The apoptosis of cancer cells was experimentally measured by terahertz (THz) biosensors based on the metamaterials (MMs). The non-bianisotropic resonance with an electric field of up to 10⁶ V/m was exhibited at 0.85 THz, where the magnetic dipoles were cancelled in the unit cell. The simulate results show the dependence of the frequency shift on the occupying ratio and refractive index of analytes. The theoretical sensitivity was calculated to 182 GHz/RIU. The experimental results imply that the resonant frequency would red shift with the increase of the concentration of cancer cells. Furthermore, the apoptosis of cancer cells HSC3 under the effect of drug concentration from 1 to 15 μM and drug action time from 24 to 72 hours were also studied by the biosensors, respectively. It shows that the trend agrees with the results measured by the biological CCK-8 kits method. Our proposed MMs-based biosensors may supply a novel viewpoint on cell apoptosis from a physical perspective and be a valuable complementary reference for biological study.

A biosensor based on electromagnetically induced transparent (EIT) metamaterials (MMs) is proposed owing to the low loss and high Q-factor. The theoretical sensitivity of the biosensor based on EIT-like MMs were evaluated up to 248.8 GHz/RIU (RIU, Refractive Index Unit). In experiments, the cancer cells A549, as an analyte, are cultured on EIT-like MMs surface. The results show that when the cell concentration increases from 0.5 × 10⁵ to 5 × 10⁵ cells/ml, the frequency shift Δf could change from 24 to 50 GHz. Moreover, the coupled oscillators model is applied to explain the effect of the refractive index of analyte in simulations and the cell concentration in experiments on the EIT-like MMs. The fitting results exhibit that the refractive index of analyte and cell concentration significantly affect the radiative damping of the bright mode resonator γ₁. The proposed EIT-like MMs biosensors show great potentials for cell measurement because any change that results in the lineshape variation in EIT-like MMs can only be attributed to the change of external dielectric environment due to the suppression of radiative losses.

Biosensors based on terahertz (THz) metasurfaces have recently attracted widespread attention. However, few have been reported so far because it is a challenge to achieve ultrasensitive multidimensional detection in the THz spectrum. Here, we propose a novel THz biosensor that consists of a metasurfaces and a metal oxide semiconductor‐like structure (MOSLS), which is based on patterned graphene–polyimide–perovskite. We varied the photoconductivity of the MOSLS via the electrostatic doping effect. The biosensor could detect whey protein down to a concentration limit of 6.25 ng/mL. Significant responses in frequency, phase, and transmission amplitude were all detected for different protein concentrations. The transmission value difference, frequency shift, and phase difference increased with the concentration of whey protein, clearly demonstrating multidimensional biosensing. Moreover, by applying lasers with different wavelengths, we have realized reversible biosensing in THz region for the first time. These results are very promising for applications of THz metasurfaces in the field of biosensing.