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ABSTRACT: Recent work has indicated the potential of light to modify the growth of neuronal cells. The two reported studies however, were performed on two independent optical set-ups and on differing cell-types at different temperatures and at different wavelengths. Therefore, it is unknown whether there is a bias for this effect to a particular wavelength which would have implications for the mechanisms for this phenomenon. Localized changes in heat have been suggested as a possible mechanism for this process, but as yet there is no direct experimental evidence to support or discount this hypothesis. In this paper, we report the first direct comparison on one cell type, of this process at two near infra-red wavelengths: 780 nm and 1064 nm using exactly the same beam shape. We show that light at both wavelengths is equally effective in initiating this process. We also directly measure the temperature rise caused by each wavelength in water and its absorption in the cellular medium. The recorded temperature rises are insufficient to change the rate of actin polymerization.
Optics Express 11/2006; 14(21):9786-93. · 3.59 Impact Factor
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ABSTRACT: Photoporation is a rapidly expanding technique for the introduction of macromolecules into single cells. However, there remains no study into the true efficiency of this procedure. Here, we present a detailed analysis of transfection efficiency and cell viability for femtosecond optical transfection using a titanium sapphire laser at 800 nm. Photoporation of 4000 Chinese Hamster ovary cells was performed, representing the largest optical transfection study reported to date. We have investigated a range of laser fluences at the cell membrane and, at 1.2 microJ/cm(2), have found an average transfection efficiency of 50 +/- 10%. Contrary to recent literature, in which 100% efficiency is claimed, our measure of efficiency accounts for all irradiated cells, including those lost as a result of laser treatment, thereby providing a true biological measure of the technique.
Optics Express 09/2006; 14(16):7125-33. · 3.59 Impact Factor
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B. Agate,
L. Paterson,
T.K. Lake,
J.E. Morris,
A.E. Carruthers,
C.T.A. Brown,
W. Sibbett,
K. Dholakia,
M. Comrie,
R. Ferguson,
P.E. Bryant,
A.C. Riches,
F. Gunn-Moore
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ABSTRACT: The introduction and subsequent expression of foreign DNA inside living mammalian cells (transfection) is achieved by photoporation with a violet diode laser. We direct a compact 405 nm laser diode source into an inverted optical microscope configuration and expose cells to 0.3 mW for 40 ms. The localized optical power density of ~1200 MW/m<sup>2</sup> is six orders of magnitude lower than that used in femtosecond photoporation (~10<sup>4</sup> TW/m<sup>2</sup>). The tightly focused laser beam (with a localised focal volume of ~10-<sup>19</sup> m<sup>3 </sup>) perforates the cell plasma membrane to allow uptake of plasmid DNA containing an antibiotic resistant gene as well as the green fluorescent protein (GFP) gene. Successfully transfected cells then expand into clonal groups which are used to create stable cell lines. The use of the violet diode laser offers a new and simple poration technique compatible with standard microscopes and is the simplest method of laser-assisted cell poration reported to date
Lasers and Electro-Optics Europe, 2005. CLEO/Europe. 2005 Conference on; 07/2005
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L. Paterson, B. Agate,
M. Comrie,
R. Ferguson,
T.K. Lake,
J.E. Morris,
A.E. Carruthers,
C.T.A. Brown,
W. Sibbett,
P.E. Bryant,
F. Gunn-Moore,
A.C. Riches,
K. Dholakia
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ABSTRACT: Stable transfection of Chinese hamster ovary (CHO-K1) cells is achieved by photoporation with a violet diode laser. This represents the simplest method of laser-assisted cell poration reported to date
Quantum Electronics and Laser Science Conference, 2005. QELS '05; 06/2005
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L Paterson, B Agate,
M Comrie,
R Ferguson,
T Lake,
J Morris,
A Carruthers,
C T Brown,
W Sibbett,
P Bryant,
F Gunn-Moore,
A Riches,
Kishan Dholakia
[show abstract]
[hide abstract]
ABSTRACT: The introduction and subsequent expression of foreign DNA inside living mammalian cells (transfection) is achieved by photoporation with a violet diode laser. We direct a compact 405 nm laser diode source into an inverted optical microscope configuration and expose cells to 0.3 mW for 40 ms. The localized optical power density of ~1200 MW/m2 is six orders of magnitude lower than that used in femtosecond photoporation (~104 TW/m2). The beam perforates the cell plasma membrane to allow uptake of plasmid DNA containing an antibiotic resistant gene as well as the green fluorescent protein (GFP) gene. Successfully transfected cells then expand into clonal groups which are used to create stable cell lines. The use of the violet diode laser offers a new and simple poration technique compatible with standard microscopes and is the simplest method of laser-assisted cell poration reported to date.
Optics Express 02/2005; 13(2):595-600. · 3.59 Impact Factor
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B. Agate,
E.U. Rafailov,
W. Sibbett,
S.M. Saltiel,
K. Koynov,
M. Tiihonen,
Shunhua Wang,
F. Laurell,
P. Battle,
T. Fry,
T. Roberts,
E. Noonan
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ABSTRACT: We demonstrate an effective means of achieving compact, truly portable, and entirely self-contained ultrafast blue light sources. Using a variety of nonlinear media to achieve simple second-harmonic generation of a femtosecond Cr:LiSAF laser, we investigate the relative merits of aperiodically poled bulk and waveguide nonlinear crystals in comparison to periodically poled structures. Such a compact and convenient source of ultrashort laser pulses in the blue spectral region could be of great interest for on-site applications spanning a host of disciplines, such as biomedical imaging, optical micromanipulation, and high-resolution spectroscopy.
IEEE Journal of Selected Topics in Quantum Electronics 12/2004; · 3.78 Impact Factor
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ABSTRACT: Recent studies have realized optical micromanipulation of extended two- and three-dimensional structures and optical binding. In many recent experiments the optical interaction between particles and their light scattering has played a key role. We use fluorescein dye within the sample medium and a femtosecond laser for optical micromanipulation. By the process of two-photon excitation we can directly observe how the light behaves during refraction and reflection within a sample of optically guided microspheres. We directly visualize the reconstruction of the Bessel light beam by excitation of two-photon fluorescence when used as an optical guide for microscopic particles dispersed within this dyed medium. This technique may assist in the visualization of optical scattering and refraction in micromanipulation and the creation of large optically bound matter crystals.
New Journal of Physics 10/2004; 6(1):136. · 4.18 Impact Factor
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ABSTRACT: We perform a comparison of optical tweezing using continuous wave (cw) and femtosecond lasers. Measurement of the relative Q-values in the femtosecond and cw regimes shows that femtosecond optical tweezers are just as effective as cw optical tweezers. We also demonstrate simultaneous optical tweezing and in-situ control of two-photon fluorescence (at 400nm) from dye-doped polymer microspheres. By switching the 800 nm tweezing laser source between femtosecond and cw regimes, we turned the fluorescent signal from the tweezed particle on and off while maintaining an equivalent tweezing action. Femtosecond lasers can thus be used for optical tweezing and simultaneously utilized to induce nonlinear multi-photon processes such as two-photon excitation or even photoporation.
Optics Express 07/2004; 12(13):3011-7. · 3.59 Impact Factor
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ABSTRACT: We present a simplified, potentially portable, and highly efficient blue-light source from a periodically poled KTP waveguide crystal with a compact femtosecond Cr:LiSAF laser. This light source generates 5.6 mW of blue average output power at 424 nm with 27 mW of incident fundamental in a single-pass extracavity arrangement at room temperature. The overall system efficiency of electrical power to blue light is 0.5%, and the internal second-harmonic generation conversion efficiency is as high as 37%. The slope efficiency of 5.5% pJ(-1) at low pulse energies is, to our knowledge, the highest slope efficiency yet reported for frequency conversion into the blue spectral region.
Optics Letters 11/2003; 28(20):1963-5. · 3.40 Impact Factor
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ABSTRACT: We present highly-efficient femtosecond blue light generation from a very simple, compact and potentially robust source. Complementary results from a periodically-poled waveguide suggest that this technique may allow the flexibility of quasi-phasematching in both the spectral and temporal domains to be exploited using compact and efficient femtosecond lasers.
Lasers and Electro-Optics Society, 2002. LEOS 2002. The 15th Annual Meeting of the IEEE; 12/2002
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ABSTRACT: 50 nm and 30 nm of smooth, continuous tuning is demonstrated in a compact Cr:LiSAF laser using single-prism and prismless approaches respectively. Pulses of ∼150 fs in duration are generated for electrical drive powers of < 1.2 W.
Lasers and Electro-Optics Society, 2002. LEOS 2002. The 15th Annual Meeting of the IEEE; 12/2002
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ABSTRACT: Methods for developing more compact femtosecond Cr:LiSAF laser
sources are examined. By careful modeling of the low threshold
performance and intracavity dispersion characteristics of these
cavities, a highly asymmetric z-cavity design with a single prism for
dispersion compensation is developed. Transform-limited pulses as short
as 113 fs and modelocked output powers up to 20 mW are demonstrated for
less than 110 mW of laser-diode pump power. The complete laser system
(including the laser diode pump system and drivers) has a footprint of
21.5 × 28 cm<sup>2</sup>, about the size of a sheet of US letter
or A4 paper
IEEE Journal of Quantum Electronics 05/2002; · 1.88 Impact Factor
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ABSTRACT: Summary form only given. We report a compact, directly diode-pumped Cr:LiSAF laser as an alternative pump source. This laser has an electrical-to-optical efficiency in excess of 1% and produces transform-limited pulses of ∼150 fs in duration at ∼865 nm. The average power is 35 mW and the repetition rate is ∼250 MHz, which implies modest peak powers of less than 1 kW. At these low power levels, efficient frequency doubling usually requires complex arrangements, especially if the pulse duration is to be preserved. In this paper we describe the use of a relatively thick doubling crystal in a single-pass, extra-cavity arrangement. Although the second harmonic pulses suffer temporal broadening, this represents an effective way to achieve efficient frequency conversion in a simplified configuration. The nonlinear crystal was potassium niobate (KNbO<sub>3</sub>) cut for non-critical phase matching at 860 nm and 22°C.
Lasers and Electro-Optics, 2002. CLEO '02. Technical Digest. Summaries of Papers Presented at the; 02/2002
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ABSTRACT: Gigahertz repetition-rate, fundamental modelocking of a directly
diode-pumped femtosecond laser is demonstrated for the first time.
Transform-limited pulses of 146 fs duration are produced from a compact
Cr:LiSAF laser incorporating a semiconductor saturable absorber mirror
and pumped by inexpensive, narrow-stripe red laser diodes
Electronics Letters 12/2001; · 0.96 Impact Factor
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ABSTRACT: Summary form only given. In this paper we present laser designs
that begin to address the issues of size, cost and fragility of
femtosecond sources. We have shown that it is possible to reduce the
threshold of femtosecond Cr:LiSAF lasers sufficiently that cheap
single-spatial-mode, narrow-stripe red laser diodes (output power ~50
mW) become viable pump sources
Lasers and Electro-Optics, 2001. CLEO '01. Technical Digest. Summaries of papers presented at the Conference on; 02/2001
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ABSTRACT: We describe efficient, compact femtosecond Cr:LiSAF lasers with a reduced component count that combine greater simplicity with improved performance. We observe transform-limited pulses as short as 136 fs centered on 859 nm at a 470 MHz repetition rate. 20 mW of average output power has been achieved for less than 100 mW of incident diode-laser pump power – an optical-to-optical conversion efficiency of over 20%. We have demonstrated an entirely portable, self-contained, battery-powered version of this laser on a breadboard, with an electrical-to-optical efficiency of almost 4%. Using four pump laser diodes, we have also achieved operational regimes providing either gigahertz repetition rates or kilowatt peak powers.
Optics Communications.
