Early Chronoamperometric Transients Extraction Improves Sensitivity for Electrochemical Immunosensors

Chronoamperometric biosensors are simple and robust but often the lack sensitivity required to detect low abundance analytes. Conventional chronoamperometry analysis relies on the limiting current, which is often compromised by background currents and poor discrimination between target-specific and nonspecific signals. Here, the extraction and integration of the information-rich early transient improve sensitivity gains and reduce measurement speed. A chronoamperometric electrochemical immunoassay for cardiac troponin I (cTnI) was used as a model system. Current–time traces were analyzed via integration to obtain the area under the curve (AUC), with integration windows defined using either fixed time intervals or a novel gradient-based thresholds. The gradient-based method dynamically selects regions of the transient based on the rate of current change, isolating the kinetically informative signal without requiring prior knowledge of optimal time windows. This approach reduced the limit of detection (LOD) from 130 to 80 pg mL–1 for chemisorbed sensors and from 233 to 40.4 pg mL–1 for physisorbed systems, while comparable sensitivity was observed for a plate-based format (1000–1018 pg mL–1). These results show that early transient analysis is most effective when redox activity is localized near the electrode surface and leads to similar results for diffusion-limited systems. This data-driven framework enhances sensitivity without modifying assay chemistry or hardware, offering a practical route toward faster, low-cost, and sensitive amperometric biosensing.