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Dilissen S, Silva PL, Smolentseva A, Kache T, Thoelen R, Hendrix J. Characterisation of biocondensate microfluidic flow using array-detector FCS. Biochim Biophys Acta Gen Subj 2024; 1868:130673. [PMID: 39029539 DOI: 10.1016/j.bbagen.2024.130673] [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] [Received: 03/30/2024] [Revised: 07/05/2024] [Accepted: 07/15/2024] [Indexed: 07/21/2024]
Abstract
BACKGROUND Biomolecular condensation via liquid-liquid phase separation (LLPS) is crucial for orchestrating cellular activities temporospatially. Although the rheological heterogeneity of biocondensates and the structural dynamics of their constituents carry critical functional information, methods to quantitatively study biocondensates are lacking. Single-molecule fluorescence research can offer insights into biocondensation mechanisms. Unfortunately, as dense condensates tend to sink inside their dilute aqueous surroundings, studying their properties via methods relying on Brownian diffusion may fail. METHODS We take a first step towards single-molecule research on condensates of Tau protein under flow in a microfluidic channel of an in-house developed microfluidic chip. Fluorescence correlation spectroscopy (FCS), a well-known technique to collect molecular characteristics within a sample, was employed with a newly commercialised technology, where FCS is performed on an array detector (AD-FCS), providing detailed diffusion and flow information. RESULTS The AD-FCS technology allowed characterising our microfluidic chip, revealing 3D flow profiles. Subsequently, AD-FCS allowed mapping the flow of Tau condensates while measuring their burst durations through the stationary laser. Lastly, AD-FCS allowed obtaining flow velocity and burst duration data, the latter of which was used to estimate the condensate size distribution within LLPS samples. CONCLUSION Studying biocondensates under flow through AD-FCS is promising for single-molecule experiments. In addition, AD-FCS shows its ability to estimate the size distribution in condensate samples in a convenient manner, prompting a new way of investigating biocondensate phase diagrams. GENERAL SIGNIFICANCE We show that AD-FCS is a valuable tool for advancing research on understanding and characterising LLPS properties of biocondensates.
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Affiliation(s)
- Stijn Dilissen
- UHasselt, Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), B3590 Diepenbeek, Belgium; UHasselt, Biomedical Device Engineering group, Institute for Materials Research (IMO-IMOMEC), Wetenschapspark 1, B3590 Diepenbeek, Belgium
| | - Pedro L Silva
- UHasselt, Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), B3590 Diepenbeek, Belgium
| | - Anastasia Smolentseva
- UHasselt, Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), B3590 Diepenbeek, Belgium
| | - Tom Kache
- UHasselt, Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), B3590 Diepenbeek, Belgium
| | - Ronald Thoelen
- UHasselt, Biomedical Device Engineering group, Institute for Materials Research (IMO-IMOMEC), Wetenschapspark 1, B3590 Diepenbeek, Belgium; IMOMEC Division, IMEC vzw, Wetenschapspark 1, B3590 Diepenbeek, Belgium
| | - Jelle Hendrix
- UHasselt, Dynamic Bioimaging Lab, Advanced Optical Microscopy Centre, Biomedical Research Institute, Agoralaan C (BIOMED), B3590 Diepenbeek, Belgium.
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2
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Bucci A, Tortarolo G, Held MO, Bega L, Perego E, Castagnetti F, Bozzoni I, Slenders E, Vicidomini G. 4D Single-particle tracking with asynchronous read-out single-photon avalanche diode array detector. Nat Commun 2024; 15:6188. [PMID: 39043637 PMCID: PMC11266502 DOI: 10.1038/s41467-024-50512-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 07/14/2024] [Indexed: 07/25/2024] Open
Abstract
Single-particle tracking techniques enable investigation of the complex functions and interactions of individual particles in biological environments. Many such techniques exist, each demonstrating trade-offs between spatiotemporal resolution, spatial and temporal range, technical complexity, and information content. To mitigate these trade-offs, we enhanced a confocal laser scanning microscope with an asynchronous read-out single-photon avalanche diode array detector. This detector provides an image of the particle's emission, precisely reflecting its position within the excitation volume. This localization is utilized in a real-time feedback system to drive the microscope scanning mechanism and ensure the particle remains centered inside the excitation volume. As each pixel is an independent single-photon detector, single-particle tracking is combined with fluorescence lifetime measurement. Our system achieves 40 nm lateral and 60 nm axial localization precision with 100 photons and sub-millisecond temporal sampling for real-time tracking. Offline tracking can refine this precision to the microsecond scale. We validated the system's spatiotemporal resolution by tracking fluorescent beads with diffusion coefficients up to 10 μm2/s. Additionally, we investigated the movement of lysosomes in living SK-N-BE cells and measured the fluorescence lifetime of the marker expressed on a membrane protein. We expect that this implementation will open other correlative imaging and tracking studies.
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Affiliation(s)
- Andrea Bucci
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
- Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi, University of Genoa, Genoa, Italy
| | - Giorgio Tortarolo
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
- Laboratory of Experimental Biophysics, EPFL, Lausanne, Switzerland
| | - Marcus Oliver Held
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Luca Bega
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Eleonora Perego
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
- Centre for Integrative Genomics, Université de Lausanne, Lausanne, Switzerland
| | - Francesco Castagnetti
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Irene Bozzoni
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnology Charles Darwin, Sapienza University, Rome, Italy
| | - Eli Slenders
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy.
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3
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Di Timoteo G, Giuliani A, Setti A, Biagi MC, Lisi M, Santini T, Grandioso A, Mariani D, Castagnetti F, Perego E, Zappone S, Lattante S, Sabatelli M, Rotili D, Vicidomini G, Bozzoni I. M 6A reduction relieves FUS-associated ALS granules. Nat Commun 2024; 15:5033. [PMID: 38866783 PMCID: PMC11169559 DOI: 10.1038/s41467-024-49416-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 05/30/2024] [Indexed: 06/14/2024] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease due to gradual motoneurons (MN) degeneration. Among the processes associated to ALS pathogenesis, there is the formation of cytoplasmic inclusions produced by aggregation of mutant proteins, among which the RNA binding protein FUS. Here we show that, in neuronal cells and in iPSC-derived MN expressing mutant FUS, such inclusions are significantly reduced in number and dissolve faster when the RNA m6A content is diminished. Interestingly, stress granules formed in ALS conditions showed a distinctive transcriptome with respect to control cells, which reverted to similar to control after m6A downregulation. Notably, cells expressing mutant FUS were characterized by higher m6A levels suggesting a possible link between m6A homeostasis and pathological aggregates. Finally, we show that FUS inclusions are reduced also in patient-derived fibroblasts treated with STM-2457, an inhibitor of METTL3 activity, paving the way for its possible use for counteracting aggregate formation in ALS.
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Grants
- ERC-2019-SyG 855923-ASTRA EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council)
- ERC-2018-CoG 818669-BrightEyes EC | EU Framework Programme for Research and Innovation H2020 | H2020 Priority Excellent Science | H2020 European Research Council (H2020 Excellent Science - European Research Council)
- AIRC IG 2019 Id. 23053 Associazione Italiana per la Ricerca sul Cancro (Italian Association for Cancer Research)
- PRIN 2017 2017P352Z4 Ministero dell'Istruzione, dell'Università e della Ricerca (Ministry of Education, University and Research)
- NextGenerationEU PNRR MUR Ministero dell'Istruzione, dell'Università e della Ricerca (Ministry of Education, University and Research)
- "National Center for Gene Therapy and Drugbased on RNA Technology" (CN00000041) Ministero dell'Istruzione, dell'Università e della Ricerca (Ministry of Education, University and Research)
- "National Center for Gene Therapy and Drug based on RNA Technology" (CN00000041) Ministero dell'Istruzione, dell'Università e della Ricerca (Ministry of Education, University and Research)
- NextGenerationEU PNRR MUR Ministero dell'Istruzione, dell'Università e della Ricerca (Ministry of Education, University and Research)
- "Sapienza" Ateneo Project 2021 n. RM12117A61C811CE Sapienza Università di Roma (Sapienza University of Rome)
- Regione Lazio PROGETTI DI GRUPPI DI RICERCA 2020 - A0375-2020-36597 Regione Lazio (Region of Lazio)
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Affiliation(s)
- Gaia Di Timoteo
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Andrea Giuliani
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Adriano Setti
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Martina C Biagi
- Center for Life Nano- & Neuro-Science@Sapienza, Fondazione Istituto Italiano di Tecnologia (IIT), Rome, 00161, Italy
| | - Michela Lisi
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Tiziana Santini
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Alessia Grandioso
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy
| | - Davide Mariani
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy
| | - Francesco Castagnetti
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy
| | - Eleonora Perego
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy
| | - Sabrina Zappone
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy
| | - Serena Lattante
- Section of Genomic Medicine, Department of Life Sciences and Public Health, Università Cattolica del Sacro Cuore, 00168, Rome, Italy
| | - Mario Sabatelli
- Section of Neurology, Department of Neuroscience, Faculty of Medicine and Surgery, Università Cattolica del Sacro Cuore, 00168, Rome, Italy
- Adult NEMO Clinical Center, Unit of Neurology, Department of Aging, Neurological, Orthopedic and Head-Neck Sciences, Fondazione Policlinico Universitario A. Gemelli IRCCS, 00168, Rome, Italy
| | - Dante Rotili
- Department of Drug Chemistry and Technologies, Sapienza University of Rome, 00185, Rome, Italy
| | - Giuseppe Vicidomini
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy
| | - Irene Bozzoni
- Department of Biology and Biotechnology Charles Darwin, Sapienza University of Rome, Rome, 00185, Italy.
- Center for Life Nano- & Neuro-Science@Sapienza, Fondazione Istituto Italiano di Tecnologia (IIT), Rome, 00161, Italy.
- Center for Human Technologies@Istituto Italiano di Tecnologia (IIT), Genoa, 16152, Italy.
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4
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Yang B, Wang C, Zhao R, Xue X, Chen T, Dou X. Single-photon avalanche diodes dynamic range and linear response enhancement by conditional probability correction. OPTICS EXPRESS 2024; 32:11992-12003. [PMID: 38571034 DOI: 10.1364/oe.513671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Accepted: 02/21/2024] [Indexed: 04/05/2024]
Abstract
Detectors based on single-photon avalanche diodes (SPADs) operating in free-running mode surfer from distorted detection signals due to the impact of afterpulse, dead time, and the non-linear detection efficiency response. This study presents a correction method based on conditional probability. In the experiments with high temporal resolution and huge dynamic range conditions, this method's residual sum of squares is near 68 times smaller than the uncorrected received data of SPAD and near 50 times smaller than deconvolution method. This method is applied to polarization lidar and CO2 lidar, and the performance shows significant improvement. This method effectively mitigates the impact of SPAD afterpulse, dead time, and detection efficiency non-linear response, making it suitable for all SPADs. Especially, our method is primarily employed for atmospheric detection.
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5
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Liu B, Li X, Zhang JP, Li X, Yuan Y, Hou GH, Zhang HJ, Zhang H, Li Y, Mezzenga R. Protein Nanotubes as Advanced Material Platforms and Delivery Systems. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2307627. [PMID: 37921269 DOI: 10.1002/adma.202307627] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 10/22/2023] [Indexed: 11/04/2023]
Abstract
Protein nanotubes (PNTs) as state-of-the-art nanocarriers are promising for various potential applications both in the food and pharmaceutical industries. Derived from edible starting sources like α-lactalbumin, lysozyme, and ovalbumin, PNTs bear properties of biocompatibility and biodegradability. Their large specific surface area and hydrophobic core facilitate chemical modification and loading of bioactive substances, respectively. Moreover, their enhanced permeability and penetration ability across biological barriers such as intestinal mucus, extracellular matrix, and thrombus clot, make it promising platforms for health-related applications. Most importantly, their simple preparation processes enable large-scale production, supporting applications in the biomedical and nanotechnological fields. Understanding the self-assembly principles is crucial for controlling their morphology, size, and shape, and thus provides the ground to a multitude of applications. Here, the current state-of-the-art of PNTs including their building materials, physicochemical properties, and self-assembly mechanisms are comprehensively reviewed. The advantages and limitations, as well as challenges and prospects for their successful applications in biomaterial and pharmaceutical sectors are then discussed and highlighted. Potential cytotoxicity of PNTs and the need of regulations as critical factors for enabling in vivo applications are also highlighted. In the end, a brief summary and future prospects for PNTs as advanced platforms and delivery systems are included.
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Affiliation(s)
- Bin Liu
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
- Department of Nutrition and Health, China Agricultural University, Beijing, 100091, P. R. China
| | - Xing Li
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Ji Peng Zhang
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Xin Li
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Yu Yuan
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Guo Hua Hou
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Hui Juan Zhang
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Hui Zhang
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Yuan Li
- Key Laboratory of Precision Nutrition and Food Quality, Research Center of Food Colloids and Delivery of Functionality, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, 100083, P. R. China
| | - Raffaele Mezzenga
- Department of Health Sciences and Technology, ETH Zurich, Zürich, 8092, Switzerland
- Department of Materials, ETH Zurich, Zürich, 8092, Switzerland
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6
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Wu M, Zhao X, Chen R, Zhang L, He W, Chen Q. Enhancing LiDAR performance using threshold photon-number-resolving detection. OPTICS EXPRESS 2024; 32:2574-2589. [PMID: 38297783 DOI: 10.1364/oe.509252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Accepted: 01/02/2024] [Indexed: 02/02/2024]
Abstract
Single-photon light detection and ranging (LiDAR) is widely used to reconstruct 3D scenes. Nevertheless, depth and reflectivity maps obtained by single-photon detection usually suffer from noise problems. Threshold LiDAR techniques using photon-number-resolving detectors were proposed to suppress noise by filtering low photon numbers, but these techniques renounce multiple levels of information and could not be compatible when it comes to high-noise low-signal regime. In this manuscript, we propose a detection scheme which combines the noise suppression of threshold detection with the signal amplification of photon-number-resolving detectors to further enhance LiDAR performance. The enhancement attained is compared to single-photon and threshold detection schemes under a wide range of signal and noise conditions, in terms of signal-to-noise-ratio (SNR), detection rate and false alarm rate, which are key metrics for LiDAR. Extensive simulations and real-world experiments show that the proposed scheme can reconstruct better depth and reflectivity maps. These results enable the development of high-efficient and low-noise LiDAR systems.
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7
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Perego E, Zappone S, Castagnetti F, Mariani D, Vitiello E, Rupert J, Zacco E, Tartaglia GG, Bozzoni I, Slenders E, Vicidomini G. Single-photon microscopy to study biomolecular condensates. Nat Commun 2023; 14:8224. [PMID: 38086853 PMCID: PMC10716487 DOI: 10.1038/s41467-023-43969-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 11/24/2023] [Indexed: 12/18/2023] Open
Abstract
Biomolecular condensates serve as membrane-less compartments within cells, concentrating proteins and nucleic acids to facilitate precise spatial and temporal orchestration of various biological processes. The diversity of these processes and the substantial variability in condensate characteristics present a formidable challenge for quantifying their molecular dynamics, surpassing the capabilities of conventional microscopy. Here, we show that our single-photon microscope provides a comprehensive live-cell spectroscopy and imaging framework for investigating biomolecular condensation. Leveraging a single-photon detector array, single-photon microscopy enhances the potential of quantitative confocal microscopy by providing access to fluorescence signals at the single-photon level. Our platform incorporates photon spatiotemporal tagging, which allowed us to perform time-lapse super-resolved imaging for molecular sub-diffraction environment organization with simultaneous monitoring of molecular mobility, interactions, and nano-environment properties through fluorescence lifetime fluctuation spectroscopy. This integrated correlative study reveals the dynamics and interactions of RNA-binding proteins involved in forming stress granules, a specific type of biomolecular condensates, across a wide range of spatial and temporal scales. Our versatile framework opens up avenues for exploring a broad spectrum of biomolecular processes beyond the formation of membrane-less organelles.
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Affiliation(s)
- Eleonora Perego
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Sabrina Zappone
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
- Dipartimento di Informatica, Bioingegneria, Robotica e Ingegneria dei Sistemi, University of Genoa, Genoa, Italy
| | - Francesco Castagnetti
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Davide Mariani
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Erika Vitiello
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Jakob Rupert
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Elsa Zacco
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Gian Gaetano Tartaglia
- RNA Systems Biology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Irene Bozzoni
- Non coding RNAs in Physiology and Pathology, Istituto Italiano di Tecnologia, Genoa, Italy
- Department of Biology and Biotechnologies 'C. Darwin', Sapienza University of Rome, Rome, Italy
| | - Eli Slenders
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy
| | - Giuseppe Vicidomini
- Molecular Microscopy and Spectroscopy, Istituto Italiano di Tecnologia, Genoa, Italy.
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Bian L, Song H, Peng L, Chang X, Yang X, Horstmeyer R, Ye L, Zhu C, Qin T, Zheng D, Zhang J. High-resolution single-photon imaging with physics-informed deep learning. Nat Commun 2023; 14:5902. [PMID: 37737270 PMCID: PMC10516985 DOI: 10.1038/s41467-023-41597-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Accepted: 09/12/2023] [Indexed: 09/23/2023] Open
Abstract
High-resolution single-photon imaging remains a big challenge due to the complex hardware manufacturing craft and noise disturbances. Here, we introduce deep learning into SPAD, enabling super-resolution single-photon imaging with enhancement of bit depth and imaging quality. We first studied the complex photon flow model of SPAD electronics to accurately characterize multiple physical noise sources, and collected a real SPAD image dataset (64 × 32 pixels, 90 scenes, 10 different bit depths, 3 different illumination flux, 2790 images in total) to calibrate noise model parameters. With this physical noise model, we synthesized a large-scale realistic single-photon image dataset (image pairs of 5 different resolutions with maximum megapixels, 17250 scenes, 10 different bit depths, 3 different illumination flux, 2.6 million images in total) for subsequent network training. To tackle the severe super-resolution challenge of SPAD inputs with low bit depth, low resolution, and heavy noise, we further built a deep transformer network with a content-adaptive self-attention mechanism and gated fusion modules, which can dig global contextual features to remove multi-source noise and extract full-frequency details. We applied the technique in a series of experiments including microfluidic inspection, Fourier ptychography, and high-speed imaging. The experiments validate the technique's state-of-the-art super-resolution SPAD imaging performance.
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Affiliation(s)
- Liheng Bian
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China.
- Yangtze Delta Region Academy of Beijing Institute of Technology (Jiaxing), Jiaxing, 314019, China.
| | - Haoze Song
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
| | - Lintao Peng
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
| | - Xuyang Chang
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
| | - Xi Yang
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Roarke Horstmeyer
- Department of Biomedical Engineering, Duke University, Durham, NC, 27708, USA
| | - Lin Ye
- School of Materials Science and Engineering, Beijing Institute of Technology, Beijing, 100081, China
| | - Chunli Zhu
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
| | - Tong Qin
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
| | - Dezhi Zheng
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China
- Yangtze Delta Region Academy of Beijing Institute of Technology (Jiaxing), Jiaxing, 314019, China
| | - Jun Zhang
- MIIT Key Laboratory of Complex-field Intelligent Sensing, Beijing Institute of Technology, Beijing, 100081, China.
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Sankaran J, Wohland T. Current capabilities and future perspectives of FCS: super-resolution microscopy, machine learning, and in vivo applications. Commun Biol 2023; 6:699. [PMID: 37419967 PMCID: PMC10328937 DOI: 10.1038/s42003-023-05069-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 06/23/2023] [Indexed: 07/09/2023] Open
Abstract
Fluorescence correlation spectroscopy (FCS) is a single molecule sensitive tool for the quantitative measurement of biomolecular dynamics and interactions. Improvements in biology, computation, and detection technology enable real-time FCS experiments with multiplexed detection even in vivo. These new imaging modalities of FCS generate data at the rate of hundreds of MB/s requiring efficient data processing tools to extract information. Here, we briefly review FCS's capabilities and limitations before discussing recent directions that address these limitations with a focus on imaging modalities of FCS, their combinations with super-resolution microscopy, new evaluation strategies, especially machine learning, and applications in vivo.
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Affiliation(s)
- Jagadish Sankaran
- Genome Institute of Singapore, Agency for Science, Technology and Research, Singapore, 138632, Singapore.
| | - Thorsten Wohland
- Department of Biological Sciences, National University of Singapore, Singapore, 117558, Singapore.
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11
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Focus image scanning microscopy for sharp and gentle super-resolved microscopy. Nat Commun 2022; 13:7723. [PMID: 36513680 PMCID: PMC9747786 DOI: 10.1038/s41467-022-35333-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 11/28/2022] [Indexed: 12/15/2022] Open
Abstract
To date, the feasibility of super-resolution microscopy for imaging live and thick samples is still limited. Stimulated emission depletion (STED) microscopy requires high-intensity illumination to achieve sub-diffraction resolution, potentially introducing photodamage to live specimens. Moreover, the out-of-focus background may degrade the signal stemming from the focal plane. Here, we propose a new method to mitigate these limitations without drawbacks. First, we enhance a STED microscope with a detector array, enabling image scanning microscopy (ISM). Therefore, we implement STED-ISM, a method that exploits the working principle of ISM to reduce the depletion intensity and achieve a target resolution. Later, we develop Focus-ISM, a strategy to improve the optical sectioning and remove the background of any ISM-based imaging technique, with or without a STED beam. The proposed approach requires minimal architectural changes to a conventional microscope but provides substantial advantages for live and thick sample imaging.
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The BrightEyes-TTM as an open-source time-tagging module for democratising single-photon microscopy. Nat Commun 2022; 13:7406. [PMID: 36456575 PMCID: PMC9715684 DOI: 10.1038/s41467-022-35064-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 11/09/2022] [Indexed: 12/03/2022] Open
Abstract
Fluorescence laser-scanning microscopy (LSM) is experiencing a revolution thanks to new single-photon (SP) array detectors, which give access to an entirely new set of single-photon information. Together with the blooming of new SP LSM techniques and the development of tailored SP array detectors, there is a growing need for (i) DAQ systems capable of handling the high-throughput and high-resolution photon information generated by these detectors, and (ii) incorporating these DAQ protocols in existing fluorescence LSMs. We developed an open-source, low-cost, multi-channel time-tagging module (TTM) based on a field-programmable gate array that can tag in parallel multiple single-photon events, with 30 ps precision, and multiple synchronisation events, with 4 ns precision. We use the TTM to demonstrate live-cell super-resolved fluorescence lifetime image scanning microscopy and fluorescence lifetime fluctuation spectroscopy. We expect that our BrightEyes-TTM will support the microscopy community in spreading SP-LSM in many life science laboratories.
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Zhang G, Yang Y, Zhang C, Cao X, Liu L, Li L, Han X. Measurement of focal light spot at single-photon level with silicon photomultipliers. Sci Rep 2022; 12:15060. [PMID: 36064950 PMCID: PMC9445098 DOI: 10.1038/s41598-022-17759-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 07/30/2022] [Indexed: 11/09/2022] Open
Abstract
Focal spot (light spot) at single-photon level have important applications in many fields. This report demonstrates a method for measuring focal spot size at the single-photon level indirectly. This method utilizes Silicon Photomultiplier (SiPM) as the single-photon sensitive detectors, combined with a nano-positioning stage. The approach involves one- or two-dimensional space scanning and a deconvolution operation, which enable evaluations of the size and spatial distribution of the focal spot formed by a single-photon-level pulsed laser. The results indicate that the average full width at half maximum of the focal spot is about 0.657 μm, which is close to the nominal resolution of the objective lens of the microscope (i.e. 0.42 μm). The proposed method has two key advantages: (1) it can measure focal spot at the single-photon level, and (2) the focal spot can easily be aligned with the detector because the array area of the Geiger mode avalanche photodiode (Gm-APD) cells in SiPM is usually on the order of square millimeter, and there is no need to put an optical slit, knife edge, or pinhole in front of the detector. The method described herein is applicable in weak focal spot detection related fields.
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Affiliation(s)
- Guoqing Zhang
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China.
| | - Yaxian Yang
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China
| | - Chen Zhang
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China
| | - Xinyue Cao
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China
| | - Lina Liu
- School of Science, Xi'an University of Technology, Xi'an, 710048, China
| | - Lianbi Li
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China
| | - Xiaoxiang Han
- School of Science, Xi'an Polytechnic University, Xi'an, 710048, China
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Ten TB, Zvoda V, Sarangi MK, Kuznetsov SV, Ansari A. "Flexible hinge" dynamics in mismatched DNA revealed by fluorescence correlation spectroscopy. J Biol Phys 2022; 48:253-272. [PMID: 35451661 PMCID: PMC9411374 DOI: 10.1007/s10867-022-09607-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 03/22/2022] [Indexed: 10/18/2022] Open
Abstract
Altered unwinding/bending fluctuations at DNA lesion sites are implicated as plausible mechanisms for damage sensing by DNA-repair proteins. These dynamics are expected to occur on similar timescales as one-dimensional (1D) diffusion of proteins on DNA if effective in stalling these proteins as they scan DNA. We examined the flexibility and dynamics of DNA oligomers containing 3 base pair (bp) mismatched sites specifically recognized in vitro by nucleotide excision repair protein Rad4 (yeast ortholog of mammalian XPC). A previous Forster resonance energy transfer (FRET) study mapped DNA conformational distributions with cytosine analog FRET pair primarily sensitive to DNA twisting/unwinding deformations (Chakraborty et al. Nucleic Acids Res. 46: 1240-1255 (2018)). These studies revealed B-DNA conformations for nonspecific (matched) constructs but significant unwinding for mismatched constructs specifically recognized by Rad4, even in the absence of Rad4. The timescales of these unwinding fluctuations, however, remained elusive. Here, we labeled DNA with Atto550/Atto647N FRET dyes suitable for fluorescence correlation spectroscopy (FCS). With these probes, we detected higher FRET in specific, mismatched DNA compared with matched DNA, reaffirming unwinding/bending deformations in mismatched DNA. FCS unveiled the dynamics of these spontaneous deformations at ~ 300 µs with no fluctuations detected for matched DNA within the ~ 600 ns-10 ms FCS time window. These studies are the first to visualize anomalous unwinding/bending fluctuations in mismatched DNA on timescales that overlap with the < 500 µs "stepping" times of repair proteins on DNA. Such "flexible hinge" dynamics at lesion sites could arrest a diffusing protein to facilitate damage interrogation and recognition.
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Affiliation(s)
- Timour B Ten
- Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Viktoriya Zvoda
- Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Manas K Sarangi
- Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL, 60607, USA
- Present Address: Department of Physics, Indian Institute of Technology, Patna, 801103, India
| | - Serguei V Kuznetsov
- Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL, 60607, USA
| | - Anjum Ansari
- Department of Physics (M/C 273), University of Illinois at Chicago, Chicago, IL, 60607, USA.
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Xu S, Yang X, Liu W, Jönsson J, Qian R, Konda PC, Zhou KC, Kreiß L, Wang H, Dai Q, Berrocal E, Horstmeyer R. Imaging Dynamics Beneath Turbid Media via Parallelized Single-Photon Detection. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2201885. [PMID: 35748188 PMCID: PMC9404405 DOI: 10.1002/advs.202201885] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/16/2022] [Indexed: 05/05/2023]
Abstract
Noninvasive optical imaging through dynamic scattering media has numerous important biomedical applications but still remains a challenging task. While standard diffuse imaging methods measure optical absorption or fluorescent emission, it is also well-established that the temporal correlation of scattered coherent light diffuses through tissue much like optical intensity. Few works to date, however, have aimed to experimentally measure and process such temporal correlation data to demonstrate deep-tissue video reconstruction of decorrelation dynamics. In this work, a single-photon avalanche diode array camera is utilized to simultaneously monitor the temporal dynamics of speckle fluctuations at the single-photon level from 12 different phantom tissue surface locations delivered via a customized fiber bundle array. Then a deep neural network is applied to convert the acquired single-photon measurements into video of scattering dynamics beneath rapidly decorrelating tissue phantoms. The ability to reconstruct images of transient (0.1-0.4 s) dynamic events occurring up to 8 mm beneath a decorrelating tissue phantom with millimeter-scale resolution is demonstrated, and it is highlighted how the model can flexibly extend to monitor flow speed within buried phantom vessels.
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Affiliation(s)
- Shiqi Xu
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
| | - Xi Yang
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
| | - Wenhui Liu
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
- Department of AutomationTsinghua UniversityBeijing100084China
| | - Joakim Jönsson
- Division of Combustion PhysicsDepartment of PhysicsLund UniversityLund22100Sweden
| | - Ruobing Qian
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
| | | | - Kevin C. Zhou
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
| | - Lucas Kreiß
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
- Institute of Medical BiotechnologyFriedrich‐Alexander‐University Erlangen‐Nürnberg (FAU)Erlangen91054Germany
| | - Haoqian Wang
- Tsinghua Shenzhen International Graduate SchoolTsinghua UniversityShenzhen518055China
| | - Qionghai Dai
- Department of AutomationTsinghua UniversityBeijing100084China
| | - Edouard Berrocal
- Division of Combustion PhysicsDepartment of PhysicsLund UniversityLund22100Sweden
| | - Roarke Horstmeyer
- Department of Biomedical EngineeringDuke UniversityDurhamNC27708USA
- Department of Electrical and Computer EngineeringDuke UniversityDurhamNC27708USA
- Department of PhysicsDuke UniversityDurhamNC27708USA
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16
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Lin J, Sun Y, Wu W, Huang K, Liang Y, Yan M, Zeng H. High-speed photon-number-resolving detection via a GHz-gated SiPM. OPTICS EXPRESS 2022; 30:7501-7510. [PMID: 35299511 DOI: 10.1364/oe.451548] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Silicon photomultipliers (SiPMs) constitute a promising candidate for photon-number-resolving (PNR) detection via spatial multiplexing, which offer advantages like high integration and low cost. Up to date, there has been continuous endeavor in boosting the PNR performances, particularly on the resolved photon numbers and operation speed. Here, we demonstrate a GHz-gated SiPM in the Geiger mode, which allows to quench the photon-induced avalanche signal within 1 ns. Specifically, the capacitive response of the SiPM has been effectively suppressed by combining the low-pass filtering and self-differencing technique, which facilitates a high-fidelity extraction of the avalanche pulse with a reduced error rate. Consequently, high-speed PNR detection has been manifested in resolving up to 14 photons for laser pulses at a repetition rate of 40 MHz. The presented high-speed PNR detector may open up new possibilities to implement applications such as large-dynamic-range optical sensing, high-capacity optical communication, and multi-photon quantum optics.
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Slenders E, Perego E, Buttafava M, Tortarolo G, Conca E, Zappone S, Pierzynska-Mach A, Villa F, Petrini EM, Barberis A, Tosi A, Vicidomini G. Cooled SPAD array detector for low light-dose fluorescence laser scanning microscopy. BIOPHYSICAL REPORTS 2021; 1:None. [PMID: 34939046 PMCID: PMC8651514 DOI: 10.1016/j.bpr.2021.100025] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 09/14/2021] [Indexed: 11/30/2022]
Abstract
The single-photon timing and sensitivity performance and the imaging ability of asynchronous-readout single-photon avalanche diode (SPAD) array detectors have opened up enormous perspectives in fluorescence (lifetime) laser scanning microscopy (FLSM), such as super-resolution image scanning microscopy and high-information content fluorescence fluctuation spectroscopy. However, the strengths of these FLSM techniques depend on the many different characteristics of the detector, such as dark noise, photon-detection efficiency, after-pulsing probability, and optical cross talk, whose overall optimization is typically a trade-off between these characteristics. To mitigate this trade-off, we present, to our knowledge, a novel SPAD array detector with an active cooling system that substantially reduces the dark noise without significantly deteriorating any other detector characteristics. In particular, we show that lowering the temperature of the sensor to −15°C significantly improves the signal/noise ratio due to a 10-fold decrease in the dark count rate compared with room temperature. As a result, for imaging, the laser power can be decreased by more than a factor of three, which is particularly beneficial for live-cell super-resolution imaging, as demonstrated in fixed and living cells expressing green-fluorescent-protein-tagged proteins. For fluorescence fluctuation spectroscopy, together with the benefit of the reduced laser power, we show that cooling the detector is necessary to remove artifacts in the correlation function, such as spurious negative correlations observed in the hot elements of the detector, i.e., elements for which dark noise is substantially higher than the median value. Overall, this detector represents a further step toward the integration of SPAD array detectors in any FLSM system.
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Pang CM, Cao XY, Xiao Y, Luo SH, Chen Q, Zhou YJ, Wang ZY. N-alkylation briefly constructs tunable multifunctional sensor materials: Multianalyte detection and reversible adsorption. iScience 2021; 24:103126. [PMID: 34632330 PMCID: PMC8487030 DOI: 10.1016/j.isci.2021.103126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 08/25/2021] [Accepted: 09/09/2021] [Indexed: 12/28/2022] Open
Abstract
A series of N-alkyl-substituted polybenzimidazoles (SPBIs), synthesized by simple condensation and N-alkylation, act as functional materials with tunable microstructures and sensing performance. For their controllable morphologies, the formation of nano-/microspheres is observed at the n(RBr)/n(PBI) feed ratio of 5:1. Products with different degrees of alkylation can recognize metal ions and nitroaromatic compounds (NACs). For example, SPBI-c, obtained at the feed ratio of 1:1, can selectively detect Cu2+, Fe3+, and NACs. By contrast, SPBI-a, obtained at the feed ratio of 0.1:1, can exclusively detect Cu2+ with high sensitivity. Their sensing mechanisms have been studied by FT-IR spectroscopy, SEM, XPS, and DFT calculations. Interestingly, the SPBIs can adsorb Cu2+ in solution and show good recyclability. These results demonstrate that polymeric materials with both sensing and adsorption applications can be realized by regulating the alkylation extent of the main chain, thus providing a new approach for the facile synthesis of multifunctional materials.
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Affiliation(s)
- Chu-Ming Pang
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
- School of Health Medicine, Guangzhou Huashang College, Guangzhou 511300, P. R. China
| | - Xi-Ying Cao
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
| | - Ying Xiao
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
| | - Shi-He Luo
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, P. R. China
| | - Qi Chen
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
| | - Yong-Jun Zhou
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
| | - Zhao-Yang Wang
- School of Chemistry, South China Normal University; Key Laboratory of Theoretical Chemistry of Environment, Ministry of Education; Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, Guangzhou 510006, P. R. China
- Key Laboratory of Functional Molecular Engineering of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, P. R. China
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Fast Gating for Raman Spectroscopy. SENSORS 2021; 21:s21082579. [PMID: 33916972 PMCID: PMC8067580 DOI: 10.3390/s21082579] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/02/2021] [Accepted: 04/02/2021] [Indexed: 11/16/2022]
Abstract
Fast gating in Raman spectroscopy is used to reject the fluorescence contribution from the sample and/or the substrate. Several techniques have been set up in the last few decades aiming either to enhance the Raman signal (CARS, SERS or Resonant Raman scattering) or to cancel out the fluorescence contribution (SERDS), and a number of reviews have already been published on these sub-topics. However, for many reasons it is sometimes necessary to reject fluorescence in traditional Raman spectroscopy, and in the last few decades a variety of papers dealt with this issue, which is still challenging due to the time scales at stake (down to picoseconds). Fast gating (<1 ns) in the time domain allows one to cut off part of the fluorescence signal and retrieve the best Raman signal, depending on the fluorescence lifetime of the sample and laser pulse duration. In particular, three different techniques have been developed to accomplish this task: optical Kerr cells, intensified Charge Coupling Devices and systems based on Single Photon Avalanche Photodiodes. The utility of time domain fast gating will be discussed, and In this work, the utility of time domain fast gating is discussed, as well as the performances of the mentioned techniques as reported in literature.
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