Hongyong Wang

Determination of Listeria Monocytogenes in Milk Samples by Signal Amplification Quartz Crystal Microbalance Sensor

A piezoelectric crystal biosensor method has been established for detection of listeria monocytogenes (LM) by gold nanoparticles (GNPs) signal amplification. Based on specific recognition of single-stranded DNA (ssDNA) hybridization, a sandwich format of ssDNA probes/complimentary ssDNA probes modified by GNPs/ssDNA of LM was fabricated. This novel strategy allows the detection limit of LM as low as 10 cfu/mL. The biosensor showed friendly biocompatibility, good specificity, acceptable stability, which provided a potential alternative tool for detection of LM in real samples. Furthermore, the developed method could be easily extended to other gene analysis schemes.

A Dip‐and‐Read Test Strip for the Determination of Nitrite in Food Samples for the Field Screening

Abstract A new test strip method for field screening of nitrite in aqueous samples based on the diazo‐coupling reaction between the nitrite and the Griess reagents has been developed. The test strip has a circular sensing zone that contains two layers: the Griess reagents act as the sensing reagent and is immobilized in the bottom layer; the top layer is a cellulose acetate membrane that can be used as a dialysis membrane to remove the matrix from the sample, which can enhance the selectivity of this method. When the test strip was directly dipped into the samples, a color change of the test strip was observed, and the intensity of color that appears on the test strip is proportional to the concentration of nitrite in the range from 0.50 to 25 µg mL−1 in food samples. Under the experimental conditions, as low as 0.20 µg mL−1 nitrite can be observed; most of anionic and cationic species as well as other sample matrixes basically do not interfere with the nitrite measurement.

A Highly Sensitive Method for Determination of Copper (II) in Water Samples for Field Screening

Abstract A new method has been developed for field screening of copper (II) in water samples, which is based on an enzyme inhibition reaction between copper (II) and nitrate reductase. The concentration of copper (II) was acquired by indirect determination the reaction product (nitrite) with a mini optical reflection sensor. Under the optimum conditions, the calibration graph was linear in the range of 5.0–50 ng mL−1. The limit of detection was 0.5 ng mL−1. This method has been used for the field screening of copper (II) with satisfactory results.