Read by QxMD icon Read

optical tweezers

Jundi Hou, Tao Luo, Ka Lam Ng, Raymond Liang, Anskar Y H Leung, Dong Sun
One of the greatest challenges in acute myeloid leukemia (AML) treatment is preventing relapse. Leukemia cells can hide in bone marrow niche or vascular niche. Hence, many chemical drugs cannot kill these cells. To characterize migration and adhesion properties of leukemia cells in specific niches, CXCR4/SDF-1α signal pathway has been widely used for investigation. AMD3100 is treated as one of the most common chemical drugs that can inhibit this signal. In the current study, we particularly investigate the effect of AMD3100 on the adhesion property of leukemia cells on stromal cells by using engineering tools, namely, optical tweezers (OT) and dielectrophoresis (DEP), to probe single cell property...
October 19, 2016: IEEE Transactions on Nanobioscience
K Lee, A Priezzhev, S Shin, Y Francois, I Meglinski
BACKGROUND: The novel measure of the red blood cells (RBC) aggregation (RBC-A) - the critical (minimum) shear stress (CSS) to prevent the cells from aggregation was found to be a promising clinically significant parameter. However, the absolute values of this parameter were found to change significantly depending on the shearing geometry (cup-and-bob, cone-plate or microchannel-flow) and have different temperature dependences along with it. The direct confirmation of these dependences aimed to find out the correct values is still pending...
October 18, 2016: Clinical Hemorheology and Microcirculation
Quanbo Jiang, Aline Pham, Serge Huant, Joel Bellessa, Cyriaque Genet, Aurélien Drezet
We report a highly efficient generation of singular surface plasmon (SP) fields by an achiral plasmonic structure consisting of Λ-shaped apertures. Our quantitative analysis, based on leakage radiation microscopy (LRM), demonstrates that the induced spin-orbit coupling can be tuned by adjusting the apex angle of the Λ-shaped aperture. Specifically, the array of Λ-shaped apertures with the apex angle 60° is shown to give rise to the directional coupling efficiency. The ring of Λ-shaped apertures with the apex angle 60° was found to generate the maximum extinction ratio (ER=11) for the SP singularities between two different polarization states...
October 1, 2016: Optics Letters
Mark S Friddin, Guido Bolognesi, Yuval Elani, Nicholas J Brooks, Robert V Law, John M Seddon, Mark A A Neil, Oscar Ces
We report a new platform technology to systematically assemble droplet interface bilayer (DIB) networks in user-defined 3D architectures from cell-sized droplets using optical tweezers. Our OptiDIB platform is the first demonstration of optical trapping to precisely construct 3D DIB networks, paving the way for the development of a new generation of modular bio-systems.
September 20, 2016: Soft Matter
Achim Löf, Jochen P Müller, Martin Benoit, Maria A Brehm
The large multimeric plasma glycoprotein von Willebrand factor (VWF) is essential for primary hemostasis by recruiting platelets to sites of vascular injury. VWF multimers respond to elevated hydrodynamic forces by elongation, thereby increasing their adhesiveness to platelets. Thus, the activation of VWF is force-induced, as is its inactivation. Due to these attributes, VWF is a highly interesting system from a biophysical point of view, and is well suited for investigation using biophysical approaches. Here, we give an overview on recent studies that predominantly employed biophysical methods to gain novel insights into multiple aspects of VWF: Electron microscopy was used to shed light on the domain structure of VWF and the mechanism of VWF secretion...
September 28, 2016: Advances in Biological Regulation
Surya Cheemalapati, Mikhail Ladanov, Bo Pang, Yuan Yuan, Piyush Koria, Younan Xia, Anna Pyayt
Understanding how plasmonic nanoparticles collectively generate heat upon exposure to light and thus increase the local temperature of the surrounding medium is critical for many applications such as plasmon-assisted microfluidics, plasmonic tweezers, and photothermal cancer therapy. Reliable temperature manipulation requires the capability to spatially and dynamically analyze local temperature profiles as a function of nanoparticle concentration and laser intensity. In this work, we present a novel method for visualization of local temperature increase using elastin-like polypeptides (ELP)...
September 26, 2016: Nanoscale
A Miniewicz, S Bartkiewicz, H Orlikowska, K Dradrach
In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye dissolved in a solvent and a laser light beam that is strongly absorbed by the dye...
October 7, 2016: Scientific Reports
Dibyendu Kumar Das, Robert J Mallis, Jonathan S Duke-Cohan, Rebecca E Hussey, Paul W Tetteh, Mark Hilton, Gerhard Wagner, Matthew J Lang, Ellis Reinherz
The pre-T cell receptor (preTCR) is a pTα-β heterodimer functioning in early αβ T-cell development. Although once thought to be ligand-autonomous, recent studies show that preTCRs participate in thymic repertoire formation through recognition of peptides bound to major histocompatibility molecules (pMHC). Using optical tweezers, we probe preTCR bonding with pMHC at the single molecule level. Like the αβTCR, the preTCR is a mechanosensor undergoing force-based structural transitions that dynamically enhance bond lifetimes, and exploiting allosteric control regulated via the Cβ FG loop region...
October 5, 2016: Journal of Biological Chemistry
N V Brilliantov, Yu A Budkov, C Seidel
We analyse theoretically and by means of molecular dynamics (MD) simulations the generation of mechanical force by a polyelectrolyte (PE) chain grafted to a plane. The PE is exposed to an external electric field that favours its adsorption on the plane. The free end of the chain is linked to a deformable target body. By varying the field, one can alter the length of the non-adsorbed part of the chain. This entails variation of the deformation of the target body and hence variation of the force arising in the body...
November 13, 2016: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Christian T Schmiegelow, Jonas Schulz, Henning Kaufmann, Thomas Ruster, Ulrich G Poschinger, Ferdinand Schmidt-Kaler
Photons can carry angular momentum, not only due to their spin, but also due to their spatial structure. This extra twist has been used, for example, to drive circular motion of microscopic particles in optical tweezers as well as to create vortices in quantum gases. Here we excite an atomic transition with a vortex laser beam and demonstrate the transfer of optical orbital angular momentum to the valence electron of a single trapped ion. We observe strongly modified selection rules showing that an atom can absorb two quanta of angular momentum from a single photon: one from the spin and another from the spatial structure of the beam...
October 3, 2016: Nature Communications
Fan Ye, Ryan P Badman, James T Inman, Mohammad Soltani, Jessica L Killian, Michelle D Wang
The advent of nanophotonic evanescent field trapping and transport platforms has permitted increasingly complex single molecule and single cell studies on-chip. Here, we present the next generation of nanophotonic Standing Wave Array Traps (nSWATs) representing a streamlined CMOS fabrication process and compact biocompatible design. These devices utilize silicon nitride (Si3N4) waveguides, operate with a biofriendly 1064 nm laser, allow for several watts of input power with minimal absorption and heating, and are protected by an anticorrosive layer for sustained on-chip microelectronics in aqueous salt buffers...
October 12, 2016: Nano Letters
Young Chul Song, Allen E Haddrell, Bryan R Bzdek, Jonathan P Reid, Thomas Bannan, David O Topping, Carl Percival, Chen Cai
Organic aerosol particles are known to often absorb/desorb water continuously with change in gas phase relative humidity (RH) without crystallization. Indeed, the prevalence of metastable ultraviscous liquid or amorphous phases in aerosol is well-established with solutes often far exceeding bulk phase solubility limits. Particles are expected to become increasingly viscous with drying, a consequence of the plasticizing effect of water. We report here measurements of the variation in aerosol particle viscosity with RH (equal to condensed phase water activity) for a range of organic solutes including alcohols (diols to hexols), saccharides (mono-, di-, and tri-), and carboxylic acids (di-, tri-, and mixtures)...
October 7, 2016: Journal of Physical Chemistry. A
Ken-Ichi Amano, Mitsuhiro Iwaki, Kota Hashimoto, Kazuhiro Fukami, Naoya Nishi, Ohgi Takahashi, Tetsuo Sakka
Some colloidal suspensions contain two types of particles-small and large particles-to improve the lubricating ability, light absorptivity, and so forth. Structural and chemical analyses of such colloidal suspensions are often performed to understand their properties. In a structural analysis study, the observation of the number density distribution of small particles around a large particle (gLS) is difficult because these particles are randomly moving within the colloidal suspension by Brownian motion. We obtain gLS using the data from a line optical tweezer (LOT) that can measure the potential of mean force between two large colloidal particles (ΦLL)...
October 11, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Shubo Cheng, Xinyu Zhang, Wenzhuo Ma, Shaohua Tao
We demonstrate optical manipulation with an optical beam generated by a fractral zone plate (FZP). The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FZP beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The FZP beam can also be used to construct three-dimensional optical tweezers for potential applications.
September 28, 2016: Scientific Reports
I S Veshchunov, W Magrini, S V Mironov, A G Godin, J-B Trebbia, A I Buzdin, Ph Tamarat, B Lounis
Magnetic field can penetrate into type II superconductors in the form of Abrikosov vortices, which are magnetic flux tubes surrounded by circulating supercurrents often trapped at defects referred to as pinning sites. Although the average properties of the vortex matter in superconductors can be tuned with magnetic fields, temperature or electric currents, handling of individual Abrikosov vortices remains challenging and has been demonstrated only with sophisticated scanning local probe microscopies. Here we introduce a far-field optical method based on local heating of the superconductor with a focused laser beam to realize a fast and precise manipulation of individual vortices, in the same way as with optical tweezers...
2016: Nature Communications
Yu Lu, Guangqing Du, Feng Chen, Qing Yang, Hao Bian, Jiale Yong, Xun Hou
In this paper, the tunable optical trapping dependence on wavelength of incident beam is theoretically investigated based on numerical simulations. The Monte Carlo method is taken into account for exploring the trapping characteristics such as average deviation and number distribution histogram of nanoparticles. It is revealed that both the width and the depth of potential well for trapping particles can be flexibly adjusted by tuning the wavelength of the incident beam. In addition, incident wavelengths for the deepest potential well and for the strongest stiffness at bottom are separated...
September 26, 2016: Scientific Reports
Linhan Lin, Xiaolei Peng, Mingsong Wang, Leonardo Scarabelli, Zhangming Mao, Luis M Liz-Marzán, Michael F Becker, Yuebing Zheng
Reversible assembly of plasmonic nanoparticles can be used to modulate their structural, electrical and optical properties. Common and versatile tools in nanoparticle manipulation and assembly are optical tweezers, but these require tightly focused and high-power (10-100 mW/µm(2)) laser beams with precise optical alignment, which significantly hinders their applications. Here we present light-directed reversible assembly of plasmonic nanoparticles with power intensity below 0.1 mW/µm(2). Our experiments and simulations reveal that such low-power assembly is enabled by thermophoretic migration of nanoparticles due to the plasmon-enhanced photothermal effect and the associated enhanced local electric field over a plasmonic substrate...
September 17, 2016: ACS Nano
Li He, Huan Li, Mo Li
Photons carry linear momentum and spin angular momentum when circularly or elliptically polarized. During light-matter interaction, transfer of linear momentum leads to optical forces, whereas transfer of angular momentum induces optical torque. Optical forces including radiation pressure and gradient forces have long been used in optical tweezers and laser cooling. In nanophotonic devices, optical forces can be significantly enhanced, leading to unprecedented optomechanical effects in both classical and quantum regimes...
September 2016: Science Advances
Pietro Strobbia, Adam Mayer, Brian M Cullum
Surface-enhanced Raman spectroscopy (SERS) sensors offer many advantages for chemical analyses, including the ability to provide chemical specific information and multiplexed detection capability at specific locations. However, to have operative SERS sensors for probing microenvironments, probes with high signal enhancement and reproducibility are necessary. To this end, dynamic enhancement of SERS (i.e., in-situ amplification of signal-to-noise and signal-to-background ratios) from individual probes has been explored...
September 13, 2016: Applied Spectroscopy
Nobuki Kudo
A high-speed in situ microscopic observation system developed for basic studies on mechanisms of sonoporation is introduced in this paper. The main part of the system is an inverted-type fluorescence microscope, and a high-speed camera of 20 MHz in maximum framing rate was used to visualize dynamics of cavitation bubbles that causes a sonoporation effect. Differential interference contrast and fluorescence techniques were used for sensitive visualization of cell changes during sonoporation. The system is also equipped with optical tweezers that can move a microbubble of several microns in size by using a donut-shaped light beam...
September 7, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"