Miaomiao Chen

Enhanced electrochemiluminescence of RuSi nanoparticles for ultrasensitive detection of ochratoxin A by energy transfer with CdTe quantum dots.

This paper develops a new approach to enhance the electrochemiluminescence (ECL) emission of the Ru(bpy)3(2+)-tripropyl amine (TPrA) system for ultrasensitive determination of ochratoxin A (OTA). Ru(bpy)3(2+)-doped silica nanoparticles (RuSi NPs) act as ECL materials, which are immobilized on the surface of electrode by chitosan to fabricate a solid-state ECL sensor. CdTe quantum dots (QDs) can enhance the ECL emission of the Ru(bpy)3(2+)-TPrA ECL system by energy transfer. This strategy can improve the sensitivity of the sensor. In this assay, we combine the ECL with molecular imprinting technique to improve the selectivity of this sensor. The template molecule could be eluted from the molecularly imprinted polymer (MIP), and the formed cavities could then selectively recognize the target. The cavities could also work as the tunnel for the transfer of coreactant TPrA to produce responsive signal. With the increase of the concentration of OTA in samples, more cavities were filled because of the rebinding of OTA to the MIP surface, resulting in a gradual decrease in ECL intensity. The results showed that the ECL decrease value depended linearly on the logarithm of the OTA concentration in the range from 1.00×10(-5) to 11.13 ng mL(-1) with lower detection limit of 3.0 fg mL(-1) (S/N=3). This ECL sensor has also been applied to detect OTA concentration in the real samples with satisfied results, and the recoveries range from 85.1% to 107.9%.

Surface-enhanced molecularly imprinted electrochemiluminescence sensor based on Ru@SiO2 for ultrasensitive detection of fumonisin B1

A novel molecularly imprinted electrochemiluminescence (MIP-ECL) sensor based on Ru(bpy)32+-doped silica nanoparticles (Ru@SiO2 NPs) is developed for highly sensitive detection of fumonisin B1 (FB1). Gold-nanoparticles (AuNPs), Ru@SiO2 NPs with chitosan (CS) composites and a molecularly imprinted polymer (MIP) are assembled on a glassy carbon electrode (GCE) to fabricate an ECL platform step by step. AuNPs could greatly promote the ECL intensity and improve the analytical sensitivity according to the localized surface plasmon resonance (LSPR) and the electrochemical effect. In this surface-enhanced electrochemiluminescence (SEECL) system, AuNPs work as the LSPR source to improve the ECL intensity and Ru@SiO2 NPs are used as ECL luminophores. In the phosphate buffer solution (PBS), the evident anodic ECL of Ru@SiO2 on the above working electrode is observed in the presence of the template molecule fumonisin B1 (FB1), which could act as the coreactant of Ru@SiO2 NPs due to the amino group of FB1. When the template molecules were eluted from the MIP, little coreactant was left, resulting in an apparent decrease of ECL signal. After the MIP-ECL sensor was incubated in FB1 solution, the template molecules rebound to the MIP surface, leading to the enhancement of ECL signal again. On the basis of these results, a facile MIP-ECL sensor has been successfully fabricated, which exhibited a linear range from 0.001 to 100ngmL-1 with a detection limit of 0.35pgmL-1 for FB1. Moreover, the proposed MIP-ECL sensor displayed an excellent application in real samples.

Surface protein imprinted magnetic nanoparticles for specific recognition of bovine hemoglobin

Molecular imprinting for the detection of protein has gained great interest in recent years. For this purpose, we prepared magnetic molecularly imprinted polymers (MIPs) for the recognition of bovine hemoglobin (BHb) through the surface imprinting technique with two-stage core–sell sol–gel polymerization on the surface of silica modified Fe3O4 nanospheres. 3-Aminopropyltriethoxylsilane and octyltrimethoxysilane were chosen as monomers to construct the MIP layer. The morphology and structure property of prepared nanoparticles were characterized by TEM, X-ray diffraction, Fourier transform infrared spectrometry, and the vibrating sample magnetometer. The obtained magnetic MIPs with high saturation magnetization (60 emu g−1) made it easy to separate the target protein from solution by an external magnetic field. The adsorption and recognition performance of this magnetic MIPs was discussed through adsorption kinetics, adsorption isotherms, special selectivity, reusability and reproducibility tests. It turned out that the magnetic MIPs showed a relatively high adsorption capacity of 124.86 mg g−1 and excellent selectivity towards BHb with a separation factor of 1.99. Moreover, the adsorption capacity of magnetic MIPs was not significantly reduced after three continuous adsorption and elution processes, which indicated their good reusability for at least three repeated cycles.

A simple and sensitive fluorometric dopamine assay based on silica-coated CdTe quantum dots

AbstractA fluorescence assay is described for the fluorometric determination of dopamine (DA). It based on the use of silica-coated CdTe quantum dots (QD@SiO2). These were fabricated through a hydrothermal process. When DA is added to a solution of the QD@SiO2 and then oxidized by oxygen under catalytic action of tyrosinase to form dopamine quinone, the fluorescence of QD@SiO2 (acquired at excitation/emission wavelengths of 310/525 nm) decreases due to an electron transfer quenching processes. The assay has a linear calibration plot in the 0.05 to 30 μM DA concentration range and a 12.5 nM detection limit (at an S/N ratio of 3). The method was applied to the determination of DA in spiked human serum samples. Graphical abstractSchematic presentation of a fluorometric dopamine (DA) assay by using silica-coated CdTe QDs (QD@SiO2). DA is oxidized by oxygen under catalytic action of tyrosinase to form dopamine quinone, and this causes the quenching of fluorescence of QD@SiO2 at excitation/emission wavelengths of 310/525 nm.

Selective and sensitive determination of ochratoxin A based on a molecularly imprinted electrochemical luminescence sensor

This paper reports a new molecularly imprinted electrochemical luminescence (MIP-ECL) sensor for the determination of ochratoxin A (OTA) with high selectivity and sensitivity. Ru(bpy)32+ was immobilized on the electrode surface as the luminescent material by using Nafion. The process of template elution and rebinding acted as a gate to control the flux of probes, which passed through the cavities and reacted on the electrode surface. When the imprinted film was rebound with OTA, the ECL signal decreased. Under optimal conditions, the MIP-ECL sensor showed a wide linear range from 0.1 ng mL−1 to 10 ng mL−1 with a detection limit (S/N = 3) of 0.03 ng mL−1. Corn samples were assayed by using this sensor, and recoveries ranging from 95.2% to 102.7% were obtained.

Fluorescence suppression of MPA stabilized CdTe QDs for direct determination of propranolol

A sensitive, convenient and rapid fluorescent sensor for effectively and directly detecting propranolol was proposed based on the fluorescence suppression of 3-mercaptopropionic acid stabilized CdTe quantum dots. The fluorescence suppression mechanism between CdTe QDs and propranolol was studied by time-resolved fluorescence spectroscopy, UV-Vis spectroscopy and fluorescence spectroscopy, and it was attributed to the simultaneous action of the inner filter effect (IFE) and dynamic quenching effect (DQE). The effects of the concentration of quantum dots, pH value of buffer solution and incubation time on the fluorescence signal of the propranolol/CdTe quantum dot system were also investigated. The results indicated that, when the experiment was conducted under optimal experimental conditions, the linear range of this assay was 0.1 μM to 2 μM and 5 μM to 200 μM, with a corresponding detection limit of 0.055 μM. Moreover, some common drug excipients and analogues of propranolol and stimulants had no apparent effect on the determination of propranolol. The proposed fluorescent sensor could be readily used for effectively and directly detecting propranolol in biological samples.