Linking cytokine signaling to vascular response: Impedance biosensing of E-selectin and IL-6 for endothelial activation assessment.

Endothelial activation is a key feature of vascular inflammation, yet rapid methods for simultaneously quantifying inflammatory cytokines and endothelial activation biomarkers remain limited. Here, we present a portable electrochemical impedance spectroscopy (EIS) biosensing platform for the label-free detection of interleukin-6 (IL-6) and E-selectin directly in human plasma. The platform utilizes ZnO-modified gold electrodes to support antibody immobilization and enhance impedance-based signal transduction, enabling rapid biomarker quantification using pre-functionalized disposable sensors. Sensor performance was characterized through surface functionalization, electrochemical impedance analysis, and equivalent circuit modeling, followed by analytical validation using calibration, spike-and-recovery, specificity, and precision studies. The biosensor demonstrated concentration-dependent impedance responses across the evaluated measurement ranges, with regression-based limits of detection of 55.77 pg/mL for IL-6 and 3.38 ng/mL for E-selectin. Analytical validation demonstrated excellent quantitative performance, including calibration coefficients of determination up to 0.98, spike-and-recovery values within 80-120%, minimal cross-reactivity with representative non-target proteins, and intra- and inter-assay coefficients of variation below 20%. Measurements were completed using less than 100 μL of plasma with a total assay time of under 10 min. The portable READ platform demonstrated analytical performance comparable to a benchtop impedance analyzer, supporting reliable quantitative biomarker detection in plasma. Collectively, this work establishes a portable multiplex electrochemical biosensing strategy for rapid inflammatory profiling and provides a foundation for future point-of-care monitoring of endothelial dysfunction and vascular inflammation.