A Terahertz Split Ring Resonator Nanosensor for Cardiac Biomarker Detection

This article presents a terahertz (THz) metamaterial-based nanosensor employing a split ring resonator (SRR) for the detection of N-terminal pro–B-type natriuretic peptide (NT-proBNP), a cardiac biomarker released in response to increased myocardial pressure and volume overload in the heart. The sensor is designed and simulated in CST Studio to enable real-time detection via changes in the refractive index of NT-proBNP associated with cardiac abnormalities. Validation is performed through equivalent circuit modeling (ECM) using the Advanced Design System (ADS). The nanosensor achieves a sensitivity of 1460 GHz/RIU, a Q-factor of 22.06, and a figure of merit (FOM) of 41.71. Assuming minimally invasive placement in the pericardium, signal attenuation is modeled using a path-loss framework that accounts for the serous and fibrous pericardial layers. Transmission line theory is applied to evaluate the intrinsic impedance, reflection coefficients, and attenuation characteristics of THz waves propagating through cardiac tissue. The model estimates the received power at a nanocontroller located at the fibrous layer and is validated using COMSOL Multiphysics. By leveraging refractive index variations induced by NT-proBNP, this nanosensor enables intrabody THz communication as a diagnostic modality. The platform is particularly suited for detecting conditions such as pericarditis, where biomarker fluctuations and pericardial thickening jointly modulate the THz signal.