Terahertz circular dichroism sensing of living cancer cells based on microstructure sensor

Terahertz (THz) waves have the advantages of being noninvasive and nonionizing because of their low radiation energy, so they have potential applications in the biomedical field, but thus far, those have been limited by the strong absorption in water and low detection sensitivity. Herein, we propose a reflective THz time-domain circular dichroism (CD) sensing system and a silicon subwavelength grating as the microstructure sensor to generate and detect the THz chiral polarization states, to realize quantitative detection of living cell numbers and qualitative identification of cell kinds in a liquid environment. Three kinds of hepatoma cell proliferation and inhibition with different concentrations of aspirin were measured by this sensing method, and the experimental results show that the sensitivities for CD resonance intensity and frequency shift can reach 3.44 dB mL/106 cells and 5.88 GHz mL/106 cells, respectively, and the minimum detection concentration is in the order of 104 cells/mL for THz detection in a liquid environment for the first time. This new THz sensing system and sensing method are expected to become a broadband, label-free, noncontact, real-time detection technology that can be used for quantitative detection and qualitative identification of cells or other active biochemical materials. [Display omitted] •THz chiral polarization state is generated and the circular dichroism is used as the sensing characterization.•Artificial dielectric grating is used as the microstructure sensor.•Strong absorption of water is avoided by the reflective THz system.•Realize the concentration sensing of HepG2 cells in a liquid culture environment.•Realize the identification of HepG2, Huh7, and H7402 cell.