Matti Kinnunen ; Alexander V. Bykov ; Juho Tuorila ; Tomi Haapalainen ; Artashes V. Karmenyan ; Valery V. Tuchin
Strong light scattering in tissues and blood reduces the usability of many optical techniques. By reducing scattering, optical clearing enables deeper light penetration and improves resolution in several optical imaging applications. We demonstrate the usage of optical tweezers and elastic light scattering to study optical clearing [one of the major mechanisms—matching of refractive indices (RIs)] at the single particle and cell level. We used polystyrene spheres and human red blood cells (RBCs) as samples and glycerol or glucose water solutions as clearing agents. Optical tweezers kept single microspheres and RBCs in place during the measurement of light scattering patterns. The results show that optical clearing reduces the scattering cross section and increases g. Glucose also decreased light scattering from a RBC. Optical clearing affected the anisotropy factor g of 23.25-μm polystyrene spheres, increasing it by 0.5% for an RI change of 2.2% (20% glycerol) and 0.3% for an RI change of 1.1% (13% glucose).
DOI
Monday, March 17, 2014
A Novel Temperature Sensor Based on Optical Trapping Technology
Yu Zhang, Peibo Liang, Zhihai Liu, Jiaojie Lei, Jun Yang, and Libo Yuan
We propose and fabricate a novel temperature sensor based on the optical trapping technology. The temperature sensing cell is constructed by putting a “test-micro-particle” enclosed in a space built by a quartz capillary tube and two opposite-inserted optical fibers. In order to make the temperature sensor have the ability of auto-ready and easy-reset, we design and fabricate the special concavities in the ends of two fibers. This ability of auto-ready and easy-reset makes the sensor convenient to be applied in industrial fields for long-term-use. These properties provide a new probably development direction in sensing research fields for the optical tweezers technology, and solve the optical tweezers measurement repeatability problems.
DOI
We propose and fabricate a novel temperature sensor based on the optical trapping technology. The temperature sensing cell is constructed by putting a “test-micro-particle” enclosed in a space built by a quartz capillary tube and two opposite-inserted optical fibers. In order to make the temperature sensor have the ability of auto-ready and easy-reset, we design and fabricate the special concavities in the ends of two fibers. This ability of auto-ready and easy-reset makes the sensor convenient to be applied in industrial fields for long-term-use. These properties provide a new probably development direction in sensing research fields for the optical tweezers technology, and solve the optical tweezers measurement repeatability problems.
DOI
Saturday, March 15, 2014
Optical manipulation of single molecules in the living cell
Kamilla Norregaard, Liselotte Jauffred, Kirstine Berg-Sørensen and Lene Broeng Oddershede
Optical tweezers are the only nano-tool capable of manipulating and performing force-measurements on individual molecules and organelles within the living cell without performing a destructive penetration through the cell wall and without the need of inserting a non-endogenous probe. Here, we describe how optical tweezers are used to manipulate individual molecules and perform accurate force and distance measurements within the complex cytoplasm of the living cell. Optical tweezers can grab individual molecules or organelles, if their optical contrast to the medium is large enough, as is the case, e.g., for lipid granules or chromosomes. However, often the molecule of interest is specifically attached to a handle manipulated by the optical trap. The most commonly used handles, their insertion into the cytoplasm, and the relevant micro-rheology of the cell are here discussed and we also review recent and exciting results achieved through optical force manipulation of individual molecules in vivo.
DOI
Optical tweezers are the only nano-tool capable of manipulating and performing force-measurements on individual molecules and organelles within the living cell without performing a destructive penetration through the cell wall and without the need of inserting a non-endogenous probe. Here, we describe how optical tweezers are used to manipulate individual molecules and perform accurate force and distance measurements within the complex cytoplasm of the living cell. Optical tweezers can grab individual molecules or organelles, if their optical contrast to the medium is large enough, as is the case, e.g., for lipid granules or chromosomes. However, often the molecule of interest is specifically attached to a handle manipulated by the optical trap. The most commonly used handles, their insertion into the cytoplasm, and the relevant micro-rheology of the cell are here discussed and we also review recent and exciting results achieved through optical force manipulation of individual molecules in vivo.
DOI
Engineered Tumor Cell Apoptosis Monitoring Method Based on Dynamic Laser Tweezers
Yuquan Zhang, Xiaojing Wu, Changjun Min, Siwei Zhu, Xiaodong Yuan, and Paul Urbach
Monitoring the cells’ apoptosis progression could provide a valuable insight into the
temporal events that initiate cell death as well as the potential for rescue of apoptotic cells. In
this paper, we engineered a novel and robust method for monitoring apoptosis of tumor
cellsbased on dynamic laser tweezers, using A549 and HeLa cell line as typical samples. The entire experiment can be completed in a few hours withsmall amount of fluid sample, presenting great advantages of celerity, micro-scaled measurement, and label-free explorations without perturbing experimental conditions in combination with other probes. Validity and stability of this method are verified experimentally in terms of physical parameters of the system. The proposed technique hasgreat potential in improving cancer treatment by monitoring the objective efficacy of tumor cell killing.
DOI
Monitoring the cells’ apoptosis progression could provide a valuable insight into the
temporal events that initiate cell death as well as the potential for rescue of apoptotic cells. In
this paper, we engineered a novel and robust method for monitoring apoptosis of tumor
cellsbased on dynamic laser tweezers, using A549 and HeLa cell line as typical samples. The entire experiment can be completed in a few hours withsmall amount of fluid sample, presenting great advantages of celerity, micro-scaled measurement, and label-free explorations without perturbing experimental conditions in combination with other probes. Validity and stability of this method are verified experimentally in terms of physical parameters of the system. The proposed technique hasgreat potential in improving cancer treatment by monitoring the objective efficacy of tumor cell killing.
DOI
Superadiabatic optical forces on a dipole: exactly solvable model for a vortex field
M V Berry and Pragya Shukla
The forces exerted by light on a small particle are modified by the particle's motion, giving a series of superadiabatic corrections to the lowest-order approximation in which the motion is neglected. The correction forces can be calculated recursively for an electric dipole modelled as a damped oscillator. In lowest order, there is, as is known, a non-potential though non-dissipative 'curl force', in addition to the familiar gradient force. In the next order, there are forces of geometric magnetism and friction, related to the geometric phase 2-form and the metric of the driving field. For the paraxial field of an optical vortex, the hierarchy of superadiabatic forces can be calculated explicitly, revealing a four-sheeted Riemann surface on which fast and slow dynamics are connected. This leads to an exact 'slow manifold', on which the dipole is driven without oscillations by the same forces as in the first two adiabatic orders, but with frequency-renormalized strengths.
DOI
The forces exerted by light on a small particle are modified by the particle's motion, giving a series of superadiabatic corrections to the lowest-order approximation in which the motion is neglected. The correction forces can be calculated recursively for an electric dipole modelled as a damped oscillator. In lowest order, there is, as is known, a non-potential though non-dissipative 'curl force', in addition to the familiar gradient force. In the next order, there are forces of geometric magnetism and friction, related to the geometric phase 2-form and the metric of the driving field. For the paraxial field of an optical vortex, the hierarchy of superadiabatic forces can be calculated explicitly, revealing a four-sheeted Riemann surface on which fast and slow dynamics are connected. This leads to an exact 'slow manifold', on which the dipole is driven without oscillations by the same forces as in the first two adiabatic orders, but with frequency-renormalized strengths.
DOI
5D-Tracking of a nanorod in a focused laser beam - a theoretical concept
Markus Grießhammer and Alexander Rohrbach
Back-focal plane (BFP) interferometry is a very fast and precise method to track the 3D position of a sphere within a focused laser beam using a simple quadrant photo diode (QPD). Here we present a concept of how to track and recover the 5D state of a cylindrical nanorod (3D position and 2 tilt angles) in a laser focus by analyzing the interference of unscattered light and light scattered at the cylinder. The analytical theoretical approach is based on Rayleigh-Gans scattering together with a local field approximation for an infinitely thin cylinder. The approximated BFP intensities compare well with those from a more rigorous numerical approach. It turns out that a displacement of the cylinder results in a modulation of the BFP intensity pattern, whereas a tilt of the cylinder results in a shift of this pattern. We therefore propose the concept of a local QPD in the BFP of a detection lens, where the QPD center is shifted by the angular coordinates of the cylinder tilt.
DOI
Back-focal plane (BFP) interferometry is a very fast and precise method to track the 3D position of a sphere within a focused laser beam using a simple quadrant photo diode (QPD). Here we present a concept of how to track and recover the 5D state of a cylindrical nanorod (3D position and 2 tilt angles) in a laser focus by analyzing the interference of unscattered light and light scattered at the cylinder. The analytical theoretical approach is based on Rayleigh-Gans scattering together with a local field approximation for an infinitely thin cylinder. The approximated BFP intensities compare well with those from a more rigorous numerical approach. It turns out that a displacement of the cylinder results in a modulation of the BFP intensity pattern, whereas a tilt of the cylinder results in a shift of this pattern. We therefore propose the concept of a local QPD in the BFP of a detection lens, where the QPD center is shifted by the angular coordinates of the cylinder tilt.
DOI
Lateral optical force on chiral particles near a surface
S. B. Wang & C. T. Chan
Light can exert radiation pressure on any object it encounters and that resulting optical force can be used to manipulate particles. It is commonly assumed that light should move a particle forward and indeed an incident plane wave with a photon momentum ħk can only push any particle, independent of its properties, in the direction of k. Here we demonstrate, using full-wave simulations, that an anomalous lateral force can be induced in a direction perpendicular to that of the incident photon momentum if a chiral particle is placed above a substrate that does not break any left–right symmetry. Analytical theory shows that the lateral force emerges from the coupling between structural chirality (the handedness of the chiral particle) and the light reflected from the substrate surface. Such coupling induces a sideway force that pushes chiral particles with opposite handedness in opposite directions.
DOI
Light can exert radiation pressure on any object it encounters and that resulting optical force can be used to manipulate particles. It is commonly assumed that light should move a particle forward and indeed an incident plane wave with a photon momentum ħk can only push any particle, independent of its properties, in the direction of k. Here we demonstrate, using full-wave simulations, that an anomalous lateral force can be induced in a direction perpendicular to that of the incident photon momentum if a chiral particle is placed above a substrate that does not break any left–right symmetry. Analytical theory shows that the lateral force emerges from the coupling between structural chirality (the handedness of the chiral particle) and the light reflected from the substrate surface. Such coupling induces a sideway force that pushes chiral particles with opposite handedness in opposite directions.
DOI
Monolithic integration of DUV-induced waveguides into plastic microfluidic chip for optical manipulation
M. Khoury, C. Vannahme, K.T. Sørensen, A. Kristensen, K. Berg-Sørensen
A monolithic polymer optofluidic chip for manipulation of microbeads in flow is demonstrated. On this chip, polymer waveguides induced by Deep UV lithography are integrated with microfluidic channels. The optical propagation losses of the waveguides are measured to be 0.66±0.130.66±0.13 dB/mm at a wavelength of λλ = 808 nm. An optimized bead tracking algorithm is implemented, allowing for determination of the optical forces acting on the particles. The algorithm features a spatio-temporal mapping of coordinates for uniting partial trajectories, without increased processing time. With an external laser power of 250 mW, a maximum scattering force of 0.84 pN is achieved for 5 μm diameter polystyrene beads in water.
DOI
A monolithic polymer optofluidic chip for manipulation of microbeads in flow is demonstrated. On this chip, polymer waveguides induced by Deep UV lithography are integrated with microfluidic channels. The optical propagation losses of the waveguides are measured to be 0.66±0.130.66±0.13 dB/mm at a wavelength of λλ = 808 nm. An optimized bead tracking algorithm is implemented, allowing for determination of the optical forces acting on the particles. The algorithm features a spatio-temporal mapping of coordinates for uniting partial trajectories, without increased processing time. With an external laser power of 250 mW, a maximum scattering force of 0.84 pN is achieved for 5 μm diameter polystyrene beads in water.
DOI
Wednesday, March 12, 2014
Yoctoliter Thermometry for Single-Molecule Investigations: A Generic Bead-on-a-Tip Temperature-Control Module
Deepak Koirala, Jibin Abraham Punnoose, Prakash Shrestha, Prof. Hanbin Mao
A new temperature-jump (T-jump) strategy avoids photo-damage of individual molecules by focusing a low-intensity laser on a black microparticle at the tip of a capillary. The black particle produces an efficient photothermal effect that enables a wide selection of lasers with powers in the milliwatt range to achieve a T-jump of 65 °C within milliseconds. To measure the temperature in situ in single-molecule experiments, the temperature-dependent mechanical unfolding of a single DNA hairpin molecule was monitored by optical tweezers within a yoctoliter volume. Using this bead-on-a-tip module and the robust single-molecule thermometer, full thermodynamic landscapes for the unfolding of this DNA hairpin were retrieved. These approaches are likely to provide powerful tools for the microanalytical investigation of dynamic processes with a combination of T-jump and single-molecule techniques.
DOI
A new temperature-jump (T-jump) strategy avoids photo-damage of individual molecules by focusing a low-intensity laser on a black microparticle at the tip of a capillary. The black particle produces an efficient photothermal effect that enables a wide selection of lasers with powers in the milliwatt range to achieve a T-jump of 65 °C within milliseconds. To measure the temperature in situ in single-molecule experiments, the temperature-dependent mechanical unfolding of a single DNA hairpin molecule was monitored by optical tweezers within a yoctoliter volume. Using this bead-on-a-tip module and the robust single-molecule thermometer, full thermodynamic landscapes for the unfolding of this DNA hairpin were retrieved. These approaches are likely to provide powerful tools for the microanalytical investigation of dynamic processes with a combination of T-jump and single-molecule techniques.
DOI
Seminal Plasma Initiates a Neisseria gonorrhoeae Transmission State
Mark T. Anderson, Lena Dewenter, Berenike Maier, H. Steven Seifert
Niche-restricted pathogens are evolutionarily linked with the specific biological fluids that are encountered during infection. Neisseria gonorrhoeae causes the genital infection gonorrhea and is exposed to seminal fluid during sexual transmission. Treatment of N. gonorrhoeae with seminal plasma or purified semen proteins lactoferrin, serum albumin, and prostate-specific antigen each facilitated type IV pilus-mediated twitching motility of the bacterium. Motility in the presence of seminal plasma was characterized by high velocity and low directional persistence. In addition, infection of epithelial cells with N. gonorrhoeae in the presence of seminal plasma resulted in enhanced microcolony formation. Close association of multiple pili in the form of bundles was also disrupted after seminal plasma treatment leading to an increase in the number of single pilus filaments on the bacterial surface. Thus, exposure of N. gonorrhoeae to seminal plasma is proposed to alter bacterial motility and aggregation characteristics to influence the processes of transmission and colonization.
DOI
Niche-restricted pathogens are evolutionarily linked with the specific biological fluids that are encountered during infection. Neisseria gonorrhoeae causes the genital infection gonorrhea and is exposed to seminal fluid during sexual transmission. Treatment of N. gonorrhoeae with seminal plasma or purified semen proteins lactoferrin, serum albumin, and prostate-specific antigen each facilitated type IV pilus-mediated twitching motility of the bacterium. Motility in the presence of seminal plasma was characterized by high velocity and low directional persistence. In addition, infection of epithelial cells with N. gonorrhoeae in the presence of seminal plasma resulted in enhanced microcolony formation. Close association of multiple pili in the form of bundles was also disrupted after seminal plasma treatment leading to an increase in the number of single pilus filaments on the bacterial surface. Thus, exposure of N. gonorrhoeae to seminal plasma is proposed to alter bacterial motility and aggregation characteristics to influence the processes of transmission and colonization.
DOI
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