Turn-on ratiometric electrochemical detection of H2O2 in one drop of whole blood sample via a novel microelectrode sensor

Oxidative stress plays an important role in the pathogenesis of many diseases, while the exact mechanism that hydrogen peroxide (H2O2) as one of the most abundant reactive oxygen species (ROS) exerts its influence on oxidative stress remains unclear. We developed a novel turn-on ratiometric electrochemical sensor for the detection of H2O2 in blood samples. The electrochemical probe 5-(1,2-dithiolan-3-yl)-N-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-phenyl)pent-anamide (BA) was designed and synthesized for the selective detection of H2O2 via a one-step amide reaction. Meanwhile, Nile Blue A (NB) was optimized as an internal reference molecule, thus enabling accurate quantification of H2O2 in a complex environment. BA and NB were then co-assembled onto a carbon fiber microelectrode (CFME) coated with Au cones. The oxidation peak current ratio between BA and NB demonstrated good linearity with the logarithm of the H2O2 concentration values ranging from 0.5 mu M to 400 mu M with a low detection limit of 0.02 mu M. The developed sensor showed remarkable selectivity against potential interferences in whole blood samples, especially for ascorbic acid, uric acid, and dopamine. In combination with the unique characteristics of CFME, such as a small size and good biocompatibility, the microsensor was used for rapid analysis of one drop of whole blood sample. This sensor not only creates a new platform for the detection of H2O2 in whole blood samples, but also provides a new design strategy of other ROS analysis for early diagnosis of ROS-related diseases, drug discovery processes, and pathological mechanisms.