Simple and label-free detection of DNA hybridization on a modified graphene nanosheets electrode.

In this study, an effective method was devised to synthesize amelogenin genes in solution and to amplify electrical detection of DNA hybridization based on graphene nanosheets (GNs) modified glassy carbon electrode (GCE). GNs are well known as effective biocompatible and conductive materials that can provide large surface area and a sufficient numbers of binding points for DNA immobilization. The biosensor fabrication processes and the electrochemical responses of probe immobilization and hybridization with target DNA were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) using [Fe(CN)6](3-/4-) as an electrochemical redox. Due to minimum nonspecific DNA adsorption, a very high specificity of DNA hybridization was achieved, and the hybridization rate of the target DNA in optimum conditions was increased significantly. With this approach, the target DNA could be quantified in a linear range from 1.0×10(-20) to 1.0×10(-14) mol L(-1) for the first segment and from 1.0×10(-13) to 1.0×10(-6) mol L(-1) for the second segment, with a detection limit of 7.1×10(-21) mol L(-1) by 3s(b). In addition, the biosensor exhibited a high level of stability and repeatability, even for the determination of DNA sequences in real samples without amplification.

Simple and label-free electrochemical impedance Amelogenin gene hybridization biosensing based on reduced graphene oxide.

The increasing desire for sensitive, easy, low-cost, and label free methods for the detection of DNA sequences has become a vital matter in biomedical research. For the first time a novel label-free biosensor for sensitive detection of Amelogenin gene (AMEL) using reduced graphene oxide modified glassy carbon electrode (GCE/RGO) has been developed. In this work, detection of DNA hybridization of the target and probe DNA was investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The optimum conditions were found for the immobilization of probe on RGO surface and its hybridization with the target DNA. CV and EIS carried out in an aqueous solution containing [Fe(CN)6](3-/4-) redox pair have been used for the biosensor characterization. The biosensor has a wide linear range from 1.0×10(-20) to 1.0×10(-14)M with the lower detection limit of 3.2×10(-21)M. Moreover, the present electrochemical detection offers some unique advantages such as ultrahigh sensitivity, simplicity, and feasibility for apparatus miniaturization in analytical tests. The excellent performance of the biosensor is attributed to large surface-to-volume ratio and high conductivity of RGO, which enhances the probe absorption and promotes direct electron transfer between probe and the electrode surface. This electrochemical DNA sensor could be used for the detection of specific ssDNA sequence in real biological samples.

Sex determination based on amelogenin DNA by modified electrode with gold nanoparticle.

We have developed a simple and renewable electrochemical biosensor based on carbon paste electrode (CPE) for the detection of DNA synthesis and hybridization. CPE was modified with gold nanoparticles (AuNPs), which are helpful for immobilization of thiolated bioreceptors. AuNPs were characterized by scanning electron microscopy (SEM). Self-assembled monolayers (SAMs) of thiolated single-stranded DNA (SH-ssDNA) of the amelogenin gene was formed on CPE. The immobilization of the probe and its hybridization with the target DNA was optimized using different experimental conditions. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrochemical response of ssDNA hybridization and DNA synthesis was measured using differential pulse voltammetry (DPV) with methylene blue (MB) as an electroactive indicator. The new biosensor can distinguish between complementary and non-complementary strands of amelogenin ssDNA. Genomic DNA was extracted from blood and was detected based on changes in the MB reduction signal. These results demonstrated that the new biosensor could be used for sex determination. The proposed biosensor in this study could be used for detection and discrimination of polymerase chain reaction (PCR) products of amelogenin DNA.