1
|
Sánchez-Hernández A, Polleys CM, Georgakoudi I. Formalin fixation and paraffin embedding interfere with the preservation of optical metabolic assessments based on endogenous NAD(P)H and FAD two-photon excited fluorescence. BIOMEDICAL OPTICS EXPRESS 2023; 14:5238-5253. [PMID: 37854574 PMCID: PMC10581792 DOI: 10.1364/boe.498297] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 08/23/2023] [Accepted: 08/30/2023] [Indexed: 10/20/2023]
Abstract
Endogenous NAD(P)H and FAD two-photon excited fluorescence (TPEF) images provide functional metabolic information with high spatial resolution for a wide range of living specimens. Preservation of metabolic function optical metrics upon fixation would facilitate studies which assess the impact of metabolic changes in the context of numerous diseases. However, robust assessments of the impact of formalin fixation, paraffin embedding, and sectioning on the preservation of optical metabolic readouts are lacking. Here, we evaluate intensity and lifetime images at excitation/emission settings optimized for NAD(P)H and FAD TPEF detection from freshly excised murine oral epithelia and corresponding bulk and sectioned fixed tissues. We find that fixation impacts the overall intensity as well as the intensity fluctuations of the images acquired. Accordingly, the depth-dependent variations of the optical redox ratio (defined as FAD/(NAD(P)H + FAD)) across squamous epithelia are not preserved following fixation. This is consistent with significant changes in the 755 nm excited spectra, which reveal broadening upon fixation and additional distortions upon paraffin embedding and sectioning. Analysis of fluorescence lifetime images acquired for excitation/emission settings optimized for NAD(P)H TPEF detection indicate that fixation alters the long lifetime of the observed fluorescence and the long lifetime intensity fraction. These parameters as well as the short TPEF lifetime are significantly modified upon embedding and sectioning. Thus, our studies highlight that the autofluorescence products formed during formalin fixation, paraffin embedding and sectioning overlap highly with NAD(P)H and FAD emission and limit the potential to utilize such tissues to assess metabolic activity.
Collapse
Affiliation(s)
| | | | - Irene Georgakoudi
- Department of Biomedical Engineering, Tufts University, Medford, MA, USA
| |
Collapse
|
2
|
Tehrani KF, Park J, Chaney EJ, Tu H, Boppart SA. Nonlinear Imaging Histopathology: A Pipeline to Correlate Gold-Standard Hematoxylin and Eosin Staining With Modern Nonlinear Microscopy. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS : A PUBLICATION OF THE IEEE LASERS AND ELECTRO-OPTICS SOCIETY 2023; 29:6800608. [PMID: 37193134 PMCID: PMC10174331 DOI: 10.1109/jstqe.2022.3233523] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Hematoxylin and eosin (H&E) staining, the century-old technique, has been the gold standard tool for pathologists to detect anomalies in tissues and diseases such as cancer. H&E staining is a cumbersome, time-consuming process that delays and wastes precious minutes during an intraoperative diagnosis. However, even in the modern era, real-time label-free imaging techniques such as simultaneous label-free autofluorescence multiharmonic (SLAM) microscopy have delivered several more layers of information to characterize a tissue with high precision. Still, they have yet to translate to the clinic. The slow translation rate can be attributed to the lack of direct comparisons between the old and new techniques. Our approach to solving this problem is to: 1) reduce dimensions by pre-sectioning the tissue in 500 μm slices, and 2) produce fiducial laser markings which appear in both SLAM and histological imaging. High peak-power femtosecond laser pulses enable ablation in a controlled and contained manner. We perform laser marking on a grid of points encompassing the SLAM region of interest. We optimize laser power, numerical aperture, and timing to produce axially extended marking, hence multilayered fiducial markers, with minimal damage to the surrounding tissues. We performed this co-registration over an area of 3 × 3 mm2 of freshly excised mouse kidney and intestine, followed by standard H&E staining. Reduced dimensionality and the use of laser markings provided a comparison of the old and new techniques, giving a wealth of correlative information and elevating the potential of translating nonlinear microscopy to the clinic for rapid pathological assessment.
Collapse
Affiliation(s)
- Kayvan Forouhesh Tehrani
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA
| | - Jaena Park
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA, and also with the Department of Bioengineering, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA
| | - Eric J Chaney
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA
| | - Haohua Tu
- Beckman Institute for Advanced Science and Technology, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA, and also with the Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA
| | - Stephen A Boppart
- Beckman Institute for Advanced Science and Technology, Department of Electrical and Computer Engineering, Department of Bioengineering, Carle Illinois College of Medicine, and Cancer Center at Illinois, University of Illinois Urbana-Champaign, Urbana, IL 61801-3028 USA
| |
Collapse
|
3
|
Sánchez-Hernández A, Polleys CM, Georgakoudi I. Formalin fixation and paraffin embedding interfere with preservation of optical metabolic assessments based on endogenous NAD(P)H and FAD two photon excited fluorescence. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.16.545363. [PMID: 37398103 PMCID: PMC10312786 DOI: 10.1101/2023.06.16.545363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Endogenous NAD(P)H and FAD two-photon excited fluorescence (TPEF) images provide functional metabolic information with high spatial resolution for a wide range of living specimens. Preservation of metabolic function optical metrics upon fixation would facilitate studies which assess the impact of metabolic changes in the context of numerous diseases. However, robust assessments of the impact of formalin fixation, paraffin embedding, and sectioning on the preservation of optical metabolic readouts are lacking. Here, we evaluate intensity and lifetime images at excitation/emission settings optimized for NAD(P)H and FAD TPEF detection from freshly excised murine oral epithelia and corresponding bulk and sectioned fixed tissues. We find that fixation impacts the overall intensity as well as the intensity fluctuations of the images acquired. Accordingly, the depth-dependent variations of the optical redox ratio (defined as FAD/(NAD(P)H + FAD)) across squamous epithelia are not preserved following fixation. This is consistent with significant changes in the 755 nm excited spectra, which reveal broadening upon fixation and additional distortions upon paraffin embedding and sectioning. Analysis of fluorescence lifetime images acquired for excitation/emission settings optimized for NAD(P)H TPEF detection indicate that fixation alters the long lifetime of the observed fluorescence and the long lifetime intensity fraction. These parameters as well as the short TPEF lifetime are significantly modified upon embedding and sectioning. Thus, our studies highlight that the autofluorescence products formed during formalin fixation, paraffin embedding and sectioning overlap highly with NAD(P)H and FAD emission and limit the potential to utilize such tissues to assess metabolic activity.
Collapse
Affiliation(s)
| | | | - Irene Georgakoudi
- Department of Biomedical Engineering, Tufts University, Medford, MA, US
| |
Collapse
|
4
|
Gao K, Liu Y, Qiao W, Xu R, Feng T, Xuan H, Li D, Zhao X, Wang A, Li T. Sub-60-fs, compact 1100-nm fiber laser system based on double-pass pre-chirp managed amplification. OPTICS LETTERS 2022; 47:5016-5019. [PMID: 36181175 DOI: 10.1364/ol.470881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/05/2022] [Indexed: 06/16/2023]
Abstract
An ytterbium-doped, single-stage, double-pass nonlinear fiber amplification system was fabricated for amplifying an 1100-nm mode-locking fiber laser. Pre-chirp managed amplification (PCMA) was applied in realizing the nonlinear amplification process with an all-polarization-maintaining (PM) fiber construction. The system can deliver 19.8-nJ, 58.7-fs, 24.4-MHz amplified signal pulses with a 10-dB spectral range spanning from 1049 nm to 1130 nm. Further experimental investigations were conducted in exploring the dynamics of the double-pass nonlinear amplification process. This compact 1100-nm ultrafast fiber laser can be implemented for multi-photon microscopy (MPM) with deep penetration depth.
Collapse
|
5
|
Hilzenrat G, Gill ET, McArthur SL. Imaging approaches for monitoring three-dimensional cell and tissue culture systems. JOURNAL OF BIOPHOTONICS 2022; 15:e202100380. [PMID: 35357086 DOI: 10.1002/jbio.202100380] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 03/27/2022] [Accepted: 03/28/2022] [Indexed: 06/14/2023]
Abstract
The past decade has seen an increasing demand for more complex, reproducible and physiologically relevant tissue cultures that can mimic the structural and biological features of living tissues. Monitoring the viability, development and responses of such tissues in real-time are challenging due to the complexities of cell culture physical characteristics and the environments in which these cultures need to be maintained in. Significant developments in optics, such as optical manipulation, improved detection and data analysis, have made optical imaging a preferred choice for many three-dimensional (3D) cell culture monitoring applications. The aim of this review is to discuss the challenges associated with imaging and monitoring 3D tissues and cell culture, and highlight topical label-free imaging tools that enable bioengineers and biophysicists to non-invasively characterise engineered living tissues.
Collapse
Affiliation(s)
- Geva Hilzenrat
- Bioengineering Engineering Group, School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Biomedical Manufacturing, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton, Victoria, Australia
| | - Emma T Gill
- Bioengineering Engineering Group, School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Biomedical Manufacturing, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton, Victoria, Australia
| | - Sally L McArthur
- Bioengineering Engineering Group, School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Hawthorn, Victoria, Australia
- Biomedical Manufacturing, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Clayton, Victoria, Australia
| |
Collapse
|
6
|
Iyer RR, Sorrells JE, Yang L, Chaney EJ, Spillman DR, Tibble BE, Renteria CA, Tu H, Žurauskas M, Marjanovic M, Boppart SA. Label-free metabolic and structural profiling of dynamic biological samples using multimodal optical microscopy with sensorless adaptive optics. Sci Rep 2022; 12:3438. [PMID: 35236862 PMCID: PMC8891278 DOI: 10.1038/s41598-022-06926-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 02/01/2022] [Indexed: 01/21/2023] Open
Abstract
Label-free optical microscopy has matured as a noninvasive tool for biological imaging; yet, it is criticized for its lack of specificity, slow acquisition and processing times, and weak and noisy optical signals that lead to inaccuracies in quantification. We introduce FOCALS (Fast Optical Coherence, Autofluorescence Lifetime imaging, and Second harmonic generation) microscopy capable of generating NAD(P)H fluorescence lifetime, second harmonic generation (SHG), and polarization-sensitive optical coherence microscopy (OCM) images simultaneously. Multimodal imaging generates quantitative metabolic and morphological profiles of biological samples in vitro, ex vivo, and in vivo. Fast analog detection of fluorescence lifetime and real-time processing on a graphical processing unit enables longitudinal imaging of biological dynamics. We detail the effect of optical aberrations on the accuracy of FLIM beyond the context of undistorting image features. To compensate for the sample-induced aberrations, we implemented a closed-loop single-shot sensorless adaptive optics solution, which uses computational adaptive optics of OCM for wavefront estimation within 2 s and improves the quality of quantitative fluorescence imaging in thick tissues. Multimodal imaging with complementary contrasts improves the specificity and enables multidimensional quantification of the optical signatures in vitro, ex vivo, and in vivo, fast acquisition and real-time processing improve imaging speed by 4-40 × while maintaining enough signal for quantitative nonlinear microscopy, and adaptive optics improves the overall versatility, which enable FOCALS microscopy to overcome the limits of traditional label-free imaging techniques.
Collapse
Affiliation(s)
- Rishyashring R. Iyer
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Janet E. Sorrells
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Lingxiao Yang
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Eric J. Chaney
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Darold R. Spillman
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Brian E. Tibble
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991The School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Carlos A. Renteria
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Haohua Tu
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Mantas Žurauskas
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Marina Marjanovic
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, USA
| | - Stephen A. Boppart
- grid.35403.310000 0004 1936 9991Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, USA ,grid.35403.310000 0004 1936 9991Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, USA
| |
Collapse
|
7
|
Peres C, Nardin C, Yang G, Mammano F. Commercially derived versatile optical architecture for two-photon STED, wavelength mixing and label-free microscopy. BIOMEDICAL OPTICS EXPRESS 2022; 13:1410-1429. [PMID: 35414982 PMCID: PMC8973165 DOI: 10.1364/boe.444525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/03/2022] [Accepted: 01/06/2022] [Indexed: 06/14/2023]
Abstract
Multimodal microscopy combines multiple non-linear techniques that take advantage of different optical processes to generate contrast and increase the amount of information that can be obtained from biological samples. However, the most advanced optical architectures are typically custom-made and often require on-site adjustment of optical components performed by trained personnel for optimal performance. Here, we describe a hybrid system we built based on a commercial upright microscope. We show that our multimodal imaging platform can be used to seamlessly perform two-photon STED, wavelength mixing and label-free microscopy in both ex vivo and in vivo turbid samples. The system is stable and endowed with remote alignment hardware that ensures long-term operability also for non-expert users, using the alignment protocol described in this article and in the related material. This optical architecture is an important step forward towards a wider practical applicability of non-linear optics to bioimaging.
Collapse
Affiliation(s)
- Chiara Peres
- CNR Institute of Biochemistry and Cell Biology, 00015 Monterotondo, Rome, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padova, 35131 Padova, Italy
| | - Chiara Nardin
- CNR Institute of Biochemistry and Cell Biology, 00015 Monterotondo, Rome, Italy
| | - Guang Yang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, 201210 Shanghai, China
| | - Fabio Mammano
- CNR Institute of Biochemistry and Cell Biology, 00015 Monterotondo, Rome, Italy
- Department of Physics and Astronomy “G. Galilei”, University of Padova, 35131 Padova, Italy
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, 201210 Shanghai, China
| |
Collapse
|
8
|
Lee J, Hestrin R, Nuccio EE, Morrison KD, Ramon CE, Samo TJ, Pett-Ridge J, Ly SS, Laurence TA, Weber PK. Label-Free Multiphoton Imaging of Microbes in Root, Mineral, and Soil Matrices with Time-Gated Coherent Raman and Fluorescence Lifetime Imaging. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:1994-2008. [PMID: 35029104 DOI: 10.1021/acs.est.1c05818] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Imaging biogeochemical interactions in complex microbial systems─such as those at the soil-root interface─is crucial to studies of climate, agriculture, and environmental health but complicated by the three-dimensional (3D) juxtaposition of materials with a wide range of optical properties. We developed a label-free multiphoton nonlinear imaging approach to provide contrast and chemical information for soil microorganisms in roots and minerals with epi-illumination by simultaneously imaging two-photon excitation fluorescence (TPEF), coherent anti-Stokes Raman scattering (CARS), second-harmonic generation (SHG), and sum-frequency mixing (SFM). We used fluorescence lifetime imaging (FLIM) and time gating to correct CARS for the autofluorescence background native to soil particles and fungal hyphae (TG-CARS) using time-correlated single-photon counting (TCSPC). We combined TPEF, TG-CARS, and FLIM to maximize image contrast for live fungi and bacteria in roots and soil matrices without fluorescence labeling. Using this instrument, we imaged symbiotic arbuscular mycorrhizal fungi (AMF) structures within unstained plant roots in 3D to 60 μm depth. High-quality imaging was possible at up to 30 μm depth in a clay particle matrix and at 15 μm in complex soil preparation. TG-CARS allowed us to identify previously unknown lipid droplets in the symbiotic fungus, Serendipita bescii. We also visualized unstained putative bacteria associated with the roots of Brachypodium distachyon in a soil microcosm. Our results show that this multimodal approach holds significant promise for rhizosphere and soil science research.
Collapse
Affiliation(s)
- Janghyuk Lee
- Materials Science Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Rachel Hestrin
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Erin E Nuccio
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Keith D Morrison
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Christina E Ramon
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Ty J Samo
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Jennifer Pett-Ridge
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
- Life and Environmental Sciences Department, University of California Merced, Merced, California 95343, United States
| | - Sonny S Ly
- Materials Science Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Ted A Laurence
- Materials Science Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Peter K Weber
- Nuclear and Chemical Sciences Division, Physical & Life Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| |
Collapse
|
9
|
Žurauskas M, Alex A, Park J, Hood SR, Boppart SA. Fluorescent nanodiamonds for characterization of nonlinear microscopy systems. PHOTONICS RESEARCH 2021; 9:2309-2318. [PMID: 37181134 PMCID: PMC10174270 DOI: 10.1364/prj.434236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Characterizing the performance of fluorescence microscopy and nonlinear imaging systems is an essential step required for imaging system optimization and quality control during longitudinal experiments. Emerging multimodal nonlinear imaging techniques require a new generation of microscopy calibration targets that are not susceptible to bleaching and can provide a contrast across the multiple modalities. Here, we present a nanodiamond-based calibration target for microscopy, designed for facilitating reproducible measurements at the object plane. The target is designed to support day-to-day instrumentation development efforts in microscopy laboratories. The images of a phantom contain information about the imaging performance of a microscopy system across multiple spectral windows and modalities. Since fluorescent nanodiamonds are not prone to bleaching, the proposed imaging target can serve as a standard, shelf-stable sample to provide rapid reference measurements for ensuring consistent performance of microscopy systems in microscopy laboratories and imaging facilities.
Collapse
Affiliation(s)
- Mantas Žurauskas
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Aneesh Alex
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- GlaxoSmithKline, Collegeville, Pennsylvania 19426, USA
| | - Jaena Park
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Steve R. Hood
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- GlaxoSmithKline, Stevenage, Hertfordshire SG1 2NY, UK
| | - Stephen A. Boppart
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
- Corresponding author:
| |
Collapse
|
10
|
Mukherjee P, Aksamitiene E, Alex A, Shi J, Bera K, Zhang C, Spillman DR, Marjanovic M, Fazio M, Seth PP, Frazier K, Hood SR, Boppart SA. Differential Uptake of Antisense Oligonucleotides in Mouse Hepatocytes and Macrophages Revealed by Simultaneous Two-Photon Excited Fluorescence and Coherent Raman Imaging. Nucleic Acid Ther 2021; 32:163-176. [PMID: 34797690 PMCID: PMC9221167 DOI: 10.1089/nat.2021.0059] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Antisense oligonucleotides (ASOs), a novel paradigm in modern therapeutics, modulate cellular gene expression by binding to complementary messenger RNA (mRNA) sequences. While advances in ASO medicinal chemistry have greatly improved the efficiency of cellular uptake, selective uptake by specific cell types has been difficult to achieve. For more efficient and selective uptake, ASOs are often conjugated with molecules with high binding affinity for transmembrane receptors. Triantennary N-acetyl-galactosamine conjugated phosphorothioate ASOs (GalNAc-PS-ASOs) were developed to enhance targeted ASO delivery into liver through the hepatocyte-specific asialoglycoprotein receptor (ASGR). We assessed the kinetics of uptake and subsequent intracellular distribution of AlexaFluor 488 (AF488)-labeled PS-ASOs and GalNAc-PS-ASOs in J774A.1 mouse macrophages and primary mouse or rat hepatocytes using simultaneous coherent anti-Stokes Raman scattering (CARS) and two-photon fluorescence (2PF) imaging. The CARS modality captured the dynamic lipid distributions and overall morphology of the cells; two-photon fluorescence (2PF) measured the time- and dose-dependent localization of ASOs delivered by a modified treatment of suspension cells. Our results show that in macrophages, the uptake rate of PS-ASOs did not significantly differ from that of GalNAc-PS-ASOs. However, in hepatocytes, GalNAc-PS-ASOs exhibited a peripheral uptake distribution compared to a polar uptake distribution observed in macrophages. The peripheral distribution correlated with a significantly larger amount of internalized GalNAc-PS-ASOs compared to the PS-ASOs. This work demonstrates the relevance of multimodal imaging for elucidating the uptake mechanism, accumulation, and fate of different ASOs in liver cells that can be used further in complex in vitro models and liver tissues to evaluate ASO distribution and activity.
Collapse
Affiliation(s)
- Prabuddha Mukherjee
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Edita Aksamitiene
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Aneesh Alex
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,In vitro/In vivo Translation, Research, GlaxoSmithKline, Collegeville, Pennsylvania, USA
| | - Jindou Shi
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Electrical and Computer Engineering and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Kajari Bera
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Chi Zhang
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Darold R Spillman
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Marina Marjanovic
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Michael Fazio
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
| | - Punit P Seth
- Ionis Pharmaceuticals, Inc., Carlsbad, California, USA
| | - Kendall Frazier
- In vitro/In vivo Translation, Research, GlaxoSmithKline, Collegeville, Pennsylvania, USA
| | - Steve R Hood
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,In vitro/In vivo Translation, Research, GlaxoSmithKline, Stevenage, United Kingdom
| | - Stephen A Boppart
- GSK Center for Optical Molecular Imaging and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Electrical and Computer Engineering and University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| |
Collapse
|
11
|
Hsiao YT, Huang YF, Borah BJ, Chen SK, Sun CK. Single-laser-based simultaneous four-wavelength excitation source for femtosecond two-photon fluorescence microscopy. BIOMEDICAL OPTICS EXPRESS 2021; 12:4661-4679. [PMID: 34513216 PMCID: PMC8407803 DOI: 10.1364/boe.428771] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 06/27/2021] [Accepted: 06/28/2021] [Indexed: 06/13/2023]
Abstract
Multicolor labeling of biological samples with large volume is required for omic-level of study such as the construction of nervous system connectome. Among the various imaging method, two photon microscope has multiple advantages over traditional single photon microscope for higher resolution and could image large 3D volumes of tissue samples with superior imaging depth. However, the growing number of fluorophores for labeling underlines the urgent need for an ultrafast laser source with the capability of providing simultaneous plural excitation wavelengths for multiple fluorophores. Here, we propose and demonstrate a single-laser-based four-wavelength excitation source for two-photon fluorescence microscopy. Using a sub-100 fs 1,070-nm Yb:fiber laser to pump an ultrashort nonlinear photonic crystal fiber in the low negative dispersion region, we introduced efficient self-phase modulation and acquired a blue-shifted spectrum dual-peaked at 812 and 960 nm with 28.5% wavelength conversion efficiency. By compressing the blue-shift near-IR spectrum to 33 fs to ensure the temporal overlap of the 812 and 960 nm peaks, the so-called sum frequency effect created the third virtual excitation wavelength effectively at 886 nm. Combined with the 1,070 nm laser source as the fourth excitation wavelength, the all-fiber-format four-wavelength excitation source enabled simultaneous four-color two-photon imaging in Brainbow AAV-labeled (TagBFP, mTFP, EYFP, and mCherry) brain samples. With an increased number of excitation wavelengths and improved excitation efficiency than typical commercial femtosecond lasers, our compact four-wavelength excitation approach can provide a versatile, efficient, and easily accessible solution for multiple-color two-photon fluorescence imaging in the field of neuroscience, biomolecular probing, and clinical applications with at least four spectrally-distinct fluorophores.
Collapse
Affiliation(s)
- Yang-Ting Hsiao
- Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
| | - Yu-Fan Huang
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan
| | - Bhaskar Jyoti Borah
- Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
| | - Shih-Kuo Chen
- Department of Life Science, National Taiwan University, Taipei 10617, Taiwan
| | - Chi-Kuang Sun
- Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan
| |
Collapse
|
12
|
Sternisha SM, Mukherjee P, Alex A, Chaney EJ, Barkalifa R, Wan B, Lee JH, Rico-Jimenez J, Žurauskas M, Spillman DR, Sripada SA, Marjanovic M, Arp Z, Galosy SS, Bhanushali DS, Hood SR, Bose S, Boppart SA. Longitudinal monitoring of cell metabolism in biopharmaceutical production using label-free fluorescence lifetime imaging microscopy. Biotechnol J 2021; 16:e2000629. [PMID: 33951311 DOI: 10.1002/biot.202000629] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 04/12/2021] [Accepted: 04/28/2021] [Indexed: 11/11/2022]
Abstract
Chinese hamster ovary (CHO) cells are routinely used in the biopharmaceutical industry for production of therapeutic monoclonal antibodies (mAbs). Although multiple offline and time-consuming measurements of spent media composition and cell viability assays are used to monitor the status of culture in biopharmaceutical manufacturing, the day-to-day changes in the cellular microenvironment need further in-depth characterization. In this study, two-photon fluorescence lifetime imaging microscopy (2P-FLIM) was used as a tool to directly probe into the health of CHO cells from a bioreactor, exploiting the autofluorescence of intracellular nicotinamide adenine dinucleotide phosphate (NAD(P)H), an enzymatic cofactor that determines the redox state of the cells. A custom-built multimodal microscope with two-photon FLIM capability was utilized to monitor changes in NAD(P)H fluorescence for longitudinal characterization of a changing environment during cell culture processes. Three different cell lines were cultured in 0.5 L shake flasks and 3 L bioreactors. The resulting FLIM data revealed differences in the fluorescence lifetime parameters, which were an indicator of alterations in metabolic activity. In addition, a simple principal component analysis (PCA) of these optical parameters was able to identify differences in metabolic progression of two cell lines cultured in bioreactors. Improved understanding of cell health during antibody production processes can result in better streamlining of process development, thereby improving product titer and verification of scale-up. To our knowledge, this is the first study to use FLIM as a label-free measure of cellular metabolism in a biopharmaceutically relevant and clinically important CHO cell line.
Collapse
Affiliation(s)
- Shawn M Sternisha
- Biopharm Product Development, GlaxoSmithKline, King of Prussia, Pennsylvania, USA
| | - Prabuddha Mukherjee
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Aneesh Alex
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,In vitro/In vivo Translation, Research, GlaxoSmithKline, Collegeville, Pennsylvania, USA
| | - Eric J Chaney
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Ronit Barkalifa
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Boyong Wan
- Biopharm Product Development, GlaxoSmithKline, King of Prussia, Pennsylvania, USA
| | - Jang Hyuk Lee
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Jose Rico-Jimenez
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Mantas Žurauskas
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Darold R Spillman
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Sobhana A Sripada
- Biopharm Product Development, GlaxoSmithKline, King of Prussia, Pennsylvania, USA.,Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, USA
| | - Marina Marjanovic
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Zane Arp
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Sybille S Galosy
- Biopharm Product Development, GlaxoSmithKline, King of Prussia, Pennsylvania, USA
| | | | - Steve R Hood
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,GlaxoSmithKline Research and Development, Stevenage, Hertfordshire, UK
| | - Sayantan Bose
- Biopharm Product Development, GlaxoSmithKline, King of Prussia, Pennsylvania, USA
| | - Stephen A Boppart
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| |
Collapse
|
13
|
Sorrells JE, Martin EM, Aksamitiene E, Mukherjee P, Alex A, Chaney EJ, Marjanovic M, Boppart SA. Label-free characterization of single extracellular vesicles using two-photon fluorescence lifetime imaging microscopy of NAD(P)H. Sci Rep 2021; 11:3308. [PMID: 33558561 PMCID: PMC7870923 DOI: 10.1038/s41598-020-80813-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2020] [Accepted: 12/22/2020] [Indexed: 12/11/2022] Open
Abstract
The heterogeneous nature of extracellular vesicles (EVs) creates the need for single EV characterization techniques. However, many common biochemical and functional EV analysis techniques lack single EV resolution. Two-photon fluorescence lifetime imaging microscopy (FLIM) is widely used to functionally characterize the reduced form of nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate (NAD(P)H) in cells and tissues. Here, we demonstrate that FLIM can also be used to image and characterize NAD(P)H in single isolated EVs. EVs were isolated using standard differential ultracentrifugation techniques from multiple cell lines and imaged using a custom two-photon FLIM system. The presented data show that the NAD(P)H fluorescence lifetimes in isolated cell-derived EVs follow a wide Gaussian distribution, indicating the presence of a range of different protein-bound and free NAD(P)H species. EV NAD(P)H fluorescence lifetime distribution has a larger standard deviation than that of cells and a significantly different fluorescence lifetime distribution than the nuclei, mitochondria, and cytosol of cells. Additionally, changes in the metabolic conditions of cells were reflected in changes in the mean fluorescence lifetime of NAD(P)H in the produced EVs. These data suggest that FLIM of NAD(P)H could be a valuable tool for EV research.
Collapse
Affiliation(s)
- Janet E Sorrells
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Elisabeth M Martin
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Edita Aksamitiene
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Prabuddha Mukherjee
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Aneesh Alex
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Eric J Chaney
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Marina Marjanovic
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Stephen A Boppart
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- GSK Center for Optical Molecular Imaging, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
- Cancer Center at Illinois, Urbana, IL, 61801, USA.
- Carle Illinois College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
| |
Collapse
|
14
|
Lee M, Herrington CS, Ravindra M, Sepp K, Davies A, Hulme AN, Brunton VG. Recent advances in the use of stimulated Raman scattering in histopathology. Analyst 2021; 146:789-802. [PMID: 33393954 DOI: 10.1039/d0an01972k] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Stimulated Raman histopathology (SRH) utilises the intrinsic vibrational properties of lipids, proteins and nucleic acids to generate contrast providing rapid image acquisition that allows visualisation of histopathological features. It is currently being trialled in the intraoperative setting, where the ability to image unprocessed samples rapidly and with high resolution offers several potential advantages over the use of conventional haematoxylin and eosin stained images. Here we review recent advances in the field including new updates in instrumentation and computer aided diagnosis. We also discuss how other non-linear modalities can be used to provide additional diagnostic contrast which together pave the way for enhanced histopathology and open up possibilities for in vivo pathology.
Collapse
Affiliation(s)
- Martin Lee
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XR, UK.
| | - C Simon Herrington
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XR, UK.
| | - Manasa Ravindra
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Kristel Sepp
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XR, UK. and EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Amy Davies
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XR, UK.
| | - Alison N Hulme
- EaStCHEM School of Chemistry, The University of Edinburgh, David Brewster Road, Edinburgh, EH9 3FJ, UK
| | - Valerie G Brunton
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road South, Edinburgh, EH4 2XR, UK.
| |
Collapse
|