The growing experimental evidence suggests that broadband, picosecond-duration THz pulses may influence biological systems and functions. While the mechanisms by which THz pulse-induced biological effects are not yet known, experiments using in vitro cell cultures, tissue models, as well as recent in vivo studies have demonstrated that THz pulses can elicit cellular and molecular changes in exposed cells and tissues in the absence of thermal effects. Recently, we demonstrated that intense, picosecond THz pulses induce phosphorylation of H2AX, indicative of DNA damage, and at the same time activate DNA damage response in human skin tissues. We also find that intense THz pulses have a profound impact on global gene expression in human skin. Many of the affected genes have important functions in epidermal differentiation and have been implicated in skin cancer and inflammatory skin conditions. The observed THzinduced changes in expression of these genes are in many cases opposite to disease-related changes, suggesting possible therapeutic applications of intense THz pulses.
Pulsed terahertz (THz) imaging has been suggested as a novel high resolution, noninvasive medical diagnostic tool.
However, little is known about the influence of pulsed THz radiation on human tissue, i.e., its genotoxicity and effects on
cell activity and cell integrity. We have carried out a comprehensive investigation of the biological effects of THz
radiation on human skin tissue using a high power THz pulse source and an in vivo full-thickness human skin tissue
model. We have observed that exposure to intense THz pulses causes DNA damage and changes in the global gene
expression profile in the exposed skin tissue. Several of the affected genes are known to play major roles in human
cancer. While the changes in the expression levels of some of them suggest possible oncogenic effects of pulsed THz
radiation, changes in the expression of the other cancer-related genes might have a protective influence. This study may
serve as a roadmap for future investigations aimed at elucidating the exact roles that all the affected genes play in skin
carcinogenesis and in response to pulsed THz radiation.
Nonlinear dynamics of free-carriers in direct bandgap semiconductors at terahertz (THz) frequencies is studied using
intense few-cycle pulses. Techniques as Z-scan, THz-pump / THz-probe, and optical-pump/ THz-probe are employed to
explore nonlinear interactions in both n-doped and photoexcited systems. The physical mechanism that gives rise to such
interactions is found to be intervalley scattering.