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David Needham - One of the best experts on this subject based on the ideXlab platform.
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Micro-Surface and -Interfacial Tensions Measured Using the Micropipette Technique: Applications in Ultrasound-Microbubbles, Oil-Recovery, Lung-Surfactants, Nanoprecipitation, and Microfluidics
MDPI AG, 2019Co-Authors: David Needham, Koji Kinoshita, Anders UtoftAbstract:This review presents a series of measurements of the surface and interfacial tensions we have been able to make using the Micropipette technique. These include: equilibrium tensions at the air-water surface and oil-water interface, as well as equilibrium and dynamic adsorption of water-soluble surfactants and water-insoluble and lipids. At its essence, the Micropipette technique is one of capillary-action, glass-wetting, and applied pressure. A Micropipette, as a parallel or tapered shaft, is mounted horizontally in a microchamber and viewed in an inverted microscope. When filled with air or oil, and inserted into an aqueous-filled chamber, the position of the surface or interface meniscus is controlled by applied Micropipette pressure. The position and hence radius of curvature of the meniscus can be moved in a controlled fashion from dimensions associated with the capillary tip (~5–10 μm), to back down the Micropipette that can taper out to 450 μm. All measurements are therefore actually made at the microscale. Following the Young–Laplace equation and geometry of the capillary, the surface or interfacial tension value is simply obtained from the radius of the meniscus in the tapered pipette and the applied pressure to keep it there. Motivated by Franklin’s early experiments that demonstrated molecularity and monolayer formation, we also give a brief potted-historical perspective that includes fundamental surfactancy driven by margarine, the first use of a Micropipette to circuitously measure bilayer membrane tensions and free energies of formation, and its basis for revolutionising the study and applications of membrane ion-channels in Droplet Interface Bilayers. Finally, we give five examples of where our measurements have had an impact on applications in micro-surfaces and microfluidics, including gas microbubbles for ultrasound contrast; interfacial tensions for micro-oil droplets in oil recovery; surface tensions and tensions-in-the surface for natural and synthetic lung surfactants; interfacial tension in nanoprecipitation; and micro-surface tensions in microfluidics
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new measurements of lung surfactant interfacial tension with Micropipette manipulation technique
Biophysical Journal, 2014Co-Authors: Koji Kinoshita, Kasper Glud, David NeedhamAbstract:Approximately 50,000-190,000 adults and 24,000 newborn per year in the U.S. develop Acute- and Neonatal-Respiratory Distress Syndrome (ARDS&NRDS), respectively. For more than a couple of decades, many researchers have been tackling the problem of how to investigate lung surfactant behavior, especially of the relationships between the lipids and the natural lung surfactant proteins, by using techniques such as the Langmuir-Trough or Pulsating Bubble Surfactometer (PBS). Currently, we are developing a new method of the Micropipette manipulation technique for lung surfactant surface tension measurement. The technique builds on previous studies that used a simple tapered micropipet to measure liquid-gas and liquid-liquid interfacial tension [1-2]. Working with Micropipettes that contain the aqueous phase but viewed in air allows us to measure interfacial tensions at controlled pressures and interfacial radii when lung surfactant material is introduced, as in delivery of liquids to the lung alveoli. The new measurements of calf lung surfactant, Infasurf, at the aqueous-air interface showed how the interfacial tension γ at 37 degree Celsius was rapidly reduced from 70.3 to 21.1 ± 0.1 mN/m. One of the advantages of this technique is that by using a second delivery pipette it can be used to observe kinetic processes like adsorption, condensation and desorption of interfacial materials. In order to provide a reversed cone shape for the delivery measurements, we modified the pipette shape to be "trumpet-shaped". We will present more details at the meeting regarding lung surfactants and synthetic systems that have been studied.References[1–2] Lee, S., D. H. Kim, and D. Needham, Langmuir, 2001. 17: 5537 & 5544.
Geza Nagy - One of the best experts on this subject based on the ideXlab platform.
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solid contact Micropipette ion selective electrode ii potassium electrode for secm and in vivo applications
Electroanalysis, 2009Co-Authors: Gergely Gyetvai, Livia Nagy, Ari Ivaska, Istvan Hernadi, Geza NagyAbstract:Micropipette ion selective electrodes are very small, but fragile, short-life time sensors with very high resistance. Their high resistance is a draw back considering application in scanning electrochemical microscopy (SECM) and in life sciences. New, low resistance potassium Micropipette electrodes were prepared, and applied. The electrode contains solid internal contact made of a carbon fiber lowered down all the way close to the orifice of the Micropipette. The internal contact potential was kept constant by applying a doped, electrochemically prepared PEDOT coating on the fiber surface. The electrode performed well in in vivo experiments both in plant and animal tissue without capacitance neutralization and in SECM.
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solid contact Micropipette ion selective electrode for potentiometric secm
Electroanalysis, 2007Co-Authors: Gergely Gyetvai, Livia Nagy, Ari Ivaska, Geza Nagy, Soren SundblomAbstract:New solid contact ammonium Micropipette electrodes (ISE), well applicable in scanning electrochemical microscopy are reported. The solid contact was made of a PEDOT nanowire coated carbon fiber, lowered down close to the orifice, and dipped inside the cocktail being in the pipette tip. This configuration provided low electrical resistance and good potential stability. Submicron tip size, usual in case of Micropipette ISE-s easily can be fabricated in this way. The applicability of the electrode in SECM has been proved in SG/TC mode imaging urease enzyme active spots in urea solutions.
Yu Sun - One of the best experts on this subject based on the ideXlab platform.
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robotic Micropipette aspiration of biological cells
International Symposium on Experimental Robotics, 2013Co-Authors: Ehsan Shojaeibaghini, Yu SunAbstract:This paper presents a system for mechanically characterizing single cells using automated Micropipette aspiration. Using vision-based control and position control, the system controls a micromanipulator, a motorized translation stage, and a custom-built pressure system to position a Micropipette (4 μm opening) to approach a cell, form a seal, and aspirate the cell into the Micropipette for quantifying the cell’s elastic and viscoelastic parameters as well as viscosity. Image processing algorithms were developed to provide controllers with real-time visual feedback and to accurately measure cell deformation behavior on line. Experiments on both solid-like and liquid-like cells demonstrated that the system is capable of efficiently performing single-cell Micropipette aspiration and has low operator skill requirements.
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controlled positioning of biological cells inside a Micropipette
International Conference on Robotics and Automation, 2012Co-Authors: Xuping Zhang, Robert F Casper, Navid Esfandiari, Clement H C Leung, Yu SunAbstract:Manipulating single cells with a Micropipette is the oldest, yet still a widely used technique. This paper discusses the positioning of a single cell to a target position inside the Micropipette after the cell is aspirated into the Micropipette. Due to the small volume of a single cell (pico-liter) and nonlinear dynamics involved, this task has high skill requirements and is labor intensive in manual operation that is solely based on trial and error and has high failure rates. We present automated techniques in this paper for achieving this task. Computer vision algorithm was developed to track a single cell inside a Micropipette for automated single-cell positioning. A closed-loop robust controller integrating the dynamics of cell motion was designed to accurately and efficiently position the cell to a target position inside the Micropipette. The system achieved high success rates of 97% for cell tracking (n=100) and demonstrated its capability of accurately positioning a cell inside the Micropipette within 8 seconds (vs. 25 seconds by highly skilled operators).
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cell contour tracking and data synchronization for real time high accuracy Micropipette aspiration
IEEE Transactions on Automation Science and Engineering, 2009Co-Authors: Xinyu Liu, Yifei Wang, Yu SunAbstract:This paper presents an automated cell contour visual measurement technique and a data synchronization mechanism for real-time, high-accuracy mechanical characterization of individual cells with Micropipette aspiration. A computer vision tracking algorithm is developed for automatically measuring cell deformation parameters in real time (30 Hz) with a resolution down to 0.21 pixel, significantly enhancing the accuracy and efficiency of Micropipette aspiration. To achieve a high characterization accuracy, the cell deformations and applied pressure changes are precisely synchronized using a data synchronization mechanism. Experimental results on both solid-like cells (interstitial cells) and liquid-like cells (neutrophils) quantitatively demonstrate that the visual tracking algorithm is capable of significantly increasing the efficiency and accuracy of Micropipette aspiration. Among several characterized mechanical parameters, the viscoelastic properties of porcine aortic valve interstitial cells were, for the first time, quantified in this study.
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real time high accuracy Micropipette aspiration for characterizing mechanical properties of biological cells
International Conference on Robotics and Automation, 2007Co-Authors: Xinyu Liu, Yifei Wang, Yu SunAbstract:This paper presents a Micropipette aspiration system and a cell contour visual tracking algorithm for realtime, high-accuracy mechanical characterization of individual cells. The computer vision tracking algorithm measures cell deformation parameters in real time (30Hz) with a resolution down to 0.21 pixel, significantly enhancing the accuracy and efficiency of the Micropipette aspiration technique. Representing another advantage over manual measurements in terms of characterization accuracies, the Micropipette aspiration system features precise synchronization between cell deformations and applied pressure changes. Experimental results on both solid-like cells (interstitial cells) and liquid-like cells (neutrophils) demonstrate the effectiveness of the system and the visual tracking algorithm. Among several characterized mechanical parameters, the viscoelastic properties of porcine aortic valve interstitial cells were, for the first time, quantified in this study.
Jamshed Ali - One of the best experts on this subject based on the ideXlab platform.
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inorganic arsenic speciation in water samples by miniaturized solid phase microextraction using a new polystyrene polydimethyl siloxane polymer in Micropipette tip of syringe system
Talanta, 2016Co-Authors: Jamshed Ali, Mustafa Tuzen, Tasneem Gul Kazi, Baki HazerAbstract:The polymer, polystyrene polydimethyl siloxane was loaded into the Micropipette tip of the syringe system as an adsorbent to developed miniaturized solid phase microextraction. Standard solutions of arsenate and arsenite were passed through the adsorbent loaded in Micropipette tip to check the adsorption behaviors. It was observed that arsenate adsorbed on the polystyrene polydimethyl siloxane in the pH rang of 6-8, while arsenite was directly passed through the Micropipette tip of syringe system. The adsorbed arsenate in Micropipette tip of syringe system were eluted by 1.0M hydrochloric acid. The total inorganic arsenic contents were obtained by the addition of oxidizing agent potassium permanganate into the studied samples before passing to the Micropipette tip of syringe system. Arsenite concentration in water samples were measured by subtracting arsenate from total inorganic arsenic concentration. Different characteristics which effect the determination of arsenate specie like amount of adsorbent, adsorption capacity, pH, pulled and pushed cycles for adsorption and desorption, volume of sample, eluent type and it volume were also studied in detail. Enrichment factor and detection limit of arsenate by desired method were 218 and 6.9ngL-1 respectively. The relative standard deviation was 4.1% (n=10, C=0.12µgL-1). Accuracy of the desired technique was confirmed by analysis of the CRMs (Lake Ontario Water TM-28.3 and Riverine Water NRCC-SLRS-4). Desired technique was significantly useful for determination of the total arsenic, arsenate, and arsenite contents in different natural water samples.
Julien Husson - One of the best experts on this subject based on the ideXlab platform.
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Micropipette force probe to quantify single cell force generation application to t cell activation
Molecular Biology of the Cell, 2017Co-Authors: Avin Babataheri, Abdul I. Barakat, Anna Sawicka, Stephanie Dogniaux, David Gonzalezrodriguez, Claire Hivroz, Julien HussonAbstract:We describe the Micropipette force probe, a novel technique that uses a Micropipette as a flexible cantilever that aspirates a coated microbead and brings it into contact with a cell. We apply the ...
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Characterizing Cell Adhesion by Using Micropipette Aspiration
Biophysical Journal, 2015Co-Authors: Brenna Hogan, Avin Babataheri, Abdul I. Barakat, Yongyun Hwang, Julien HussonAbstract:We have developed a technique to directly quantify cell-substrate adhesion force using Micropipette aspiration. The Micropipette is positioned perpendicular to the surface of an adherent cell and a constant-rate aspiration pressure is applied. Since the Micropipette diameter and the aspiration pressure are our control parameters, we have direct knowledge of the aspiration force, whereas the cell behavior is monitored either in brightfield or interference reflection microscopy. This setup thus allows us to explore a range of geometric parameters, such as projected cell area, adhesion area, or pipette size, as well as dynamical parameters such as the loading rate. We find that cell detachment is a well-defined event occurring at a critical aspiration pressure, and that the detachment force scales with the cell adhesion area (for a given Micropipette diameter and loading rate), which defines a critical stress. Taking into account the cell adhesion area, intrinsic parameters of the adhesion bonds, and the loading rate, a minimal model provides an expression for the critical stress that helps rationalize our experimental results.