Ratiometric Microscale Electrochemical Sensor for In-Situ Monitoring of Oxidative Stress Induced Ascorbic Acid Fluctuations in Single Cells

Accurate in-situ monitoring of antioxidant ascorbic acid (AA) fluctuations at the single-cell level is of great significance for early diagnosis and intervention of oxidative stress-related neurodegenerative diseases. The development of robust sensing platform for the monitoring of intracellular AA is crucial to comprehend the heterogeneity and antioxidation mechanism of cells. Herein, a microscale electrochemical sensor (microsensor) was constructed for in-situ detection of AA in single cells based on poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (PEDOT-rGO) with methylene blue (MB) as an inner reference signal. The PEDOT-rGO layer provided efficient electron transport channels and catalytic active sites, which markedly reduced the oxidation potential of AA and enhanced the detection sensitivity. The synergistic PEDOT-rGO and MB molecules offered ratiometric output pattern to improve the detection accuracy, which achieved sensitive detection of AA with a detection limit of 0.79 μM. Notably, the ratiometric microsensor enabled the real-time monitoring of endogenous AA fluctuations in single PC12 cells under hydrogen peroxide stimulation. Furthermore, the microsensor confirmed that the supplementation of exogenous AA improved the intracellular AA level to defend against oxidative stress. The proposed strategy provided a simple and reliable platform for evaluating AA fluctuations at the single-cell level, holding promising prospects in the monitoring and treatment of neurological disorders.