Verification of Non-thermal Effects of 0.3–0.6 THz-Waves on Human Cultured Cells

Cellular effects of terahertz waves

SIGNIFICANCE

An increasing interest in the area of biological effects at exposure of tissues and cells to the terahertz (THz) radiation is driven by a rapid progress in THz biophotonics, observed during the past decades. Despite the attractiveness of THz technology for medical diagnosis and therapy, there is still quite limited knowledge about safe limits of THz exposure. Different modes of THz exposure of tissues and cells, including continuous-wave versus pulsed radiation, various powers, and number and duration of exposure cycles, ought to be systematically studied.

AIM

We provide an overview of recent research results in the area of biological effects at exposure of tissues and cells to THz waves.

APPROACH

We start with a brief overview of general features of the THz-wave-tissue interactions, as well as modern THz emitters, with an emphasis on those that are reliable for studying the biological effects of THz waves. Then, we consider three levels of biological system organization, at which the exposure effects are considered: (i) solutions of biological molecules; (ii) cultures of cells, individual cells, and cell structures; and (iii) entire organs or organisms; special attention is devoted to the cellular level. We distinguish thermal and nonthermal mechanisms of THz-wave-cell interactions and discuss a problem of adequate estimation of the THz biological effects' specificity. The problem of experimental data reproducibility, caused by rareness of the THz experimental setups and an absence of unitary protocols, is also considered.

RESULTS

The summarized data demonstrate the current stage of the research activity and knowledge about the THz exposure on living objects.

CONCLUSIONS

This review helps the biomedical optics community to summarize up-to-date knowledge in the area of cell exposure to THz radiation, and paves the ways for the development of THz safety standards and THz therapeutic applications.

Terahertz pulses induce segment renewal via cell proliferation and differentiation overriding the endogenous regeneration program of the earthworm Eisenia andrei

Terahertz (THz) irradiation of excised Eisenia andrei earthworms is shown to cause overriding of the genetically determined, endogenously mediated segment renewing capacity of the model animal. Single-cycle THz pulses of 5 µJ energy, 0.30 THz mean frequency, 293 kV/cm peak electric field, and 1 kHz repetition rate stimulated the cell proliferation (indicated by the high number of mitotic cells) and both histogenesis and organogenesis, producing a significantly higher number of regenerated segments. The most conspicuous alteration in THz-treated animals was the more intense development of the new central nervous system and blood vessels. These results clearly demonstrate that THz pulses are capable to efficiently trigger biological processes and suggest potential applications in medicine.

Detection of living cervical cancer cells by transient terahertz spectroscopy

The photonic energy of terahertz wave is in the same order of magnitude as the rotational and vibrational energy levels of organic and biological macromolecules, so it has unique advantages in detecting cells and biological macromolecules. However, in the life environment, the dynamic time scale of cell-environment interaction and structural conformation change of biological macromolecules are within picosecond to millisecond, and water has strong absorption to terahertz wave, which has become the bottleneck problem for the detection of cells and biological macromolecules by terahertz technology. In this article, we developed a set of terahertz single measurement system based on the tilt wave front of grating pulse technique. The system was employed for the terahertz detection of trace living cervical cancer cells. We achieved transient detection of the terahertz pulse time-domain waveform of the living HeLa cells. The characteristic absorption peaks were identified by Lambert-Beer law, respectively, at 0.49, 0.71, 1.04, 1.07, 1.26 and 1.37 THz. The absorbance is proportional to the cell concentration.

Study on the effects of terahertz radiation on gene networks of Escherichia coli by means of fluorescent biosensors

Three novel fluorescent biosensors sensitive to terahertz (THz) radiation were developed via transformation of Escherichia coli (E. coli) cells with plasmids, in which a promotor of genes matA, safA, or chbB controls the expression of a fluorescent protein. The biosensors were exposed to THz radiation from two sources: a high-intensity pulsed short-wave free electron laser and a low-intensity continuous long-wave IMPATT-diode-based device. The threshold and dynamics of fluorescence were found to depend on radiation parameters and exposure time. Heat shock or chemical stress yielded the absence of fluorescence induction. The biosensors are evaluated to be suitable for studying influence of THz radiation on the activity of gene networks related with considered gene promoters.

Computational absorption and reflection studies of normal human skin at 0.45 THz

Applications using terahertz (THz) frequency radiation will inevitably lead to increased human exposure. The power density and specific absorption rate (SAR) simulations of thin skin at 0.45 THz show the bulk of the energy being absorbed in the upper stratum spinosum, and the maximal temperature rise is in the lower stratum spinosum. There are regions of SAR increase of 100% above the local average at the stratum spinosum/stratum basale boundary. The dead Stratum Corneum layer protects underlying tissues in thick skin. Reflection studies suggest that acute angles and the use of polarised incident radiation may enhance the assessment of diabetic neuropathy.