A microfluidic integrated Q-BIC terahertz metasurface sensor for ultrasensitive detection of glioma biomarker GFAP

Glial fibrillary acidic protein (GFAP) is an important biomarker associated with glial cell injury and glioma progression. The serum levels of GFAP antigens and antibodies are closely correlated with tumor grade and clinical characteristics. To achieve high-precision and rapid detection, this study develops a terahertz (THz) metasurface that integrates quasi-bound states in the continuum (Q-BIC) with microfluidic technology. Structural asymmetry excites Q-BIC resonances, significantly enhancing the interaction between the THz electromagnetic field and target analytes. Meanwhile, SU-8 microfluidic channels are integrated to suppress water-induced interference during liquid-phase detection. The experimental results show that the detection line for the GFAP antigens by this sensor is 0.77 pg/mL, and the detection line for the GFAP antibodies is 1.03 pg/mL. Within a wide concentration range from 1 pg/mL to 100 ng/mL, the modulation depths of the resonance amplitude exhibit strong linear relationships with concentration, indicating a broad dynamic sensing range. To address the weak spectral differences at ultralow concentrations, a signal-processing strategy combining continuous wavelet transform and differential analysis is employed. This approach improves spectral resolution and detection reliability, enabling both qualitative identification and quantitative analysis. Overall, the proposed THz sensing platform exhibits ultrasensitive and good reproducibility, providing a promising tool for brain tumor screening and monitoring.