In recent years, terahertz radiation sources are increasingly being exploited in military and civil applications. However, only a few studies have so far been conducted to examine the biological effects associated with terahertz radiation. In this study, we evaluated the cellular response of mesenchymal mouse stem cells exposed to THz radiation. We apply low-power radiation from both a pulsed broad-band (centered at 10 THz) source and from a CW laser (2.52 THz) source. Modeling, empirical characterization, and monitoring techniques were applied to minimize the impact of radiation-induced increases in temperature. qRT-PCR was used to evaluate changes in the transcriptional activity of selected hyperthermic genes. We found that temperature increases were minimal, and that the differential expression of the investigated heat shock proteins (HSP105, HSP90, and CPR) was unaffected, while the expression of certain other genes (Adiponectin, GLUT4, and PPARG) showed clear effects of the THz irradiation after prolonged, broad-band exposure.

Human dermal fibroblasts exhibit comparable cellular and molecular effects when exposed to THz radiation and hyperthermic stress. These findings suggest that radiation at 2.52 THz generates primarily thermal effects in mammalian cells. Therefore, we conclude that THz-induced bioeffects may be accurately predicted with conventional thermal damage models.

Terahertz spectrometers and imaging systems are currently being evaluated as biomedical tools for skin burn assessment. These systems show promise, but due to their size and weight, they have restricted portability, and are impractical for military and battlefield settings where space is limited. In this study, we developed and tested the performance of a compact, light, and portable THz time-domain spectroscopy (THz-TDS) device. Optical properties were collected with this system from 0.1 to 1.6 THz for water, ethanol, and several ex vivo porcine tissues (muscle, adipose, skin). For all samples tested, we found that the index of refraction (n) decreases with frequency, while the absorption coefficient (μ(a)) increases with frequency. Muscle, adipose, and frozen/thawed skin samples exhibited comparable n values ranging between 2.5 and 2.0, whereas the n values for freshly harvested skin were roughly 40% lower. Additionally, we found that the freshly harvested samples exhibited higher μ(a) values than the frozen/thawed skin samples. Overall, for all liquids and tissues tested, we found that our system measured optical property values that were consistent with those reported in the literature. These results suggest that our compact THz spectrometer performed comparable to its larger counterparts, and therefore may be a useful and practical tool for skin health assessment.

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Collective motions of water and of many biological macromolecules have characteristic time scales on the order of a picosecond. As a result, these biomolecules can strongly absorb terahertz (THz) radiation. Due to this absorption, THz radiation can exert a diverse range of effects on biological structures. For example, THz radiation has been shown to impact the structure, functional activity, and dynamics of macromolecules such as DNA and proteins. THz radiation can affect several gene expression pathways and, consequently, can alter various biochemical and physiological processes in cells. Indeed, THz radiation has been shown to influence the expression of several genes within different cell types. However, a complete view of the global transcriptional responses and the intracellular canonical pathways specifically triggered by THz radiation has not been elucidated. In this study, we performed a global profiling of transcripts in human cells exposed to 2.52 THz radiation and compared the exposure responses to a thermally-matched bulk-heating (BH) protocol. Our resultsshow that both THz radiation and BH induce a significant change in the expression of numerous mRNAs and microRNAs. The data also show that THz radiation triggers specific intracellular canonical pathways that are not affected in the BH-exposed cells. This study implies that THz radiation may be a useful, non-contact tool for the selective control of specific genes and cellular processes.

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