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Niu L.M.,Hebei Medical University | Liu Y.,Tangshan Gongren Hospital | Lian K.Q.,Hebei Medical University | Ma L.,Hebei Medical University | And 2 more authors.
Arabian Journal of Chemistry | Year: 2015

DNA usually adsorbs gold nanoparticles by virtue of mercapto or amino groups at one end of a DNA molecule. However, in this paper, we report a sensitive biosensor constructed using unmodified DNA molecules with consecutive adenines (CA DNA) and gold nanoparticles (GNPs). The CA DNA-GNP composite was fabricated on gold electrodes and characterized by using of scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and the electrochemical method. Using an electrochemical quartz crystal microbalance (EQCM), the mechanism by which the CA DNA and GNPs combined was also studied. The modified electrode exhibited an ultrasensitive response to diquat. Differential pulse voltammetry (DPV) was used to study the linear relationships between concentrations and reduction peak currents, ranging from 1.0×10-9 M to 1.2×10-6 M. The detection limit of it is 2.0×10-10 M. The feasibility of the proposed assay for use in human urine and grain was investigated, and the satisfactory results were obtained. © 2015 The Authors. Source

Xu X.,Hebei Medical University | Xu X.,Key Laboratory of Forensic Medicine of Hebei Province | Zhang H.,Hebei Medical University | Shi H.,Hebei Medical University | And 3 more authors.
Analytical Biochemistry | Year: 2012

A sensitive simple method is presented for the determination of three major catecholamines in human urine by capillary electrophoresis (CE) with on-line chemiluminescence (CL) detection. This was also the first time that the luminol-Ag(III) complex CL system was used for CE detection. This method was based on the enhancing effect of epinephrine (EP), norepinephrine (NE), and dopamine (DA) on the CL reaction between luminol and the Ag(III) complex in alkaline solution. The separations and determinations were performed with an electrophoretic buffer consisting of 20.0 mM sodium borate and 1.0 mM luminol. Under optimized conditions, the three catecholamines were baseline separated and detected in less than 8 min. Detection limits of 7.9 × 10-8 M, 1.0 × 10-7 M, and 6.9 × 10-8 M were observed for EP, NE, and DA, respectively. Relative standard deviation (RSD) values for the peak height were 4.7% to 5.4% (n = 5). Our proposed method was applied to the determinations of the catecholamines in urine samples from 12 healthy individuals and 26 pheochromocytoma patients. Our results suggest that this method might be useful to monitor the catecholamine levels in routine screening and to diagnose pheochromocytoma. © 2012 Elsevier Inc. All rights reserved. Source

Xu X.,Hebei Medical University | Xu X.,Key Laboratory of Forensic Medicine of Hebei Province | Shi H.,Hebei Medical University | Ma L.,Hebei Medical University | And 3 more authors.
Luminescence | Year: 2011

A novel flow injection analysis-direct chemiluminescence (FI-CL) method has been developed for determination of trace amounts of dopamine (DA) based on the enhancing effect of DA on the CL reaction of luminol with an Ag(III) complex in alkaline solution. Under optimum conditions, CL intensities are proportional to the concentration of DA in the range of 1.0 × 10-10 to 4.0 × 10-8 mol L-1. The detection limit is 3.0 × 10-11 mol L-1 for DA (3s), with a relative standard deviation (n = 13) of 2.3% for 1.0 × 10-8 mol L-1 DA. This method has also been applied for the determination of DA in commercial pharmaceutical injection samples. On the basis of the CL spectra and the results of the free-radical trapping experiment of this work, a reaction mechanism for this CL reaction is proposed and discussed. Copyright © 2010 John Wiley & Sons, Ltd. Source

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