A novel nanogold-single wall carbon nanotube modified sensor for the electrochemical determination of 8-hydroxyguanine, a diabetes risk biomarker.

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.