Yunhui Yang

A nano-porous CeO2/chitosan composite film as the immobilization matrix for colorectal cancer DNA sequence-selective electrochemical biosensor

CeO(2)/Chitosan (CHIT) composite matrix was firstly developed for the single-stranded DNA (ssDNA) probe immobilization and the fabrication of DNA biosensor related to the colorectal cancer gene. Such matrix combined the advantages of CeO(2) and chitosan, with good biocompatibility, nontoxicity and excellent electronic conductivity, showing the enhanced loading of ssDNA probe on the surface of electrode. The preparation method is quite simple and inexpensive. The hybridization detection was accomplished by using methylene blue (MB), an electroactive lable, as the indicator. The differential pulse voltammetry (DPV) was employed to record the signal response of MB and determine the amount of colorectal cancer target DNA sequence. The experimental conditions were optimized. The established biosensor has high detection sensitivity, a relatively wide linear range from 1.59x10(-11) to 1.16x10(-7)molL(-1) and the ability to discriminate completely complementary target sequence and four-base-mismatched sequence.

Organic-inorganic matrix for electrochemical immunoassay: Detection of human IgG based on ZnO/chitosan composite.

A new strategy to construct amperometric immunosensor for human IgG assay based on ZnO/chitosan composite as sensing platform has been described. This material, which combined the advantages of inorganic species, ZnO and organic polymer, chitosan, can maintain biological activity well. A sequential sandwich immunoassay format was performed on the ZnO/chitosan composite supported by glass carbon electrode (GCE) using goat-anti-human IgG antibody (IgG Ab) and human IgG as a model system. Amperometry was used to determine the amount of horse-radish peroxidase (HRP) fixed on the sensor surface, which was related to the content of the desired human IgG. Assay conditions that were optimized included the amount of labeled antibody, the incubation time and temperature, the pH of the substrate solution, etc. Using hydroquinone as a mediator, amperometric detection at -150mV (versus SCE) resulted in a detection range 2.5-500ngmL(-1), with a detection limit of 1.2ngmL(-1). The simple manipulations of the construction of ZnO/chitosan composite, as well as low-cost and broad linear range, are the main features of the proposed immunosensing method.

A Sequence‐Selective Electrochemical DNA Biosensor Based on HRP‐Labeled Probe for Colorectal Cancer DNA Detection

Abstract A highly‐sensitive sequence‐selective DNA sensor based on HRP‐labeled probe to detect specific K‐ras gene which is highly associated with colorectal cancer has been reported. Capture probe modified with–SH was first chemically adsorbed on the gold electrode through self‐assembly. Then, the hybridization of a complementary nucleic acid (target DNA:K‐ras gene) and HRP labeled oligonucleotide detection probe occurred in a sandwich way. Finally, H2O2 electroreduction current catalyzed by HRP was measured amperometrically in the presence of hydroquinon as mediator. The sequence selectivity is double guaranteed by the complementary hybridization of target DNA with capture and detection probes. The experimental conditions were optimized. The linear range is 1.17×10−11∼1.17×10−7 mol l−1 with a detection limit of 5.85×10−12 mol l−1. The electrode with capture probe can be reused after regeneration in boiling water.

A Mediator-free Horseradish Peroxidase Biosensor Based on Concanavalin A

Abstract A media-free horseradish peroxidase (HRP) biosensor has been developed. First, HRP was adsorbed by gold nanoparticles and then immobilized on the bare gold electrode surface by activated concanavalin A (Con A). The factors influencing the performance of the resulting biosensor were studied in detail. The optimum conditions were pH 7.0 and an applied potential of −150 mV. The electrode provided a linear response to H2O2 over a concentration range of 5.0×10−6 to 1.2×10−2 M with a detection limit of 2.9×10−6 M. The system was applied for the determination of the samples, and the results obtained were satisfactory.