Measurement of the traction force of biological cells by digital holography.
Ontology highlight
ABSTRACT:
SUBMITTER: Yu X
PROVIDER: S-EPMC3255332 | biostudies-other | 2012 Jan
REPOSITORIES: biostudies-other
Similar Datasets
Project description:We demonstrate digital plasmonic holography for direct in-plane imaging with propagating surface-plasmon waves. Imaging with surface plasmons suffers from the lack of simple in-plane lenses and mirrors. Lens-less digital holography techniques, however, rely on digitally decoding an interference pattern between a reference wave and an object wave. With far-field diffractive optics, this decoding scheme provides a full recording, i.e., a hologram, of the amplitude and phase of the object wave, giving three-dimensional information from a two-dimensional recording. For plasmonics, only a one-dimensional recording is needed, and both the phase and amplitude of the propagating plasmons can be extracted for high-resolution in-plane imaging. Here, we demonstrate lens-less, point-source digital plasmonic holography using two methods to record the plasmonic holograms: a dual-probe near-field scanning optical microscope and lithographically defined circular fluorescent screens. The point-source geometry gives in-plane magnification, allowing for high-resolution imaging with relatively lower-resolution microscope objectives. These results pave the way for a new form of in-plane plasmonic imaging, gathering the full complex wave, without the need for plasmonic mirrors or lenses.
| S-EPMC6107013 | biostudies-literature
Project description:Mechanical traction forces exerted by adherent cells on their surroundings serve an important role in a multitude of cellular and physiological processes including cell motility and multicellular rearrangements. For endothelial cells, contraction also provides a means to disrupt cell-cell junctions during inflammation to increase permeability between blood and interstitial tissue compartments. The degree of contractility exhibited by endothelial cells is influenced by numerous soluble factors, such as thrombin, histamine, lysophosphatidic acid, sphingosine-1-phosphate, and vascular endothelial growth factor (VEGF). Upon binding to cell surface receptors, these agents trigger changes in cytoskeletal organization, adhesion and myosin II activity to varying degrees. While conventional antibody-based biochemical assays are suitable for detecting relatively large changes in biomarkers of contractility in an end-point format, they cannot resolve subtle or rapid changes in contractility and cannot do so noninvasively. To overcome these limitations, we developed an approach to measure the contractile response of single cells exposed to contractility agonists with high spatiotemporal resolution. A previously developed traction force sensor, comprised of dense arrays of elastomeric microposts on which cells are cultured, was combined with custom, semi-automated software developed here to extract strain energy measurements from thousands of time-lapse images of micropost arrays deformed by adherent cells. Using this approach we corroborated the differential effects of known agonists of contractility and characterized the dynamics of their effects. All of these agonists produced a characteristic first-order rise and plateau in forces, except VEGF, which stimulated an early transient spike in strain energy followed by a sustained increase. This novel, two-phase contractile response was present in a subpopulation of cells, was mediated through both VEGFR2 and ROCK activation, and its magnitude was modulated by receptor internalization. Interestingly, the concentration of VEGF could shift the proportion of cells that responded with a spike versus only a gradual increase in forces. Furthermore, cells repeatedly exposed to VEGF were found to contract with different dynamics after pretreatment, suggesting that exposure history can impact the mechanical response. These studies highlight the importance of direct measurements of traction force dynamics as a tool for studies of mechanotransduction.
| S-EPMC3112004 | biostudies-literature
Project description:One of the main drawbacks of Digital Holography (DH) is the coherent nature of the light source, which severely corrupts the quality of holographic reconstructions. Although numerous techniques to reduce noise in DH have provided good results, holographic noise suppression remains a challenging task. We propose a novel framework that combines the concepts of encoding multiple uncorrelated digital holograms, block grouping and collaborative filtering to achieve quasi noise-free DH reconstructions. The optimized joint action of these different image-denoising methods permits the removal of up to 98% of the noise while preserving the image contrast. The resulting quality of the hologram reconstructions is comparable to the quality achievable with non-coherent techniques and far beyond the current state of art in DH. Experimental validation is provided for both single-wavelength and multi-wavelength DH, and a comparison with the most used holographic denoising methods is performed.
| S-EPMC6059929 | biostudies-literature
Project description:Traction Force Microscopy (TFM) computes the forces exerted at the surface of an elastic material by measuring induced deformations in volume. It is used to determine the pattern of the adhesion forces exerted by cells or by cellular assemblies grown onto a soft deformable substrate. Typically, colloidal particles are dispersed in the substrate and their displacement is monitored by fluorescent microscopy. As with any other fluorescent techniques, the accuracy in measuring a particule's position is ultimately limited by the number of evaluated fluorescent photons. Here, we present a TFM technique based on the detection of probe particle displacements by holographic tracking microscopy. We show that nanometer scale resolutions of the particle displacements can be obtained and determine the maximum volume fraction of markers in the substrate. We demonstrate the feasibility of the technique experimentally and measure the three-dimensional force fields exerted by colorectal cancer cells cultivated onto a polyacrylamide gel substrate.
| S-EPMC5813032 | biostudies-literature
Project description:ObjectiveTo enable early prediction of strong traction force vacuum extraction.DesignObservational cohort.SettingKarolinska University Hospital delivery ward, tertiary unit.Population and sample sizeTerm mid and low metal cup vacuum extraction deliveries June 2012-February 2015, n = 277.MethodsTraction forces during vacuum extraction were collected prospectively using an intelligent handle. Levels of traction force were analysed pairwise by subjective category strong versus non-strong extraction, in order to define an objective predictive value for strong extraction.Statistical analysisA logistic regression model based on the shrinkage and selection method lasso was used to identify the predictive capacity of the different traction force variables.PredictorsTotal (time force integral, Newton minutes) and peak traction (Newton) force in the first to third pull; difference in traction force between the second and first pull, as well as the third and first pull respectively. Accumulated traction force at the second and third pull.OutcomeSubjectively categorized extraction as strong versus non-strong.ResultsThe prevalence of strong extraction was 26%. Prediction including the first and second pull: AUC 0,85 (CI 0,80-0,90); specificity 0,76; sensitivity 0,87; PPV 0,56; NPV 0,94. Prediction including the first to third pull: AUC 0,86 (CI 0,80-0,91); specificity 0,87; sensitivity 0,70; PPV 0,65; NPV 0,89.ConclusionTraction force measurement during vacuum extraction can help exclude strong category extraction from the second pull. From the third pull, two-thirds of strong extractions can be predicted.
| S-EPMC5336195 | biostudies-literature
Project description:High-throughput single-cell analysis is a challenging task. Label-free tomographic phase microscopy is an excellent candidate to perform this task. However, in-line tomography is very difficult to implement in practice because it requires a complex set-up for rotating the sample and examining the cell along several directions. We demonstrate that by exploiting the random rolling of cells while they are flowing along a microfluidic channel, it is possible to obtain in-line phase-contrast tomography, if smart strategies for wavefront analysis are adopted. In fact, surprisingly, a priori knowledge of the three-dimensional position and orientation of rotating cells is no longer needed because this information can be completely retrieved through digital holography wavefront numerical analysis. This approach makes continuous-flow cytotomography suitable for practical operation in real-world, single-cell analysis and with a substantial simplification of the optical system; that is, no mechanical scanning or multi-direction probing is required. A demonstration is given for two completely different classes of biosamples: red blood cells and diatom algae. An accurate characterization of both types of cells is reported, despite their very different nature and material content, thus showing that the proposed method can be extended by adopting two alternate strategies of wavefront analysis to many classes of cells.
| S-EPMC6062169 | biostudies-literature
Project description:There has been a compelling demand of fabricating high-resolution complex three-dimensional (3D) structures in nanotechnology. While two-photon lithography (TPL) largely satisfies the need since its introduction, its low writing speed and high cost make it impractical for many large-scale applications. We report a digital holography-based TPL platform that realizes parallel printing with up to 2000 individually programmable laser foci to fabricate complex 3D structures with 90 nm resolution. This effectively improves the fabrication rate to 2,000,000 voxels/sec. The promising result is enabled by the polymerization kinetics under a low-repetition-rate regenerative laser amplifier, where the smallest features are defined via a single laser pulse at 1 kHz. We have fabricated large-scale metastructures and optical devices of up to centimeter-scale to validate the predicted writing speed, resolution, and cost. The results confirm our method provides an effective solution for scaling up TPL for applications beyond laboratory prototyping.
| S-EPMC10043265 | biostudies-literature
Project description:Native cell-material interactions occur on materials differing in their structural composition, chemistry, and physical compliance. While the last two decades have shown the importance of traction forces during cell-material interactions, they have been almost exclusively presented on purely elastic in vitro materials. Yet, most bodily tissue materials exhibit some level of viscoelasticity, which could play an important role in how cells sense and transduce tractions. To expand the realm of cell traction measurements and to encompass all materials from elastic to viscoelastic, this paper presents a general, and comprehensive approach for quantifying 3D cell tractions in viscoelastic materials. This methodology includes the experimental characterization of the time-dependent material properties for any viscoelastic material with the subsequent mathematical implementation of the determined material model into a 3D traction force microscopy (3D TFM) framework. Utilizing this new 3D viscoelastic TFM (3D VTFM) approach, we quantify the influence of viscosity on the overall material traction calculations and quantify the error associated with omitting time-dependent material effects, as is the case for all other TFM formulations. We anticipate that the 3D VTFM technique will open up new avenues of cell-material investigations on even more physiologically relevant time-dependent materials including collagen and fibrin gels.
| S-EPMC4176508 | biostudies-literature
Project description:Quantifying small, rapidly progressing three-dimensional forces generated by cells remains a major challenge towards a more complete understanding of mechanobiology. Traction force microscopy is one of the most broadly applied force probing technologies but ascertaining three-dimensional information typically necessitates slow, multi-frame z-stack acquisition with limited sensitivity. Here, by performing traction force microscopy using fast single-frame astigmatic imaging coupled with total internal reflection fluorescence microscopy we improve the temporal resolution of three-dimensional mechanical force quantification up to 10-fold compared to its related super-resolution modalities. 2.5D astigmatic traction force microscopy (aTFM) thus enables live-cell force measurements approaching physiological sensitivity.
| S-EPMC8042066 | biostudies-literature
Project description:BackgroundLow and mid station vacuum assisted deliveries (VAD) are delicate manual procedures that entail a high degree of subjectivity from the operator and are associated with adverse neonatal outcome. Little has been done to improve the procedure, including the technical development, traction force and the possibility of objective documentation. We aimed to explore if a digital handle with instant haptic feedback on traction force would reduce the neonatal risk during low or mid station VAD.MethodsA two centre, randomised superiority trial at Karolinska University Hospital, Sweden, 2016-2018. Cases were randomised bedside to either a conventional or a digital handle attached to a Bird metal cup (50 mm, 80 kPa). The digital handle measured applied force including an instant notification by vibration when high levels of traction force were predicted according to a predefined algorithm. Primary outcome was a composite of hypoxic ischaemic encephalopathy, intracranial haemorrhage, seizures, death and/or subgaleal hematoma. Three hundred eighty low and mid VAD in each group were estimated to decrease primary outcome from six to 2 %.ResultsAfter 2 years, an interim analyse was undertaken. Meeting the inclusion criteria, 567 vacuum extractions were randomized to the use of a digital handle (n = 296) or a conventional handle (n = 271). Primary outcome did not differ between the two groups: (2.7% digital handle vs 2.6% conventional handle). The incidence of primary outcome differed significantly between the two delivery wards (4% vs 0.9%, p < 0.05). A recalculation of power revealed that 800 cases would be needed in each group to show a decrease in primary outcome from three to 1 %. This was not feasible, and the study therefore closed.ConclusionsThe incidence of primary outcome was lower than estimated and the study was underpowered. However, the difference between the two delivery wards might reflect varying degree of experience of the technical equipment. An objective documentation of the extraction procedure is an attractive alternative in respect to safety and clinical training. To demonstrate improved safety, a multicentre study is required to reach an adequate cohort. This was beyond the scope of the study.Trial registrationClinicalTrials.gov NCT03071783 , March 1, 2017, retrospectively registered.
| S-EPMC7913459 | biostudies-literature