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Abstract
Over the last half century, the autofluorescence of the metabolic cofactors NADH (reduced nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) has been quantified in a variety of cell types and disease states. With the spread of nonlinear optical microscopy techniques in biomedical research, NADH and FAD imaging has offered an attractive solution to noninvasively monitor cell and tissue status and elucidate dynamic changes in cell or tissue metabolism. Various tools and methods to measure the temporal, spectral, and spatial properties of NADH and FAD autofluorescence have been developed. Specifically, an optical redox ratio of cofactor fluorescence intensities and NADH fluorescence lifetime parameters have been used in numerous applications, but significant work remains to mature this technology for understanding dynamic changes in metabolism. This article describes the current understanding of our optical sensitivity to different metabolic pathways and highlights current challenges in the field. Recent progress in addressing these challenges and acquiring more quantitative information in faster and more metabolically relevant formats is also discussed.
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Affiliation(s)
- Irene Georgakoudi
- Department of Biomedical Engineering, Tufts University, Medford, Massachusetts, USA;
- Genetics, Molecular and Cellular Biology Program, Graduate School of Biomedical Sciences, Tufts University, Boston, Massachusetts, USA
| | - Kyle P Quinn
- Department of Biomedical Engineering and the Arkansas Integrative Metabolic Research Center, University of Arkansas, Fayetteville, Arkansas, USA
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Wang P, Kitano M, Keomanee-Dizon K, Truong TV, Fraser SE, Cutrale F. A single-shot hyperspectral phasor camera for fast, multi-color fluorescence microscopy. CELL REPORTS METHODS 2023; 3:100441. [PMID: 37159674 PMCID: PMC10162951 DOI: 10.1016/j.crmeth.2023.100441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 11/16/2022] [Accepted: 03/09/2023] [Indexed: 05/11/2023]
Abstract
Hyperspectral fluorescence imaging improves multiplexed observations of biological samples by utilizing multiple color channels across the spectral range to compensate for spectral overlap between labels. Typically, spectral resolution comes at a cost of decreased detection efficiency, which both hampers imaging speed and increases photo-toxicity to the samples. Here, we present a high-speed, high-efficiency snapshot spectral acquisition method, based on optical compression of the fluorescence spectra via Fourier transform, that overcomes the challenges of discrete spectral sampling: single-shot hyperspectral phasor camera (SHy-Cam). SHy-Cam captures fluorescence spatial and spectral information in a single exposure with a standard scientific CMOS camera, with photon efficiency of over 80%, easily and with acquisition rates exceeding 30 datasets per second, making it a powerful tool for multi-color in vivo imaging. Its simple design, using readily available optical components, and its easy integration provide a low-cost solution for multi-color fluorescence imaging with increased efficiency and speed.
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Affiliation(s)
- Pu Wang
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Biomedical Engineering, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
| | - Masahiro Kitano
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Molecular and Computational Biology, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
| | - Kevin Keomanee-Dizon
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Joseph Henry Laboratories of Physics, Princeton University, Princeton, NJ 08544, USA
| | - Thai V. Truong
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Molecular and Computational Biology, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
| | - Scott E. Fraser
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Biomedical Engineering, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Molecular and Computational Biology, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
| | - Francesco Cutrale
- Translational Imaging Center, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
- Biomedical Engineering, University of Southern California, 1002 West Childs Way, Los Angeles, CA 90089, USA
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Batey JE, Yang M, Giang H, Dong B. Ultrahigh-Throughput Single-Particle Hyperspectral Imaging of Gold Nanoparticles. Anal Chem 2023; 95:5479-5483. [PMID: 36883846 DOI: 10.1021/acs.analchem.2c05336] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023]
Abstract
Gold nanoparticles (AuNPs) have become increasingly useful in recent years for their roles in nanomedicine, cellular biology, energy storage and conversion, photocatalysis, and more. At the single-particle level, AuNPs have heterogeneous physical and chemical properties which are not resolvable in ensemble measurements. In the present study, we developed an ultrahigh-throughput spectroscopy and microscopy imaging system for characterization of AuNPs at the single-particle level using phasor analysis. The developed method enables quantification of spectra and spatial information on large numbers of AuNPs with a single snapshot of an image (1024 × 1024 pixels) at high temporal resolution (26 fps) and localization precision (sub-5 nm). We characterized the localized surface plasmonic resonance (SPR) scattering spectra of gold nanospheres (AuNSs) of four different sizes (40-100 nm). Comparing to the conventional optical grating method which suffers low efficiency in characterization due to spectral interference caused by nearby nanoparticles, the phasor approach enables high-throughput analysis of single-particle SPR properties in high particle density. Up to 10-fold greater efficiency of single-particle spectro-microscopy analysis using the spectra phasor approach when compared to a conventional optical grating method was demonstrated.
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Affiliation(s)
- James Ethan Batey
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Meek Yang
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Hannah Giang
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
| | - Bin Dong
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
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Díaz M, Malacrida L. Advanced Fluorescence Microscopy Methods to Study Dynamics of Fluorescent Proteins In Vivo. Methods Mol Biol 2023; 2564:53-74. [PMID: 36107337 DOI: 10.1007/978-1-0716-2667-2_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Fluorescent proteins are standard tools for addressing biological questions in a cell biology laboratory. The genetic tagging of protein of interest with fluorescent proteins opens the opportunity to follow them in vivo and to understand their interactions and dynamics. In addition, the latest advances in optical microscopy image acquisition and processing allow us to study many cellular processes in vivo. Techniques such as fluorescence lifetime microscopy and hyperspectral imaging provide valuable tools for understanding fluorescent protein interactions and their photophysics. Finally, fluorescence fluctuation analysis opens the possibility to address questions of molecular diffusion, protein-protein interactions, and oligomerization, among others, yielding quantitative information on the subject of study. This chapter will cover some of the more important advances in cutting-edge technologies and methods that, combined with fluorescent proteins, open new frontiers for biological studies.
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Affiliation(s)
- Marcela Díaz
- Advanced Bioimaging Unit, Institut Pasteur of Montevideo & Universidad de la República, Montevideo, Uruguay
| | - Leonel Malacrida
- Advanced Bioimaging Unit, Institut Pasteur of Montevideo & Universidad de la República, Montevideo, Uruguay.
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
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Spectral phasor analysis enables multiplexed microscopy with bioluminescent probes. Nat Methods 2022; 19:801-802. [PMID: 35739312 DOI: 10.1038/s41592-022-01530-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Multiplexed bioluminescence microscopy via phasor analysis. Nat Methods 2022; 19:893-898. [PMID: 35739310 DOI: 10.1038/s41592-022-01529-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 05/18/2022] [Indexed: 12/19/2022]
Abstract
Bioluminescence imaging with luciferase-luciferin pairs is a well-established technique for visualizing biological processes across tissues and whole organisms. Applications at the microscale, by contrast, have been hindered by a lack of detection platforms and easily resolved probes. We addressed this limitation by combining bioluminescence with phasor analysis, a method commonly used to distinguish spectrally similar fluorophores. We built a camera-based microscope equipped with special optical filters to directly assign phasor locations to unique luciferase-luciferin pairs. Six bioluminescent reporters were easily resolved in live cells, and the readouts were quantitative and instantaneous. Multiplexed imaging was also performed over extended time periods. Bioluminescent phasor further provided direct measures of resonance energy transfer in single cells, setting the stage for dynamic measures of cellular and molecular features. The merger of bioluminescence with phasor analysis fills a long-standing void in imaging capabilities, and will bolster future efforts to visualize biological events in real time and over multiple length scales.
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Xu D. Application of Microspectral Imaging in Motor and Sensory Nerve Classification. JOURNAL OF HEALTHCARE ENGINEERING 2021; 2021:4954540. [PMID: 34912533 PMCID: PMC8668288 DOI: 10.1155/2021/4954540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 11/06/2021] [Indexed: 11/24/2022]
Abstract
Objective It aimed to explore the application of the microscopic hyperspectral technique in motor and sensory nerve classification. Methods The self-developed microscopic hyperspectral acquisition system was applied to collect the data of anterior and posterior spinal cord sections of white rabbits. The joint correction algorithm was employed to preprocess the collected data, such as noise reduction. On the basis of pure linear light source index, a new pixel purification algorithm based on cross contrast was proposed to extract more regions of interest, which was used for feature extraction of motor and sensory nerves. Besides, the ML algorithm was employed to classify motor and sensory nerves based on feature extraction results. Results The joint correction algorithm was adopted to preprocess the data collected by the microscopic hyperspectral technique, so as to eliminate the influence of the incident light source and the system and improve the classification accuracy. The axon and myelin spectrum curves of the two kinds of nerves in the stained specimens had the same trend, but the values of all kinds of spectrum of sensory nerves were higher than those of motor nerves. However, the myelin sheath spectrum curves of motor nerves in the unstained specimens were greatly different from the curves of sensory nerves. The axon spectrum curves had the same trend, but the axon spectrum values of sensory nerves were higher than those of motor nerves. The ML algorithm had high accuracy and fast speed in motor and sensory nerve classification, and the classification effect of stained specimens was better than that of unstained specimens. Conclusion The microscopic hyperspectral technique had high feasibility in sensory and motor nerve classification and was worthy of further research and promotion.
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Affiliation(s)
- Du Xu
- Xi'an University of Posts and Telecommunications, Shanxi, Xi'an 710100, China
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Torrado B, Dvornikov A, Gratton E. Method of transmission filters to measure emission spectra in strongly scattering media. BIOMEDICAL OPTICS EXPRESS 2021; 12:3760-3774. [PMID: 34457378 PMCID: PMC8367243 DOI: 10.1364/boe.422236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 04/20/2021] [Accepted: 05/20/2021] [Indexed: 06/13/2023]
Abstract
We describe a method based on a pair of transmission filters placed in the emission path of a microscope to resolve the emission wavelength of every point in an image. The method can be applied to any type of imaging device that provides the light in the wavelength transmission range of the filters. Unique characteristics of the filter approach are that the light does not need to be collimated and the wavelength response does not depend on the scattering of the sample or tissue. The pair of filters are used to produce the spectral phasor of the transmitted light, which is sufficient to perform spectral deconvolution over a broad wavelength range. The method is sensitive enough to distinguish free and protein-bound NADH and can be used in metabolic studies.
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Hedde PN, Cinco R, Malacrida L, Kamaid A, Gratton E. Phasor-based hyperspectral snapshot microscopy allows fast imaging of live, three-dimensional tissues for biomedical applications. Commun Biol 2021; 4:721. [PMID: 34117344 PMCID: PMC8195998 DOI: 10.1038/s42003-021-02266-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 05/26/2021] [Indexed: 01/31/2023] Open
Abstract
Hyperspectral imaging is highly sought after in many fields including mineralogy and geology, environment and agriculture, astronomy and, importantly, biomedical imaging and biological fluorescence. We developed ultrafast phasor-based hyperspectral snapshot microscopy based on sine/cosine interference filters for biomedical imaging not feasible with conventional hyperspectral detection methods. Current approaches rely on slow spatial or spectral scanning limiting their application in living biological tissues, while faster snapshot methods such as image mapping spectrometry and multispectral interferometry are limited in spatial and/or spectral resolution, are computationally demanding, and imaging devices are very expensive to manufacture. Leveraging light sheet microscopy, phasor-based hyperspectral snapshot microscopy improved imaging speed 10-100 fold which, combined with minimal light exposure and high detection efficiency, enabled hyperspectral metabolic imaging of live, three-dimensional mouse tissues not feasible with other methods. As a fit-free method that does not require any a priori information often unavailable in complex and evolving biological systems, the rule of linear combinations of the phasor could spectrally resolve subtle differences between cell types in the developing zebrafish retina and spectrally separate and track multiple organelles in 3D cultured cells over time. The sine/cosine snapshot method is adaptable to any microscope or imaging device thus making hyperspectral imaging and fit-free analysis based on linear combinations broadly available to researchers and the public.
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Affiliation(s)
- Per Niklas Hedde
- grid.266093.80000 0001 0668 7243Laboratory for Fluorescence Dynamics, University of California, Irvine, CA USA ,grid.266093.80000 0001 0668 7243Department of Pharmaceutical Sciences, University of California, Irvine, CA USA ,grid.266093.80000 0001 0668 7243Beckman Laser Institute & Medical Clinic, University of California, Irvine, CA USA
| | - Rachel Cinco
- grid.266093.80000 0001 0668 7243Laboratory for Fluorescence Dynamics, University of California, Irvine, CA USA
| | - Leonel Malacrida
- grid.11630.350000000121657640Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay ,grid.11630.350000000121657640Advanced Bioimaging Unit, Institut Pasteur of Montevideo and Universidad de la República, Montevideo, Uruguay
| | - Andrés Kamaid
- grid.11630.350000000121657640Advanced Bioimaging Unit, Institut Pasteur of Montevideo and Universidad de la República, Montevideo, Uruguay
| | - Enrico Gratton
- grid.266093.80000 0001 0668 7243Laboratory for Fluorescence Dynamics, University of California, Irvine, CA USA ,grid.266093.80000 0001 0668 7243Beckman Laser Institute & Medical Clinic, University of California, Irvine, CA USA
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Malacrida L, Ranjit S, Jameson DM, Gratton E. The Phasor Plot: A Universal Circle to Advance Fluorescence Lifetime Analysis and Interpretation. Annu Rev Biophys 2021; 50:575-593. [PMID: 33957055 DOI: 10.1146/annurev-biophys-062920-063631] [Citation(s) in RCA: 50] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The phasor approach to fluorescence lifetime imaging has become a common method to analyze complicated fluorescence signals from biological samples. The appeal of the phasor representation of complex fluorescence decays in biological systems is that a visual representation of the decay of entire cells or tissues can be used to easily interpret fundamental biological states related to metabolism and oxidative stress. Phenotyping based on autofluorescence provides new avenues for disease characterization and diagnostics. The phasor approach is a transformation of complex fluorescence decays that does not use fits to model decays and therefore has the same information content as the original data. The phasor plot is unique for a given system, is highly reproducible, and provides a robust method to evaluate the existence of molecular interactions such as Förster resonance energy transfer or the response of ion indicators. Recent advances permitquantification of multiple components from phasor plots in fluorescence lifetime imaging microscopy, which is not presently possible using data fitting methods, especially in biological systems.
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Affiliation(s)
- Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, California 92697, USA; .,Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República, 11600 Montevideo, Uruguay.,Advanced Bioimaging Unit, Institut Pasteur Montevideo and Universidad de la República-Uruguay, 11400 Montevideo, Uruguay
| | - Suman Ranjit
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, California 92697, USA; .,Department of Biochemistry and Molecular & Cellular Biology, Georgetown University, Washington, DC 20057, USA
| | - David M Jameson
- Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, Hawaii 96813, USA
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, California 92697, USA;
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Vallmitjana A, Dvornikov A, Torrado B, Jameson DM, Ranjit S, Gratton E. Resolution of 4 components in the same pixel in FLIM images using the phasor approach. Methods Appl Fluoresc 2020; 8:035001. [PMID: 32235070 DOI: 10.1088/2050-6120/ab8570] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
In several cellular systems, the phasor FLIM approach has shown the existence of more than 2 components in the same pixel, a typical example being free and bound NADH. In order to properly quantify the concentrations and the spatial distributions of fluorescence components associated with different molecular species we developed a general method to resolve 3 and 4 components in the same pixel using the phasor approach. The method is based on the law of linear combination of components valid after transformation of the decay curves to phasors for each pixel in the image. In principle, the linear combination rule is valid for an arbitrary number of components. For 3 components we use only the phasor position for the first harmonic, which has a small error, while for 4 components we need the phasor location at higher harmonics that have intrinsically more noise. As a result of the noise in the higher harmonics, caused by limited photon statistics, we are able to use linear algebra to resolve 4 components given the position of the phasors of 4 independent components in mixtures of dyes and 3 components for dyes in cellular systems.
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Affiliation(s)
- Alexander Vallmitjana
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California, Irvine, CA, United States of America
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Dvornikov A, Malacrida L, Gratton E. The DIVER Microscope for Imaging in Scattering Media. Methods Protoc 2019; 2:E53. [PMID: 31234383 PMCID: PMC6632175 DOI: 10.3390/mps2020053] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 06/06/2019] [Accepted: 06/19/2019] [Indexed: 01/31/2023] Open
Abstract
We describe an advanced DIVER (Deep Imaging Via Emission Recovery) detection system for two-photon fluorescence microscopy that allows imaging in multiple scattering media, including biological tissues, up to a depth of a few mm with micron resolution. This detection system is more sensitive to low level light signals than conventional epi-detection used in two-photon fluorescence microscopes. The DIVER detector efficiently collects scattered emission photons from a wide area of turbid samples at almost any entrance angle in a 2π spherical angle. Using an epi-detection scheme only photons coming from a relatively small area of a sample and at narrow acceptance angle can be detected. The transmission geometry of the DIVER imaging system makes it exceptionally suitable for Second and Third Harmonic Generation (SHG, THG) signal detection. It also has in-depth fluorescence lifetime imaging (FLIM) capability. Using special optical filters with sin-cos spectral response, hyperspectral analysis of images acquired in-depth in scattering media can be performed. The system was successfully employed in imaging of various biological tissues. The DIVER detector can be plugged into a standard microscope stage and used as an external detector with upright commercial two-photon microscopes.
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Affiliation(s)
- Alexander Dvornikov
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA.
| | - Leonel Malacrida
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA.
- Departamento de Fisiopatología, Hospital de Clínicas, Facultad de Medicina, Universidad de la República-Uruguay, Montevideo 11400, Uruguay.
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California Irvine, Irvine, CA 92697, USA.
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Maltas J, Palo D, Wong CK, Stefan S, O'Connor J, Al Aayedi N, Gaire M, Kinn D, Urayama P. A metabolic interpretation for the response of cellular autofluorescence to chemical perturbations assessed using spectral phasor analysis. RSC Adv 2018; 8:41526-41535. [PMID: 35559319 PMCID: PMC9092013 DOI: 10.1039/c8ra07691j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2018] [Accepted: 11/29/2018] [Indexed: 12/05/2022] Open
Abstract
Analytical approaches for sensing cellular NADH conformation from autofluorescence signals have significance because NADH is a metabolic indicator and endogenous biomarker. Recently, spectral detection of multiple cellular NADH forms during chemically-induced metabolic response was reported, however because NADH is solvatochromic and the spectral change is small, the possibility of a non-metabolic interpretation needs to be considered. Here we investigate the response of UV-excited autofluorescence to a range of well-known chemicals affecting fermentation, respiration, and oxidative-stress pathways in Saccharomyces cerevisiae. The two-component nature of the spectral response is assessed using phasor analysis. By considering a series of physically similar and dissimilar chemicals acting on multiple pathways, we show how the two-component nature of a spectral response is of metabolic origin, indicative of whether a single or several pathways have been affected. The two-component nature of the autofluorescence response is indicative of whether a single or several pathways are affected.![]()
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Affiliation(s)
- Jeff Maltas
- Department of Physics
- Miami University
- Oxford
- USA
| | - Dylan Palo
- Department of Physics
- Miami University
- Oxford
- USA
| | | | | | | | | | - Madhu Gaire
- Department of Physics
- Miami University
- Oxford
- USA
| | - Diana Kinn
- Department of Physics
- Miami University
- Oxford
- USA
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