Toward Enhanced Cardiovascular Risk Assessment: A Spatial Multiplexing Biosensor for Individual Dual-Mode Detection of Cardiac Troponin I and Interleukin-6

Early diagnosis of cardiovascular diseases requires precise detection of multiple biomarkers, yet simultaneous analysis of these biomarkers without cross-talk remains a major challenge. To overcome this limitation, we developed a novel dual-zone biosensing platform capable of generating independent multimode signals for the parallel detection of cardiac troponin I (cTnI, the gold-standard biomarker) and interleukin-6 (IL-6, a key inflammatory marker). This platform features two spatially resolved zones, Zone I integrates rhodamine B (RhB) with a cadmium sulfide@bismuth tungstate (CdS@Bi₂WO₆) composite, allowing dual-signal detection of cTnI via photoelectrochemical (PEC) and smartphone-based fluorescent (FL) methods. Zone II is functionalized with dsDNA/methylene blue (MB), enabling dual-signal detection of IL-6 through PEC and electrochemical (EC) techniques. The biosensor exhibits excellent analytical performance, including high specificity against interfering species, a broad dynamic range covering clinically relevant concentrations, and high detection sensitivity (cTnI: 1 ∼ 50,000 pg mL^-1 for PEC, 10 ∼ 50,000 pg mL^-1 for FL; IL-6:1 ∼ 20,000 pg mL^-1 for PEC, 1 ∼ 20,000 pg mL^-1 for EC.) with low limits of detection (cTnI: 0.27 pg mL^-1 for PEC, 0.86 pg mL^-1 for FL; IL-6:0.57 pg mL^-1 for PEC, 0.65 pg mL^-1 for EC.). Importantly, it maintains robust functionality in human serum and shows strong correlation with established clinical methods. This work provides a generalizable framework for developing multiplexed biosensors that combine orthogonal detection principles, effectively addressing key challenges in multicomponent bioanalysis, which is a significant advancement in the field of clinical diagnostics.