Autofluorescence Spectroscopy and Imaging II

A special issue of Photochem (ISSN 2673-7256).

Deadline for manuscript submissions: closed (31 May 2022) | Viewed by 20067

Special Issue Editor


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Guest Editor
Institute of Molecular Genetics, National Research Council (IGM-CNR), c/o Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
Interests: photobiology; UV-visible autofluorescence analysis; endogenous fluorophores; label-free and real-time diagnosis; optical biopsy
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Special Issue Information

Dear Colleagues,

Autofluorescence defines the ability of biological substrates to give rise to fluorescence emission when excited with light at a suitable wavelength, in the absence of fixation or labelling with exogenous dyes. Various kinds of natural biomolecules may act as endogenous fluorophores and contribute to different extents to the overall autofluorescence signal of a biological substrate. The ubiquitous presence in living organisms of endogenous fluorophores and their possible changes, dependent on their close involvement in cell metabolic and catabolic pathways or participation to tissue architecture under normal or diseased conditions, is at the basis of unceasing and countless studies and of technological advances for label-free, real-time analytical and diagnostic applications. In biomedicine, autofluorescence-based diagnostic procedures rely on endogenous fluorophores typical of animal cells and tissues, such as collagen and elastin, relatable to tissue structure and its alteration, lipofuscins and porphyrins or glycation end products of lipids and proteins, relatable to oxidative stress and metabolic diseases, NAD(P)H and flavins, relatable to cell energy metabolism, and reductive biosynthesis. In the vegetable kingdom, chlorophylls and carotenoids involved in light harvesting and the consequent chemical energy production and in antioxidant protection are increasingly considered as biomarkers for applications ranging from the remote surveillance of plant pathologies and environment pollution, to the monitoring of biomass production. In addition to these common topics, many additional endogenous fluorophores can act as valuable biomarkers, for example, lignin, relevant to wood quality, or flavonoids, valuable for plant physiological activities or for their antioxidant role as food components or additives. 

In this context, the unceasing attention to the multiple aspects of autofluorescence is attested to by the various contributions already collected in the first edition of the Special Issue, in parallel with other works recently published in Molecules. Therefore, the second edition of the Special Issue on autofluorescence is expected to attract new contributions on the various aspects of autofluorescence and its related technological advances and to further promote knowledge and development of wide ranging in situ, label-free, and real-time analytical and diagnostic procedures.

You may choose our Joint Special Issue in Molecules.

Dr. Anna Cleta Croce
Guest Editor

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Keywords

  • autofluorescence
  • NA(P)DH
  • flavins
  • lipofuscins
  • proteins
  • collagen
  • porphyrins
  • bile pigments
  • carotenoids and retinoids
  • chlorophyll
  • cultured cells
  • animal tissues and organs
  • biological fluids
  • energy/lipid metabolism
  • mitochondria
  • oxidative stress
  • plants
  • food
  • environment
  • optical redox
  • spectroscopy
  • imaging
  • time resolved analysis
  • multiphoton excitation

Related Special Issue

Published Papers (5 papers)

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Editorial

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4 pages, 192 KiB  
Editorial
Autofluorescence Spectroscopy and Imaging II: A Special Issue Aimed to Promote Optically Based Studies on Biological Substrates
by Anna C. Croce
Photochem 2022, 2(1), 1-4; https://0-doi-org.brum.beds.ac.uk/10.3390/photochem2010001 - 29 Dec 2021
Cited by 1 | Viewed by 1679
Abstract
The Journal Molecules, in particular the Photochemistry Section, and the younger Journal Photochem are active in promoting the advances and practical applications based on the interaction of light with the various biological substrates from both animal and vegetal systems [...] Full article
(This article belongs to the Special Issue Autofluorescence Spectroscopy and Imaging II)

Research

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12 pages, 1931 KiB  
Article
Fluorescence and Phosphorescence of Flavylium Cation Analogues of Anthocyanins
by Gustavo T. M. Silva, Cassio P. Silva, Karen M. Silva, Renan M. Pioli, Tássia S. Costa, Vinícius V. Marto, Adilson A. Freitas, Jennifer Rozendo, Lucas M. O. S. Martins, Victor F. Cavalcante, Liuqing Sun, Adelia J. A. Aquino, Vânia M. T. Carneiro and Frank H. Quina
Photochem 2022, 2(2), 423-434; https://0-doi-org.brum.beds.ac.uk/10.3390/photochem2020029 - 08 Jun 2022
Cited by 6 | Viewed by 2067
Abstract
Fluorescence spectra and lifetimes were determined for 16 synthetic flavylium cation analogues of anthocyanin plant pigments in dry acetonitrile acidified with trifluoroacetic acid (TFA). Phosphorescence was also observed from the lowest excited triplet state for all of the flavylium cations at 77 K [...] Read more.
Fluorescence spectra and lifetimes were determined for 16 synthetic flavylium cation analogues of anthocyanin plant pigments in dry acetonitrile acidified with trifluoroacetic acid (TFA). Phosphorescence was also observed from the lowest excited triplet state for all of the flavylium cations at 77 K in a rigid TFA-acidified isopropanol glass. The fluorescence quantum yields and lifetimes depend in a systematic manner on the nature and position of the substituents on the flavylium chromophore and three specific substitution patterns associated with significant decreases in the fluorescence quantum yield were identified. A 4′-bromo or 4′-iodo substituent in the B-ring of the flavylium cation produced a small but normal heavy-atom effect, reducing the fluorescence quantum yield and the phosphorescence lifetime relative to analogues without the halogen atom. In contrast, three flavylium cations with a 3′-bromo substituent exhibited an “inverse” heavy atom effect, i.e., an increase in the fluorescence quantum yield rather than a decrease, which was rationalized on the basis of the nodal properties of the natural transition orbitals (NTOs) involved in the S0→S1 radiative transition. Full article
(This article belongs to the Special Issue Autofluorescence Spectroscopy and Imaging II)
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Review

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17 pages, 1387 KiB  
Review
Exploring the Potential of Fluorescence Spectroscopy for the Discrimination between Fresh and Frozen-Thawed Muscle Foods
by Abdo Hassoun
Photochem 2021, 1(2), 247-263; https://0-doi-org.brum.beds.ac.uk/10.3390/photochem1020015 - 02 Sep 2021
Cited by 21 | Viewed by 4059
Abstract
Substitution of frozen-thawed food products for fresh ones is a significant authenticity issue being extensively investigated over the past few years by various conventional methods, but little success has been achieved. Fluorescence spectroscopy is a sensitive and selective spectroscopic technique that has been [...] Read more.
Substitution of frozen-thawed food products for fresh ones is a significant authenticity issue being extensively investigated over the past few years by various conventional methods, but little success has been achieved. Fluorescence spectroscopy is a sensitive and selective spectroscopic technique that has been widely applied recently to deal with various food quality and authenticity issues. The technique is based on the excitation of certain photosensitive components (known as fluorophores) to fluoresce in the UV and visible spectral ranges. Fluorescence spectroscopy can be performed to obtain simple classical two-dimensional fluorescence spectra (excitation/emission), synchronous or three-dimensional excitation–emission matrices (excitation/emission/fluorescence signal). The technique can be used in front-face or right-angle configurations and can be even combined with hyperspectral imaging, requiring the use of multivariate data analysis to extract useful information. In this review, we summarize the recent progress in applications of fluorescence spectroscopy to differentiate truly fresh foods from frozen-thawed products. The basics of the technique will be briefly presented and some relevant examples, focusing especially on fish and meat products, will be given. It is believed that interdisciplinary collaboration between researchers working with data analysis and spectroscopy, as well as industry and regulatory authorities would help to overcome the current shortcomings, holding the great promise of fluorescence spectroscopy for fighting food fraud in the food industry. Full article
(This article belongs to the Special Issue Autofluorescence Spectroscopy and Imaging II)
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22 pages, 338 KiB  
Review
A Review of Recent Studies Employing Hyperspectral Imaging for the Determination of Food Adulteration
by Havva Tümay Temiz and Berdan Ulaş
Photochem 2021, 1(2), 125-146; https://0-doi-org.brum.beds.ac.uk/10.3390/photochem1020008 - 08 Jul 2021
Cited by 15 | Viewed by 4165
Abstract
Applications of hyperspectral imaging (HSI) methods in food adulteration detection have been surveyed in this study. Subsequent to the research on existing literature, studies were evaluated based on different food categories. Tea, coffee, and cocoa; nuts and seeds; herbs and spices; honey and [...] Read more.
Applications of hyperspectral imaging (HSI) methods in food adulteration detection have been surveyed in this study. Subsequent to the research on existing literature, studies were evaluated based on different food categories. Tea, coffee, and cocoa; nuts and seeds; herbs and spices; honey and oil; milk and milk products; meat and meat products; cereal and cereal products; and fish and fishery products are the eight different categories investigated within the context of the present study. A summary of studies on these topics was made, and articles reported in 2019 and 2020 were explained in detail. Research objectives, data acquisition systems, and algorithms for data analysis have been introduced briefly with a particular focus on feature wavelength selection methods. In light of the information extracted from the related literature, methods and alternative approaches to increasing the success of HSI based methods are presented. Furthermore, challenges and future perspectives are discussed. Full article
(This article belongs to the Special Issue Autofluorescence Spectroscopy and Imaging II)
58 pages, 18490 KiB  
Review
Light and Autofluorescence, Multitasking Features in Living Organisms
by Anna C. Croce
Photochem 2021, 1(2), 67-124; https://0-doi-org.brum.beds.ac.uk/10.3390/photochem1020007 - 03 Jul 2021
Cited by 20 | Viewed by 6761
Abstract
Organisms belonging to all life kingdoms may have the natural capacity to fluoresce. Autofluorescence events depend on the presence of natural biomolecules, namely endogenous fluorophores, with suitable chemical properties in terms of conjugated double bonds, aromatic or more complex structures with oxidized and [...] Read more.
Organisms belonging to all life kingdoms may have the natural capacity to fluoresce. Autofluorescence events depend on the presence of natural biomolecules, namely endogenous fluorophores, with suitable chemical properties in terms of conjugated double bonds, aromatic or more complex structures with oxidized and crosslinked bonds, ensuring an energy status able to permit electronic transitions matching with the energy of light in the UV-visible-near-IR spectral range. Emission of light from biological substrates has been reported since a long time, inspiring unceasing and countless studies. Early notes on autofluorescence of vegetables have been soon followed by attention to animals. Investigations on full living organisms from the wild environment have been driven prevalently by ecological and taxonomical purposes, while studies on cells, tissues and organs have been mainly promoted by diagnostic aims. Interest in autofluorescence is also growing as a sensing biomarker in food production and in more various industrial processes. The associated technological advances have supported investigations ranging from the pure photochemical characterization of specific endogenous fluorophores to their possible functional meanings and biological relevance, making fluorescence a valuable intrinsic biomarker for industrial and diagnostic applications, in a sort of real time, in situ biochemical analysis. This review aims to provide a wide-ranging report on the most investigated natural fluorescing biomolecules, from microorganisms to plants and animals of different taxonomic degrees, with their biological, environmental or biomedical issues relevant for the human health. Hence, some notes in the different sections dealing with different biological subject are also interlaced with human related issues. Light based events in biological subjects have inspired an almost countless literature, making it almost impossible to recall here all associated published works, forcing to apologize for the overlooked reports. This Review is thus proposed as an inspiring source for Readers, addressing them to additional literature for an expanded information on specific topics of more interest. Full article
(This article belongs to the Special Issue Autofluorescence Spectroscopy and Imaging II)
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