scholarly journals Single-Cell Elasticity Measurement with an Optically Actuated Microrobot

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 882
Author(s):  
István Grexa ◽  
Tamás Fekete ◽  
Judit Molnár ◽  
Kinga Molnár ◽  
Gaszton Vizsnyiczai ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Target Cells ◽  
Lateral Direction ◽  
Two Photon ◽  
Holographic Optical Tweezers ◽  
Feasible Alternative ◽  
A Cell ◽  
Cell Elasticity ◽  
Force Range ◽  
Elasticity Measurement

A cell elasticity measurement method is introduced that uses polymer microtools actuated by holographic optical tweezers. The microtools were prepared with two-photon polymerization. Their shape enables the approach of the cells in any lateral direction. In the presented case, endothelial cells grown on vertical polymer walls were probed by the tools in a lateral direction. The use of specially shaped microtools prevents the target cells from photodamage that may arise during optical trapping. The position of the tools was recorded simply with video microscopy and analyzed with image processing methods. We critically compare the resulting Young’s modulus values to those in the literature obtained by other methods. The application of optical tweezers extends the force range available for cell indentations measurements down to the fN regime. Our approach demonstrates a feasible alternative to the usual vertical indentation experiments.

scholarly journals Micro-Dumbbells—A Versatile Tool for Optical Tweezers

2018 ◽  
Author(s):  
Weronika Lamperska ◽  
Sławomir Drobczyński ◽  
Michał Nawrot ◽  
Piotr Wasylczyk ◽  
Jan Masajada
Keyword(s):  
Laser Beam ◽  
Optical Tweezers ◽  
Optical Trapping ◽  
Viscosity Measurements ◽  
Two Photon ◽  
Vibration Detection ◽  
Holographic Optical Tweezers ◽  
Versatile Tool ◽  
Micro Tool

Manipulation of micro- and nano-sized objects with optical tweezers is a well established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographic optical tweezers. The 40 µm long dumbbell-shaped tool, fabricated with two-photon laser 3D photolithography has two beads for efficient optical trapping and a probing spike on one end. We demonstrate fluids viscosity measurements and vibration detection as examples of possible applications.

Simultaneous printing and deformation of microsystems via two-photon lithography and holographic optical tweezers

2019 ◽  
Vol 6 (2) ◽  
pp. 350-355 ◽  
Author(s):  
Samira Chizari ◽  
Lucas A. Shaw ◽  
Jonathan B. Hopkins
Keyword(s):  
Optical Tweezers ◽  
Strain Energy ◽  
Two Photon ◽  
Holographic Optical Tweezers

Microstructures with embedded strain energy are fabricated by an advanced approach that combines two-photon lithography with holographic optical tweezers.

scholarly journals Diminished LcrV Secretion Attenuates Yersinia pseudotuberculosis Virulence

2007 ◽  
Vol 189 (23) ◽  
pp. 8417-8429 ◽  
Author(s):  
Jeanette E. Bröms ◽  
Matthew S. Francis ◽  
Åke Forsberg
Keyword(s):  
Type Iii Secretion ◽  
Yersinia Pseudotuberculosis ◽  
Signal Sequence ◽  
Infection Model ◽  
Target Cells ◽  
Cell Infection ◽  
Host Cell Membrane ◽  
Type Iii ◽  
A Cell

ABSTRACT Many gram-negative bacterial pathogenicity factors that function beyond the outer membrane are secreted via a contact-dependent type III secretion system. Two types of substrates are predestined for this mode of secretion, namely, antihost effectors that are translocated directly into target cells and the translocators required for targeting of the effectors across the host cell membrane. N-terminal secretion signals are important for recognition of the protein cargo by the type III secretion machinery. Even though such signals are known for several effectors, a consensus signal sequence is not obvious. One of the translocators, LcrV, has been attributed other functions in addition to its role in translocation. These functions include regulation, presumably via interaction with LcrG inside bacteria, and immunomodulation via interaction with Toll-like receptor 2. Here we wanted to address the significance of the specific targeting of LcrV to the exterior for its function in regulation, effector targeting, and virulence. The results, highlighting key N-terminal amino acids important for LcrV secretion, allowed us to dissect the role of LcrV in regulation from that in effector targeting/virulence. While only low levels of exported LcrV were required for in vitro effector translocation, as deduced by a cell infection assay, fully functional export of LcrV was found to be a prerequisite for its role in virulence in the systemic murine infection model.

ROTATIONAL PROPERTIES OF MICRO-SLABS DRIVEN BY LINEARLY-POLARIZED LIGHT

2005 ◽  
Vol 14 (03) ◽  
pp. 375-382 ◽  
Author(s):  
CHIH-LANG LIN ◽  
IRÈNE WANG ◽  
MARC PIERRE ◽  
ISABELLE COLOMBIER ◽  
CHANTAL ANDRAUD ◽  
...  
Keyword(s):  
Optical Tweezers ◽  
Polarized Light ◽  
Polarization Plane ◽  
Light Polarization ◽  
Good Prediction ◽  
Polarization Anisotropy ◽  
Two Photon ◽  
Flat Slabs ◽  
Linearly Polarized ◽  
Optical Torque

We study the rotational motion of objects trapped in a focused laser beam (optical tweezers). Micrometer-sized flat slabs are fabricated using two-photon photopolymerization. These objects, trapped by linearly-polarized light, tend to align parallel to the polarization plane. This alignment effect is attributed to the polarization anisotropy resulting from the object shape and we present a simple electromagnetic approach to estimate the resulting optical torque. Micro-rotors of different sizes are studied experimentally. We characterize the behavior of micro-objects when the light polarization is rotated at constant speed. Our theoretical approach gives a good prediction of how the size of micro-objects affects their rotation efficiency.

Moving average process underlying the holographic–optical–tweezers experiments

2014 ◽  
Vol 53 (10) ◽  
pp. B254 ◽  
Author(s):  
Jakub Ślęzak ◽  
Sławomir Drobczyński ◽  
Karina Weron ◽  
Jan Masajada
Keyword(s):  
Optical Tweezers ◽  
Moving Average ◽  
Average Process ◽  
Moving Average Process ◽  
Holographic Optical Tweezers

scholarly journals CRISPR-mediated isogenic cell-SELEX approach for generating highly specific aptamers against native membrane proteins

2020 ◽  
Author(s):  
Jonah C. Rosch ◽  
Emma H. Neal ◽  
Daniel A. Balikov ◽  
Mohsin Rahim ◽  
Ethan S. Lippmann
Keyword(s):  
Membrane Proteins ◽  
Glucose Transporter ◽  
High Specificity ◽  
Epithelial Cell Line ◽  
Target Cells ◽  
Wild Type ◽  
Simultaneous Exposure ◽  
Affinity Reagents ◽  
A Cell

AbstractIntroductionThe generation of affinity reagents that bind native membrane proteins with high specificity remains challenging. Most in vitro selection paradigms utilize different cell types for positive and negative rounds of selection (where the positive selection is against a cell that expresses the desired membrane protein and the negative selection is against a cell that lacks the protein). However, this strategy can yield affinity reagents that bind unintended membrane proteins on the target cells. To address this issue, we developed a systematic evolution of ligands by exponential enrichment (SELEX) scheme that utilizes isogenic pairs of cells generated via CRISPR techniques.MethodsUsing a Caco-2 epithelial cell line with constitutive Cas9 expression, we knocked out the SLC2A1 gene (encoding the GLUT1 glucose transporter) via lipofection with synthetic gRNAs. Cell-SELEX rounds were carried out against wild-type and GLUT1-null cells using a single-strand DNA (ssDNA) library. Next-generation sequencing (NGS) was used to quantify enrichment of prospective binders to the wild-type cells.Results10 rounds of cell-SELEX were conducted via simultaneous exposure of ssDNA pools to wild-type and GLUT1-null Caco-2 cells under continuous perfusion. The top binders identified from NGS were validated by flow cytometry and immunostaining for their specificity to the GLUT1 receptor.ConclusionsOur data indicate that highly specific aptamers can be isolated with a SELEX strategy that utilizes isogenic cell lines. This approach should be broadly useful for generating affinity reagents that selectively bind to membrane proteins in their native conformations on the cell surface.

scholarly journals Determining Trap Compliances, Microsphere Size Variations, and Response Linearities in Single DNA Molecule Elasticity Measurements with Optical Tweezers

2021 ◽  
Vol 8 ◽  
Author(s):  
Youbin Mo ◽  
Mounir Fizari ◽  
Kristina Koharchik ◽  
Douglas E. Smith
Keyword(s):  
Optical Tweezers ◽  
Dna Elasticity ◽  
Dna Stretching ◽  
Dna Molecule ◽  
Scale Factors ◽  
Length Measurements ◽  
Microsphere Size ◽  
Force Range ◽  
Single Dna Molecule ◽  
Displacement Measurements

We previously introduced the use of DNA molecules for calibration of biophysical force and displacement measurements with optical tweezers. Force and length scale factors can be determined from measurements of DNA stretching. Trap compliance can be determined by fitting the data to a nonlinear DNA elasticity model, however, noise/drift/offsets in the measurement can affect the reliability of this determination. Here we demonstrate a more robust method that uses a linear approximation for DNA elasticity applied to high force range (25–45 pN) data. We show that this method can be used to assess how small variations in microsphere sizes affect DNA length measurements and demonstrate methods for correcting for these errors. We further show that these measurements can be used to check assumed linearities of system responses. Finally, we demonstrate methods combining microsphere imaging and DNA stretching to check the compliance and positioning of individual traps.

scholarly journals Primary generation of cytolytic T lymphocytes in the absence of DNA synthesis.

1979 ◽  
Vol 150 (1) ◽  
pp. 196-201 ◽  
Author(s):  
H R MacDonald ◽  
R K Less
Keyword(s):  
T Lymphocytes ◽  
Dna Synthesis ◽  
Cytolytic Activity ◽  
Target Cells ◽  
Cytolytic T Lymphocytes ◽  
Spleen Cells ◽  
Con A ◽  
A Cell ◽  
Stimulation Of

The requirement for DNA synthesis during the primary differentiation of cytolytic T lymphocytes (CTL) had been investigated. CTL were induced polyclonally in vitro by stimulation of normal C57BL/6 spleen cells with concanavalin A (Con A)and their cytolytic activity was tested against 51Cr-labeled target cells in the presence of Bacto Phytohemagglutinin M. With this system, CTL activity could first be detected 48 h after exposure of spleen cells to Con A. Addition of cytosine arabinoside at concentrations sufficient to reduce DNA synthesis by 95-98% in Con A-stimulated cultures did not significantly inhibit the generation of cytolytic activity on a cell-to-cell basis. These results demonstrate that derepression of the genetic information required for the expression of CTL function can occur in the absence of detectable DNA synthesis.

scholarly journals Precise, contactless measurements of the surface tension of picolitre aerosol droplets

2016 ◽  
Vol 7 (1) ◽  
pp. 274-285 ◽  
Author(s):  
Bryan R. Bzdek ◽  
Rory M. Power ◽  
Stephen H. Simpson ◽  
Jonathan P. Reid ◽  
C. Patrick Royall
Keyword(s):  
Surface Tension ◽  
Optical Tweezers ◽  
Holographic Optical Tweezers ◽  
Contactless Measurements

Precise measurements of the surface tension and viscosity of airborne picolitre droplets can be accomplished using holographic optical tweezers.

Sign in / Sign up

Export Citation Format

Share Document