Terahertz zaps alter gene activity in stem cells

                         

Using the apparatus, which effectively exposes iPSCs to terahertz radiation, the researchers found that terahertz light pulses change the activity of genes influenced by zinc-dependent transcription factors. Credit: Mindy Takamiya/Kyoto University iCeMS (CC BY-NC-SA 4.0)

https://phys.org/news/2020-10-terahertz-zaps-gene-stem-cells.html

Terahertz light pulses change gene expression in stem cells, report researchers from Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS) and Tokai University in Japan in the journal Optics Letters. The findings come thanks to a new tool, with implications for stem cell research and regenerative therapy development.

Terahertz waves fall in the far infrared/microwave part of the electromagnetic spectrum and can be produced by powerful lasers. Scientists have used terahertz pulses to control the properties of solid-state materials. They also have potential for manipulating living cells, as they don't damage them the way that ultraviolet or infrared light does. Research so far has led to contradictory findings about their effects on cells, possibly because of the way the experiments have been conducted.

iCeMS microengineer Ken-ichiro Kamei and physicist Hideki Hirori worked with colleagues to develop a better tool for investigating what happens when terahertz pulses are shone on human cells. The apparatus overcomes issues with previous techniques by placing cells in tiny microwells that have the same area as the terahertz light.

The team used the apparatus to explore the effects of terahertz radiation on induced pluripotent stem cells (iPSCs). These are cells that have been taken from skin or blood and changed into stem cells. Scientists are seeking to turn them into other types of cells and tissues to help treat diseases like muscular dystrophy.

"Terahertz pulses can generate a strong electric field without touching or damaging cells," says Hirori. "We tested their effect on iPSCs and discovered that the activity of some gene networks changes as a result of terahertz light exposure."

For example, they found the pulses activated genes involved in motor neuron survival and mitochondrial function. They also deactivated genes involved in cell differentiation, the process in which stem cells change into specialized body cells.

Further investigation found that these genes were influenced by zinc-dependent transcription factors. The scientists believe the terahertz pulses generate an electric field that causes zinc ions to move inside cells, impacting the function of transcription factors, which in turn activate or deactivate the genes they are responsible for.

Hirori says the findings could aid efforts to develop a technology that can manipulate iPSC differentiation into specific cells by turning off specific genes while keeping others on, paving the way for regenerative therapies for a wide range of diseases.

Making steps toward improved data storage

Terahertz electromagnetic pulse controlling the physical structure of data-storage material. Credit: Kyoto University/Hirori Lab
 https://phys.org/news/2018-11-storage.html#jCp

A team of scientists has created the world's most powerful electromagnetic pulses in the terahertz range to control in fine detail how a data-storage material switches physical form. This discovery could contribute to scaled-down memory devices, eventually revolutionizing how computers handle information.

Compact discs might be out of fashion, but they may have inspired the next generation of computer nanotechnology. A glass layer in CDs consists of a phase-change material that can be encoded with information when light pulses cause crystals in small regions of the layer to either grow or melt.

Phase-change materials triggered by electrical impulses—rather than light—would offer new memory technologies with more stable and faster operation than that possible in many current types of memory devices. In addition, downscaling memory sites in phase-change materials could increase memory density. But this remains challenging because of the difficulty of controlling the crystallization and amorphization (melting) processes.

Addressing this issue in an article in Physical Review Letters, a team of scientists led by Kyoto University observed nanometer-scale growth of individual crystals in a phase-change material composed of germanium, antimony and tellurium—or GST—after applying high-powered terahertz pulses as a trigger.

"One reason crystallization and amorphization of GST under an electric field are difficult to control is the heat diffusion effects in the micrometer scale associated with electrical inputs, which also contribute to the crystallization," explains group leader Hideki Hirori. "Fortunately, terahertz technologies have matured to the point where we can use short pulses to generate strong electric fields while suppressing heating effects."

Hirori and his coworkers developed a terahertz pulse generator that delivered ultra-short and highly intense terahertz pulses across a pair of gold antennas. These pulses created an electric field in the GST sample comparable to that of an electrically switched device. Importantly, this approach greatly reduced the heat diffusion because of the extremely short duration of terahertz pulses—around 1 picosecond, or 10-12 seconds—enabling fine control over the rate and direction of GST crystallization. A region of crystallization grew in a straight line between the gold antennas in the direction of the field, at a few nanometers per pulse.

When the team tracked stepwise changes in crystallization while increasing the number of terahertz pulses, they were surprised to find that after a certain point, crystal conductivity rapidly sped up instead of rising in line with the increase in terahertz strength. The researchers hypothesize that electrons jumping between states in the crystal added an unexpected source of heat to the system, boosting crystallization.

Hirori explains: "Our experiment reveals how nanoscale and direction-controlled growth of crystals in GST can be achieved. We also identified a phenomenon which should assist in the design of new devices and ultimately realize the fast and stable digital information handling potential that this material promises."

 Explore further: Asymmetric plasmonic antennas deliver femtosecond pulses for fast optoelectronics

More information: Yasuyuki Sanari et al, Zener Tunneling Breakdown in Phase-Change Materials Revealed by Intense Terahertz Pulses, Physical Review Letters (2018). DOI: 10.1103/PhysRevLett.121.165702

Terahertz wave activates filamentation of actin: A novel possibility of manipulating cellular functions Read more at: https://phys.org/news/2018-08-terahertz-filamentation-actin-possibility-cellular.html#jCp

Credit: Tohoku University

https://phys.org/news/2018-08-terahertz-filamentation-actin-possibility-cellular.html

A team of researchers has discovered that terahertz (THz) wave irradiation activates the filamentation of actin protein. Drs. Shota Yamazaki and Masahiko Harata (Graduate School of Agricultural Science, Tohoku University); Dr. Yuichi Ogawa (Graduate School of Agriculture, Kyoto University); Dr. Hiromichi Hoshina (THz imaging and the sensing team at RIKEN); and Dr. Toshitaka Idehara (FIR-UF at University of Fukui) have made this important discovery, which offers a new possibility for the manipulation of cellular functions.

Actin forms filaments through its polymerization in cells, and functions as a major component of cellular architecture. Actin plays a central role in various cellular functions, including wound healing and the metastasis of cancer cells. In addition, a portion of actin exists in the cell nucleus and regulates gene regulation. For example, actin is required for gene reprograming, which is required for establishing iPS (induced pluripotent) cells. In this research, the polymerization reaction of purified actin protein was monitored under irradiation of THz wave, and it was found that the THz wave activates the filamentation of actin.Due to the recent development of high power THz (1012 Hz) wave sources, many researchers have begun to explore its application for material manipulation. One of the advantages of THz wave irradiation is its lower photon energy as compared to visible light. Therefore, THz wave prevents the ionization of molecules. THz wave enables "soft" manipulation of macromolecules such as proteins, enabling changes to their higher-order structure without damaging the samples.

Actin governs various functions of cells. Therefore, a variety of drugs have been developed for controlling actin filamentation, and applications of these drugs for medical purposes have been explored. However, these drugs are inefficient in their delivery into, and clearance from, cells. THz irradiation is a non-invasive method and could overcome these identified problems in drugs. THz wave is expected to become a novel tool for the manipulation of cellular functions through modifying actin filamentation. This research team is now trying to understand the basic mechanism of the THz assisting filamentation to extend this technology to various proteins so that THz irradiation can be widely applied to various biological technologies.

Terahertz Pulse Generates 1,000-Fold Increase in Electron Density

http://int.saci.kyoto-u.ac.jp/?p=2336
The study of carrier multiplication has become an essential part of many-body physics and materials science. Assistant Prof Hideki Hirori and co-workers observed that when exposed to a single-cycle electric field pulse at the 1000 GHz (terahertz) frequency range, a sample of standard semiconductor material (gallium arsenide, GaAs) burst an avalanche of electron-hole pairs (excitons) 1,000-times more abundant than initial states only on the picosecond (10-12 s) time scale. The observed bright luminescence associated with carrier multiplication suggests that carriers coherently driven by a strong electric field can efficiently gain enough kinetic energy to induce a series of impact ionizations. These just-released results with the world strongest terahertz pulses demonstrate the rich potential that lies in the study of terahertz radiation.

This carrier multiplication directly affects nonlinear transport phenomena in ultra-high-speed transistors and plays a key role in designing efficient solar cells and electroluminescent emitters and highly sensitive photon detectors.

Related Information 1. H. Hirori, K. Shinokita, M. Shirai, S. Tani, Y. Kadoya, and K. Tanaka: Nature Commun. 2, 594 (2011).
2. H. Hirori, A. Doi, F. Blanchard, and K. Tanaka: Appl. Phys. Lett. 98, 091106 (2011).

Terahertz pulse increases electron density 1,000-fold

http://www.eurekalert.org/pub_releases/2011-12/ific-tpi121811.php

Findings point to advances in transistor and solar cell development

		IMAGE: A picosecond terahertz pulse causes an avalanche of excitons to burst forth from semiconductor GaAs. Click here for more information.

Kyoto, Japan -- Researchers at Kyoto University have announced a breakthrough with broad implications for semiconductor-based devices. The findings, announced in the December 20 issue of the journal Nature Communications, may lead to the development of ultra-high-speed transistors and high-efficiency photovoltaic cells.
Working with standard semiconductor material (gallium arsenide, GaAs), the team observed that exposing the sample to a terahertz (1,000 gigahertz) range electric field pulse caused an avalanche of electron-hole pairs (excitons) to burst forth. This single-cycle pulse, lasting merely a picosecond (10^-12 s), resulted in a 1,000-fold increase in exciton density compared with the initial state of the sample.
"The terahertz pulse exposes the sample to an intense 1 MV/cm^2 electric field," explains Hideki Hirori, team leader and Assistant Professor at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS). "The resulting exciton avalanche can be confirmed by a bright, near-infrared luminescence, demonstrating a three-order of magnitude increase in the number of carriers."
Research in Kyoto using terahertz waves is led by Professor Koichiro Tanaka, whose lab at the iCeMS pursues numerous applications including the development of new biological imaging technologies.
"Since terahertz waves are sensitive to water, our goal is to create a microscope that will allow us to look inside living cells in real time," says Prof. Tanaka. "These just-released results using semiconductors are an entirely different field of science, but they demonstrate the rich potential that lies in the study of terahertz waves."

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The article, "Extraordinary carrier multiplication gated by a picosecond electric field pulse" by H. Hirori, K. Shinokita, M. Shirai, S. Tani, Y. Kadoya, and K. Tanaka was published online in the December 20, 2011 issue ofNature Communications.
Acknowledgements: This work was supported by Grant-in-Aid for Young Scientists (B) (Grant No. 21760038) of the Japan Society for the Promotion of Science, and also Grant-in-Aid for Scientific Research on Innovative Area "Optical science of dynamically correlated electrons (DYCE)" (Grant No. 20104007) and Grant-in-Aid for Creative Scientific Research (Grant No. 18GS0208) of the Ministry of Education, Culture, Sports, Science and Technology, Japan.
About the iCeMSThe Institute for Integrated Cell-Material Sciences (iCeMS) at Kyoto University in Japan aims to advance the integration of cell and material sciences -- both traditionally strong fields for the university -- in a uniquely innovative global research environment. The iCeMS combines the biosciences, chemistry, materials science, and physics to capture the potential power of stem cells (e.g., ES/iPS cells) and of mesoscopic sciences (e.g., porous coordination polymers). Such developments hold the promise of significant advances in medicine, pharmaceutical studies, the environment, and industry.

Softening crystals without heat

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As if borrowing from a scene in a science fiction movie, researchers at Kyoto University have successfully developed a kind of tractor beam that can be used to manipulate the network of the molecules. In a paper soon to be published in Physical Review Letters, the team has demonstrated a technique using terahertz pulses that could have broad applications in the chemical and pharmaceutical industries.

Terahertz waves, an area of specialty for the Koichiro Tanaka lab at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS), exist in a frequency range beyond the infrared and before the microwave band. Also popularly referred to as T-rays, this form of radiation can pass through many materials but is non-ionizing, characteristics which make the waves useful in the imaging field.

In this case, intense terahertz pulses were used to successfully increase the amplitude of movement between amino-acid molecules in crystalline form, essentially softening the crystals. Previous softening methods have always correspondingly raised the temperature, resulting in unwanted changes to the crystals' structure and properties.

"What we have demonstrated is that it is possible to use intense terahertz pulses to climb 20 ladder steps on the anharmonic intermolecular potential in the microcrystals," explains Dr. Masaya Nagai, an assistant professor at Kyoto University's Department of Physics and a coauthor of the paper. "This opens the door," he continues, "to the possibility of manipulating large molecules, thereby increasing understanding of the properties of molecular complexes such as proteins."

The team is expectant that the technique they have developed could eventually lead to advances in chemical synthesis as well as in the refining of organic molecular crystals for pharmaceutical purposes.

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