Paper-based electrochemical device for the determination of H2S in murine lysates for liquid biopsy application

Hydrogen Sulfide (H₂S) is a biologically active endogenous gas, produced in mammalian tissues, which plays a critical role in several pathophysiological processes, including oncogenesis. Recent studies have indicated that this gas-transmitter may exert diametrically opposite effects on neoplastic cell proliferation, depending on the duration and concentration of H₂S exposure. Due to this dual role, antineoplastic drugs, aimed at modulating H₂S levels, are attracting considerable interest in both research and clinical settings. Furthermore, H₂S could serve as a diagnostic marker, potentially indicating the presence of tumors in various body fluids. Traditionally, H₂S is detected using spectrophotometric, chromatography, and fluorometric methods. However, the use of electrochemical sensors is a promising strategy to speed up and simplify operations. In this context, an electrochemical sensor, screen-printed on filter paper, and then modified with Prussian blue, was developed. After the optimization of various experimental parameters, such as the concentration of Prussian Blue to be used for the electrode modification and the constant potential applied during the chronoamperometric measurements, the sensor was analytically characterized in standard solution, achieving a good repeatability and a detection limit of 3 μM. The sensor was then applied to determine H₂S in several biological samples, including a murine skin lysate, two pharmacologically treated neoplastic murine lysates, and an untreated neoplastic murine lysate, obtaining results in agreement with those observed with the standard H2S determination method, demonstrating the applicability of the developed electroanalytical method for liquid biopsy.