scholarly journals New tools to study biophysical properties of single molecules and single cells

2007 ◽  
Vol 79 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Márcio S. Rocha ◽  
Oscar N. Mesquita
Keyword(s):  
Optical Tweezers ◽  
Osmotic Shock ◽  
Single Cells ◽  
Single Molecules ◽  
Numerical Aperture ◽  
Single Individual ◽  
Biophysical Properties ◽  
Individual Object ◽  
Transparent Objects ◽  
Volume Measurements

We present a review on two new tools to study biophysical properties of single molecules and single cells. A laser incident through a high numerical aperture microscope objective can trap small dielectric particles near the focus. This arrangement is named optical tweezers. This technique has the advantage to permit manipulation of a single individual object. We use optical tweezers to measure the entropic elasticity of a single DNA molecule and its interaction with the drug Psoralen. Optical tweezers are also used to hold a kidney cell MDCK away from the substrate to allow precise volume measurements of this single cell during an osmotic shock. This procedure allows us to obtain information about membrane water permeability and regulatory volume increase. Defocusing microscopy is a recent technique invented in our laboratory, which allows the observation of transparent objects, by simply defocusing the microscope in a controlled way. Our physical model of a defocused microscope shows that the image contrast observed in this case is proportional to the defocus distance and to the curvature of the transparent object. Defocusing microscopy is very useful to study motility and mechanical properties of cells. We show here the application of defocusing microscopy to measurements of macrophage surface fluctuations and their influence on phagocytosis.

scholarly journals Nano‐Optical Tweezers: Methods and Applications for Trapping Single Molecules and Nanoparticles

ChemPhysChem ◽  
2021 ◽  
Vol 22 (14) ◽  
pp. 1408-1408
Author(s):  
Joshua D. Kolbow ◽  
Nathan C. Lindquist ◽  
Christopher T. Ertsgaard ◽  
Daehan Yoo ◽  
Sang‐Hyun Oh
Keyword(s):  
Optical Tweezers ◽  
Single Molecules

A microfluidic device for reversible environmental changes around single cells using optical tweezers for cell selection and positioning

Lab on a Chip ◽  
2010 ◽  
Vol 10 (5) ◽  
pp. 617-625 ◽  
Author(s):  
Emma Eriksson ◽  
Kristin Sott ◽  
Fredrik Lundqvist ◽  
Martin Sveningsson ◽  
Jan Scrimgeour ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Microfluidic Device ◽  
Environmental Changes ◽  
Single Cells ◽  
Cell Selection

scholarly journals Mie scatter corrections in single cell infrared microspectroscopy

2016 ◽  
Vol 187 ◽  
pp. 235-257 ◽  
Author(s):  
Tatiana Konevskikh ◽  
Rozalia Lukacs ◽  
Reinhold Blümel ◽  
Arkadi Ponossov ◽  
Achim Kohler
Keyword(s):  
Iterative Algorithm ◽  
Single Cells ◽  
Scatter Correction ◽  
Numerical Aperture ◽  
Mie Scattering ◽  
Infrared Light ◽  
Approximation Formula ◽  
Meta Model ◽  
Independent Parameters ◽  
Absorbance Spectra

Strong Mie scattering signatures hamper the chemical interpretation and multivariate analysis of the infrared microscopy spectra of single cells and tissues. During recent years, several numerical Mie scatter correction algorithms for the infrared spectroscopy of single cells have been published. In the paper at hand, we critically reviewed existing algorithms for the correction of Mie scattering and suggest improvements. We developed an iterative algorithm based on Extended Multiplicative Scatter Correction (EMSC), for the retrieval of pure absorbance spectra from highly distorted infrared spectra of single cells. The new algorithm uses the van de Hulst approximation formula for the extinction efficiency employing a complex refractive index. The iterative algorithm involves the establishment of an EMSC meta-model. While existing iterative algorithms for the correction of resonant Mie scattering employ three independent parameters for establishing a meta-model, we could decrease the number of parameters from three to two independent parameters, which reduced the calculation time for the Mie scattering curves for the iterative EMSC meta-model by a factor of 10. Moreover, by employing the Hilbert transform for evaluating the Kramers–Kronig relations based on a FFT algorithm in Matlab, we further improved the speed of the algorithm by a factor of 100. For testing the algorithm we simulate distorted apparent absorbance spectra by utilizing the exact theory for the scattering of infrared light at absorbing spheres, taking into account the high numerical aperture of infrared microscopes employed for the analysis of single cells and tissues. In addition, the algorithm was applied to measured absorbance spectra of single lung cancer cells.

scholarly journals Strongly Focused Circularly Polarized Optical Vortices Regulated by a Fractal Conical Lens

2019 ◽  
Vol 10 (1) ◽  
pp. 28
Author(s):  
Zhirong Liu ◽  
Kelin Huang ◽  
Anlian Yang ◽  
Xun Wang ◽  
Philip H. Jones
Keyword(s):  
Angular Momentum ◽  
Optical Tweezers ◽  
Numerical Aperture ◽  
Optical Element ◽  
Optical Vortex ◽  
Optical Vortices ◽  
Circularly Polarized ◽  
Strong Focusing ◽  
New Type ◽  
Vortex Beams

In this paper, a recently-proposed pure-phase optical element, the fractal conical lens (FCL), is introduced for the regulation of strongly-focused circularly-polarized optical vortices in a high numerical aperture (NA) optical system. Strong focusing characteristics of circularly polarized optical vortices through a high NA system in cases with and without a FCL are investigated comparatively. Moreover, the conversion between spin angular momentum (SAM) and orbital angular momentum (OAM) of the focused optical vortex in the focal vicinity is also analyzed. Results revealed that a FCL of different stage S could significantly regulate the distributions of tight focusing intensity and angular momentum of the circularly polarized optical vortex. The interesting results obtained here may be advantageous when using a FCL to shape vortex beams or utilizing circularly polarized vortex beams to exploit new-type optical tweezers.

scholarly journals Manipulation of Suspended Single Cells by Microfluidics and Optical Tweezers

2010 ◽  
Vol 3 (3) ◽  
pp. 213-228 ◽  
Author(s):  
Nathalie Nève ◽  
Sean S. Kohles ◽  
Shelley R. Winn ◽  
Derek C. Tretheway
Keyword(s):  
Optical Tweezers ◽  
Single Cells

scholarly journals Connecting the Dots between Mechanosensitive Channel Abundance, Osmotic Shock, and Survival at Single-Cell Resolution

2018 ◽  
Vol 200 (23) ◽  
Author(s):  
Griffin Chure ◽  
Heun Jin Lee ◽  
Akiko Rasmussen ◽  
Rob Phillips
Keyword(s):  
Cell Survival ◽  
Single Cell ◽  
Osmotic Shock ◽  
Single Cells ◽  
Mechanosensitive Channel ◽  
Membrane Tension ◽  
Wild Type ◽  
Content Type ◽  
E Coli ◽  
Structural Methods

ABSTRACTRapid changes in extracellular osmolarity are one of many insults microbial cells face on a daily basis. To protect against such shocks,Escherichia coliand other microbes express several types of transmembrane channels that open and close in response to changes in membrane tension. InE. coli, one of the most abundant channels is the mechanosensitive channel of large conductance (MscL). While this channel has been heavily characterized through structural methods, electrophysiology, and theoretical modeling, our understanding of its physiological role in preventing cell death by alleviating high membrane tension remains tenuous. In this work, we examine the contribution of MscL alone to cell survival after osmotic shock at single-cell resolution using quantitative fluorescence microscopy. We conducted these experiments in anE. colistrain which is lacking all mechanosensitive channel genes save for MscL, whose expression was tuned across 3 orders of magnitude through modifications of the Shine-Dalgarno sequence. While theoretical models suggest that only a few MscL channels would be needed to alleviate even large changes in osmotic pressure, we find that between 500 and 700 channels per cell are needed to convey upwards of 80% survival. This number agrees with the average MscL copy number measured in wild-typeE. colicells through proteomic studies and quantitative Western blotting. Furthermore, we observed zero survival events in cells with fewer than ∼100 channels per cell. This work opens new questions concerning the contribution of other mechanosensitive channels to survival, as well as regulation of their activity.IMPORTANCEMechanosensitive (MS) channels are transmembrane protein complexes which open and close in response to changes in membrane tension as a result of osmotic shock. Despite extensive biophysical characterization, the contribution of these channels to cell survival remains largely unknown. In this work, we used quantitative video microscopy to measure the abundance of a single species of MS channel in single cells, followed by their survival after a large osmotic shock. We observed total death of the population with fewer than ∼100 channels per cell and determined that approximately 500 to 700 channels were needed for 80% survival. The number of channels we found to confer nearly full survival is consistent with the counts of the numbers of channels in wild-type cells in several earlier studies. These results prompt further studies to dissect the contribution of other channel species to survival.

scholarly journals Construction of 3D Cellular Composites with Stem Cells Derived from Adipose Tissue and Endothelial Cells by Use of Optical Tweezers in a Natural Polymer Solution

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1759 ◽  
Author(s):  
Takehiro Yamazaki ◽  
Toshifumi Kishimoto ◽  
Paweł Leszczyński ◽  
Koichiro Sadakane ◽  
Takahiro Kenmotsu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Adipose Tissue ◽  
Optical Tweezers ◽  
Single Cells ◽  
Three Dimensional ◽  
Cell Types ◽  
Cellular Interactions ◽  
Research Fields ◽  
Wide Range

To better understand the regulation and function of cellular interactions, three-dimensional (3D) assemblies of single cells and subsequent functional analysis are gaining popularity in many research fields. While we have developed strategies to build stable cellular structures using optical tweezers in a minimally invasive state, methods for manipulating a wide range of cell types have yet to be established. To mimic organ-like structures, the construction of 3D cellular assemblies with variety of cell types is essential. Our recent studies have shown that the presence of nonspecific soluble polymers in aqueous solution is the key to creating stable 3D cellular assemblies efficiently. The present study further expands on the construction of 3D single cell assemblies using two different cell types. We have successfully generated 3D cellular assemblies, using GFP-labeled adipose tissue-derived stem cells and endothelial cells by using optical tweezers. Our findings will support the development of future applications to further characterize cellular interactions in tissue regeneration.

scholarly journals Digital Microfluidics for Single Bacteria Capture and Selective Retrieval Using Optical Tweezers

Micromachines ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 308 ◽  
Author(s):  
Phalguni Tewari Kumar ◽  
Deborah Decrop ◽  
Saba Safdar ◽  
Ioannis Passaris ◽  
Tadej Kokalj ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Cell Sorting ◽  
Magnetic Beads ◽  
Single Cells ◽  
Digital Microfluidics ◽  
Cell Behavior ◽  
Bacterial Cells ◽  
Microfluidic Platforms ◽  
Dynamic Cell ◽  
Downstream Analysis

When screening microbial populations or consortia for interesting cells, their selective retrieval for further study can be of great interest. To this end, traditional fluorescence activated cell sorting (FACS) and optical tweezers (OT) enabled methods have typically been used. However, the former, although allowing cell sorting, fails to track dynamic cell behavior, while the latter has been limited to complex channel-based microfluidic platforms. In this study, digital microfluidics (DMF) was integrated with OT for selective trapping, relocation, and further proliferation of single bacterial cells, while offering continuous imaging of cells to evaluate dynamic cell behavior. To enable this, magnetic beads coated with Salmonella Typhimurium-targeting antibodies were seeded in the microwell array of the DMF platform, and used to capture single cells of a fluorescent S. Typhimurium population. Next, OT were used to select a bead with a bacterium of interest, based on its fluorescent expression, and to relocate this bead to a different microwell on the same or different array. Using an agar patch affixed on top, the relocated bacterium was subsequently allowed to proliferate. Our OT-integrated DMF platform thus successfully enabled selective trapping, retrieval, relocation, and proliferation of bacteria of interest at single-cell level, thereby enabling their downstream analysis.

Microfluidics Supporting an Optical Instrument for Multimodal Single Cell Biomechanics

2007 ◽  
Author(s):  
Nathalie Ne`ve ◽  
James K. Lingwood ◽  
Shelley R. Winn ◽  
Derek C. Tretheway ◽  
Sean S. Kohles
Keyword(s):  
Particle Image Velocimetry ◽  
Hydrostatic Pressure ◽  
Single Cell ◽  
Optical Tweezers ◽  
Particle Image ◽  
Single Cells ◽  
Optical Instrument ◽  
Image Velocimetry ◽  
Wide Range ◽  
Induced Stresses

Interfacing a novel micron-resolution particle image velocimetry and dual optical tweezers system (μPIVOT) with microfluidics facilitates the exposure of an individual biologic cell to a wide range of static and dynamic mechanical stress conditions. Single cells can be manipulated in a sequence of mechanical stresses (hydrostatic pressure variations, tension or compression, as well as shear and extensional fluid induced stresses) while measuring cellular deformation. The unique multimodal load states enable a new realm of single cell biomechanical studies.

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