Evaluating in-vitro cellular toxicity through the analysis of nitrite ions variation at printed electrochemical strips

: Nitric oxide (NO) is a pivotal mediator of numerous physiological and pathological events, with its reactive derivatives, nitrite and nitrate, reflecting both cellular signaling and stress conditions. Among these, nitrite is widely recognised as a stable surrogate marker of NO production, and its accumulation is associated with inflammation, cardiovascular dysfunction, and tumor progression. Conventional quantification relies on the Griess assay, which, although reliable, requires multiple reagents, extended handling, and spectrophotometric instrumentation. Here, we present a simple and inexpensive electrochemical platform based on screen-printed electrodes on a flexible polyester film for the direct determination of nitrite in the supernatants of lipopolysaccharide (LPS)-stimulated macrophages. The device achieves micromolar sensitivity, with a limit of detection of approximately 1.7 μM, and its results correlate closely with the Griess method (Pearson's r = 0.980, p < 0.001) without any electrode modification. Beyond detection, the sensor was successfully employed to monitor the anti-inflammatory response to three mechanistically distinct drugs (erucin, naproxen, and deflazacort), demonstrating its suitability for probing cellular toxicity in different systems. Combining portability, low cost, and operational simplicity, this platform provides a practical alternative to conventional assays for quickly evaluating the therapeutic efficacy in in-vitro models.