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Gohma A, Adachi N, Yonemaru Y, Horiba D, Higuchi K, Nishiwaki D, Yokoi E, Ue Y, Miyawaki A, Monai H. Spatial frequency-based correction of the spherical aberration in living brain imaging. Microscopy (Oxf) 2024; 73:37-46. [PMID: 37315186 PMCID: PMC10849036 DOI: 10.1093/jmicro/dfad035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 05/30/2023] [Accepted: 06/12/2023] [Indexed: 06/16/2023] Open
Abstract
Optical errors, including spherical aberrations, hinder high-resolution imaging of biological samples due to biochemical components and physical properties. We developed the Deep-C microscope system to achieve aberration-free images, employing a motorized correction collar and contrast-based calculations. However, current contrast-maximization techniques, such as the Brenner gradient method, inadequately assess specific frequency bands. The Peak-C method addresses this issue, but its arbitrary neighbor selection and susceptibility to the noise limit its effectiveness. In this paper, we emphasize the importance of a broad spatial frequency range for accurate spherical aberration correction and propose Peak-F. This spatial frequency-based system utilizes a fast Fourier transform as a bandpass filter. This approach overcomes Peak-C's limitations and comprehensively covers the low-frequency domain of image spatial frequencies.
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Affiliation(s)
- Aoi Gohma
- Department of Biological Sciences, Graduate School of Humanities and Sciences, Ochanomizu University, Ohtsuka, Bunkyo-ku, Tokyo 112-8610, Japan
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Naoya Adachi
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Yasuo Yonemaru
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Daiki Horiba
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Kaori Higuchi
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Daisuke Nishiwaki
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Eiji Yokoi
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Yoshihiro Ue
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Atsushi Miyawaki
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
| | - Hiromu Monai
- Department of Biological Sciences, Graduate School of Humanities and Sciences, Ochanomizu University, Ohtsuka, Bunkyo-ku, Tokyo 112-8610, Japan
- RIKEN Center for Brain Science-Evident Open Collaboration Center, Center for Brain Science (CBS), RIKEN, 2-1, Hirosawa, Wako-shi, Saitama 351-0106, Japan
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2
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Improving Multiphoton Microscopy by Combining Spherical Aberration Patterns and Variable Axicons. PHOTONICS 2021. [DOI: 10.3390/photonics8120573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Multiphoton (MP) microscopy is a well-established method for the non-invasive imaging of biological tissues. However, its optical sectioning capabilities are reduced due to specimen-induced aberrations. Both the manipulation of spherical aberration (SA) and the use of axicons have been reported to be useful techniques to bypass this limitation. We propose the combination of SA patterns and variable axicons to further improve the quality of MP microscopy images. This approach provides enhanced images at different depth locations whose quality is better than those corresponding to the use of SA or axicons separately. Thus, the procedure proposed herein facilitates the visualization of details and increases the depth observable at high resolution.
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3
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Yamaguchi K, Otomo K, Kozawa Y, Tsutsumi M, Inose T, Hirai K, Sato S, Nemoto T, Uji-i H. Adaptive Optical Two-Photon Microscopy for Surface-Profiled Living Biological Specimens. ACS OMEGA 2021; 6:438-447. [PMID: 33458495 PMCID: PMC7807736 DOI: 10.1021/acsomega.0c04888] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 11/05/2020] [Indexed: 05/08/2023]
Abstract
We developed adaptive optical (AO) two-photon excitation microscopy by introducing a spatial light modulator (SLM) in a commercially available microscopy system. For correcting optical aberrations caused by refractive index (RI) interfaces at a specimen's surface, spatial phase distributions of the incident excitation laser light were calculated using 3D coordination of the RI interface with a 3D ray-tracing method. Based on the calculation, we applied a 2D phase-shift distribution to a SLM and achieved the proper point spread function. AO two-photon microscopy improved the fluorescence image contrast in optical phantom mimicking biological specimens. Furthermore, it enhanced the fluorescence intensity from tubulin-labeling dyes in living multicellular tumor spheroids and allowed successful visualization of dendritic spines in the cortical layer V of living mouse brains in the secondary motor region with a curved surface. The AO approach is useful for observing dynamic physiological activities in deep regions of various living biological specimens with curved surfaces.
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Affiliation(s)
- Kazushi Yamaguchi
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- Research
Institute for Electronic Science, Hokkaido
University, 060-0814 Sapporo, Hokkaido, Japan
- Division
of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
| | - Kohei Otomo
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- Research
Institute for Electronic Science, Hokkaido
University, 060-0814 Sapporo, Hokkaido, Japan
- Division
of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
- Exploratory
Research Center on Life and Living Systems, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
- Department
of Physiological Sciences, The Graduate
School for Advanced Study, 240-0193 Hayama, Kanagawa, Japan
| | - Yuichi Kozawa
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 980-8577 Sendai, Miyagi, Japan
| | - Motosuke Tsutsumi
- Research
Institute for Electronic Science, Hokkaido
University, 060-0814 Sapporo, Hokkaido, Japan
- Division
of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
- Exploratory
Research Center on Life and Living Systems, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
| | - Tomoko Inose
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- Research
Institute for Electronic Science, Hokkaido
University, 060-0814 Sapporo, Hokkaido, Japan
| | - Kenji Hirai
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- Research
Institute for Electronic Science, Hokkaido
University, 001-0020 Sapporo, Hokkaido, Japan
| | - Shunichi Sato
- Institute
of Multidisciplinary Research for Advanced Materials, Tohoku University, 980-8577 Sendai, Miyagi, Japan
| | - Tomomi Nemoto
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- Research
Institute for Electronic Science, Hokkaido
University, 060-0814 Sapporo, Hokkaido, Japan
- Division
of Biophotonics, National Institute for Physiological Sciences, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
- Exploratory
Research Center on Life and Living Systems, National Institutes of Natural Sciences, 444-8787 Okazaki, Aichi, Japan
- Department
of Physiological Sciences, The Graduate
School for Advanced Study, 240-0193 Hayama, Kanagawa, Japan
| | - Hiroshi Uji-i
- Graduate
School of Information Science and Technology, Hokkaido University, 060-0814 Sapporo, Hokkaido, Japan
- KU
Leuven, Department of Chemistry, Celestijinenlaan 200F, 3001 Heverlee, Leuven, Belgium
- Research
Institute for Electronic Science, Hokkaido
University, 001-0020 Sapporo, Hokkaido, Japan
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4
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Galiñanes GL, Marchand PJ, Turcotte R, Pellat S, Ji N, Huber D. Optical alignment device for two-photon microscopy. BIOMEDICAL OPTICS EXPRESS 2018; 9:3624-3639. [PMID: 30338144 PMCID: PMC6191613 DOI: 10.1364/boe.9.003624] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/14/2018] [Accepted: 06/15/2018] [Indexed: 05/10/2023]
Abstract
Two-photon excitation fluorescence microscopy has revolutionized our understanding of brain structure and function through the high resolution and large penetration depth it offers. Investigating neural structures in vivo requires gaining optical access to the brain, which is typically achieved by replacing a part of the skull with one or several layers of cover glass windows. To compensate for the spherical aberrations caused by the presence of these layers of glass, collar-correction objectives are typically used. However, the efficiency of this correction has been shown to depend significantly on the tilt angle between the glass window surface and the optical axis of the imaging system. Here, we first expand these observations and characterize the effect of the tilt angle on the collected fluorescence signal with thicker windows (double cover slide) and compare these results with an objective devoid of collar-correction. Second, we present a simple optical alignment device designed to rapidly minimize the tilt angle in vivo and align the optical axis of the microscope perpendicularly to the glass window to an angle below 0.25°, thereby significantly improving the imaging quality. Finally, we describe a tilt-correction procedure for users in an in vivo setting, enabling the accurate alignment with a resolution of <0.2° in only few iterations.
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Affiliation(s)
- Gregorio L. Galiñanes
- Department of Basic Neurosciences, University of Geneva, Rue Michel Servet 1, 1206 Geneva,
Switzerland
| | - Paul J. Marchand
- Department of Basic Neurosciences, University of Geneva, Rue Michel Servet 1, 1206 Geneva,
Switzerland
| | - Raphaël Turcotte
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147,
USA
- Current address: Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT,
UK
| | - Sebastien Pellat
- Department of Basic Neurosciences, University of Geneva, Rue Michel Servet 1, 1206 Geneva,
Switzerland
| | - Na Ji
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147,
USA
- Current address: Department of Physics, Department of Molecular & Cell Biology, Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720,
USA
| | - Daniel Huber
- Department of Basic Neurosciences, University of Geneva, Rue Michel Servet 1, 1206 Geneva,
Switzerland
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5
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Nobis M, Warren SC, Lucas MC, Murphy KJ, Herrmann D, Timpson P. Molecular mobility and activity in an intravital imaging setting - implications for cancer progression and targeting. J Cell Sci 2018; 131:131/5/jcs206995. [PMID: 29511095 DOI: 10.1242/jcs.206995] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Molecular mobility, localisation and spatiotemporal activity are at the core of cell biological processes and deregulation of these dynamic events can underpin disease development and progression. Recent advances in intravital imaging techniques in mice are providing new avenues to study real-time molecular behaviour in intact tissues within a live organism and to gain exciting insights into the intricate regulation of live cell biology at the microscale level. The monitoring of fluorescently labelled proteins and agents can be combined with autofluorescent properties of the microenvironment to provide a comprehensive snapshot of in vivo cell biology. In this Review, we summarise recent intravital microscopy approaches in mice, in processes ranging from normal development and homeostasis to disease progression and treatment in cancer, where we emphasise the utility of intravital imaging to observe dynamic and transient events in vivo We also highlight the recent integration of advanced subcellular imaging techniques into the intravital imaging pipeline, which can provide in-depth biological information beyond the single-cell level. We conclude with an outlook of ongoing developments in intravital microscopy towards imaging in humans, as well as provide an overview of the challenges the intravital imaging community currently faces and outline potential ways for overcoming these hurdles.
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Affiliation(s)
- Max Nobis
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
| | - Sean C Warren
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
| | - Morghan C Lucas
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
| | - Kendelle J Murphy
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
| | - David Herrmann
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
| | - Paul Timpson
- The Garvan Institute of Medical Research and The Kinghorn Cancer Centre, Cancer Division, St. Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, NSW 2010, Australia
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6
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Turcotte R, Liang Y, Ji N. Adaptive optical versus spherical aberration corrections for in vivo brain imaging. BIOMEDICAL OPTICS EXPRESS 2017; 8:3891-3902. [PMID: 28856058 PMCID: PMC5560849 DOI: 10.1364/boe.8.003891] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2017] [Revised: 07/25/2017] [Accepted: 07/25/2017] [Indexed: 05/21/2023]
Abstract
Adjusting the objective correction collar is a widely used approach to correct spherical aberrations (SA) in optical microscopy. In this work, we characterized and compared its performance with adaptive optics in the context of in vivo brain imaging with two-photon fluorescence microscopy. We found that the presence of sample tilt had a deleterious effect on the performance of SA-only correction. At large tilt angles, adjusting the correction collar even worsened image quality. In contrast, adaptive optical correction always recovered optimal imaging performance regardless of sample tilt. The extent of improvement with adaptive optics was dependent on object size, with smaller objects having larger relative gains in signal intensity and image sharpness. These observations translate into a superior performance of adaptive optics for structural and functional brain imaging applications in vivo, as we confirmed experimentally.
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7
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Miller MA, Weissleder R. Imaging the pharmacology of nanomaterials by intravital microscopy: Toward understanding their biological behavior. Adv Drug Deliv Rev 2017; 113:61-86. [PMID: 27266447 PMCID: PMC5136524 DOI: 10.1016/j.addr.2016.05.023] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 05/25/2016] [Indexed: 12/15/2022]
Abstract
Therapeutic nanoparticles (NPs) can deliver cytotoxic chemotherapeutics and other drugs more safely and efficiently to patients; furthermore, selective delivery to target tissues can theoretically be accomplished actively through coating NPs with molecular ligands, and passively through exploiting physiological "enhanced permeability and retention" features. However, clinical trial results have been mixed in showing improved efficacy with drug nanoencapsulation, largely due to heterogeneous NP accumulation at target sites across patients. Thus, a clear need exists to better understand why many NP strategies fail in vivo and not result in significantly improved tumor uptake or therapeutic response. Multicolor in vivo confocal fluorescence imaging (intravital microscopy; IVM) enables integrated pharmacokinetic and pharmacodynamic (PK/PD) measurement at the single-cell level, and has helped answer key questions regarding the biological mechanisms of in vivo NP behavior. This review summarizes progress to date and also describes useful technical strategies for successful IVM experimentation.
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Affiliation(s)
- Miles A Miller
- Center for Systems Biology, Massachusetts General Hospital, 185 Cambridge St, Boston, MA 02114, USA
| | - Ralph Weissleder
- Center for Systems Biology, Massachusetts General Hospital, 185 Cambridge St, Boston, MA 02114, USA; Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Boston, MA 02115, USA.
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8
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Shirinifard A, McCollum CW, Bolin MB, Gustafsson JÅ, Glazier JA, Clendenon SG. 3D quantitative analyses of angiogenic sprout growth dynamics. Dev Dyn 2013; 242:518-26. [PMID: 23417958 DOI: 10.1002/dvdy.23946] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 01/16/2013] [Accepted: 02/03/2013] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Zebrafish intersegmental vessel (ISV) growth is widely used to study angiogenesis and to screen drugs and toxins that perturb angiogenesis. Most current ISV growth assays observe the presence or absence of ISVs or perturbation of ISV morphology but do not measure growth dynamics. We have developed a four-dimensional (4D, space plus time) quantitative analysis of angiogenic sprout growth dynamics for characterization of both normal and perturbed growth. RESULTS We tracked the positions of the ISV base and tip for each ISV sprout in 4D. Despite immobilization, zebrafish embryos translocated globally and non-uniformly during development. We used displacement of the ISV base and the angle between the ISV and the dorsal aorta to correct for displacement and rotation during development. From corrected tip cell coordinates, we computed average ISV trajectories. We fitted a quadratic curve to the average ISV trajectories to produce a canonical ISV trajectory for each experimental group, arsenic treated and untreated. From the canonical ISV trajectories, we computed curvature, average directed migration speed and directionality. Canonical trajectories from treated (arsenic exposed) and untreated groups differed in curvature, average directed migration speed and angle between the ISV and dorsal aorta. CONCLUSIONS 4D analysis of angiogenic sprout growth dynamics: (1) Allows quantitative assessment of ISV growth dynamics and perturbation, and (2) provides critical inputs for computational models of angiogenesis.
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Affiliation(s)
- Abbas Shirinifard
- Biocomplexity Institute and Department of Physics, Indiana University Bloomington, Bloomington, Indiana 47405-7003, USA.
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9
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Clendenon SG, Ward HH, Dunn KW, Bacallao R. High resolution 4-dimension imaging of metanephric embryonic kidney morphogenesis. Kidney Int 2013; 83:757-61. [PMID: 23325081 PMCID: PMC3658135 DOI: 10.1038/ki.2012.464] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
High-resolution three-dimensional imaging of fixed embryonic kidney tissues has advanced considerably in the past decade. Here we developed a new process for imaging whole metanephric organ culture at cell resolution in three dimensions over time. This technique combines the use of the newly available generation of infrared-optimized long working distance, high numerical aperture objectives and multiphoton fluorescence microscopy with a new system for vital staining of metanephric organ cultures with bodipy ceramide. This allows all cells in the organ culture to be visualized over time, enabling detailed observation of tissue morphogenesis. Thus, our method offers a powerful new approach for visualizing and understanding early events in renal development and for extending observations made in genetically manipulated models.
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Affiliation(s)
- Sherry G Clendenon
- Department of Physics, Biocomplexity Institute, Indiana University, Bloomington, Indiana 47405, USA.
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10
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Labouta HI, Hampel M, Thude S, Reutlinger K, Kostka KH, Schneider M. Depth profiling of gold nanoparticles and characterization of point spread functions in reconstructed and human skin using multiphoton microscopy. JOURNAL OF BIOPHOTONICS 2012; 5:85-96. [PMID: 22147676 DOI: 10.1002/jbio.201100069] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Multiphoton microscopy has become popular in studying dermal nanoparticle penetration. This necessitates studying the imaging parameters of multiphoton microscopy in skin as an imaging medium, in terms of achievable detection depths and the resolution limit. This would simulate real-case scenarios rather than depending on theoretical values determined under ideal conditions. This study has focused on depth profiling of sub-resolution gold nanoparticles (AuNP) in reconstructed (fixed and unfixed) and human skin using multiphoton microscopy. Point spread functions (PSF) were determined for the used water-immersion objective of 63×/NA = 1.2. Factors such as skin-tissue compactness and the presence of wrinkles were found to deteriorate the accuracy of depth profiling. A broad range of AuNP detectable depths (20-100 μm) in reconstructed skin was observed. AuNP could only be detected up to ∼14 μm depth in human skin. Lateral (0.5 ± 0.1 μm) and axial (1.0 ± 0.3 μm) PSF in reconstructed and human specimens were determined. Skin cells and intercellular components didn't degrade the PSF with depth. In summary, the imaging parameters of multiphoton microscopy in skin and practical limitations encountered in tracking nanoparticle penetration using this approach were investigated.
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Affiliation(s)
- Hagar I Labouta
- Department of Pharmaceutical Nanotechnology, Saarland University, Campus A4 1, 66123 Saarbrücken, Germany
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11
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Young P, Clendenon S, Byars J, Decca R, Dunn K. The effects of spherical aberration on multiphoton fluorescence excitation microscopy. J Microsc 2011; 242:157-65. [PMID: 21118240 PMCID: PMC4449278 DOI: 10.1111/j.1365-2818.2010.03449.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Multiphoton fluorescence excitation microscopy is almost invariably conducted with samples whose refractive index differ from that of the objective immersion medium, conditions that cause spherical aberration. Due to the quadratic nature of multiphoton fluorescence excitation, spherical aberration is expected to profoundly affect the depth dependence of fluorescence excitation. In order to determine the effect of refractive index mismatch in multiphoton fluorescence excitation microscopy, we measured signal attenuation, photobleaching rates and resolution degradation with depth in homogeneous samples with minimal light scattering and absorption over a range of refractive indices. These studies demonstrate that signal levels and resolution both rapidly decline with depth into refractive index mismatched samples. Analyses of photobleaching rates indicate that the preponderance of signal attenuation with depth results from decreased rates of fluorescence excitation, even in a system with a descanned emission collection pathway. Similar results were obtained in analyses of fluorescence microspheres embedded in rat kidney tissue, demonstrating that spherical aberration is an important limiting factor in multiphoton fluorescence excitation microscopy of biological samples.
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Affiliation(s)
- P.A. Young
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, U.S.A
| | - S.G. Clendenon
- Department of Physics, Indiana University, Bloomington, Indiana, U.S.A
| | - J.M. Byars
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, U.S.A
| | - R.S. Decca
- Department of Physics, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, U.S.A
| | - K.W. Dunn
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana, U.S.A
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12
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Young PA, Clendenon SG, Byars JM, Dunn KW. The effects of refractive index heterogeneity within kidney tissue on multiphoton fluorescence excitation microscopy. J Microsc 2011; 242:148-56. [PMID: 21118239 PMCID: PMC4450360 DOI: 10.1111/j.1365-2818.2010.03448.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Although multiphoton fluorescence excitation microscopy has improved the depth at which useful fluorescence images can be collected in biological tissues, the reach of multiphoton fluorescence excitation microscopy is nonetheless limited by tissue scattering and spherical aberration. Scattering can be reduced in fixed samples by mounting in a medium whose refractive index closely matches that of the fixed material. Using optical 'clearing', the effects of refractive index heterogeneity on signal attenuation with depth are investigated. Quantitative measurements show that by mounting kidney tissue in a high refractive index medium, less than 50% of signal attenuates in 100 μm of depth.
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Affiliation(s)
- P A Young
- Department of Medicine, Division of Nephrology, Indiana University School of Medicine, Indianapolis, Indiana 46202–5188, USA
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