Development of an electrochemical sensor for nitric oxide based on carbon paste electrode modified with Nafion, gold nanoparticles and graphene nanoribbons

Various physiological as well as pathophysiological processes in the cardiovascular system, in the immune response or in neurotransmission depend on changes of the concentration of nitric oxide (NO). Due to the instability of this ubiquitous signal molecule in vivo and in vitro, its rapid and direct detection is necessary to obtain meaningful results. Therefore, the development of a method for the rapid electrochemical detection of nitric oxide at 0.72 V (vs. Ag/AgCl) using a carbon paste electrode, modified by drop casting, is presented. As modifying solution, a nanocomposite consisting of Nafion, graphene nanoribbons, and gold nanoparticles was prepared. The voltammetric investigations with the optimized sensor were performed at room temperature in phosphate buffer solution (0.1 M, pH 7.4) as supporting electrolyte. Based on differential pulse voltammetry measurements, the obtained results for the analytical signal showed good linear response in the range of 0.39-2.34 mu M and 2.34-104.7 mu M with a correlation coefficient of 0.9941 and 0.9984, respectively. For both linear ranges, the repeatability as well as the reproducibility was <5% and <10%, respectively. A concentration of 40 nM was determined for the detection limit, whereas the limit of quantification was 130 nM. In addition, the influence of physiological interferences was also investigated and resulted in negligible effects. Finally, the sensor was successfully used to measure the NO release of NO donors. Based on the results obtained, the new sensor provides a simple and fast method for a direct voltammetric determination of low nitric oxide concentrations in solutions.