhibiting the activity of acetylcholinesterase or cholinesterase in the nerves, causing a series of poisoning symptoms. In order to achieve the quantitative analysis of chlorpyrifos residues in agricultural products, an aptamer-controlled signal molecule release method was developed in this study. The signal molecule 4-ATP of surface-enhanced Raman spectroscopy (SERS) was loaded into aminated mesoporous silica nanoparticles (MSNs-NH2) prepared by the one pot method, and then coated with an aptamer of chlorpyrifos through electrostatic interaction. The specific binding of the aptamer and chlorpyrifos led to the release of 4-ATP, and the amount of 4-ATP released was positively correlated with the amount of chlorpyrifos. Finally, the standard curve of chlorpyrifos quantitative detection based on SERS was established. Meanwhile, Ag-carrying mesoporous silica (Ag@MSNs) was prepared as the reinforcement substrate for SERS detection. The results showed that there was a good linear correlation between the Raman intensity and the concentration of chlorpyrifos at 25–250 ng/mL, and the limit of detection (LOD) was 19.87 ng/mL. The recoveries of chlorpyrifos in the apple and tomato samples were 90.08–102.2%, with RSD < 3.32%. This method has high sensitivity, specificity, reproducibility and stability, and can be used for the quantitative detection of chlorpyrifos in the environment and agricultural products.
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