Determination of femto Newton forces and fluid viscosity using optical tweezers: application to Leishmania amazonensis

Fontes, Adriana; Giorgio, Selma; Castro, Archimedes B. de; Neto, Vivaldo Moura; Pozzo, Liliana de Ysasa; Marques, Gustavo P.; Barbosa, L. C.; César, Carlos L.

doi:10.1117/12.586427

Cited by 7 publications

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“…After calibration, assuming a geometrical optics model, by measuring the displacement of the bead from the equilibrium position, it was possible to determine the numerical values for the optical force and consequently for the flagellum force of the parasite. Previous calibration of this procedure against hydrodynamic force showed good results [Fontes et al, 2005]. The displacements of the bead from the equilibrium position were obtained by measuring the scattered light of the laser used in the optical tweezers with a quadrant detector (QP506SD2 -Pacific Sensor Incorporated) [Rice et al, 2003;Rohrbach and Stelzer, 2002;Gittes and Schmidt, 1998; Allersma et al, 1998].…”

Section: Methodsmentioning

confidence: 99%

Studying taxis in real time using optical tweezers: Applications for Leishmania amazonensis parasites

Pozzo

Fontes

Thomaz

et al. 2009

Micron

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Section: Methodsmentioning

confidence: 99%

Studying taxis in real time using optical tweezers: Applications for Leishmania amazonensis parasites

Pozzo

Fontes

Thomaz

et al. 2009

Micron

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“…Previous calibration of this procedure against hydrodynamic force showed good results. 6 All the measurements were carried out at room temperature ͑25°C͒. All the measurements were recorded in real time and captured by the computer.…”

Section: Methodsmentioning

confidence: 99%

Measuring electrical and mechanical properties of red blood cells with double optical tweezers

et al. 2008

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Red blood cell (RBC) aggregation in the blood stream is prevented by the zeta potential created by its negatively charged membrane. There are techniques, however, to decrease the zeta potential and allow cell agglutination, which are the basis of most of antigen-antibody tests used in immunohematology. We propose the use of optical tweezers to measure membrane viscosity, adhesion, zeta potential, and the double layer thickness of charges (DLT) formed around the cell in an electrolytic solution. For the membrane viscosity experiment, we trap a bead attached to RBCs and measure the force to slide one RBC over the other as a function of the velocity. Adhesion is quantified by displacing two RBCs apart until disagglutination. The DLT is measured using the force on the bead attached to a single RBC in response to an applied voltage. The zeta potential is obtained by measuring the terminal velocity after releasing the RBC from the trap at the last applied voltage. We believe that the methodology proposed here can provide information about agglutination, help to improve the tests usually performed in transfusion services, and be applied for zeta potential measurements in other samples.

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“…The displacement of the bead due to the parasite's flagellum propulsion was then measured to determine the numerical values for the optical force and, consequently, for the force of the parasite. Previous calibration of this procedure against hydrodynamic force showed good results [1].By trapping and moving T. cruzi to the vicinities of midgut cells we observed a change of behavior of the parasite. It projects its flagellum towards the cell as show in figure 1.…”

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confidence: 66%

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confidence: 99%

Trypanosoma cruzi Quantitative Chemotaxis Characterization by Optical Tweezers

et al. 2009

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One of the fundamental goals in parasitology is the fully understanding of parasite-host cell interactions. This is still more important when it comes to non-curable diseases, like Chagas disease caused by Trypanosoma cruzi. In this work, we propose a methodology to study microorganisms chemotaxis in real time using an Optical Tweezers system. Quantitative measurements of taxis, mainly chemotaxis, are essential to elucidate the infection process. For a better understanding of chemotaxis it is necessary to know not only the sense and direction of the parasite's force but also its intensity. Optical Tweezers allowed real time measurements of the force vectors, strength and direction, of living parasites under chemical or other kinds of gradients. This seems to be the ideal tool to perform observations of taxis response of cells and microorganisms with high sensitivity to capture instantaneous responses to a given stimulus. We applied this methodology to investigate the T. cruzi under distinct situations: the parasite alone and in the presence of its insect-vector Rhodnius prolixus. A quadrant detector allowed us to measure the sense and direction of the forces.The propulsion forces of the flagellum of the protozoan was measured with an optical tweezers by using a polystyrene bead, connected to the parasite, as a force transducer. We assume a geometrical optics model to calibrate the force as a function of the bead displacement from the equilibrium position. The displacement of the bead due to the parasite's flagellum propulsion was then measured to determine the numerical values for the optical force and, consequently, for the force of the parasite. Previous calibration of this procedure against hydrodynamic force showed good results [1].By trapping and moving T. cruzi to the vicinities of midgut cells we observed a change of behavior of the parasite. It projects its flagellum towards the cell as show in figure 1. This clearly shows how the microorganism (inside the yellow circle) can sense the presence of others cells and respond to it. This behavior contrasts with its behavior more than 50 µm away from the midgut cells where it just shows an erratic without any prefered direction movement. This is confirmed by quantitative measurements of chemotaxis.

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Determination of femto Newton forces and fluid viscosity using optical tweezers: application to Leishmania amazonensis

Cited by 7 publications

References 0 publications

Studying taxis in real time using optical tweezers: Applications for Leishmania amazonensis parasites

Studying taxis in real time using optical tweezers: Applications for Leishmania amazonensis parasites

Measuring electrical and mechanical properties of red blood cells with double optical tweezers

Trypanosoma cruzi Quantitative Chemotaxis Characterization by Optical Tweezers

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