|
JBO guest editors introduce the Special Section Celebrating Thirty Years of Multiphoton Microscopy in the Biomedical Sciences. |
|
After the invention of the microscope by Antoni van Leeuwenhoek in the 1670s, the ability to investigate structures and mechanisms at the microscopic level has allowed scientists to better grasp the often misunderstood relationship between microscopic and macroscopic behavior. Furthermore, imaging specimens through a microscope preserves the temporal and spatial relationships that are frequently lost in traditional biochemical techniques, and produces a two- or three- or four-dimensional resolution that other laboratory methods cannot. There are several microscope techniques that have been established for cellular imaging; among them, the benefits of fluorescence microscopy (FM) techniques are numerous. FM plays a vital role in the biological and biomedical sciences where fluorescence probe specificity and sensitivity can provide important information regarding the biochemical, biophysical, and structural status of cells.1 Recent advancements in light sources, detection systems, data acquisition methods, image analysis, and display methods have further broadened the applications in which fluorescence microscopy can successfully be applied.2 In particular, the rapid advancements of confocal and multiphoton microscopy over the past three decades have been major contributors to our understanding of dynamic processes in cells, tissues, and live animals.3–5 Considering the historical perspective of multiphoton microscopy, in 1931, Maria Göppert-Mayer reported the quantum mechanical formulation of two-photon molecular excitation in her doctoral thesis.6 Two-photon excited fluorescence was finally demonstrated by Kaiser and Garrett7 shortly after the invention of the laser in 1960. Sheppard and co-workers developed the SHG microscope8 for solid state specimens and Denk et al. developed a non-linear fluorescence microscope and first showed that it can be applied to image biological system non-invasively.9 Laser scanning multiphoton fluorescence microscopy was developed by Denk et al. in 1990.9 Since then, the usage and the development of multiphoton microscopy has increased tremendously (see Fig. 1). More importantly, the commercialization of multiphoton imaging systems by Bio-Rad did increase awareness and application of this technology in biomedical imaging. It should also be recognized that laser companies (Spectra Physics and Coherent) played a key role in introducing tunable (700-1100 nm; currently from 680 to 1300 nm) femtosecond infrared-pulsed laser systems (Ti: sapphire) for multiphoton imaging. Moreover, the future will bring even easier-to-use equipment and increased sensitivity, which will allow greater flexibility in the simultaneous imaging of multiple fluorophores while images are collected over time and at greater depths inside tissue/live animals. To describe the multiphoton excitation process in brief, an infrared femtosecond pulsed laser is required to create multiphoton absorption in a biological sample. Multiphoton excitation occurs at only a single, diffraction-limited spot where the photon flux is great enough to allow absorption of more than one photon. For example, for one-photon excitation, a wavelength of 480 nm CW (continuous wave) is selected for GFP, but for two-photon excitation, a single 960 nm wavelength from a Ti: sapphire pulsed laser is used. For most of the fluorophores, the two-photon absorption cross-section is blue shifted. Multiphoton images have better signal-to-noise compared to confocal images because of a considerably reduced amount of light scattering due to infrared wavelengths used for 2-photon imaging. In addition, autofluorescence and photobleaching are minimized, as there is no absorption throughout the specimen beyond the focal volume or focal plane. The contributions and usage of multiphoton microscopy in the areas of biological and biomedical sciences over the last 30 years have generated a high level of interest among scientists and students. As shown in Fig. 1, there has been tremendous increase in publications in the area of technology development and the usage of the multiphoton microscopy in various areas of research. To mention a few, on the technology development side, there are a number of miniaturized and fiber-optics-based two-photon microscopy developments, three-photon microscopy10,11 and longer wavelength applications to image deep inside tissue and animal specimens,12 and second and third harmonic generation microscopy in tissue and live animals.13 There is also two- and three-photon lifetime imaging, metabolism-related imaging (NADH, FAD, tryptophan);14–18 calcium, pH, and oxygen19 membrane potential measurements; amino acid tryptophan imaging; multiphoton tomography; coherent anti-Stokes Raman scattering (CARS) imaging;20 and single molecule detection, super resolution.21–23 Closer to human pathologies there is stem cell research, clinical applications in surgery, cancer diagnosis and treatment, and very specifically, skin cancer diagnosis, best highlighted by the commercialization of multiphoton microscopy by JenLab for skin cancer diagnosis.24 ReferencesJ. Pawley, Handbook of Biological Confocal Microscopy, Springer Science & Business Media(2010). Google Scholar
A. Periasamy, Methods in Cellular Imaging, Oxford University Press, New York
(2001). Google Scholar
L. Marcu, P. M. French and D. S. Elson, Fluorescence Lifetime Spectroscopy and Imaging: Principles and Applications in Biomedical Diagnostics, CRC Press(2014). Google Scholar
K. König, Multiphoton Microscopy and Fluorescence Lifetime Imaging: Applications in Biology and Medicine, De Gruyter, Berlin, Boston
(2018). Google Scholar
B. R. Masters and P. So, Handbook of Biomedical Nonlinear Optical Microscopy, Oxford University Press, Oxford
(2008). Google Scholar
M. Göppert-Mayer,
“Über elementarakte mit zwei quantensprüngen,”
Ann. Phys., 401
(3), 273
–294
(1931). https://doi.org/10.1002/(ISSN)1521-3889 Google Scholar
W. Kaiser and C. Garrett,
“Two-photon excitation in ,”
Phys. Rev. Lett., 7
(6), 229
–231
(1961). https://doi.org/10.1103/PhysRevLett.7.229 PRLTAO 0031-9007 Google Scholar
J. Gannaway and C. Sheppard,
“Second-harmonic imaging in the scanning optical microscope,”
Opt. Quantum Electron., 10
(5), 435
–439
(1978). https://doi.org/10.1007/BF00620308 OQELDI 0306-8919 Google Scholar
W. Denk, J. H. Strickler and W. W. Webb,
“Two-photon laser scanning fluorescence microscopy,”
Science, 248
(4951), 73
–76
(1990). https://doi.org/10.1126/science.2321027 SCIEAS 0036-8075 Google Scholar
S. W. Hell et al.,
“Three-photon excitation in fluorescence microscopy,”
J. Biomed. Opt., 1
(1), 71
–75
(1996). https://doi.org/10.1117/12.229062 JBOPFO 1083-3668 Google Scholar
S. W. Chu et al.,
“High-resolution simultaneous three-photon fluorescence and third-harmonic-generation microscopy,”
Microsc. Res. Tech., 66
(4), 193
–197
(2005). https://doi.org/10.1002/(ISSN)1097-0029 MRTEEO 1059-910X Google Scholar
N. G. Horton et al.,
“In vivo three-photon microscopy of subcortical structures within an intact mouse brain,”
Nat. Photonics, 7
(3), 205
–209
(2013). https://doi.org/10.1038/nphoton.2012.336 NPAHBY 1749-4885 Google Scholar
S. Chakraborty et al.,
“Additive-color multi-harmonic generation microscopy for simultaneous label-free differentiation of plaques, tangles, and neuronal axons,”
Biomed. Opt. Express, 11
(2), 571
–585
(2020). https://doi.org/10.1364/BOE.378447 BOEICL 2156-7085 Google Scholar
V. Jyothikumar, Y. Sun and A. Periasamy,
“Investigation of tryptophan-NADH interactions in live human cells using three-photon fluorescence lifetime imaging and Forster resonance energy transfer microscopy n1,”
J. Biomed. Opt., 18
(6), 060501
(2013). https://doi.org/10.1117/1.JBO.18.6.060501 JBOPFO 1083-3668 Google Scholar
A. J. Walsh et al.,
“Optical metabolic imaging of live tissue cultures,”
Proc. SPIE, 8588 858820
(2013). https://doi.org/10.1117/12.2001863 PSISDG 0277-786X Google Scholar
H. Wallrabe et al.,
“Segmented cell analyses to measure redox states of autofluorescent NAD(P)H, FAD & Trp in cancer cells by FLIM,”
Sci. Rep., 8
(1), 79
(2018). https://doi.org/10.1038/s41598-017-18634-x SRCEC3 2045-2322 Google Scholar
A. Periasamy and R. M. Clegg, FLIM Microscopy in Biology and Medicine, Chapman and Hall/CRC(2009). Google Scholar
W. Becker, Advanced Time-Correlated Single Photon Counting Applications, Springer(2015). Google Scholar
H. C. Gerritsen et al.,
“Fluorescence lifetime imaging of oxygen in living cells,”
J. Fluoresc., 7
(1), 11
–15
(1997). https://doi.org/10.1007/BF02764572 JOFLEN 1053-0509 Google Scholar
J.-X. Cheng and X. S. Xie, Coherent Raman Scattering Microscopy, CRC Press(2016). Google Scholar
T. A. Klar et al.,
“Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission,”
Proc. Natl. Acad. Sci. U.S.A., 97
(15), 8206
–8210
(2000). https://doi.org/10.1073/pnas.97.15.8206 PNASA6 0027-8424 Google Scholar
K. R. Chi,
“Super-resolution microscopy: breaking the limits,”
Nat. Methods, 6
(1), 15
–18
(2009). https://doi.org/10.1038/nmeth.f.234 1548-7091 Google Scholar
B.-C. Chen et al.,
“Lattice light-sheet microscopy: imaging molecules to embryos at high spatiotemporal resolution,”
Science, 346
(6208), 1257998
(2014). https://doi.org/10.1126/science.1257998 SCIEAS 0036-8075 Google Scholar
S. Seidenari et al.,
“Multiphoton laser microscopy and fluorescence lifetime imaging for the evaluation of the skin,”
Dermatol. Res. Pract., 2012 810749
(2012). https://doi.org/10.1155/2012/810749 Google Scholar
|
