Yuanping Li

Sensitive detection of lip genes by electrochemical DNA sensor and its application in polymerase chain reaction amplicons from Phanerochaete chrysosporium

An electrochemical DNA sensor based on the sandwich hybridization recognition of target sequence of lignin peroxidase (lip) genes on a gold electrode was developed. A monolayer of thiolated capture probe was formed on a gold electrode through self-assembling. Following hybridizations with target nucleic acid and biotinylated detection probe, streptavidin-horseradish peroxidase (HRP) conjugate was applied to the electrode. The DNA conformation and surface coverage on electrode were characterized by impedance spectroscopy and square wave voltammetry. The experimental variables were optimized to maximize the hybridization efficiency, detection sensitivity and speed up the assay time. The amperometric current response to HRP-catalyzed reaction was linearly related to the natural logarithm of the target nucleic acid concentration in the range from 0.6 to 30 nM, with the correlation coefficient of 0.9722. The detection limit was 0.03 nM. Synthesized oligonucleotide as well as Phanerochaete chrysosporium lip gene fragments amplified using polymerase chain reaction and digested by restriction endonucleases were tested. The DNA sensor exhibited good precision, stability, sensitivity, and selectivity, and discriminated satisfactorily against mismatched nucleic acid samples of similar lengths.

Quantitative detection of trace mercury in environmental media using a three-dimensional electrochemical sensor with an anionic intercalator

Mercury, one of the most widespread highly toxic heavy metals, has severe detrimental effects on human health and the environment. It is significant to develop a sensitive and reliable method of accurately detecting trace levels of mercuric ions in environmental media to meet the ever-increasing demands of ongoing environmental monitoring programs. A three-dimensional mercuric ion sensor was constructed using mercury-specific oligonucleotides, gold nanoclusters, and an anionic intercalator. Due to the steric reaction field in the electrode surface microenvironment formed by the gold nanoclusters, the sensor could spatially capture mercuric ions with electroactive indication to realize trace mercury measurements with high sensitivity; the sensor exhibited strong environmental adaptability, high selectivity, and other advantages. Under optimal conditions, mercuric ions could be detected in the range from 0.05 to 350 nM, and the detection limit was 0.01 nM. The mercuric ion sensor was compared with atomic fluorescence spectrometry to analyze municipal wastewater and river water samples. In addition, the sensor performance was also analyzed according to derived formulae. This accurate method has the potential to be deployed in the field for measurements of mercury in environmental media.