Sensitive detection of the concentrations for normal epithelial cells based on Fano resonance metamaterial biosensors in terahertz range

In this paper, we have cultured normal epithelial cells (HaCaT) as analytes to detect the sensitivity of a biosensor based on Fano resonance metamaterials (FRMMs). The frequency shift Δf of the transmission spectrum was experimentally measured at three different concentrations (0.2×10⁵, 0.5×10⁵, and 5×10⁵  cell/ml) of HaCaT cells. By employing the FRMMs-based biosensor, the detection concentration of HaCaT cells can approximately arrive at 0.2×10⁵  cell/ml; further, the corresponding Δf is 25 GHz, which reaches the measurement limit of the THz-TDS system. Additionally, the increase of HaCaT cell concentration causes a different redshift of Δf from 24-50 GHz, and the maximum of Δf can reach 50 GHz when the HaCaT cell concentration is at 5×10⁵ cell/ml. Similarly, the simulated results show that the Δf depends on the numbers of analytes with a semiball shape and the refractive index of analytes. The theoretical sensitivity was calculated to be 481 GHz/RIU. The proposed FRMMs-based biosensor paves a fascinating platform for biological and biomedical applications and may become a valuable complementary reference for traditional biological research.