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Apostolos G Doukas - One of the best experts on this subject based on the ideXlab platform.
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cell loading with laser generated Stress Waves the role of the Stress gradient
Pharmaceutical Research, 1999Co-Authors: Stephen E Mulholland, Daniel J Mcauliffe, Apostolos G DoukasAbstract:Purpose. To determine the dependence of the permeabilzation of the plasma membrane on the characteristics of laser-generated Stress Waves.
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Cell Loading with Laser-Generated Stress Waves: The Role of the Stress Gradient
Pharmaceutical Research, 1999Co-Authors: Stephen E Mulholland, Daniel J Mcauliffe, Apostolos G DoukasAbstract:Purpose . To determine the dependence of the permeabilzation of the plasma membrane on the characteristics of laser-generated Stress Waves. Methods . Laser pulses can generate Stress Waves by ablation. Depending on the laser wavelength, fluence, and target material, Stress Waves of different characteristics (rise time, peak Stress) can be generated. Human red blood cells were subjected to Stress Waves and the permeability changes were measured by uptake of extracellular dye molecules. Results . A fast rise time (high Stress gradient) of the Stress wave was required for the permeabilization of the plasma membrane. While the membrane was permeable, the cells could rapidly uptake molecules from the surrounding medium by diffusion. Conclusions . Stress Waves provide a potentially powerful tool for drug delivery.
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Laser-generated Stress Waves in medicine: From tissue injury to drug delivery
1998Co-Authors: Apostolos G DoukasAbstract:Stress Waves are generated by one of the following mechanisms: Optical breakdown, ablation, and rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to Stress Waves under a variety of conditions. Stress Waves can kill cells, decrease cell viability, and increase the permeability of the plasma membrane and the stratum comeum. Stress Waves can induce deleterious effects during medical procedures of high power lasers or facilitate therapeutic modalities, such as topical drug delivery.
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physical characteristics and biological effects of laser induced Stress Waves
Ultrasound in Medicine and Biology, 1996Co-Authors: Apostolos G Doukas, Thomas J FlotteAbstract:Abstract Laser-induced Stress Waves can be generated by one of the following mechanisms: optical breakdown, ablation, or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to Stress Waves with different characteristics and under different conditions. The effects of Stress Waves on cells and tissues can be quite disparate. Stress Waves can fracture tissue, kill cells, decrease cell viability and increase the permeability of the plasma membrane. They can induce deleterious effects during medical procedures of high power, short pulse lasers or, alternatively, may facilitate new therapeutic modalities, such as drug delivery and gene therapy. This review covers the generation of laser-induced Stress Waves and their effects on cell cultures and tissue.
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alteration of cell membrane by Stress Waves in vitro
Ultrasound in Medicine and Biology, 1996Co-Authors: Shun Lee, Thomas J Flotte, T Anderson, Hong Zhang, Apostolos G DoukasAbstract:Abstract Experiments on the biological effects of laser-induced Stress Waves indicate that there is a transient increase in the permeability of the cell membrane. A cell viability assay (propidium iodide exclusion) shows that mouse breast sarcoma cells are viable after a Stress wave. The kinetics of this transient membrane permeability are measured using time-resolved fluorescence imaging. The efflux of a membrane-impermeable fluorescent probe (calcein) following the application of a 300-bar Stress wave implies that there is an increase in the membrane permeability. This efflux ceases within 80 s after a Stress wave, suggesting that the membrane is no longer permeable to the fluorescent probe. Fitting the observed kinetics to a simple diffusion model yields an average initial diffusion constant of 2.2 ± 1.3 × 10 −7 cm 2 /s for mouse breast sarcoma cells following the application of a laser-induced Stress wave.
Vijay Gupta - One of the best experts on this subject based on the ideXlab platform.
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the influence of laser induced nanosecond rise time Stress Waves on the microstructure and surface chemical activity of single crystal cu nanopillars
Journal of Applied Physics, 2013Co-Authors: George Youssef, Ryan Crum, Sergey V Prikhodko, Dariush Seif, Giacomo Po, Nasr M Ghoniem, S Kodambaka, Vijay GuptaAbstract:An apparatus and test procedure for fabrication and loading of single crystal metal nanopillars under extremely high pressures (>1 GPa) and strain rates (>107 s−1), using laser-generated Stress Waves, are presented. Single-crystalline Cu pillars (∼1.20 μm in tall and ∼0.45 μm in diameter) prepared via focused ion beam milling of Cu(001) substrates are shock-loaded using this approach with the dilatational Stress Waves propagating along the [001] axis of the pillars. Transmission electron microscopy observations of shock-loaded pillars show that dislocation density decreases and that their orientation changes with increasing Stress wave amplitude, indicative of dislocation motion. The shock-loaded pillars exhibit enhanced chemical reactivity when submerged in oil and isopropyl alcohol solutions, due likely to the exposure of clean surfaces via surface spallation and formation of surface steps and nanoscale facets through dislocation motion to the surface of the pillars, resulting in growth of thin oxide films on the surfaces of the pillars.
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Dynamic response of polyurea subjected to nanosecond rise-time Stress Waves
Mechanics of Time-Dependent Materials, 2012Co-Authors: George Youssef, Vijay GuptaAbstract:Shaped charges and explosively formed projectiles used in modern warfare can attain speeds as high as 30,000 ft/s. Impacts from these threats are expected to load the armor materials in the 10 to 100 ns timeframe. During this time, the material strains are quite limited but the strain rates are extremely high. To develop armors against such threats it is imperative to understand the dynamic constitutive behavior of materials in the tens of nanoseconds timeframe. Material behavior in this parameter space cannot be obtained by even the most sophisticated plate-impact and split-Hopkinson bar setups that exist within the high energy materials field today. This paper introduces an apparatus and a test method that are based on laser-generated Stress Waves to obtain such material behaviors. Although applicable to any material system, the test procedures are demonstrated on polyurea which shows unusual dynamic properties. Thin polyurea layers were deformed using laser-generated Stress Waves with 1–2 ns rise times and 16 ns total duration. The total strain in the samples was less than 3%. Because of the transient nature of the Stress wave, the strain rate varied throughout the deformation history of the sample. A peak value of 1.1×10^5 s^−1 was calculated. It was found that the Stress-strain characteristics, determined from experimentally recorded incident and transmitted wave profiles, matched satisfactorily with those computed from a 2D wave mechanics simulation in which the polyurea was modeled as a linearly viscoelastic solid with constants derived from the quasi-static experiments. Thus, the test data conformed to the Time-Temperature Superposition (TTS) principle even at extremely high strain rates of our test. This then extends the previous observations of Zhao et al. (Mech. Time-Depend. Mater. 11:289–308, 2007 ) who showed the applicability of the TTS principle for polyurea in the linearly viscoelastic regime up to peak strain rates of 1200 s^−1.
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rupture of fat cells using laser generated ultra short Stress Waves
Lasers in Surgery and Medicine, 2003Co-Authors: Kenrick Kuwahara, Hayes B Gladstone, Vijay Gupta, V Kireev, Victor A NeelAbstract:Background and Objectives Ultrasound-assisted liposuction has been investigated as an aid to breakup fat for its less traumatic removal, and minimizing the post-operative recovery period. This research focused on understanding the mechanism of fat interaction with laser-generated ultra short Stress Waves with high amplitudes. Study Design/Materials and Methods Freshly extracted human fat was secured in an Aluminum (Al) cavity. Sixteen nanoseconds duration Stress Waves were generated by exfoliating the bottom surface of the Al cavity by focusing 3 nanoseconds-long YAG laser pulses over a 2 mm diameter area at 10 Hz with a maximum pulse energy of 0.95 J. The lipids released due to cell rupture were extracted and measured Results Four minutes of pulsing released about 0.005 g, which was over 1% of the initial weight of the tissue. In situ temperature rise of only 5°C was measured at the maximum Stress wave loading duration of 5 minutes. This was evidenced by histological sections, which showed no burn artifacts. Conclusions This research shows that ultra short Stress Waves can mechanically cavitate fat in vitro without significant damage to adjacent structures, and forms the basis for future clinical work. Lasers Surg. Med. 32:279–285, 2003. © 2003 Wiley-Liss, Inc.
Pei Zhong - One of the best experts on this subject based on the ideXlab platform.
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the role of Stress Waves and cavitation in stone comminution in shock wave lithotripsy
Ultrasound in Medicine and Biology, 2002Co-Authors: Songlin Zhu, F H Cocks, Glenn M Preminger, Pei ZhongAbstract:Using an experimental system that mimics stone fragmentation in the renal pelvis, we have investigated the role of Stress Waves and cavitation in stone comminution in shock-wave lithotripsy (SWL). Spherical plaster-of-Paris stone phantoms (D = 10 mm) were exposed to 25, 50, 100, 200, 300 and 500 shocks at the beam focus of a Dornier HM-3 lithotripter operated at 20 kV and a pulse repetition rate of 1 Hz. The stone phantoms were immersed either in degassed water or in castor oil to delineate the contribution of Stress Waves and cavitation to stone comminution. It was found that, while in degassed water there is a progressive disintegration of the stone phantoms into small pieces, the fragments produced in castor oil are fairly sizable. From 25 to 500 shocks, clinically passable fragments (< 2 mm) produced in degassed water increases from 3% to 66%, whereas, in castor oil, the corresponding values are from 2% to 11%. Similar observations were confirmed using kidney stones with a primary composition of calcium oxalate monohydrate. After 200 shocks, 89% of the fragments of the kidney stones treated in degassed water became passable, but only 22% of the fragments of the kidney stones treated in castor oil were less than 2 mm in size. This apparent size limitation of the stone fragments produced primarily by Stress Waves (in castor oil) is likely caused by the destructive superposition of the Stress Waves reverberating inside the fragments, when their sizes are less than half of the compressive wavelength in the stone material. On the other hand, if a stone is only exposed to cavitation bubbles induced in SWL, the resultant fragmentation is much less effective than that produced by the combination of Stress Waves and cavitation. It is concluded that, although Stress wave-induced fracture is important for the initial disintegration of kidney stones, cavitation is necessary to produce fine passable fragments, which are most critical for the success of clinical SWL. Stress Waves and cavitation work synergistically, rather than independently, to produce effective and successful disintegration of renal calculi in SWL
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the role of Stress Waves and cavitation in stone comminution in shock wave lithotripsy
Ultrasound in Medicine and Biology, 2002Co-Authors: F H Cocks, Glenn M Preminger, Pei ZhongAbstract:Abstract Using an experimental system that mimics stone fragmentation in the renal pelvis, we have investigated the role of Stress Waves and cavitation in stone comminution in shock-wave lithotripsy (SWL). Spherical plaster-of-Paris stone phantoms ( D = 10 mm) were exposed to 25, 50, 100, 200, 300 and 500 shocks at the beam focus of a Dornier HM-3 lithotripter operated at 20 kV and a pulse repetition rate of 1 Hz. The stone phantoms were immersed either in degassed water or in castor oil to delineate the contribution of Stress Waves and cavitation to stone comminution. It was found that, while in degassed water there is a progressive disintegration of the stone phantoms into small pieces, the fragments produced in castor oil are fairly sizable. From 25 to 500 shocks, clinically passable fragments (
Shunichi Sato - One of the best experts on this subject based on the ideXlab platform.
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targeted gene transfer into rat facial muscles by nanosecond pulsed laser induced Stress Waves
Journal of Biomedical Optics, 2011Co-Authors: Akihiro Kurita, Takeshi Matsunobu, Yasushi Satoh, Takahiro Ando, Shunichi Sato, Minoru Obara, Akihiro ShiotaniAbstract:We investigate the feasibility of using nanosecond pulsed laser-induced Stress Waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis.
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Improved Transfection Efficiency by the use of Lipofectamine-Modified Plasmid DNA in Laser-Induced Stress Wave-Assisted Gene Transfer: In Vitro Study
LEOS 2006 - 19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2006Co-Authors: Mitsuhiro Terakawa, Yasushi Satoh, Shunichi Sato, Hiroshi Ashida, Risa Otsuka, Kunio Takishima, Hideyuki Okano, Minoru ObaraAbstract:We investigated the effect of chemical-modification of plasmid DNA in gene transfection using laser-induced Stress Waves. Drastic increase in transfection efficiency was demonstrated in vitro, due to the effect of the plasmid DNA modification
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targeted dna transfection into the mouse central nervous system using laser induced Stress Waves
Journal of Biomedical Optics, 2005Co-Authors: Yasushi Satoh, Minoru Obara, Yasunari Kanda, Mitsuhiro Terakawa, Katsushige Mizuno, Yasuhiro Watanabe, Shogo Endo, Hidetoshi Ooigawa, Hiroshi Nawashiro, Shunichi SatoAbstract:We investigated the feasibility of gene transfer into the mouse central nervous system (CNS) by applying nanosecond pulsed laser-induced Stress Waves (LISWs). Intraventricular or hippocampal injection of a reporter gene [enhanced green fluorescent protein (EGFP)] followed by application of LISWs showed this method to be efficient in the CNS of newborn and adult mice. Cells expressing EGFP reside at least 3.5 mm from the surface of the tissue, while no apparent damage was detected. Additionally, expression of EGFP was limited to the area that was exposed to LISWs. Using this method, the formulation of plasmid DNA by cationic transfer reagent polyethylenimine proved to be effective for improving transfer efficiency into the CNS.
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in vivo targeted gene transfer in skin by the use of laser induced Stress Waves
Lasers in Surgery and Medicine, 2004Co-Authors: Makoto Ogura, Shunichi Sato, Kuniaki Nakanishi, Maki Uenoyama, Tetsuro Kiyozumi, Daizo Saitoh, Tomosumi Ikeda, Hiroshi Ashida, Minoru ObaraAbstract:Background and Objectives Much interest has been shown in the use of lasers for nonviral targeted gene transfer, since the spatial characteristics of laser light are quite well defined. The aim of this study was to demonstrate in vivo gene transfer by the use of laser-induced Stress Waves (LISWs). Study Design/Materials and Methods After reporter genes had been intradermally injected to rat skin in vivo, a laser target was placed on the gene-injected skin. LISWs were generated by the irradiation of an elastic laser target with 532-nm nanosecond laser pulses of a Q-switched Nd:YAG laser. Results Levels of luciferase activities for the skin exposed to LISWs were two orders of magnitude higher than those for the skin injected with naked DNA. Expressions of enhanced green fluorescent protein (EGFP) and β-galactosidase were observed only in the area that was exposed to LISWs, and in addition, epidermal cells were selectively transfected. No major side effects were observed, and luciferase activity levels as high as 105 RLU per mg of protein were sustained even 5 days after gene transfer. Conclusion Highly efficient and site-specific gene transfer can be achieved by applying a few pulses of nanosecond pulsed LISWs to rat skin in vivo. Lasers Surg. Med. 34:242–248, 2004. © 2004 Wiley-Liss, Inc.
Minoru Obara - One of the best experts on this subject based on the ideXlab platform.
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targeted gene transfer into rat facial muscles by nanosecond pulsed laser induced Stress Waves
Journal of Biomedical Optics, 2011Co-Authors: Akihiro Kurita, Takeshi Matsunobu, Yasushi Satoh, Takahiro Ando, Shunichi Sato, Minoru Obara, Akihiro ShiotaniAbstract:We investigate the feasibility of using nanosecond pulsed laser-induced Stress Waves (LISWs) for gene transfer into rat facial muscles. LISWs are generated by irradiating a black natural rubber disk placed on the target tissue with nanosecond pulsed laser light from the second harmonics (532 nm) of a Q-switched Nd:YAG laser, which is widely used in head and neck surgery and proven to be safe. After injection of plasmid deoxyribose nucleic acid (DNA) coding for Lac Z into rat facial muscles, pulsed laser is used to irradiate the laser target on the skin surface without incision or exposure of muscles. Lac Z expression is detected by X-gal staining of excised rat facial skin and muscles. Strong Lac Z expression is observed seven days after gene transfer, and sustained for up to 14 days. Gene transfer is achieved in facial muscles several millimeters deep from the surface. Gene expression is localized to the tissue exposed to LISWs. No tissue damage from LISWs is observed. LISW is a promising nonviral target gene transfer method because of its high spatial controllability, easy applicability, and minimal invasiveness. Gene transfer using LISW to produce therapeutic proteins such as growth factors could be used to treat nerve injury and paralysis.
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Improved Transfection Efficiency by the use of Lipofectamine-Modified Plasmid DNA in Laser-Induced Stress Wave-Assisted Gene Transfer: In Vitro Study
LEOS 2006 - 19th Annual Meeting of the IEEE Lasers and Electro-Optics Society, 2006Co-Authors: Mitsuhiro Terakawa, Yasushi Satoh, Shunichi Sato, Hiroshi Ashida, Risa Otsuka, Kunio Takishima, Hideyuki Okano, Minoru ObaraAbstract:We investigated the effect of chemical-modification of plasmid DNA in gene transfection using laser-induced Stress Waves. Drastic increase in transfection efficiency was demonstrated in vitro, due to the effect of the plasmid DNA modification
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targeted dna transfection into the mouse central nervous system using laser induced Stress Waves
Journal of Biomedical Optics, 2005Co-Authors: Yasushi Satoh, Minoru Obara, Yasunari Kanda, Mitsuhiro Terakawa, Katsushige Mizuno, Yasuhiro Watanabe, Shogo Endo, Hidetoshi Ooigawa, Hiroshi Nawashiro, Shunichi SatoAbstract:We investigated the feasibility of gene transfer into the mouse central nervous system (CNS) by applying nanosecond pulsed laser-induced Stress Waves (LISWs). Intraventricular or hippocampal injection of a reporter gene [enhanced green fluorescent protein (EGFP)] followed by application of LISWs showed this method to be efficient in the CNS of newborn and adult mice. Cells expressing EGFP reside at least 3.5 mm from the surface of the tissue, while no apparent damage was detected. Additionally, expression of EGFP was limited to the area that was exposed to LISWs. Using this method, the formulation of plasmid DNA by cationic transfer reagent polyethylenimine proved to be effective for improving transfer efficiency into the CNS.
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in vivo targeted gene transfer in skin by the use of laser induced Stress Waves
Lasers in Surgery and Medicine, 2004Co-Authors: Makoto Ogura, Shunichi Sato, Kuniaki Nakanishi, Maki Uenoyama, Tetsuro Kiyozumi, Daizo Saitoh, Tomosumi Ikeda, Hiroshi Ashida, Minoru ObaraAbstract:Background and Objectives Much interest has been shown in the use of lasers for nonviral targeted gene transfer, since the spatial characteristics of laser light are quite well defined. The aim of this study was to demonstrate in vivo gene transfer by the use of laser-induced Stress Waves (LISWs). Study Design/Materials and Methods After reporter genes had been intradermally injected to rat skin in vivo, a laser target was placed on the gene-injected skin. LISWs were generated by the irradiation of an elastic laser target with 532-nm nanosecond laser pulses of a Q-switched Nd:YAG laser. Results Levels of luciferase activities for the skin exposed to LISWs were two orders of magnitude higher than those for the skin injected with naked DNA. Expressions of enhanced green fluorescent protein (EGFP) and β-galactosidase were observed only in the area that was exposed to LISWs, and in addition, epidermal cells were selectively transfected. No major side effects were observed, and luciferase activity levels as high as 105 RLU per mg of protein were sustained even 5 days after gene transfer. Conclusion Highly efficient and site-specific gene transfer can be achieved by applying a few pulses of nanosecond pulsed LISWs to rat skin in vivo. Lasers Surg. Med. 34:242–248, 2004. © 2004 Wiley-Liss, Inc.