Data on the effects of high-intensity pulsed THz radiation (peak intensity ~30 GW/cm2 , electric field strength ~3.5 MV/cm) on human skin fibroblasts have been obtained for the first time. A quantitative assessment of the number of histone H2AX phosphorylation foci in a cell as a function of irradiation time and THz pulse energy was obtained. It has been shown that the appearance of foci is not associated with either oxidative (cells retain their morphology, cytoskeleton structure, and the content of reactive oxygen species does not exceed the control values) or thermal stress. Long-term irradiation of cells did not reduce their proliferative index.
The results on application of femtosecond laser pulses for microsurgery of mammalian embryos at various stages of preimplantation development are reported. Novel techniques of laser-based embryo marking and controlled laser-assisted embryo hatching are discussed.
We report on the investigation of the biological effects of high-power pulsed broadband terahertz (THz) radiation on human skin fibroblasts. Cells were exposed to THz pulses with peak intensity ~30 GW/cm2 and electrical field strength ~3.5 MV/cm for 1.5 hours. Phosphorylation of H2AX (γH2AX foci) can be caused by different reasons including DNA double stand breaks, heat induction and can be related to chromosomes stability. However, the γH2AX foci seem to be a proper marker for detection of the effect of intense terahertz pulses on cells. The kinetics of phosphorylated histone H2AX foci post terahertz radiation exposure is analyzed. We found that the number of phosphorylated H2AX foci in human skin fibroblasts remained almost unchanged within 24 hours following terahertz exposure.
Terahertz (THz) waves can influence a diverse range of cellular processes. The use of high-power THz sources in biological studies may lead to major advances in understanding biological systems and help to determine safe exposure levels for existing THz technologies. We are devoted to the development of an experimental system for irradiating cells with intense broadband THz pulses. Subpicosecond pulses of THz radiation with intensities of 32 GW / cm2 and electric field strength up to 3.5 MV/cm are obtained by optical rectification, using an OH1 organic crystal, of near-infrared femtosecond pulses generated by a Cr:forsterite laser. The system has been developed to allow cells to be kept in suitable conditions for long-term exposure and to be irradiated with THz pulses in single-point mode as well as in scanning mode. The transmission in the THz region of various plastic dishes for cell culture is estimated.
In this study, we aimed to develop a novel femtosecond laser-based technique for individual embryo tagging. We have demonstrated for the first time the possibility to create individual alphanumeric codes be means of femtosecond laser microsurgery directly on embryo’s outer shell. Femtosecond laser pulses (wavelength of 514 nm, pulse duration of 280 fs, repetition rate of 2.5 kHz, pulse energy of 20 nJ) were applied for precise alphanumeric code engraving on the zona pellucida of mouse embryos at the zygote stage. The code consisted of 4-5 characters (numerical and/or alphabetical) typically. Embryo quality assessment was performed every 24 hours post laser-assisted marking by light microscopy and compared with that of non-treated control embryos. The codes engraved could be clearly recognized until the thinning of the zona pellucida prior to hatching. No differences in morphology and developmental rates of laser-treated embryos and control embryos were found. Our results demonstrate the suitability of femtosecond laser as a novel tool for noninvasive embryo tagging, enabling embryo identification from day 0.5 post coitum to at least early blastocyst stage. The technique proposed is relatively fast, reliable and simple, and can be fully automated in the future. It can be performed in a contactless mode under sterile conditions and does not require any additional equipment (except microscope) to visualize the code and to identify the embryo. As far as femtosecond lasers offer several important advantages (such as high precision, minimal invasiveness, versatility etc.) over conventional milli/microsecond lasers we believe that further advances in ultrafast laser technology aimed at reducing complexity, size and high price of femtosecond lasers will help them gain popularity in the field of assisted reproduction.
Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.
We report on the results of using self-developed combined laser system consisting of a femtosecond laser scalpel
(Cr:Forsterite seed oscillator and a regenerative amplifier, 620 nm, 100 fs, 10 Hz) and optical tweezers (cw laser, 1064
nm) for performing noncontact laser-mediated polar body (PB) and trophectoderm (TE) biopsy of early mammalian
embryos. To perform PB biopsy the femtosecond laser scalpel was initially used to drill an opening in the zona
pellucida, and then the PB was extracted out of the zygote with the optical tweezers. Unlike PB biopsy, TE biopsy
allows diagnosing maternally-derived as well as paternally-derived defects. Moreover, as multiple TE cells can be taken
from the embryo, more reliable diagnosis can be done. TE biopsy was performed by applying laser pulses to dissect the
desired amount of TE cells that had just left the zona pellucida during the hatching. Optical tweezers were then used to
trap and move the dissected TE cells in a prescribed way. Laser power in optical tweezers and energy of femtosecond
laser pulses were thoroughly optimized to prevent cell damage and obtain high viability rates. In conclusion, the
proposed techniques of laser-based embryo biopsy enable accurate, contamination-free, simple and quick
microprocessing of living cells.
The experimental results of investigation of X-ray radiation provided by interaction of intense femtosecond laser pulses with Fe-clusters are presented. A new method of iron particles formation at room temperature by the photo-dissociation of Fe(CO)5 vapor is applied. The X-ray radiation was studied using photodiodes and high efficiency focusing crystal von Hamos spectrometer with a CCD linear array as X-ray detector. The results of investigation of clusters formation, spectral measurements in photon energy range E=1÷13 keV and estimation of X-ray radiation yield are presented.
A compact, tabletop terawatt forsterite laser (1.24 μm /100 mJ/ 80 fs) is used for generation of fast hard x-ray radiation from laser-produced plasmas. Plasmas are created on massive solid Fe and Cu targets. X-ray radiation is studied using a focusing crystal von Hamos spectrometer with a CCD linear array as x-ray detector. High efficiency of the spectrometer in a wide spectral range allows us to record x-ray spectra by one laser shot. Intense Kα radiation is studied with high spectral resolution (λ/δλ~1000) at various focusing conditions: main laser radiation and second harmonic radiation. With a copper target the Kα radiation yield was equal to 4×109 photon/pulse in 4π steradian, that corresponds to conversion efficiency of 0.02%. Processes responsible for ultrafast hard x-ray radiation are discussed.
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