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Elias TM, Brown EB, Brown EB. Expanding the applicability of multiphoton fluorescence recovery after photobleaching by incorporating shear stress in laminar flow. JOURNAL OF BIOMEDICAL OPTICS 2023; 28:076502. [PMID: 37484975 PMCID: PMC10362154 DOI: 10.1117/1.jbo.28.7.076502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 07/10/2023] [Accepted: 07/11/2023] [Indexed: 07/25/2023]
Abstract
Significance Multi-photon fluorescence recovery after photobleaching (MPFRAP) is a nonlinear microscopy technique used to measure the diffusion coefficient of fluorescently tagged molecules in solution. Previous MPFRAP fitting models calculate the diffusion coefficient in systems with diffusion or diffusion in laminar flow. Aim We propose an MPFRAP fitting model that accounts for shear stress in laminar flow, making it a more applicable technique for in vitro and in vivo studies involving diffusion. Approach Fluorescence recovery curves are generated using high-throughput molecular dynamics simulations and then fit to all three models (diffusion, diffusion and flow, and diffusion and shear flow) to define the limits within which accurate diffusion coefficients are produced. Diffusion is simulated as a random walk with a variable horizontal bias to account for shear flow. Results Contour maps of the accuracy of the fitted diffusion coefficient as a function of scaled velocity and scaled shear rate show the parameter space within which each model produces accurate diffusion coefficients; the shear-flow model covers a larger area than the previous models. Conclusion The shear-flow model allows MPFRAP to be a viable optical tool for studying more biophysical systems than previous models.
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Affiliation(s)
- Tresa M. Elias
- University of Rochester, Department of Biomedical Engineering, Rochester, New York, United States
| | - Edward B. Brown
- Manhattan College, Department of Physics, Riverdale, New York, United States
| | - Edward B. Brown
- University of Rochester, Department of Biomedical Engineering, Rochester, New York, United States
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2
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Recent Advances in Fluorescence Recovery after Photobleaching for Decoupling Transport and Kinetics of Biomacromolecules in Cellular Physiology. Polymers (Basel) 2022; 14:polym14091913. [PMID: 35567083 PMCID: PMC9105003 DOI: 10.3390/polym14091913] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/27/2022] [Accepted: 04/29/2022] [Indexed: 12/16/2022] Open
Abstract
Among the new molecular tools available to scientists and engineers, some of the most useful include fluorescently tagged biomolecules. Tools, such as green fluorescence protein (GFP), have been applied to perform semi-quantitative studies on biological signal transduction and cellular structural dynamics involved in the physiology of healthy and disease states. Such studies focus on drug pharmacokinetics, receptor-mediated endocytosis, nuclear mechanobiology, viral infections, and cancer metastasis. In 1976, fluorescence recovery after photobleaching (FRAP), which involves the monitoring of fluorescence emission recovery within a photobleached spot, was developed. FRAP allowed investigators to probe two-dimensional (2D) diffusion of fluorescently-labelled biomolecules. Since then, FRAP has been refined through the advancements of optics, charged-coupled-device (CCD) cameras, confocal microscopes, and molecular probes. FRAP is now a highly quantitative tool used for transport and kinetic studies in the cytosol, organelles, and membrane of a cell. In this work, the authors intend to provide a review of recent advances in FRAP. The authors include epifluorescence spot FRAP, total internal reflection (TIR)/FRAP, and confocal microscope-based FRAP. The underlying mathematical models are also described. Finally, our understanding of coupled transport and kinetics as determined by FRAP will be discussed and the potential for future advances suggested.
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3
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Smith AJ, Yao X, Dix JA, Jin BJ, Verkman AS. Test of the 'glymphatic' hypothesis demonstrates diffusive and aquaporin-4-independent solute transport in rodent brain parenchyma. eLife 2017; 6:27679. [PMID: 28826498 PMCID: PMC5578736 DOI: 10.7554/elife.27679] [Citation(s) in RCA: 226] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 08/18/2017] [Indexed: 12/11/2022] Open
Abstract
Transport of solutes through brain involves diffusion and convection. The importance of convective flow in the subarachnoid and paravascular spaces has long been recognized; a recently proposed ‘glymphatic’ clearance mechanism additionally suggests that aquaporin-4 (AQP4) water channels facilitate convective transport through brain parenchyma. Here, the major experimental underpinnings of the glymphatic mechanism were re-examined by measurements of solute movement in mouse brain following intracisternal or intraparenchymal solute injection. We found that: (i) transport of fluorescent dextrans in brain parenchyma depended on dextran size in a manner consistent with diffusive rather than convective transport; (ii) transport of dextrans in the parenchymal extracellular space, measured by 2-photon fluorescence recovery after photobleaching, was not affected just after cardiorespiratory arrest; and (iii) Aqp4 gene deletion did not impair transport of fluorescent solutes from sub-arachnoid space to brain in mice or rats. Our results do not support the proposed glymphatic mechanism of convective solute transport in brain parenchyma.
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Affiliation(s)
- Alex J Smith
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Xiaoming Yao
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - James A Dix
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Byung-Ju Jin
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
| | - Alan S Verkman
- Department of Medicine, University of California, San Francisco, San Francisco, United States.,Department of Physiology, University of California, San Francisco, San Francisco, United States
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4
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Fluorescence recovery after photobleaching in material and life sciences: putting theory into practice. Q Rev Biophys 2015; 48:323-87. [PMID: 26314367 DOI: 10.1017/s0033583515000013] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
AbstractFluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure–interaction–diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.
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5
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Bouta EM, Li J, Ju Y, Brown EB, Ritchlin CT, Xing L, Schwarz EM. The role of the lymphatic system in inflammatory-erosive arthritis. Semin Cell Dev Biol 2015; 38:90-7. [PMID: 25598390 DOI: 10.1016/j.semcdb.2015.01.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 12/21/2014] [Accepted: 01/05/2015] [Indexed: 01/13/2023]
Abstract
Rheumatoid arthritis (RA) is a prevalent inflammatory joint disease with enigmatic flares, which causes swelling, pain, and irreversible connective tissue damage. Recently, it has been demonstrated in murine models of RA that the popliteal lymph node (PLN) is a biomarker of arthritic flare, as it "expands" in size and contrast enhancement during a prolonged asymptomatic phase, prior to when it "collapses" with accelerated synovitis and joint erosion. This PLN collapse is associated with adjacent knee flare, decreases in PLN volume and contrast enhancement, lymphatic pulse and pumping pressure, and an increase in PLN pressure. Currently, it is known that PLN collapse is accompanied by a translocation of B cells from the follicles to the sinuses, effectively clogging the lymphatic sinuses of the PLN, and that B cell depletion therapy ameliorates arthritic flare by eliminating these B cells and restoring passive lymphatic flow from inflamed joints. Here we review the technological advances that have launched this area of research, describe future directions to help elucidate the potential mechanism of PLN collapse, and speculate on clinical translation towards new diagnostics and therapies for RA.
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Affiliation(s)
- Echoe M Bouta
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Biomedical Engineering, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Jie Li
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Yawen Ju
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Edward B Brown
- Department of Biomedical Engineering, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Cancer Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Christopher T Ritchlin
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Division of Allergy, Immunology, Rheumatology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Lianping Xing
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States
| | - Edward M Schwarz
- Center for Musculoskeletal Research, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Biomedical Engineering, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Cancer Center, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Division of Allergy, Immunology, Rheumatology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States; Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, NY, United States.
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Sullivan KD, Majewska AK, Brown EB. Single- and two-photon fluorescence recovery after photobleaching. Cold Spring Harb Protoc 2015; 2015:pdb.top083519. [PMID: 25561627 DOI: 10.1101/pdb.top083519] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Fluorescence recovery after photobleaching (FRAP) is a microscopy technique for measuring the kinetics of fluorescently labeled molecules and can be applied both in vitro and in vivo for two- and three-dimensional systems. This introduction discusses the three basic FRAP methods: traditional FRAP, multiphoton FRAP (MPFRAP), and FRAP with spatial Fourier analysis (SFA-FRAP). Each discussion is accompanied by a description of the mathematical analysis appropriate for situations in which the recovery kinetics is dictated by free diffusion. In some experiments, the recovery kinetics is dictated by the boundary conditions of the system, and FRAP is then used to quantify the connectivity of various compartments. Because the appropriate mathematical analysis is independent of the bleaching method, the analysis of compartmental connectivity is discussed last, in a separate section.
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Bouta EM, Wood RW, Brown EB, Rahimi H, Ritchlin CT, Schwarz EM. In vivo quantification of lymph viscosity and pressure in lymphatic vessels and draining lymph nodes of arthritic joints in mice. J Physiol 2014; 592:1213-23. [PMID: 24421350 DOI: 10.1113/jphysiol.2013.266700] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Rheumatoid arthritis (RA) is a chronic inflammatory joint disease with episodic flares. In TNF-Tg mice, a model of inflammatory-erosive arthritis, the popliteal lymph node (PLN) enlarges during the pre-arthritic 'expanding' phase, and then 'collapses' with adjacent knee flare associated with the loss of the intrinsic lymphatic pulse. As the mechanisms responsible are unknown, we developed in vivo methods to quantify lymph viscosity and pressure in mice with wild-type (WT), expanding and collapsed PLN. While no differences in viscosity were detected via multiphoton fluorescence recovery after photobleaching (MP-FRAP) of injected FITC-BSA, a 32.6% decrease in lymph speed was observed in vessels afferent to collapsed PLN (P < 0.05). Direct measurement of intra-lymph node pressure (LNP) demonstrated a decrease in expanding PLN versus WT pressure (3.41 ± 0.43 vs. 6.86 ± 0.56 cmH2O; P < 0.01), which dramatically increased to 9.92 ± 1.79 cmH2O in collapsed PLN. Lymphatic pumping pressure (LPP), measured indirectly by slowly releasing a pressurized cuff occluding indocyanine green (ICG), demonstrated an increase in vessels afferent to expanding PLN versus WT (18.76 ± 2.34 vs. 11.04 ± 1.47 cmH2O; P < 0.01), which dropped to 2.61 ± 0.72 cmH2O (P < 0.001) after PLN collapse. Herein, we document the first in vivo measurements of murine lymph viscosity and lymphatic pressure, and provide evidence to support the hypothesis that lymphangiogenesis and lymphatic transport are compensatory mechanisms to prevent synovitis via increased drainage of inflamed joints. Furthermore, the decrease in lymphatic flow and loss of LPP during PLN collapse are consistent with decreased drainage from the joint during arthritic flare, and validate these biomarkers of RA progression and possibly other chronic inflammatory conditions.
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Affiliation(s)
- Echoe M Bouta
- The Center for Musculoskeletal Research, University of Rochester Medical Center, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA.
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Shi C, Cisewski SE, Bell PD, Yao H. Measurement of three-dimensional anisotropic diffusion by multiphoton fluorescence recovery after photobleaching. Ann Biomed Eng 2013; 42:555-65. [PMID: 24248560 DOI: 10.1007/s10439-013-0939-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 11/09/2013] [Indexed: 11/25/2022]
Abstract
The multiphoton fluorescence recovery after photobleaching (MP-FRAP) technique has been developed to measure the three-dimensional (3D) solute diffusion within biological systems. However, current 3D MP-FRAP models are based on isotropic diffusion and spatial domain analysis. The 3D anisotropic diffusion and frequency domain analysis for MP-FRAP measurements are rarely studied. In this study, a new technique is demonstrated for the quantitative and non-destructive determination of 3D anisotropic solute diffusion tensors within biological fibrosis tissues by multiphoton photobleaching and spatial Fourier analysis (SFA). Compared to the spatial domain analysis based MP-FRAP techniques, this SFA-based method has the capability for determining the 3D anisotropic diffusion tensors as well as the flexibility for satisfying initial and boundary conditions. First, a close-form solution of the 3D anisotropic diffusion equation is derived by solely using SFA. Next, this new method is validated by computer-simulated MP-FRAP experiments with pre-defined 3D anisotropic diffusion tensors as well as experimental diffusion measurements of FITC-Dextran (FD) molecules in aqueous glycerol solutions. Finally, this MP-FRAP technique is applied to the measurement of 3D anisotropic diffusion tensors of FD molecules within porcine tendon tissues. This study provides a new tool for complete determination of 3D anisotropic solute diffusion tensor in biological tissues.
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Affiliation(s)
- Changcheng Shi
- CU-MUSC Bioengineering Program, Department of Bioengineering, Clemson University, 173 Ashley Avenue, P.O. Box 250508, Charleston, SC, 29425, USA
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9
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FRAP in Pharmaceutical Research: Practical Guidelines and Applications in Drug Delivery. Pharm Res 2013; 31:255-70. [DOI: 10.1007/s11095-013-1146-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 07/09/2013] [Indexed: 01/02/2023]
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10
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Vogt C, Ball V, Mutterer J, Schaaf P, Voegel JC, Senger B, Lavalle P. Mobility of Proteins in Highly Hydrated Polyelectrolyte Multilayer Films. J Phys Chem B 2012; 116:5269-78. [DOI: 10.1021/jp300028v] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Cédric Vogt
- Institut National de la Santé et de la Recherche Médicale, Unité 977, 11 rue Humann, 67085 Strasbourg Cedex, France
- Faculté de Chirurgie
Dentaire, Université de Strasbourg, 1 place de l’Hôpital, 67000 Strasbourg, France
| | - Vincent Ball
- Institut National de la Santé et de la Recherche Médicale, Unité 977, 11 rue Humann, 67085 Strasbourg Cedex, France
- Faculté de Chirurgie
Dentaire, Université de Strasbourg, 1 place de l’Hôpital, 67000 Strasbourg, France
| | - Jérôme Mutterer
- Centre National de la Recherche
Scientifique, UPR 2357, Institut de Biologie Moléculaire des Plantes, 12 rue du Général Zimmer,
67084 Strasbourg Cedex, France
| | - Pierre Schaaf
- Centre National de la Recherche
Scientifique, UPR 22, Institut Charles Sadron, 23 rue du Loess, BP 84047, 67034 Strasbourg Cedex 2, France
| | - Jean-Claude Voegel
- Institut National de la Santé et de la Recherche Médicale, Unité 977, 11 rue Humann, 67085 Strasbourg Cedex, France
- Faculté de Chirurgie
Dentaire, Université de Strasbourg, 1 place de l’Hôpital, 67000 Strasbourg, France
| | - Bernard Senger
- Institut National de la Santé et de la Recherche Médicale, Unité 977, 11 rue Humann, 67085 Strasbourg Cedex, France
- Faculté de Chirurgie
Dentaire, Université de Strasbourg, 1 place de l’Hôpital, 67000 Strasbourg, France
| | - Philippe Lavalle
- Institut National de la Santé et de la Recherche Médicale, Unité 977, 11 rue Humann, 67085 Strasbourg Cedex, France
- Faculté de Chirurgie
Dentaire, Université de Strasbourg, 1 place de l’Hôpital, 67000 Strasbourg, France
- Hôpitaux Universitaires de Strasbourg, 1 place de l’Hôpital,
67000 Strasbourg, France
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Bouta EM, Wood RW, Perry SW, Brown EB, Ritchlin CT, Xing L, Schwarz EM. Measuring intranodal pressure and lymph viscosity to elucidate mechanisms of arthritic flare and therapeutic outcomes. Ann N Y Acad Sci 2012; 1240:47-52. [PMID: 22172039 DOI: 10.1111/j.1749-6632.2011.06237.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Rheumatoid arthritis (RA) is a chronic autoimmune disease with episodic flares in affected joints; the etiology of RA is largely unknown. Recent studies in mice demonstrated that alterations in lymphatics from affected joints precede flares. Thus, we aimed to develop novel methods for measuring lymph node pressure and lymph viscosity in limbs of mice. Pressure measurements were performed by inserting a glass micropipette connected to a pressure transducer into popliteal lymph nodes (PLN) or axillary lymph nodes (ALN) of mice; subsequently, we determined that the lymphatic pressures of water were 9 and 12 cm, respectively. We are also developing methods for measuring lymph viscosity in lymphatic vessels afferent to PLN, which can be measured by multiphoton fluorescence recovery after photobleaching (MP-FRAP) of fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) injected into the hind footpad. These results demonstrate the potential of lymph node pressure and lymph viscosity measurements, and future studies to test these outcomes as biomarkers of arthritic flare are warranted.
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Affiliation(s)
- Echoe M Bouta
- Center for Musculoskeletal Research, Department of Biomedical Engineering, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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12
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Huang K, Chen L, Lv S, Xiong J. Protoporphyrin IX photobleaching of subcellular distributed sites of leukemic HL60 cells based on ALA-PDT <i>in vitro</i>. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/jbise.2012.59068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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13
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Sullivan KD, Brown EB. Multiphoton fluorescence recovery after photobleaching in bounded systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:051916. [PMID: 21728580 PMCID: PMC3413246 DOI: 10.1103/physreve.83.051916] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 01/17/2011] [Indexed: 05/31/2023]
Abstract
Multiphoton fluorescence recovery after photobleaching (MP-FRAP) is a laser microscopy technique used to measure diffusion coefficients of macromolecules in biological systems. The three-dimensional resolution and superior depth penetration within scattering samples offered by MP-FRAP make it an important tool for investigating both in vitro and in vivo systems. However, biological systems frequently confine diffusion within solid barriers, and to date the effect of such barriers on the measurement of absolute diffusion coefficients via MP-FRAP has not been studied. We have used Monte Carlo simulations of diffusion and MP-FRAP to understand the effect of barriers of varying geometries and positions relative to the two-photon focal volume. Furthermore, we supply ranges of barrier positions within which MP-FRAP can confidently be employed to measure accurate diffusion coefficients. Finally, we produce two new MP-FRAP models that can produce accurate diffusion coefficients in the presence of a single plane boundary or parallel infinite plane boundaries positioned parallel to the optical axis, up to the resolution limit of the multiphoton laser scanning microscope.
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Affiliation(s)
- Kelley D. Sullivan
- Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
| | - Edward B. Brown
- Department of Biomedical Engineering, University of Rochester, Rochester, New York 14627, USA
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Sullivan KD, Brown EB. Measuring diffusion coefficients via two-photon fluorescence recovery after photobleaching. J Vis Exp 2010:1636. [PMID: 20190730 DOI: 10.3791/1636] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Multi-fluorescence recovery after photobleaching is a microscopy technique used to measure the diffusion coefficient (or analogous transport parameters) of macromolecules, and can be applied to both in vitro and in vivo biological systems. Multi-fluorescence recovery after photobleaching is performed by photobleaching a region of interest within a fluorescent sample using an intense laser flash, then attenuating the beam and monitoring the fluorescence as still-fluorescent molecules from outside the region of interest diffuse in to replace the photobleached molecules. We will begin our demonstration by aligning the laser beam through the Pockels Cell (laser modulator) and along the optical path through the laser scan box and objective lens to the sample. For simplicity, we will use a sample of aqueous fluorescent dye. We will then determine the proper experimental parameters for our sample including, monitor and bleaching powers, bleach duration, bin widths (for photon counting), and fluorescence recovery time. Next, we will describe the procedure for taking recovery curves, a process that can be largely automated via LabVIEW (National Instruments, Austin, TX) for enhanced throughput. Finally, the diffusion coefficient is determined by fitting the recovery data to the appropriate mathematical model using a least-squares fitting algorithm, readily programmable using software such as MATLAB (The Mathworks, Natick, MA).
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