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Spectral-optical-tweezer-assisted fluorescence multiplexing system for QDs-encoded bead-array bioassay
摘要： As an efficient tool in the multiplexed detection of biomolecules, bead-array could achieve separation-free detection to multiple targets, making it suitable to analyze valuable and scarce samples like antigen and antibody from living organism. Herein, we propose a spectral-optical-tweezer-assisted fluorescence multiplexing system to analyze biomolecule-conjugated bead-array. Using optical tweezer, we trapped and locked beads at the focus to accept stimulation, offering a stable and optimized analysis condition. Moving the system focus and scanning the sample slide, we achieved emissions collection to QDs-encoded bead-array after the multiplexed detection. The emission spectra of fluorescence were collected and recorded by the spectrometer. By recognizing locations of decoding peaks and counting the intensities of label signals of emission spectra, we achieved qualitative and quantitative detection to targets. As proof-of-concept studies, we use this system to carry out multiplexed detection to various types of anti-IgG in the single sample and the detection limit reaches 1.52 pM with a linear range from 0.31 to 10 nM. Through further optimization of experimental conditions, we achieved specific detection to target IgG with sandwich method in human serum and the detection limit reaches as low as 0.23 pM with a linear range from 0.88 to 28 pM, validating the practical application of this method in real samples.
关键词： bead-array,QDs encoding,optical tweezers,multiplexed biodetection
更新于2025-09-23 15:23:52
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The Investigation of WGM Effective Potential from Micro PANDA Ring Resonator
摘要： In this work, the whispering gallery mode effective potential generated by micro PANDA ring resonator for a two level system of atom–electric field coupling is investigated and presented. The depth of trapping potential is proportional to electric intensity and damping rate of transition of dipole polarization. The trial harmonics potential well is established by using dipole potential under ac Stark effect. The optimum intensity and lifetime for each WGM trapping wavelengths under the effect of thermal noise is reported.
关键词： optical tweezers,Trapping potential,atomic qubit
更新于2025-09-23 15:23:52
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Bio-Molecular Applications of Recent Developments in Optical Tweezers
摘要： In the past three decades, the ability to optically manipulate biomolecules has spurred a new era of medical and biophysical research. Optical tweezers (OT) have enabled experimenters to trap, sort, and probe cells, as well as discern the structural dynamics of proteins and nucleic acids at single molecule level. The steady improvement in OT’s resolving power has progressively pushed the envelope of their applications; there are, however, some inherent limitations that are prompting researchers to look for alternatives to the conventional techniques. To begin with, OT are restricted by their one-dimensional approach, which makes it difficult to conjure an exhaustive three-dimensional picture of biological systems. The high-intensity trapping laser can damage biological samples, a fact that restricts the feasibility of in vivo applications. Finally, direct manipulation of biological matter at nanometer scale remains a significant challenge for conventional OT. A significant amount of literature has been dedicated in the last 10 years to address the aforementioned shortcomings. Innovations in laser technology and advances in various other spheres of applied physics have been capitalized upon to evolve the next generation OT systems. In this review, we elucidate a few of these developments, with particular focus on their biological applications. The manipulation of nanoscopic objects has been achieved by means of plasmonic optical tweezers (POT), which utilize localized surface plasmons to generate optical traps with enhanced trapping potential, and photonic crystal optical tweezers (PhC OT), which attain the same goal by employing different photonic crystal geometries. Femtosecond optical tweezers (fs OT), constructed by replacing the continuous wave (cw) laser source with a femtosecond laser, promise to greatly reduce the damage to living samples. Finally, one way to transcend the one-dimensional nature of the data gained by OT is to couple them to the other large family of single molecule tools, i.e., fluorescence-based imaging techniques. We discuss the distinct advantages of the aforementioned techniques as well as the alternative experimental perspective they provide in comparison to conventional OT.
关键词： plasmonic optical tweezers,femtosecond optical tweezers,photonic crystal optical tweezers,fluorescence,single molecule and cell studies
更新于2025-09-23 15:22:29
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Step Sizes and Rate Constants of Single-headed Cytoplasmic Dynein Measured with Optical Tweezers
摘要： A power stroke of dynein is thought to be responsible for the stepping of dimeric dynein. However, the actual size of the displacement driven by a power stroke has not been directly measured. Here, the displacements of single-headed cytoplasmic dynein were measured by optical tweezers. The mean displacement of dynein interacting with microtubule was ~8 nm at 100 μM ATP, and decreased sigmoidally with a decrease in the ATP concentration. The ATP dependence of the mean displacement was explained by a model that some dynein molecules bind to microtubule in pre-stroke conformation and generate 8-nm displacement, while others bind in the post-stroke one and detach without producing a power stroke. Biochemical assays showed that the binding affinity of the post-stroke dynein to a microtubule was ~5 times higher than that of pre-stroke dynein, and the dissociation rate was ~4 times lower. Taking account of these rates, we conclude that the displacement driven by a power stroke is 8.3 nm. A working model of dimeric dynein driven by the 8-nm power stroke was proposed.
关键词： power stroke,optical tweezers,ATP,microtubule,dynein
更新于2025-09-23 15:21:21
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Axion sensor
摘要： Optical tweezers are a popular tool for manipulating and sorting individual nanoparticles. Now, Avinash Kumar and John Bechhoefer from Simon Fraser University, Canada have shown that when equipped with a suitable feedback scheme tweezers can be used to create a more complicated force field, such as single- or double-well harmonic potentials, for controlling particle dynamics. In the experiments, a polarized 532-nm laser was used for trapping and detection. The polarization of the detection beam was rotated by 90° with a half-wave plate so that a polarized beam splitter could separate the detection beam from backscattered light arising from the trapping laser. Quadrant photodiodes were used to detect the particle’s fluctuation and dynamics. Two feedback loops continuously regulated a pair of acousto-optic deflectors to compensate for any fluctuation in the total intensity. The shape of the double-well potential was reconstructed from the Boltzmann distribution of the position measurements. The well separation was 10.6 nm, which is far below the diffraction limit (≈ 220 nm). The ability to create and control energy landscapes at scales comparable to the size of proteins offers intriguing possibilities for biophysical applications.
关键词： biophysical applications,nanoparticles,optical tweezers,force field
更新于2025-09-23 15:21:21
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Probing Cell Mechanics with Bead-Free Optical Tweezers in the <em>Drosophila</em> Embryo
摘要： Morphogenesis requires coordination between genetic patterning and mechanical forces to robustly shape the cells and tissues. Hence, a challenge to understand morphogenetic processes is to directly measure cellular forces and mechanical properties in vivo during embryogenesis. Here, we present a setup of optical tweezers coupled to a light sheet microscope, which allows to directly apply forces on cell-cell contacts of the early Drosophila embryo, while imaging at a speed of several frames per second. This technique has the advantage that it does not require the injection of beads into the embryo, usually used as intermediate probes on which optical forces are exerted. We detail step by step the implementation of the setup, and propose tools to extract mechanical information from the experiments. By monitoring the displacements of cell-cell contacts in real time, one can perform tension measurements and investigate cell contacts' rheology.
关键词： Drosophila embryo,Developmental Biology,in vivo imaging,optical tweezers,Light sheet microscopy,force measurements,Issue 141,cell mechanics
更新于2025-09-23 15:21:01
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Optical Tweezers: A Force to Be Reckoned With
摘要： The 2018 Nobel Prize in Physics has been awarded jointly to Arthur Ashkin for the discovery and development of optical tweezers and their applications to biological systems and to Ge′ rard Mourou and Donna Strickland for the invention of laser chirped pulse ampli?cation. Here we focus on Arthur Ashkin and how his revolutionary work opened a window into the world of molecular mechanics and spurred the rise of single-molecule biophysics.
关键词： Arthur Ashkin,Optical Tweezers,Single-Molecule Biophysics,Nobel Prize,Physics
更新于2025-09-23 15:21:01
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Nanoscale virtual potentials using optical tweezers
摘要： We combine optical tweezers with feedback to impose arbitrary potentials on a colloidal particle. The feedback trap detects a particle’s position, calculates a force based on an imposed “virtual potential,” and shifts the trap center to generate the desired force. We create virtual harmonic and double-well potentials to manipulate particles. The harmonic potentials can be chosen to be either weaker or stiffer than the underlying optical trap. Using this ?exibility, we create an isotropic trap in three dimensions. Finally, we show that we can create a virtual double-well potential with ?xed well separation and adjustable barrier height. These are accomplished at length scales down to 11 nm, a feat that is dif?cult or impossible to create with standard optical-tweezer techniques such as time sharing, dual beams, or spatial light modulators.
关键词： optical tweezers,colloidal particle,virtual potential,nanoscale,feedback trap
更新于2025-09-23 15:21:01
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Nanoplastic Analysis by On-line Coupling of Raman Microscopy and Field-Flow Fractionation Enabled by Optical Tweezers
摘要： Nanoplastic pollution is of emerging environmental concern, but current analytical approaches are facing limitations in this size range. However, the coupling of nanoparticle separation with chemical characterization bears potential to close this gap. Here, we realize the hyphenation of particle separation / characterization (field-flow fractionation (FFF), UV and multi angle light scattering (MALS)) with subsequent chemical identification by on-line Raman microspectroscopy (RM). The problem of low Raman scattering was overcome by trapping particles with 2D optical tweezers. This setup enabled RM to identify particles of different materials (polymers and inorganic) in the size range from 200 nm to 5 μm, with concentrations in the order of 1 mg/L (109 particles L-1). The hyphenation was realized for asymmetric flow FFF (AF4) and centrifugal FFF (CF3), which separate particles based on different properties. This technique shows potential for application in nanoplastic analysis, as well as many other fields of nanomaterials.
关键词： Nanoplastic,Particle Separation,Optical Tweezers,Raman Microscopy,Field-Flow Fractionation
更新于2025-09-23 15:19:57
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Chiral optical tweezers for optically active particles in the T-matrix formalism
摘要： Modeling optical tweezers in the T-matrix formalism has been of key importance for accurate and efficient calculations of optical forces and their comparison with experiments. Here we extend this formalism to the modeling of chiral optomechanics and optical tweezers where chiral light is used for optical manipulation and trapping of optically active particles. We first use the Bohren decomposition to deal with the light scattering of chiral light on optically active particles. Thus, we show analytically that all the observables (cross sections, asymmetry parameters) are split into a helicity dependent and independent part and study a practical example of a complex resin particle with inner copper-coated stainless steel helices. Then, we apply this chiral T-matrix framework to optical tweezers where a tightly focused chiral field is used to trap an optically active spherical particle, calculate the chiral behaviour of optical trapping stiffnesses and their size scaling, and extend calculations to chiral nanowires and clusters of astrophysical interest. Such general light scattering framework opens perspectives for modeling optical forces on biological materials where optically active amino acids and carbohydrates are present.
关键词： chiral light,T-matrix formalism,optical forces,optically active particles,chiral optical tweezers
更新于2025-09-19 17:15:36