Juankun Zhang

Fast determination of the tetracyclines in milk samples by the aptamer biosensor.

A novel aptamer biosensor for fast tetracyclines determination was established and illustrated in this paper. The tetracyclines aptamer as a specific affinity molecule was immobilized on the surface of the glassy carbon (GC) electrodes. It can specifically bind tetracyclines quickly in milk and other samples without sample treatment. Subsequently, the electrochemical signals are produced and measured accurately. The linear relationship between the currents and the tetracyclines concentration is 0.1-100 ng ml(-1). The sensitivity limit of the device is 1 ng ml(-1). The detection time is 5 min.

Label-Free Electrochemical Detection of Tetracycline by an Aptamer Nano-Biosensor

A novel aptamer nano-porous silicon (PS) biosensor was investigated for the rapid determination of tetracyclines. Electrochemical impedance spectroscopy (EIS) was used to analyze the behavior of the sensor. The specific binding of tetracycline to the aptamer biosensor led to a decrease in impedance. The corresponding impedance spectra (Nyquist plots) were obtained when serial concentrations of tetracycline were added into the system. An equivalent electrical circuit was used to fit the impedance data. The linear range of the sensor was 2.1–62.4 nM.

Synthesis of Molecularly Imprinted Polymer for Sensitive Penicillin Determination in Milk

Abstract Penicillin G (PG) in milk is unsafe for human and is a big problem for the foods industry. Hence, the better analytical and eliminative techniques are demanded. We investigated a PG molecular imprinted polymer (MIP), which can sensitively detect and extract the PG from milk and other samples. The MIP synthesis involved a β-lactam antibiotics PG, methacrylic acid (MAA) and dimethyl formamide (DMF). Its properties were analyzed with Scatchard plot, which showed that there were two affinity sites of the PG polymer. The first equilibrium dissociation constant of the high-affinity binding sites Kd1 was 1.14 × 10−4 mol/L and the binding capacity Qmax1 was 46.01 µmol/g; the second equilibrium dissociation constant of the low-affinity binding sites Kd2 was 1.35 × 10−3 mol/L and the binding capacity Qmax2 was 72.55 µmol/g. Furthermore, two PG determination methods using the polymer were developed. The first was carried out quantitatively with a spectrophotometer and the detection limit was 1 ppm. The other one was the combination of the MIP particles with milk fermentation for PG analysis and the sensitivity was 10 ppb.

A Novel Molecularly Imprinted Sensor for Direct Tartrazine Detection

A novel molecularly imprinted polymer polypyrrole sensor for rapid direct tartrazine determination was established and is reported in this paper. Polypyrrole as a specific affinity molecule was immobilized on the surface of a glassy carbon electrode. It specifically bound to tartrazine quickly without sample pretreatment. Subsequently, the electrochemical signals were produced and measured accurately. The device possesses many advantages, such as high specific recognition properties, good chemical and mechanical stability, simplicity, low cost of preparation, and sensitive and label-free determination. A linear relationship between the current and the tartrazine concentration was observed from 1 to 10 nM, and a detection limit of 1 nM was achieved.

A label free electrochemical nanobiosensor study

Abstract Nano-porous silicon (PS) is an attractive material for incorporation into biosensors, because it has a large surface area combined with the ability to generate both optical and electrical signals. In this paper, we describe a label-free nanobiosensor for bovine serum albumin (BSA). Nano-porous silicon produced in our laboratory was functionalized prior to immobilization of anti-BSA antibody on the surface. Reaction with BSA in phosphate buffered saline (PBS) buffer resulted in an impedance change which was inversely proportional to the concentration of the analyte. The system PBS buffer/antigen-antibody/PS constitutes an electrolyte-insulator-semiconductor (EIS) structure, thus furnishing an impedance EIS nanobiosensor. The linear range of the sensor was 0–0.27 mg mL−1 and the sensitivity was less than 10 µg mL−1.

Nano-porous light-emitting silicon chip as a potential biosensor platform

Abstract Nano‐porous silicon (PS) offers a potential platform for biosensors with benefits both in terms of light emission and the large functional surface area. A light emitting PS chip with a stable and functional surface was fabricated in our laboratory. When protein was deposited on it, the light emission was reduced in proportion to the protein concentration. Based on this property, we developed a rudimentary demonstration of a label‐free sensor to detect bovine serum albumin (BSA). A serial concentration of BSA was applied to the light chip and the reduction in light emission was measured. The reduction of the light intensity was linearly related to the concentration of the BSA at concentrations below 10−5 M. The detection limit was 8×10−9 M.