Electrochemical detection of 8-hydroxyguanine using screen-printed carbon electrodes modified with carboxy-functionalized multi-walled carbon nanotubes

Abstract

The paper presents the findings of an optimization and validation results of electrochemical detection of 8-hydroxyguanine, a major marker of oxidative stress, using disposable screen-printed carbon electrode (SPCE) modified with carboxy-functionalized multi-walled carbon nanotubes (MWCNTs-COOH). Several types of bare and modified SPCEs were tested and modification with MWCNTs-COOH was found superior in terms of measured current response, level of background currents, and sensitivity in oxidation of 8-hydroxyguanine. The effect of pH and composition of supporting electrolyte on current response and peak potential were also evaluated. Validation parameters were calculated for optimum pH 7 of 0.01 mol dm−3 phosphate buffer. The sensor showed the highest sensitivity of 0.0625 µA dm3 μmol−1 within the linear range 0.3–12 μmol dm−3 with a limit of detection as low as 0.57 μmol dm−3. Extended linear range 0.3–240 μmol dm−3 is feasible with a sensitivity of 0.0523 µA dm3 μmol−1. Intra-day and inter-day assays within 3 days were performed to verify the repeatability of modified screen-printed carbon sensors. Finally, the sensor was utilized for electrochemical monitoring of stability of 8-hydroxyguanine when stored in room temperature, in the refrigerator, or frozen and thawed.