To assess the performance of the rGO-Co₃O₄-Pt/SPEs platform in a biological environment, SWV was used to evaluate oxidative stress in HL-1 cardiac cells under control conditions and following DOX treatment. DOX causes cardiotoxicity by generating excessive ROS, disrupting cellular homeostasis and damaging lipids, proteins, and DNA. It also triggers calcium dysregulation in cardiomyocytes, leading to oxidative stress and impaired cardiac function . As illustrated in Figure , the rGO-Co₃O₄-Pt-modified electrode exhibited significantly higher current responses in DOX-treated cells compared to either the bare electrode or untreated cells. These findings clearly show that DOX increases ROS production, confirming higher oxidative stress and demonstrating the sensitivity of nanocomposites to effectively detect H₂O₂. Whereas in the case of the control, a low or negligible response was observed, as expected. These results validate the selectivity of the rGO-Co₃O₄-Pt/SPEs platform, demonstrating its ability to avoid significant false-positive signals in the absence of elevated ROS. Such selectivity is essential for reliably differentiating between normal and stressed cellular states.