This paper presents qualitative analysis of terahertz time-domain spectroscopy application for cancer diagnosis by measurement of the optical properties and spectral characteristics of cancer cells. For this purpose, the cultivation of two cancer cells, U-251 (glioblastoma brain) and A549 (lung adenocarcinoma), were carried out, then their refractive index, absorption coefficient and dielectric constant were measured, and the optical properties of tumor cells were compared with the optical properties of healthy cells (fibroblasts). Tumor cells contain more OH-components in comparison with healthy cells. Since terahertz radiation is heavily absorbed by water, there are differences in the spectra of healthy and oncological cells. To obtain the optical properties and spectral characteristics of the researched objects, a terahertz time-domain spectroscopy method in the transmission mode was used. The researched cell lines were cultured in vitro. Optical properties and spectral characteristics of the samples were calculated by the thin film method and Fourier transform. The results show the differences of refractive index, absorption coefficient and dielectric permittivity between the oncological cell lines U- 251, A549 and the healthy cells in the frequency range 0.2-1 THz. It was found that cancer cells have higher values of refractive indices and absorption coefficients than those of healthy cells. Brain glioblastoma (U-251) has a transmission peak at the frequency of 0.24 THz. The results obtained in this work can form the basis for the diagnosis of brain and lung cancer with the use of terahertz time-domain spectroscopy.
The glucose level of blood can be obtained by terahertz time-domain spectroscopy using refractive index measurement method. The detected refractive indices vary from person to person since the impact of bilirubin and creatinine wasn’t considered. 14 human blood samples were tested using terahertz time-domain spectroscopy. The experiment results show that under the certain concentration of glucose, the refractive index of blood decreases with the increase of bilirubin and creatinine concentration, and thus the concentration of other blood components may also influence on the refractive index of blood. The feasibility of using terahertz time-domain spectroscopy to determine the level of glucose, bilirubin and creatinine qualitatively and quantitatively is provided.
The paper presents the results of the studies of influence of optical radiation with wavelengths of 520 and 780 nm on human glial cells (U251) at the range of exposure times ~ 1-15 min. It was found that after the first minute of irradiation at the wavelength of 780 nm, the relative number of apoptotic cells significantly increased. The result corroborates the concept of biological hazard of optical radiation for tumor cells, and suggests that the approach has a great potential in clinical application for the treatment of human glioma.
In this work, we study infrared optical pump-induced changes in terahertz conductivity of multi-layer graphene on a silicon substrate using terahertz time-domain spectroscopy. Results indicate that the conductivity and optical parameters of investigated material strongly depend on a pumping intensity and the presence of FeCl<sub>3</sub> molecules intercalation. The findings are helpful for determining the most optically tunable material towards designing of optically controllable terahertz devices based on new two-dimensional material beyond graphene monolayer.
The work is dedicated to design of epsilon-near-zero metamaterials (ENZ) in terahertz frequency range. Two materials were investigated: the first material is the one-layered single-wire medium (SWM) and the second material consists of the planar parallel metal stripes on the layer of polyethylene terephthalate (PET). The wired medium was designed using analytical approximation of thin wire structures and verified by numerical simulations. The striped metamaterial was designed using numerical simulations software and its performance was experimentally verified by terahertz timedomain spectroscopy.
This work is devoted to investigation of optical properties (dispersion of refractive index, permittivity and absorption coefficient) of human nails in THz frequency range. These data were obtained by THz time-domain spectroscopy (TDS) technique in transmission mode. These results may be used to develop non-invasive technique of human pathologies control using nail as reference sample in reflection mode of THz TDS.