Showing papers by "Min Gu published in 2010"
TL;DR: It is shown that direct interactions with APCs provide the cue for polarization of T cells, and T cells have selectively adapted a number of evolutionarily conserved mechanisms to generate diversity through asymmetric cell division.
Abstract: Asymmetric cell division is a potential means by which cell fate choices during an immune response are orchestrated. Defining the molecular mechanisms that underlie asymmetric division of T cells is paramount for determining the role of this process in the generation of effector and memory T cell subsets. In other cell types, asymmetric cell division is regulated by conserved polarity protein complexes that control the localization of cell fate determinants and spindle orientation during division. We have developed a tractable, in vitro model of naive CD8 + T cells undergoing initial division while attached to dendritic cells during Ag presentation to investigate whether similar mechanisms might regulate asymmetric division of T cells. Using this system, we show that direct interactions with APCs provide the cue for polarization of T cells. Interestingly, the immunological synapse disseminates before division even though the T cells retain contact with the APC. The cue from the APC is translated into polarization of cell fate determinants via the polarity network of the Par3 and Scribble complexes, and orientation of the mitotic spindle during division is orchestrated by the partner of inscuteable/G protein complex. These findings suggest that T cells have selectively adapted a number of evolutionarily conserved mechanisms to generate diversity through asymmetric cell division.
122 citations
TL;DR: In this paper, progress on the gold-nanoparticle-enhanced photothermal therapy is reviewed, and the effects of various parameters on the therapeutic efficiency and mechanisms of gold nanoparticles assisted cancer therapy are discussed.
Abstract: In this paper, progress on the gold-nanoparticle-enhanced photothermal therapy is reviewed. Size- and shape-dependent optical absorption of gold nanoparticles, the effects of various parameters on the therapeutic efficiency, and the mechanisms of gold-nanoparticle-assisted cancer therapy are discussed. Future research directions of gold-nanoparticle-assisted cancer photothermal therapy are also suggested.
111 citations
TL;DR: Gold nanorods-enhanced luminescence imaging coupled with apoptosis induction of cancer cells provides a medically safe femtosecond laser-based imaging and microsurgery system for cancer diagnosis and treatment.
109 citations
TL;DR: In this article, a phosphine-free selenium nanocrystal precursor solution was synthesized by heating elemental Selenium powder in 1-octadecene (ODE) and the mixture was characterized by UV−vis absorption, photoluminescence excitation (PLE), nuclear magnetic resonance (NMR), Se X-ray absorption spectroscopy (Se-XAS), electron impact mass spectrometry (EIMS), and inductively coupled plasma atomic emission spectrograph (ICP-AES) to establish identifiable spectroscopic and chemical
Abstract: A phosphine-free selenium nanocrystal precursor solution has been synthesized by heating elemental selenium powder in 1-octadecene (ODE). This mixture was characterized by UV−vis absorption, photoluminescence excitation (PLE), nuclear magnetic resonance (NMR), Se X-ray absorption spectroscopy (Se-XAS), electron impact mass spectrometry (EIMS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) to establish identifiable spectroscopic and chemical signatures that can be correlated to the chemical efficacy of the precursor for the growth of metal selenide nanocrystals. Highly temperature dependent rates of selenium dissolution and deactivation of the resultant precursor are demonstrated and optimal preparation times for the most reactive precursor are determined. Distinctive features in the PLE spectrum provide a rapid estimate of the reactivity of the as-prepared Se-ODE precursor. NMR and XAS data strongly indicate both Se−Se and Se−C bonding are present in the precursor solution, suggest...
95 citations
TL;DR: The high resolution of SHG imaging from the endomicroscope shows that SHG Imaging can reveal additional information about the orientation and degree of organisation of proteins and collagen fibers than two-photon-excited fluorescence imaging.
Abstract: A compact endomicroscope is the only solution for transferring second harmonic generation (SHG) imaging into in vivo imaging and real time monitoring the content and structure of collagen. This is important for early diagnoses of different diseases associated with collagen change. A compact nonlinear endomicroscope using a double clad fiber (DCF) is newly employed in SHG imaging. The experiment shows the core of the DCF can maintain the linear polarization of the excitation laser beam in particular directions, and the degree of polarization of the excitation laser beam directly affects signal to noise ratio of SHG imaging. The nonlinear endomicroscope can display clear three dimensional (3D) SHG images of mouse tail tendon without the aid of contrast agents, which reveals the collagen fiber structure at different depths. The high resolution of SHG imaging from the endomicroscope shows that SHG imaging can reveal additional information about the orientation and degree of organisation of proteins and collagen fibers than two-photon-excited fluorescence imaging. Therefore SHG imaging offers endomicroscopy with additional channel of imaging for understanding more about biological phenomena.
61 citations
TL;DR: Through manipulating the incident polarization states of laser beams as well as the apodization of a objective and adjusting the numerical aperture of an objective, focal fields dominantly with either one transverse component or one longitudinal component can be generated.
Abstract: In this paper the polarization states of linearly and radially polarized plane wave and doughnut beams in the focal volume of high numerical aperture objectives are studied. Through manipulating the incident polarization states of laser beams as well as the apodization of an objective and adjusting the numerical aperture of an objective, focal fields dominantly with either one transverse component or one longitudinal component can be generated. Furthermore, tailored polarization distributions with three polarization components of the same strength are also found.
59 citations
TL;DR: In this article, a radially polarized beam was used for photothermal therapy of cancer cells labeled with gold nanorods, which reduced the energy fluence for effective cancer cell damage to one fifth of that required for a linearly polarized beam, which is only 9.3% of the medical safety level.
Abstract: We report on the use of a radially polarized beam for photothermal therapy of cancer cells labeled with gold nanorods. Due to a three-dimensionally distributed electromagnetic field in the focal volume, the radially polarized beam is proven to be a highly efficient laser mode to excite gold nanorods randomly oriented in cancer cells. As a result, the energy fluence for effective cancer cell damage is reduced to one fifth of that required for a linearly polarized beam, which is only 9.3% of the medical safety level.
50 citations
TL;DR: Sub-wavelength nanostructures on the surface of As(2)S(3) chalcogenide glasses are fabricated by appropriately controlling the irradiation condition of single-beam direct femtosecond laser writing using direct laser writing by single-pulse irradiation.
Abstract: We report on the fabrication of sub-wavelength nanostructures on the surface of As2S3 chalcogenide glasses by appropriately controlling the irradiation condition of single-beam direct femtosecond laser writing. Nanogratings with a period of 180 nm were realized by multipulse irradiation. More importantly controllable nanoholes as small as 200 nm in diameter (one quarter of the illumination wavelength) were, for the first time, achieved in As2S3 using direct laser writing by single-pulse irradiation.
40 citations
TL;DR: The non-linear nanocomposite has been proven to be suitable for the fabrication of 3D micro/nano photonic devices using two-photon polymerization and shows stop gaps with more than 60% suppression in transmission at the telecommunications wavelength region.
Abstract: A nanocomposite consisting of a photosensitive organic inorganic hybrid polymer functionalized with PbS quantum dots has been developed using a sol gel process. The uniformly dispersed nanocomposite exhibits ultrahigh third-order non-linearity (-3.2 x 10(-12) cm(2) W(-1)) because of the strong quantum confinement of small-sized and narrowly distributed quantum dots. The non-linear nanocomposite has been proven to be suitable for the fabrication of 3D micro/nano photonic devices using two-photon polymerization. The fabricated photonic crystals show stop gaps with more than 60% suppression in transmission at the telecommunications wavelength region.
38 citations
TL;DR: In this article, the authors extend the PHT to incorporate retardation of the Coulomb interaction and investigate the effects of retardation on plasmons within metallic structures, and compare these results using other methods, such as Mie scattering theory and the finite integration technique, and observe a good agreement in both electrostatic and retardation regimes.
Abstract: Plasmon hybridization theory (PHT) is an analytical model developed for understanding plasmonic interactions within complex metallic nanostructures, and gives a useful insight for optimizing design parameters. However, this theory is based on the electrostatic limit, which restricts the model to nanostructures much smaller than the free space wavelength of light. Here, we extend the PHT to incorporate retardation of the Coulomb interaction and investigate the effects of retardation on plasmons within metallic structures. We compare these results using other methods, such as Mie scattering theory and the finite integration technique, and observe a good agreement in both electrostatic and retardation regimes. Plasmons within metallic nanospheres and nanotubes are shown to have significant retardation in certain regimes, causing red-shifting to plasmon wavelengths, and we discuss the implications of retardation for plasmonic devices.
TL;DR: Three-dimensional (3D) nanoscale focusing of radially polarized light in far field by a simple plasmonic lens composed of an annular slit and a single concentric groove is reported and provides an admirable choice for the nano-optical devices.
Abstract: Three-dimensional (3D) nanoscale focusing of radially polarized light in far field by a simple plasmonic lens composed of an annular slit and a single concentric groove is reported. The numerical calculations reveal that the incident light is coupled to surface plasmon polaritons (SPP) by the annular slit and a focal spot with a size less than a half of the illumination wavelength is formed in the far field due to the constructive interference of the scattered light by the groove. More importantly, the focal length can be modulated by changing the groove diameter. This structure provides an admirable choice for the nano-optical devices.
TL;DR: Localized plasmon resonances are proposed in a new concept of 3D photonic crystals stacked by hybrid rods made of dielectric-cores and metallic-nanoshells which can be flexibly tuned by mediating the dielectrics cores.
Abstract: Localized plasmon resonances are proposed in a new concept of 3D photonic crystals stacked by hybrid rods made of dielectric-cores and metallic-nanoshells. The resonant plasmon coupling of inner and outer surfaces of the metallic-nanoshells forms the localized plasmon resonances which can be flexibly tuned by mediating the dielectric cores. At the resonance wavelengths, the strong electromagnetic wave-plasmon interaction leads to the enhancement in the structural absorption by more than 20 times. The tunability of the enhanced absorption is demonstrated in experiments.
TL;DR: The authors discuss the development of a 5-D device that could hold up to 2,000 times more data than a conventional DVD and other milestones on the road to multi-dimensional optical memory with petabyte capacity.
Abstract: Recent advances in optical data storage have led to the development of a 5-D device that could hold up to 2,000 times more data than a conventional DVD. These authors discuss this and other milestones on the road to multi-dimensional optical memory with petabyte capacity.
TL;DR: For the first time, a miniaturized nonlinear optical endomicroscope is used to achieve microtreatment of cancer cells labeled with gold nanorods, indicating that a combination of nonlinear endomicrobialscopy with gold nanoparticles is potentially viable for minimally invasive cancer treatment.
Abstract: Near-infrared laser-based microsurgery is promising for noninvasive cancer treatment. To make it a safe technique, a therapeutic process should be controllable and energy efficient, which requires the cancer cells to be identifiable and observable. In this work, for the first time we use a miniaturized nonlinear optical endomicroscope to achieve microtreatment of cancer cells labeled with gold nanorods. Due to the high two-photon-excited photoluminescence of gold nanorods, HeLa cells inside a tissue phantom up to 250 µm deep can be imaged by the nonlinear optical endomicroscope. This facilitates microsurgery of selected cancer cells by inducing instant damage through the necrosis process, or by stopping cell proliferation through the apoptosis process. The results indicate that a combination of nonlinear endomicroscopy with gold nanoparticles is potentially viable for minimally invasive cancer treatment.
TL;DR: The double-clad fiber coupler is developed to be used in two-photon-excited fluorescence endomicroscopy to replace a dichroic mirror and separate the fluorescence signal from the excitation laser beam.
Abstract: A double-clad fiber coupler is developed to be used in two-photon-excited fluorescence endomicroscopy to replace a dichroic mirror and separate the fluorescence signal from the excitation laser beam. With the double-clad fiber coupler, the endomicroscope becomes more compact, easier to be aligned, and more stable in alignment. The double-clad fiber coupler can transmit 62% of the excitation laser beam through the core. The fluorescence collection efficiency of the double-clad fiber coupler is 34%, which is, to the best of our knowledge, the highest fluorescence collection efficiency achieved by couplers used in two-photon-excited fluorescence endomicroscopes. As a result, the contrast of endomicroscopy imaging is enhanced.
TL;DR: Analyzing the dispersive properties of the 3D woodpile metallic photonic crystals and performing thorough numerical simulations for the finite number of layers found that the magnitude, band width, and tunability of enhanced absorption can be easily optimized, which can be of significance to design an efficient photonic crystal thermal emitter.
Abstract: We present a detailed theoretical analysis which reveals a useful insight to understand the resonant dissipative behavior of 3D woodpile metallic photonic crystals in the spectral response. We observe that a small amount of structural parameter modifications can induce great flexibility to alter the properties of the absorption resonance with even an extremely narrow band width of ~13 nm. Analyzing the dispersive properties of the 3D woodpile metallic photonic crystals and performing thorough numerical simulations for the finite number of layers we found that the magnitude, band width, and tunability of enhanced absorption can be easily optimized, which can be of significance to design an efficient photonic crystal thermal emitter.
TL;DR: In this paper, an active 3D photonic crystal (PC) was fabricated in polymer-QD composites with demonstrated spontaneous emission control from nanocrystal quantum dots (QDs).
Abstract: Controlling spontaneous emission (SE) is of fundamental importance to a diverse range of photonic applications including but not limited to quantum optics, low power displays, solar energy harvesting and optical communications. Characterized by photonic bandgap (PBG) property, three-dimensional (3D) photonic crystals (PCs) have emerged as a promising synthetic material, which can manipulate photons in much the same way as a semiconductor does to electrons. Emission tunable nanocrystal quantum dots (QDs) are ideal point sources to be embedded into 3D PCs towards active devices. The challenge however lies in the combination of QDs with 3D PCs without degradation of their emission properties. Polymer materials stand out for this purpose due to their flexibility of incorporating active materials. Combining the versatile multi-photon 3D micro-fabrication techniques, active 3D PCs have been fabricated in polymer-QD composites with demonstrated control of SE from QDs. With this milestone novel miniaturized photonic devices can thus be envisaged.
TL;DR: An optical tweezer sensor is presented that is able to measure the shear stress acting on microspheres of different sizes that model cell based biological operations and allows for direct shear Stress detection at arbitrary positions in straight and curved microfluidic devices.
Abstract: We present an optical tweezer sensor for shear stress mapping in microfluidic systems of different internal geometries. The sensor is able to measure the shear stress acting on microspheres of different sizes that model cell based biological operations. Without the need for a spatial modulator or a holographic disk, the sensor allows for direct shear stress detection at arbitrary positions in straight and curved microfluidic devices. Analytical calculations are carried out and compared with the experimental results. It is observed that a decrease in the microsphere size results in an increase in the shear stress the particle experiences.
Book•
14 Jun 2010TL;DR: In this paper, the authors provide a focused and systematic treatment of femtosecond biophotonic methods, combining theory, practice and applications, walking the reader through imaging, manipulation and fabrication techniques.
Abstract: The introduction of femtosecond pulse lasers has provided numerous new methods for non-destructive diagnostic analysis of biological samples. This book is the first to provide a focused and systematic treatment of femtosecond biophotonic methods. Each chapter combines theory, practice and applications, walking the reader through imaging, manipulation and fabrication techniques. Beginning with an explanation of nonlinear and multiphoton microscopy, subsequent chapters address the techniques for optical trapping and the development of laser tweezers. In a conclusion that brings together the various topics of the book, the authors discuss the growing field of femtosecond micro-engineering. The wide range of applications for femtosecond biophotonics means this book will appeal to researchers and practitioners in the fields of biomedical engineering, biophysics, life sciences and medicine.
TL;DR: Software simulation confirmed that the woodpile effective refractive index underwent an excess of 30% increase and a chemical bath deposition protocol has been adapted to deposit high-n/non-linear chalcogenide CdS on the surface of Ormocer woodpiles.
Abstract: Woodpile photonic crystals are amongst the preferred candidates for the next generation of photonics components. However, the photocurable resists used to produce them still lack the optical properties (high-n, non-linearity) suitable for photonics applications. A chemical bath deposition protocol has been adapted to deposit high-n/non-linear chalcogenide CdS on the surface of Ormocer® woodpiles. The deposition parameters have been adjusted to obtain heterogeneous growth of CdS layers on the Ormocer® surface. The layers shift the photonic band-gap and increase its amplitude by more than 15%. Software simulation confirmed that the woodpile effective refractive index underwent an excess of 30% increase.
TL;DR: In this paper, the photorefractive performance of a CdSe quantum-dot-dispersed less expensive polymer of poly(styrene-co-acrylonitrile) was characterized through a photocurrent experiment and a two-beam coupling experiment, respectively.
Abstract: This paper reports on the enhanced photorefractive behavior of a CdSe quantum-dot-dispersed less expensive polymer of poly(styrene-co-acrylonitrile). The capability of CdSe quantum dots used as photosensitizers and the associated photorefractive performance are characterized through a photocurrent experiment and a two-beam coupling experiment, respectively. An enhanced two-beam coupling gain coefficient of 12.2 cm−1 at 46 V/μm was observed owning to the reduced potential barrier. The photorefractive performance per CdSe quantum dot is three orders of magnitude higher than that in the sample sensitized by trinitrofluorenone in poly(styrene-co-acrylonitrile), and almost ten times higher than that in the CdSe quantum-dot-sensitized poly(N-vinylcarbazole) polymers.
TL;DR: A compact microfluidic device with 96 microchambers allocated within four circular units was designed and examined for cell distribution and a controllable and quantitative cell distribution is achievable in this device.
Abstract: A compact microfluidic device with 96 microchambers allocated within four circular units was designed and examined for cell distribution. In each unit, cells were distributed to the surrounding chambers radially from the center. The circular arrangement of the chambers makes the design simple and compact. A controllable and quantitative cell distribution is achievable in this device. This design is significant to the microfluidic applications where controllable distribution of cells in multipule microchambers is demanded.
TL;DR: A super-resolution method is presented for optically imaging the spatial distribution of semiconductor nanocrystals with nanometre localisation and highly resolved multiple photoluminescence trajectories of hundreds of single semiconductor Nanocrystals are obtained simultaneously.
Abstract: Here we present a multifunctional algorithm. Firstly a super-resolution method is presented for optically imaging the spatial distribution of semiconductor nanocrystals with nanometre localisation. Secondly highly resolved multiple photoluminescence trajectories of hundreds of single semiconductor nanocrystals are obtained simultaneously.
Patent•
15 Apr 2010
TL;DR: An optical data storage product, including a data storage medium containing mutually spaced bodies selectively responsive to light of respective different wavelengths and respective different polarisations, can be found in this article, where each group of bodies in each region can be selectively modified to store digital data in said region using light of a corresponding one of a plurality of said wavelengths and a corresponding ones of said polarisations and having an intensity exceeding a threshold intensity.
Abstract: An optical data storage product, including a data storage medium containing mutually spaced bodies selectively responsive to light of respective different wavelengths and respective different polarisations, said bodies being distributed in a plurality of selectably addressable regions of said data storage medium such that each region contains groups of said bodies selectively responsive to light of respective different combinations of wavelength and polarisation, wherein each group of bodies in each region can be selectively modified to store digital data in said region using light of a corresponding one of a plurality of said wavelengths and a corresponding one of a plurality of said polarisations and having an intensity exceeding a threshold intensity.
TL;DR: In this article, femtosecond laser etching of poly(methyl methacrylate) and aluminium substrates has enabled the production of micrometre resolution moulds that can be accurately replicated using soft lithography.
Abstract: Microfabrication using femtosecond pulse lasers is enabling access to a range of structures, surfaces and materials that was not previously available for scientific and engineering applications. The ability to produce micrometre sized features directly in polymer and metal substrates is demonstrated with applications in cell biology. The size, shape and aspect ratio of the etched features can be precisely controlled through the manipulation of the fluence of the laser etching process with respect to the properties of the target material. Femtosecond laser etching of poly(methyl methacrylate) and aluminium substrates has enabled the production of micrometre resolution moulds that can be accurately replicated using soft lithography. The moulded surfaces are used in the imaging of T cells and demonstrate the improved ability to observe biological events over time periods greater than 10 h. These results indicate the great potential femtosecond pulse lasers may have in the future manufacturing of microstructured surfaces and devices.
TL;DR: In this paper, a metallic-nanoshelled rectangular dielectric rod is proposed to flexibly enhance and tune the structural absorption of a 3D woodpile photonic crystal with both the rectangular cavity resonance and the photonic band gap effect.
Abstract: A metallic-nanoshelled rectangular dielectric rod is proposed to flexibly enhance and tune the structural absorption. Due to the ultra-small thickness of the metallic-nanoshells, electromagnetic (EM) waves can penetrate into the rods and rectangular cavity resonances can be formed. At the cavity resonances, the strong EM wave?matter interaction results in an enhancement in the structural absorption by more than one order of magnitude. By stacking the nanoshelled rods, a three-dimensional (3D) woodpile photonic crystal with both the rectangular cavity resonance and the photonic band gap effect is realized. As a result, the structural absorption of the nanoshelled 3D photonic crystal is significantly enhanced to ~99.99% at the resonant wavelength.
TL;DR: In this paper, the coherence times for the supercontinuum field generated by cross coupling into the photonic crystal fiber were investigated. But the coherent times of the field were not shown to be independent of the optical axis.
Abstract: Under the conditions of vectorial diffraction, an increase in refraction at the extremities of the lens rotates the incident polarization state which transfers energy from the initial state to the orthogonal transverse field and the longitudinalfield, which is known as depolarization. Since thefield is a vectorialfield containing three polarization components, the theory for the degree of coherence isfirst extended to incorporate cross-correlation effectswithinthesevectorialcomponentswhicharecalculatedthroughacoherencymatrix.Theuseofthismatrix providesaninsightintointerestingcorrelationeffectsbetweencopropagatingvectorialfieldssuchasthecoupled modes (linear polarized modes) of the supercontinuum generated by a photonic crystal fiber. An investigation is presented on the coherence times for the supercontinuumfield generated by cross coupling into the photonic crystalfiber. The coherence times under cross-coupling conditions show that the degree of coherence of the two coupled modes from thefiber are different, which is due to the differences in phase. For a supercontinuum with a linear polarization state, the coherence times along the x, y, and zaxes are different, with the most significant change occurring along the optical axis ( z) where the coherence time changes by an order of magnitude when the numerical aperture is increased from 0.1 to 1.
TL;DR: In this article, the use of Rhodamine dye as a temperature sensitive based fluorescence indicator for the characterization of heating in a pressure driven microfluidic device with high spatial resolution is described.
TL;DR: The authors present a review of the various near- field optical manipulation techniques and then report on the observation of erythrocyte pearl chains by a near-field optical tweezer.
Abstract: The ever-evolving topic of optical micromanipulation has established itself as a discipline over the last three decades, and is of much interest to a wide research community due to constantly emerging new applications across the various key disciplines. Performing optical manipulation using evanescent waves is termed near-field optical manipulation, which is essentially the manipulation of particles in the non-diffractive regime. The concept of the breaking of diffraction limit is the spur driving near-field optics studies, as opposed to all far field optical applications where light cannot be focused to a spot smaller than the diffraction limited value, which is about half the wavelength of light in the medium. The authors present a review of the various near-field optical manipulation techniques and then report on the observation of erythrocyte pearl chains by a near-field optical tweezer. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)