1. Fullerene C60 modified gold electrode and nanogold modified indium tin oxide electrode for prednisolone determination
Rajendra N Goyal, Munetaka Oyama, Neeta Bachheti, Sudhanshu P Singh Bioelectrochemistry. 2009 Feb;74(2):272-7. doi: 10.1016/j.bioelechem.2008.10.001. Epub 2008 Oct 25.
The electrochemical determination of prednisolone has been investigated at fullerene-C(60)-modified gold (C(60)/Au) electrode and gold nanoparticles modified indium tin oxide (nano Au/ITO) electrode in phosphate buffer solution (PBS) of pH 7.2. During oxidation of prednisolone, an anodic peak with peak potential (E(p)) at 570 mV and 400 mV appeared at nano Au/ITO and C(60)/Au electrode, respectively. The experimental results revealed that gold nanoparticles as well as fullerene (C(60)) promote the rate of prednisolone oxidation by increasing the peak current (i(p)) and oxidizing at lower peak potentials as compared to the respective bare electrodes due to their electrocatalytic effect. The linear concentration range at both the electrodes was in the range of 1 microM to 0.10 mM. The detection limit obtained at C(60)/Au electrode was 26 nM, while at nano Au/ITO electrode the detection limit was 90 nM. The applicability of the method to direct assays of human urine and whole blood sample is described to use the method for testing cases of doping by athletes.
2. A novel nanogold-single wall carbon nanotube modified sensor for the electrochemical determination of 8-hydroxyguanine, a diabetes risk biomarker
Sunita Bishnoi, Rajendra N Goyal, Yoon-Bo Shim Bioelectrochemistry. 2014 Oct;99:24-9. doi: 10.1016/j.bioelechem.2014.06.003. Epub 2014 Jun 15.
An electrochemical study of the oxidation of 8-hydroxyguanine (8-OH-Gua) at gold nanoparticles attached to single walled carbon nanotube modified edge plane pyrolytic graphite electrode (AuNP-SWCNT/EPPGE) has been carried out to develop a method for the self diagnosis of diabetes. The level of 8-OH-Gua, an important biomarker of oxidative DNA damage, is higher in urine of diabetic patients than control subjects. A detailed comparison has been made between the square wave voltammetric (SWV) response of SWCNT/EPPGE and AuNP-SWCNT/EPPGE towards the oxidation of 8-OH-Gua in respect of several essential analytical parameters viz. sensitivity, detection limit, peak current and peak potential. The AuNP-SWCNT/EPPGE exhibited a well defined anodic peak at potential of ~221 mV for the oxidation of 8-OH-Gua as compared to ~312 mV using SWCNT/EPPGE at pH=7.2. Under optimized conditions linear calibration curve for 8-OH-Gua is obtained over a concentration range of 0.01-10.0 nM in phosphate buffer solution (PBS) of pH=7.2 with detection limit and sensitivity of 5.0 (±0.1) pM and 4.9 (±0.1) μA nM(-1), respectively. The oxidation of 8-OH-Gua occurred in a pH dependent process and the electrode reaction followed adsorption controlled pathway. The electrode exhibited an efficient catalytic response with good reproducibility and stability. The method has been found selective and successfully implemented for the determination of 8-OH-Gua in urine samples of diabetic patients.
3. Highly sensitive and selective determination of pyrazinamide at poly-L-methionine/reduced graphene oxide modified electrode by differential pulse voltammetry in human blood plasma and urine samples
Srikanth Cheemalapati, Balamurugan Devadas, Shen-Ming Chen J Colloid Interface Sci. 2014 Mar 15;418:132-9. doi: 10.1016/j.jcis.2013.11.084. Epub 2013 Dec 7.
In this current study we used electrochemically active film which contains poly-L-methionine (PMET) and electrochemically reduced graphene oxide (ERGO) on glassy carbon electrode (GCE) for pyrazinamide (PZM) detection. The electrocatalytic response of analyte at PMET/ERGO/GCE film was measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In addition, electrochemical impedance studies revealed that the smaller R(ct) value observed at PMET/ERGO film modified GCE which authenticates its good conductivity and faster electron transfer rate. The prepared PMET/ERGO/GCE film exhibits excellent DPV response towards PZM and the reduction peak current increased linearly with respect to PZM concentration in the linear range between 0.4 μM to 1129 μM with a sensitivity of 0.266 μA μM(-1) cm(-2). Real sample studies were carried out in human blood plasma and urine samples, which offered good recovery and revealed the promising practicality of the sensor for PZM detection. The proposed sensor displayed a good selectivity, repeatability, sensitivity with appreciable consistency and good reproducibility. In addition, the proposed electrochemical sensor showed good results towards the commercial pharmaceutical PZM samples.