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ABSTRACT: A novel and simple synchronous electrochemical synthesis of poly(xanthurenic acid, Xa) -electrochemically reduced graphene oxide nanocomposite (PXa-ERGNO) via cyclic voltammetry (CV) was reported, where graphene oxide (GNO) and Xa monomer were adopted as precursors. The resulting PXa-ERGNO nanocomposite was characterized by scanning electron microscopy, Fourier Transform infrared spectroscopy, CV and electrochemical impedance spectroscopy (EIS). The π-π* interactions between the conjugated GNO layers and aromatic ring of Xa enhanced the electropolymerization efficiency accompanied with an increased electrochemical response of PXa. The rich carboxyl groups of PXa-ERGNO film were applied to stably immobilize the probe DNA with amino groups at 5' end via covalent bonding. The captured probe could sensitively and selectively recognize its target DNA via EIS. The dynamic detection range was from 1.0 × 10-14 mol/L to 1.0 × 10-8 mol/L with a detection limit of 4.2 × 10-15 mol/L due to the synergistic effect of integrated PXa-ERGNO nanocomposite. This graphene-based electrochemical platform showed intrinsic advantage, such as simplicity, good stability, and high sensitivity, which could serve as an ideal platform for the biosensing field.
ACS Applied Materials & Interfaces 04/2013; · 4.53 Impact Factor
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ABSTRACT: A sensitive electrochemical impedimetric DNA biosensor based on the integration of tin oxide (SnO2) nanoparticles, chitosan (CHIT) and multi-walled carbon nanotubes (MWNTs) is presented in this paper. The MWNTs-SnO2-CHIT composite modified gold electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with individual MWNTs-CHIT, SnO2-CHIT and bare gold electrode, this composite showed the most obvious electrochemical signal of the redox probe [Fe(CN)6](3-/4-). According to the change of the electron transfer resistance (Ret) induced by the hybridization, target DNA was successfully detected via EIS. This DNA electrochemical biosensor was applied to detect phosphinothricin acetyltransferase (PAT) gene in transgenic corn. The synergistic effect of the MWNTs-SnO2-CHIT remarkably enhanced DNA immobilization and hybridization detection. The dynamic detection range was from 1.0×10(-11)mol/L to 1.0×10(-6)mol/L with a detection limit of 2.5×10(-12)mol/L. This sensing platform showed inner advantage, such as simplicity, good stability, and high sensitivity.
Colloids and surfaces. B, Biointerfaces 01/2013; · 2.60 Impact Factor
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ABSTRACT: In very recent years, polyaniline or its derivatives have been adopted to efficiently immobilize probe DNA via π-π interaction between conjugated interface and DNA bases. In this work, self-doped polyaniline (SPAN)-DNA hybrid was adopted as the platform to construct a DNA biosensor with label-free, reagentless and electrochemical self-signal amplifying features. This was achieved by the π-π interaction between conjugated SPAN and DNA bases, also the intrinsic differences between single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The tightly cross-linked hybrid was tethered to Au electrode, which had been anchored by p-aminothiophenol (PATP) self-assembled monolayer (SAM) previously, based on the phosphoramidate bond between PATP and ssDNA. SPAN in the recognition surface exhibited well-defined redox signals under neutral conditions. Due to the intrinsic property differences between ssDNA and dsDNA, such as rigidity, π-stacked bases, charge distribution and long-range electron transfer, SPAN-DNA underwent a major conformational change after hybridization. The redox behaviors of SPAN were modulated by DNA, which served as signals to monitor hybridization. As an example, the gene fragment related to one of the screening genes for the genetically modified plants, cauliflower mosaic virus 35S gene was satisfactorily detected with this strategy. Under optimal conditions, the dynamic range for the DNA assay was from 1.0 × 10(-14) mol L(-1) to 1.0 × 10(-8) mol L(-1) with the detection limit of 2.3 × 10(-15) mol L(-1). This work presents the construction of a recognition surface for the highly-sensitive electrochemical DNA hybridization detection via the self-signal amplifying procedure of conjugated SPAN-DNA hybrid. Unlike most signal amplifying processes using outer indicators, complex labels or other reagents, this procedure possesses simplicity and convenience.
The Analyst 01/2013; · 4.23 Impact Factor
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ABSTRACT: An impedimetric and freely switchable DNA sensor based on electrochemically reduced graphene oxide (ERGNO) and polyaniline (PANI) film was presented, where ERGNO was prepared on PANI modified glassy carbon electrode (GCE). When the probe DNA was noncovalently assembled on the surface of electrode through π-π(⁎) stacking between the ring of nucleobases and the rich-conjugated structure of the nanocomposite, the electron transfer resistance value of [Fe(CN)(6)](3-/4-) increased. The negative ssDNA and the steric hindrance blocked the effective electron transfer channel of the [Fe(CN)(6)](3-/4-). After hybridization with the complementary DNA, the formation of helix induced dsDNA to release from the surface of conjugated nanocomposite, accompanied with the curtailment of the impedimetric value. The selectivity and sensitivity of this DNA sensing platform were characterized using electrochemical impedance spectroscopy in detail. The fabricated biosensor exhibited excellent performance for the detection of specific DNA sequence with a wide linear range (1.0×10(-15) to 1.0×10(-8)mol/L) and a low detection limit of 2.5×10(-16)mol/L due to the synergistic effect of ERGNO/PANI nanocomposites. The hosphinothricin acetyltransferase gene (PAT) was also detected to show the switchable ability of ERGNO/PANI.
Biosensors & bioelectronics 11/2012; 42C:415-418. · 5.43 Impact Factor
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ABSTRACT: Fabrication of an electrochemical impedimetric DNA biosensor based on the integration of Au-Pt alloy nanoparticles (Au-Pt(NPs)) and electropolymerized polytyramine (Pty) film for the detection of phosphoenolpyruvate carboxylase (PEP) gene is described in this article, where Pty films acted as an ideal combination platform for Au-Pt(NPs) via electrostatic adsorption. The electrochemical properties of the Au-Pt(NPs)/Pty, the characteristics of the immobilization and hybridization of DNA were investigated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy (EIS), respectively. Primary study indicated that Au-Pt(NPs)/Pty had a synergistic effect on the electrochemical signal of [Fe(CN)(6)](3-/4-), which served as the classic redox probe in the most electrochemical impedimetric sensors. DNA sequence-specific of PEP transgene existed in some transgenic crops was detected by this EIS protocol. The dynamic detection range of this DNA electrochemical biosensor to the DNA target sequence was from 1.0×10(-12)M to 1.0×10(-7)M. The detection limit was measured to be 3.6×10(-13)M. The DNA biosensor also had good selectivity, stability and reproducibility.
Colloids and surfaces. B, Biointerfaces 04/2012; 97:150-4. · 2.60 Impact Factor
