Clopyralid detection by using a molecularly imprinted electrochemical luminescence sensor based on the “gate-controlled” effect

Stable and reproducible MIP-ECL sensors for ultra-sensitive and accurate quantitative detection of Estrone

Estrone (E1), as an endogenous estrogen, has a variety of physiological functions in human body and is of great significance to human health. On the other hand, it is a widely distributed and highly disturbing environmental endocrine disruptor in water. Therefore, there is an urgent need to develop a sensitive, rapid, and inexpensive method for the on-site determination of E1, which is not only for clinical diagnosis and treatment, but also for the investigation and monitoring of endogenous estrogen pollution in environmental water. In this study, Ru(bpy)3 2+/MWCNTs/Nafion/gold electrodes were prepared by surface electrostatic adsorption and ion exchange. A molecularly imprinted membrane (MIP) with the capability to recognize E1 molecules was prepared by sol-gel method, and the electrodes were modified with MIP to form an electrochemical luminescence sensor (MIP-ECL). This method simultaneously possesses ECL's advantage of high sensitivity and MIP's advantage of high selectivity. Moreover, the addition of carboxylated multi-walled carbon nanotubes (MWCNT-COOH) improved the functionalization of the gold electrode surface and increased the binding sites of MIP. Meanwhile, the good conductivity of MWCNTs promoted electron transfer and further improved the sensitivity of the sensor. The sensor showed a wide linear interval in which the E1 concentrations can range from 0.1 μg/L to 200 μg/L, along with a high linear correlation coefficient (R 2 = 0.999). The linear regression equation of the sensor was Y = 243.64x-79.989, and the detection limit (LOD) was 0.0047 μg/L. To validate our sensor, actual samples were also measured by the reference method (LC-MS/MS), and it was found that the relative deviation of quantitative results of the two different methods was less than 4.1%. This indicates that the quantitative results obtained by this sensor are accurate and can be used for rapid in situ determination of E1 in clinical samples and environmental water.

Extremely Sensitive Molecularly Imprinted ECL Sensor with Multiple Probes Released from Liposomes Immobilized by a Light-Triggered Click Reaction

A molecularly imprinted electrochemiluminescence sensor was prepared for sensitive and selective determination of aminotriazole via a novel strategy of multiple Ru(bpy)₃Cl₂ probes released from liposomes immobilized by a light-triggered click reaction. This sensing strategy provides a platform for trace detection of amino-containing pesticides. The target on the molecularly imprinted membrane connected to the Ru(bpy)₃Cl₂-encapsulated liposomes via the click reaction. After the destabilizing agent Triton X-100 was added, numerous Ru(bpy)₃Cl₂ molecules were released by liposomes on the molecularly imprinted polymer electrode. The ECL response of the sensor was linearly proportional to the logarithm of the aminotriazole concentration ranging from 5.00 × 10^-18 to 1.00 × 10^-12 mol/L, and the detection limit was 1.15 × 10^-18 mol/L. The sensitivity of the detection was significantly improved, and the analysis process was simplified.

A molecularly imprinted sensor with enzymatic enhancement of electrochemiluminescence of quantum dots for ultratrace clopyralid determination

A new molecularly imprinted polymer electrochemiluminescence (ECL) sensor was developed for the detection of clopyralid (CPD) based on enzyme-biocatalyzed amplification. CdTe quantum dots were immobilized on the surface of an electrode by reaction with p-aminothiophenol preadsorbed on the electrode. Then a molecularly imprinted film was formed by electrochemical polymerization of o-phenylenediamine in the presence of CPD on the CdTe-modified gold electrode. During the analytical cycle, horseradish peroxidase (HRP)-labeled CPD was replaced by CPD in the sample. The amount of HRP on the molecularly imprinted polymer electrode decreased, and then less H₂O₂ was catalytically decomposed. Subsequently, the ECL intensity of the CdTe-H₂O₂ system was enhanced. There was a good linear relationship between ECL intensity and the concentration of CPD in the range from 2.0 × 10^-11 to 2.5 × 10^-10 mol/L and in the range from 2.5 × 10^-10 to 3.5 × 10^-8 mol/L. The detection limit was 4.1 × 10^-12 mol/L. The sensor was applied to determine CPD in vegetable samples. Graphical abstract A molecularly imprinted electrochemiluminescence sensor was fabricated for ultratrace clopyralid determination. The sensitivity was significantly improved with the enhancement of the ECL intensity of quantum dot via the enzymatic reaction of HRP.

3D porous graphene-porous PdCu alloy nanoparticles-molecularly imprinted poly(para-aminobenzoic acid) composite for the electrocatalytic assay of melamine

In this work, a three-dimensional hybrid film with in- and out-of-plane pores was fabricated by using porous graphene as framework structure and porous PdCu alloy nanoparticles as building blocks. The porous PdCu alloy nanoparticles were prepared by chemical dealloying with acetic acid. The hierarchical pores had abundant active catalytic sites, and the material exhibited remarkable catalytic activity toward the oxidation of hydrazine. Based on this hybrid film, an electrochemical sensor of melamine was developed by further introducing melamine imprinted electro-polymer of para-aminobenzoic acid. Melamine was detected by differential pulse voltammetry using hydrazine as electrochemical probe. The detection signal was amplified due to the catalytic oxidation of hydrazine at this hybrid film. The linear determination range was 0.01-1 μM and the detection limit was 2 nM (S/N = 3). The sensor displayed high recognition capacity toward melamine and also showed good reproducibility and stability. It is promising in the determination of melamine in real samples.