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1,134 results on '"Van Leeuwen, Ton G."'

9. Simultaneous measurement of localized diffusion and flow using optical coherence tomography

Author

Weiss, Nicolás, van Leeuwen, Ton G., and Kalkman, Jeroen

Subjects
Physics - Optics, Physics - Fluid Dynamics, Physics - Medical Physics
Abstract

We report on the simultaneous and localized measurements of the diffusion coefficient and flow velocity based on the normalized autocorrelation function using optical coherence tomography (OCT). Our results on a flowing solution of polystyrene spheres show that the flow velocity and the diffusion coefficient can be reliably estimated in a regime determined by the sample diffusivity, the local flow velocity, and the Gaussian beam waist. We experimentally show that a smaller beam waist results in an improvement of the velocity sensitivity at cost of the precision and accuracy of the estimation of the diffusion coefficient. Further, we show that the decay of the OCT autocorrelation due to flow depends only on the Gaussian beam waist irrespective of the sample position with respect to the focus position.

Published
2014
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10. Poloxamer-188 as a wetting agent for microfluidic resistive pulse sensing measurements of extracellular vesicles.

Author

Shahsavari, Mona, Nieuwland, Rienk, van Leeuwen, Ton G., and van der Pol, Edwin

Subjects
WETTING agents, EXTRACELLULAR vesicles, BLOOD plasma, SERUM albumin, VESICLES (Cytology), FLOW cytometry, EXTRACELLULAR fluid
Abstract

Introduction: Microfluidic resistive pulse sensing (MRPS) can determine the concentration and size distribution of extracellular vesicles (EVs) by measuring the electrical resistance of single EVs passing through a pore. To ensure that the sample flows through the pore, the sample needs to contain a wetting agent, such as bovine serum albumin (BSA). BSA leaves EVs intact but occasionally results in unstable MRPS measurements. Here, we aim to find a new wetting agent by evaluating Poloxamer-188 and Tween-20. Methods: An EV test sample was prepared using an outdated erythrocyte blood bank concentrate. The EV test sample was diluted in Dulbecco's phosphate-buffered saline (DPBS) or DPBS containing 0.10% BSA (w/v), 0.050% Poloxamer-188 (v/v) or 1.00% Tween-20 (v/v). The effect of the wetting agents on the concentration and size distribution of EVs was determined by flow cytometry. To evaluate the precision of sample volume determination with MRPS, the interquartile range (IQR) of the particles transit time through the pore was examined. To validate that DPBS containing Poloxamer-188 yields reliable MRPS measurements, the repeatability of MRPS in measuring blood plasma samples was examined. Results: Flow cytometry results show that the size distribution of EVs in Tween 20, in contrast to Poloxamer-188, differs from the control measurements (DPBS and DPBS containing BSA). MRPS results show that Poloxamer-188 improves the precision of sample volume determination compared to BSA and Tween-20, because the IQR of the transit time of EVs in the test sample is 11 μs, which is lower than 56 μs for BSA and 16 μs for Tween-20. Furthermore, the IQR of the transit time of particles in blood samples with Poloxamer-188 are 14, 16, and 14 μs, which confirms the reliability of MRPS measurements. Conclusion: The solution of 0.050% Poloxamer-188 in DPBS does not lyse EVs and results in repeatable and unimpeded MRPS measurements. [ABSTRACT FROM AUTHOR]

Published
2024
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17. The 'nanobig rods' class of gold nanorods: optimized dimensions for improved in vivo therapeutic and imaging efficacy

Author

Ungureanu, Constantin, Koning, Gerben A., van Leeuwen, Ton G., and Manohar, Srirang

Subjects
Physics - Medical Physics
Abstract

Currently, gold nanorods can be synthesized in a wide range of sizes. However, for intended biological applications gold nanorods with approximate dimensions 50 nm x 15 nm are used. We investigate by computer simulation the effect of particle dimensions on the optical and thermal properties in the context of the specific applications of photoacoustic imaging. In addition we discuss the influence of particle size in overcoming the following biophysical barriers when administrated in vivo: extravasation, avoidance of uptake by organs of the reticuloendothelial system, penetration through the interstitium, binding capability and uptake by the target cells. Although more complex biological influences can be introduced in future analysis, the present work illustrates that larger gold nanorods, designated by us as "nanobig rods", may perform relatively better at meeting the requirements for successful in vivo applications compared to their smaller counterparts which are conventionally used.

Published
2013
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19. Speed-of-sound compensated photoacoustic tomography for accurate imaging

Author

Jose, Jithin, Willemink, Rene G. H., Steenbergen, Wiendelt, Slump, Cornelis H., van Leeuwen, Ton G., and Manohar, Srirang

Subjects
Physics - Medical Physics
Abstract

In most photoacoustic (PA) measurements, variations in speed-of-sound (SOS) of the subject are neglected under the assumption of acoustic homogeneity. Biological tissue with spatially heterogeneous SOS cannot be accurately reconstructed under this assumption. We present experimental and image reconstruction methods with which 2-D SOS distributions can be accurately acquired and reconstructed, and with which the SOS map can be used subsequently to reconstruct highly accurate PA tomograms. We begin with a 2-D iterative reconstruction approach in an ultrasound transmission tomography (UTT) setting, which uses ray refracted paths instead of straight ray paths to recover accurate SOS images of the subject. Subsequently, we use the SOS distribution in a new 2-D iterative approach, where refraction of rays originating from PA sources are accounted for in accurately retrieving the distribution of these sources. Both the SOS reconstruction and SOS-compensated PA reconstruction methods utilize the Eikonal equation to model acoustic wavefront propagation, which is solved using a high accuracy fast marching method (HAFMM). We validate the new reconstruction algorithms using numerical phantoms. For experiments we use the PER-PACT method which can be used to simultaneously acquire SOS and PA data from subjects. We test the reconstruction algorithms using experimental data acquired with the PER-PACT setup from challenging physical phantoms. The results show that it is important to take SOS inhomogeneities into account. The iterative reconstruction algorithms, that model acoustic refractive effects, yield artifact-free highly accurate images. Our approach of using the hybrid measurement method and the new reconstruction algorithms, is successful in substantially improving the quality of PA images with a minimization of blurring and artefacts., Comment: Accepted Medical Physics (American Association of Physicists in Medicine). Date of submission 28 May 2012; date of acceptance 15 October 2012

Published
2012
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31. A compendium of single extracellular vesicle flow cytometry

Author

Welsh, Joshua A., primary, Arkesteijn, Ger J. A., additional, Bremer, Michel, additional, Cimorelli, Michael, additional, Dignat‐George, Françoise, additional, Giebel, Bernd, additional, Görgens, André, additional, Hendrix, An, additional, Kuiper, Martine, additional, Lacroix, Romaric, additional, Lannigan, Joanne, additional, van Leeuwen, Ton G., additional, Lozano‐Andrés, Estefanía, additional, Rao, Shoaib, additional, Robert, Stéphane, additional, de Rond, Leonie, additional, Tang, Vera A., additional, Tertel, Tobias, additional, Yan, Xiaomei, additional, Wauben, Marca H. M., additional, Nolan, John P., additional, Jones, Jennifer C., additional, Nieuwland, Rienk, additional, and van der Pol, Edwin, additional

Published
2023
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34. A compendium of single extracellular vesicle flow cytometry

Author

Welsh, Joshua A., Arkesteijn, Ger J. A., Bremer, Michel, Cimorelli, Michael, Dignat-George, Françoise, Giebel, Bernd, Görgens, André, Hendrix, An, Kuiper, Martine, Lacroix, Romaric, Lannigan, Joanne, van Leeuwen, Ton G., Lozano-Andrés, Estefanía, Rao, Shoaib, Robert, Stéphane, de Rond, Leonie, Tang, Vera A., Tertel, Tobias, Yan, Xiaomei, Wauben, Marca H. M., Nolan, John P., Jones, Jennifer C., Nieuwland, Rienk, and van der Pol, Edwin

Subjects
Medizin
Abstract

Flow cytometry (FCM) offers a multiparametric technology capable of characterizing single extracellular vesicles (EVs). However, most flow cytometers are designed to detect cells, which are larger than EVs. Whereas cells exceed the background noise, signals originating from EVs partly overlap with the background noise, thereby making EVs more difficult to detect than cells. This technical mismatch together with complexity of EV-containing fluids causes limitations and challenges with conducting, interpreting and reproducing EV FCM experiments. To address and overcome these challenges, researchers from the International Society for Extracellular Vesicles (ISEV), International Society for Advancement of Cytometry (ISAC), and the International Society on Thrombosis and Haemostasis (ISTH) joined forces and initiated the EV FCM working group. To improve the interpretation, reporting, and reproducibility of future EV FCM data, the EV FCM working group published an ISEV position manuscript outlining a framework of minimum information that should be reported about an FCM experiment on single EVs (MIFlowCyt-EV). However, the framework contains limited background information. Therefore, the goal of this compendium is to provide the background information necessary to design and conduct reproducible EV FCM experiments. This compendium contains background information on EVs, the interaction between light and EVs, FCM hardware, experimental design and preanalytical procedures, sample preparation, assay controls, instrument data acquisition and calibration, EV characterization, and data reporting. Although this compendium focuses on EVs, many concepts and explanations could also be applied to FCM detection of other particles within the EV size range, such as bacteria, lipoprotein particles, milk fat globules, and viruses. CA extern

Published
2023

41. Pulsed Laser Tissue Interaction

Author

Walsh, Joseph T., van Leeuwen, Ton G., Jansen, E. Duco, Motamedi, Massoud, Welch, Ashley J., Welch, Ashley J., editor, and van Gemert, Martin J.C., editor

Published
2011
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