Triple-Function-Intensified Photoelectric Immunosensing Platform for One-Step Detection of Cardiac Troponin I

Integrating semiconductor nanowires with a nanoplasmonic metal surface substrate enables a real-time photocurrent response, offering a promising immunosensing platform. However, achieving one-step biorecognition detection of cardiac troponin I (cTnI) biomarker remains a challenge. Herein, we present the development of an antenna-engaged nanowire-inspired porous heterostructure comprising polydopamine-functionalized titanium dioxide nanowires integrated with an Au plasmonic layer (PDA/TNW/Au-PL) for ultrasensitive immunosensors under homemade white light-emitting diodes (LEDs). This deliberate combination of Au-PL, TNWs, and PDA-based trilayer hybrid electrode design adopts the following unique triple-function signal intensification characteristics: (i) interfacial engineering of type II heterojunction and Schottky junction synergistically improve the separation efficiency of electron-hole pairs, thereby significantly improving the photoelectric performance; (ii) strong absorbance across the entire visible range spectrum (400-800 nm) facilitates exceptional plasmonic resonance, enhancing light-harvesting efficiency; and (iii) the nanowire-inspired PDA layer-based nanocavities not only enhance the mobility of charge carriers but also enable the rapid, direct binding of the cTnI antibody onto the PDA surface within 10 min. Therefore, a one-step immunosensing protocol for label-free cTnI detection with a detection time of approximately 30 min is achieved without the requirement of secondary antibodies, amplification labels, or redox mediators. It demonstrates a wide linear sensing range from 0.001 to 1000 ng mL^-1, with an ultralow detection limit of 0.001 ng mL^-1. Our research provides a strong impetus for point-of-care diagnostics, enabling immediate and accurate therapeutic decision-making.