1
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Song J, Gong R, Song S, Abbas G, Ma Y, Li Y. The value of electrochemical ratiometry in immunosensing: A systematic study. Biosens Bioelectron 2024:116817. [PMID: 39368847 DOI: 10.1016/j.bios.2024.116817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2024] [Revised: 09/24/2024] [Accepted: 09/25/2024] [Indexed: 10/07/2024]
Abstract
Reluctant reproducibility and accuracy make electrochemical immunosensors suffering from high possibility of false negative/positive results, and it is the main obstacle that hinders them into an eligible alternative technology to the gold-standard method. It has been demonstrated sporadically previously that ratiometry helps deal with this issue but to what extent this could be beneficial and why it could fulfill is yet to be explored. In this study, to the best of our knowledge, for the first time, we have attempted to answer these questions through comprehensive experiments. For this purpose, labeled and label-free electrochemical immunosensors for SARS-CoV-2 pseudovirus quantification are constructed as a model electrochemical immunosensor. Conventional and ratiometric immunosensors are prepared by using electrochemically synthesized graphene modified electrodes coupled with various electrochemical probe pairs. It was found that the electrocatalyst modification at the electrode interface makes the predominant contribution to immunosensor sensitivity, while appropriate ratiometry provided electrochemical immunosensors with significantly enhanced reproducibility, accuracy, as well as sensing stability. Further, the experiments confirmed that the improvement in sensor performance achieved by ratiometry is primarily through overcoming the inherent errors and dynamic variations of the base electrode. It is also demonstrated electrochemical immunosensors made thereof could easily rival the performances of the gold-standard PCR method, in the view of immunoassay diagnosis. Therefore, it is of great promise to evolve electrochemical immunosensors into an eligible substitute technique towards the prevalent nucleic acid detection method in point-of-care testing (POCT), with the aid of electrochemical ratiometry.
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Affiliation(s)
- Jin Song
- Biology Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, 250103, China
| | - Rui Gong
- Faculty of Synthetic Biology, Shenzhen University of Advanced Technology, Shenzhen, 518107, China
| | - Shibo Song
- Endoscopy Center, Peking University First Hospital, Beijing, 100034, China
| | - Ghulam Abbas
- Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China
| | - Yaohong Ma
- Biology Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, 250103, China
| | - Yiwei Li
- Biology Institute, Qilu University of Technology (Shandong Academy of Sciences), Jinan, 250103, China.
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2
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Youngworth R, Roux B. Simulating the Voltage-Dependent Fluorescence of Di-8-ANEPPS in a Lipid Membrane. J Phys Chem Lett 2023; 14:8268-8276. [PMID: 37676243 PMCID: PMC10510438 DOI: 10.1021/acs.jpclett.3c01257] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 08/25/2023] [Indexed: 09/08/2023]
Abstract
Voltage-sensitive fluorescent dyes such as di-8-ANEPPS (di-8-aminonaphthylethylenepyridinium propylsulfonate) are powerful tools to study biological membranes. Its fluorescence is affected by changes in the membrane potential and other factors, requiring extensive calibration to extract meaningful quantitative results. The amphiphilic di-8-ANEPPS molecule is expected to bind at the membrane-solution interface. However, atomic-level information is sparse about its position and orientation in the membrane, especially in regards to how the latter dynamically fluctuates to affect the observed fluorescence. In the present work, molecular dynamics simulations of the ground and excited states of di-8-ANEPPS embedded in a DPPC membrane as represented by classical force fields were used to investigate how the fluorescence is affected by externally applied potential. The calculations reproduce the shifts in the wavelength of emission as a function of voltage that are observed experimentally, indicating that the approach can help better understand the various factors that can affect the fluorescence of membrane-bound dyes.
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Affiliation(s)
- Rachael Youngworth
- Department
of Chemistry, The University of Chicago, 5735 S. Ellis Avenue, Chicago, Illinois 60637, United States
| | - Benoît Roux
- Department
of Biochemistry and Molecular Biology, The
University of Chicago, 929 E. 57th Street W225, Chicago, Illinois 60637, United States
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3
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Nikolaev DM, Mironov VN, Shtyrov AA, Kvashnin ID, Mereshchenko AS, Vasin AV, Panov MS, Ryazantsev MN. Fluorescence Imaging of Cell Membrane Potential: From Relative Changes to Absolute Values. Int J Mol Sci 2023; 24:2435. [PMID: 36768759 PMCID: PMC9916766 DOI: 10.3390/ijms24032435] [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: 01/05/2023] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
Membrane potential is a fundamental property of biological cells. Changes in membrane potential characterize a vast number of vital biological processes, such as the activity of neurons and cardiomyocytes, tumorogenesis, cell-cycle progression, etc. A common strategy to record membrane potential changes that occur in the process of interest is to utilize organic dyes or genetically-encoded voltage indicators with voltage-dependent fluorescence. Sensors are introduced into target cells, and alterations of fluorescence intensity are recorded with optical methods. Techniques that allow recording relative changes of membrane potential and do not take into account fluorescence alterations due to factors other than membrane voltage are already widely used in modern biological and biomedical studies. Such techniques have been reviewed previously in many works. However, in order to investigate a number of processes, especially long-term processes, the measured signal must be corrected to exclude the contribution from voltage-independent factors or even absolute values of cell membrane potential have to be evaluated. Techniques that enable such measurements are the subject of this review.
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Affiliation(s)
- Dmitrii M. Nikolaev
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Vladimir N. Mironov
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Andrey A. Shtyrov
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Iaroslav D. Kvashnin
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Andrey S. Mereshchenko
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
| | - Andrey V. Vasin
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
| | - Maxim S. Panov
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
- Center for Biophysical Studies, Saint Petersburg State Chemical Pharmaceutical University, 14 Professor Popov str., lit. A, 197022 Saint Petersburg, Russia
| | - Mikhail N. Ryazantsev
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
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4
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Starosta R, Santos TC, Dinis de Sousa AF, Santos MS, Corvo ML, Tomaz AI, de Almeida RFM. Assessing the role of membrane lipids in the action of ruthenium(III) anticancer compounds. Front Mol Biosci 2023; 9:1059116. [PMID: 36660430 PMCID: PMC9845782 DOI: 10.3389/fmolb.2022.1059116] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 12/12/2022] [Indexed: 01/05/2023] Open
Abstract
This work addresses the possible role of the cell membrane in the molecular mechanism of action of two salan-type ruthenium complexes that were previously shown to be active against human tumor cells, namely [Ru(III)(L1)(PPh3)Cl] and [Ru(III)(L2)(PPh3)Cl] (where L1 is 6,6'-(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(3-methoxyphenol); and L2 is 2,2'-(1R,2R)-cyclohexane-1,2-diylbis(azanediyl)bis(methylene)bis(4-methoxyphenol)). One-component membrane models were first used, a disordered fluid bilayer of dioleoylphosphatodylcholine (DOPC), and an ordered rigid gel bilayer of dipalmitoylphosphatidylcholine. In addition, two quaternary mixtures of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and cholesterol were used to mimic the lipid composition either of mammalian plasma membrane (1:1:1:1 mol ratio) or of a cancer cell line membrane (36.2:23.6:6.8:33.4 mol ratio). The results show that both salan ligands L1 and L2 bind relatively strongly to DOPC bilayers, but without significantly affecting their structure. The ruthenium complexes have moderate affinity for DOPC. However, their impact on the membranes was notable, leading to a significant increase in the permeability of the lipid vesicles. None of the compounds compromised liposome integrity, as revealed by dynamic light scattering. Fluorescence spectroscopy studies revealed changes in the biophysical properties of all membrane models analyzed in the presence of the two complexes, which promoted an increased fluidity and water penetration into the lipid bilayer in the one-component systems. In the quaternary mixtures, one of the complexes had an analogous effect (increasing water penetration), whereas the other complex reorganized the liquid ordered and liquid disordered domains. Thus, small structural differences in the metal ligands may lead to different outcomes. To better understand the effect of these complexes in cancer cells, the membrane dipole potential was also measured. For both Ru complexes, an increase in the dipole potential was observed for the cancer cell membrane model, while no alteration was detected on the non-cancer plasma membrane model. Our results show that the action of the Ru(III) complexes tested involves changes in the biophysical properties of the plasma membrane, and that it also depends on membrane lipid composition, which is frequently altered in cancer cells when compared to their normal counterparts.
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Affiliation(s)
- Radoslaw Starosta
- Faculty of Chemistry, University of Wroclaw, Wroclaw, Poland,Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Telma C. Santos
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Andreia F. Dinis de Sousa
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Maria Soledade Santos
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - M. Luisa Corvo
- Research Institute for Medicines (iMed.ULisboa), Faculdade de Farmácia, Universidade de Lisboa, Lisbon, Portugal
| | - Ana Isabel Tomaz
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal,*Correspondence: Rodrigo F. M. de Almeida, ; Ana Isabel Tomaz,
| | - Rodrigo F. M. de Almeida
- Centro de Química Estrutural, Institute of Molecular Sciences, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal,*Correspondence: Rodrigo F. M. de Almeida, ; Ana Isabel Tomaz,
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5
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Xu M, Wang X, Liu X. Detection of Heavy Metal Ions by Ratiometric Photoelectric Sensor. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2022; 70:11468-11480. [PMID: 36074997 DOI: 10.1021/acs.jafc.2c03916] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In recent years, heavy metal pollution has become increasingly serious. Heavy metals exist in an environment mainly in the form of ions (heavy metal ions, HMs). They can contaminate food, water, soil, and the atmosphere, leading to serious harm to plants and animals. With high bioavailability and nonbiodegradability, HMs can accumulate through biomagnification. Consequently, heavy metal pollution has become the cause of many fatal diseases threatening human health and ecological environment. Therefore, the accurate detection of HMs is vital and necessary. In this paper, the harm and limit standards of heavy metals were systematically summarized and the common analysis methods were overviewed and compared. Specifically, the latest research progress of ratiometric photoelectric sensor, including optical and electrical sensor, were mainly described. The research status and advantages and disadvantages of a photoelectric sensor were summarized. Furthermore, the future directions were proposed, which provided the reference for the further research and application of the ratiometric photoelectric sensor.
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Affiliation(s)
- Mingming Xu
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210009, China
| | - Xiaoying Wang
- Key Laboratory of Environmental Medicine Engineering, Ministry of Education, School of Public Health, Southeast University, Nanjing 210009, China
| | - Xiangping Liu
- Nanjing Municipal Center for Disease Control and Prevention, Nanjing 210003, China
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6
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Sarkar P, Chattopadhyay A. Membrane Dipole Potential: An Emerging Approach to Explore Membrane Organization and Function. J Phys Chem B 2022; 126:4415-4430. [PMID: 35696090 DOI: 10.1021/acs.jpcb.2c02476] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Biological membranes are complex organized molecular assemblies of lipids and proteins that provide cells and membrane-bound intracellular organelles their individual identities by morphological compartmentalization. Membrane dipole potential originates from the electrostatic potential difference within the membrane due to the nonrandom arrangement (orientation) of amphiphile and solvent (water) dipoles at the membrane interface. In this Feature Article, we will focus on the measurement of dipole potential using electrochromic fluorescent probes and highlight interesting applications. In addition, we will focus on ratiometric fluorescence microscopic imaging technique to measure dipole potential in cellular membranes, a technique that can be used to address novel problems in cell biology which are otherwise difficult to address using available approaches. We envision that membrane dipole potential could turn out to be a convenient tool in exploring the complex interplay between membrane lipids and proteins and could provide novel insights in membrane organization and function.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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7
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Yudovich S, Marzouqe A, Kantorovitsch J, Teblum E, Chen T, Enderlein J, Miller EW, Weiss S. Electrically Controlling and Optically Observing the Membrane Potential of Supported Lipid Bilayers. Biophys J 2022; 121:2624-2637. [PMID: 35619563 DOI: 10.1016/j.bpj.2022.05.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 04/26/2022] [Accepted: 05/23/2022] [Indexed: 11/02/2022] Open
Abstract
Supported lipid bilayers are a well-developed model system for the study of membranes and their associated proteins, such as membrane channels, enzymes, and receptors. These versatile model membranes can be made from various components, ranging from simple synthetic phospholipids to complex mixtures of constituents, mimicking the cell membrane with its relevant physiochemical and molecular phenomena. In addition, the high stability of supported lipid bilayers allows for their study via a wide array of experimental probes. In this work, we describe a platform for supported lipid bilayers that is accessible both electrically and optically, and demonstrate direct optical observation of the transmembrane potential of supported lipid bilayers. We show that the polarization of the supported membrane can be electrically controlled and optically probed using voltage-sensitive dyes. Membrane polarization dynamics is understood through electrochemical impedance spectroscopy and the analysis of an equivalent electrical circuit model. In addition, we describe the effect of the conducting electrode layer on the fluorescence of the optical probe through metal-induced energy transfer, and show that while this energy transfer has an adverse effect on the voltage sensitivity of the fluorescent probe, its strong distance dependency allows for axial localization of fluorescent emitters with ultrahigh accuracy. We conclude with a discussion on possible applications of this platform for the study of voltage-dependent membrane proteins and other processes in membrane biology and surface science.
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Affiliation(s)
- Shimon Yudovich
- Department of Physics, Bar-Ilan University, Ramat-Gan, 52900, Israel; Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel.
| | - Adan Marzouqe
- Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel; Department of Chemistry, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Joseph Kantorovitsch
- Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Eti Teblum
- Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Tao Chen
- Third Institute of Physics-Biophysics, Georg August University, 37077 Göttingen, Germany
| | - Jörg Enderlein
- Third Institute of Physics-Biophysics, Georg August University, 37077 Göttingen, Germany; Cluster of Excellence "Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells" (MBExC), Georg August University, Germany
| | - Evan W Miller
- Departments of Chemistry, Molecular & Cell Biology, and Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, United States
| | - Shimon Weiss
- Department of Physics, Bar-Ilan University, Ramat-Gan, 52900, Israel; Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel; Departments of Chemistry and Biochemistry, Physiology, and California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095.
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8
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Farkas DL. Biomedical Applications of Translational Optical Imaging: From Molecules to Humans. Molecules 2021; 26:molecules26216651. [PMID: 34771060 PMCID: PMC8587670 DOI: 10.3390/molecules26216651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 08/24/2021] [Accepted: 08/24/2021] [Indexed: 11/16/2022] Open
Abstract
Light is a powerful investigational tool in biomedicine, at all levels of structural organization. Its multitude of features (intensity, wavelength, polarization, interference, coherence, timing, non-linear absorption, and even interactions with itself) able to create contrast, and thus images that detail the makeup and functioning of the living state can and should be combined for maximum effect, especially if one seeks simultaneously high spatiotemporal resolution and discrimination ability within a living organism. The resulting high relevance should be directed towards a better understanding, detection of abnormalities, and ultimately cogent, precise, and effective intervention. The new optical methods and their combinations needed to address modern surgery in the operating room of the future, and major diseases such as cancer and neurodegeneration are reviewed here, with emphasis on our own work and highlighting selected applications focusing on quantitation, early detection, treatment assessment, and clinical relevance, and more generally matching the quality of the optical detection approach to the complexity of the disease. This should provide guidance for future advanced theranostics, emphasizing a tighter coupling-spatially and temporally-between detection, diagnosis, and treatment, in the hope that technologic sophistication such as that of a Mars rover can be translationally deployed in the clinic, for saving and improving lives.
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Affiliation(s)
- Daniel L. Farkas
- PhotoNanoscopy and Acceleritas Corporations, 13412 Ventura Boulevard, Sherman Oaks, CA 91423, USA; ; Tel.: +1-310-600-7102
- Clinical Photonics Corporation, 8591 Skyline Drive, Los Angeles, CA 90046, USA
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA 90089, USA
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9
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Hiyoshi K, Shiraishi A, Fukuda N, Tsuda S. In vivo wide-field voltage imaging in zebrafish with voltage-sensitive dye and genetically encoded voltage indicator. Dev Growth Differ 2021; 63:417-428. [PMID: 34411280 DOI: 10.1111/dgd.12744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 07/01/2021] [Accepted: 07/04/2021] [Indexed: 11/28/2022]
Abstract
The brain consists of neural circuits, which are assemblies of various neuron types. For understanding how the brain works, it is essential to identify the functions of each type of neuron and neuronal circuits. Recent advances in our understanding of brain function and its development have been achieved using light to detect neuronal activity. Optical measurement of membrane potentials through voltage imaging is a desirable approach, enabling fast, direct, and simultaneous detection of membrane potentials in a population of neurons. Its high speed and directness can help detect synaptic and action potentials and hyperpolarization, which encode critical information for brain function. Here, we describe in vivo voltage imaging procedures that we have recently established using zebrafish, a powerful animal model in developmental biology and neuroscience. By applying two types of voltage sensors, voltage-sensitive dyes (VSDs, Di-4-ANEPPS) and genetically encoded voltage indicators (GEVIs, ASAP1), spatiotemporal dynamics of voltage signals can be detected in the whole cerebellum and spinal cord in awake fish at single-cell and neuronal population levels. Combining this method with other approaches, such as optogenetics, behavioral analysis, and electrophysiology would facilitate a deeper understanding of the network dynamics of the brain circuitry and its development.
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Affiliation(s)
- Kanae Hiyoshi
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Japan
| | - Asuka Shiraishi
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Japan
| | - Narumi Fukuda
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Japan
| | - Sachiko Tsuda
- Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama City, Japan.,Integrative Research Center for Life Sciences and Biotechnology, Saitama University, Saitama City, Japan
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10
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Abstract
Membrane potential (Vmem) is a fundamental biophysical signal present in all cells. Vmem signals range in time from milliseconds to days, and they span lengths from microns to centimeters. Vmem affects many cellular processes, ranging from neurotransmitter release to cell cycle control to tissue patterning. However, existing tools are not suitable for Vmem quantification in many of these areas. In this review, we outline the diverse biology of Vmem, drafting a wish list of features for a Vmem sensing platform. We then use these guidelines to discuss electrode-based and optical platforms for interrogating Vmem. On the one hand, electrode-based strategies exhibit excellent quantification but are most effective in short-term, cellular recordings. On the other hand, optical strategies provide easier access to diverse samples but generally only detect relative changes in Vmem. By combining the respective strengths of these technologies, recent advances in optical quantification of absolute Vmem enable new inquiries into Vmem biology.
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Affiliation(s)
- Julia R Lazzari-Dean
- Department of Chemistry, University of California, Berkeley, California 94720, USA; ,
| | - Anneliese M M Gest
- Department of Chemistry, University of California, Berkeley, California 94720, USA; ,
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, California 94720, USA; ,
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
- Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, USA
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11
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Acker CD, Yan P, Loew LM. Recent progress in optical voltage-sensor technology and applications to cardiac research: from single cells to whole hearts. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 154:3-10. [PMID: 31474387 PMCID: PMC7048644 DOI: 10.1016/j.pbiomolbio.2019.07.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2019] [Revised: 07/16/2019] [Accepted: 07/31/2019] [Indexed: 12/25/2022]
Abstract
The first workshop on Novel Optics-based approaches for Cardiac Electrophysiology (NOtiCE) was held in Florence Italy in 2018. Here, we learned how optical approaches have shaped our basic understanding of cardiac electrophysiology and how new technologies and approaches are being developed and validated to advance the field. Several technologies are being developed that may one day allow for new clinical approaches for diagnosing cardiac disorders and possibly intervening to treat human patients. In this review, we discuss several technologies and approaches to optical voltage imaging with voltage-sensitive dyes. We highlight the development and application of fluorinated and long wavelength voltage-sensitive dyes. These optical voltage sensors have now been applied and well validated in several different assays from cultured human stem cell-derived cardiomyocytes to whole hearts in-vivo. Imaging concepts such as dual wavelength ratiometric techniques, which are crucial to maximizing the information from optical sensors by increasing the useful signal and eliminating noise and artifacts, are presented. Finally, novel voltage sensors including photoacoustic voltage-sensitive dyes, their current capabilities and potential advantages, are introduced.
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Affiliation(s)
- Corey D Acker
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, 400 Farmington Avenue, Farmington, CT, 06030, USA.
| | - Ping Yan
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, 400 Farmington Avenue, Farmington, CT, 06030, USA
| | - Leslie M Loew
- R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut School of Medicine, 400 Farmington Avenue, Farmington, CT, 06030, USA
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12
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Kwon J, Ko S, Lee J, Na J, Sung J, Lee HJ, Lee S, Chung S, Choi HJ. Nanoelectrode-mediated single neuron activation. NANOSCALE 2020; 12:4709-4718. [PMID: 32049079 DOI: 10.1039/c9nr10559j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Elucidating cellular dynamics at the level of a single neuron and its associated role within neuronal circuits is essential for interpreting the complex nature of the brain. To investigate the operation of neural activity within its network, it is necessary to precisely manipulate the activation of each neuron and verify its propagation path via the synaptic connection. In this study, by exploiting the intrinsic physical and electrical advantages of a nanoelectrode, a vertical nanowire multi electrode array (VNMEA) is developed as a neuronal activation platform presenting the spatially confined effect on the intracellular space of individual cells. VNMEA makes a distinct difference between the interior and exterior cell potential and the current density, deriving the superior effects on activating Ca2+ responses compared to extracellular methods under the same conditions, with about 2.9-fold higher amplitude of Ca2+ elevation and a 2.6-fold faster recovery rate. Moreover, the synchronized propagation of evoked activities is shown in connected neurons implying cell-to-cell communications following the intracellular stimulation. The simulation and experimental consequences prove the outstanding property of temporal/spatial confinement of VNMEA-mediated intracellular stimulation to activate a single neuron and show its potential in localizing spiking neurons within neuronal populations, which may be utilized to reveal the connection and activation modalities of neural networks.
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Affiliation(s)
- Juyoung Kwon
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Sukjin Ko
- Brain Korea 21 Plus Project for Medical Science, Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
| | - Jaejun Lee
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Jukwan Na
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Jaesuk Sung
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Hyo-Jung Lee
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Seonghyeon Lee
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
| | - Seungsoo Chung
- Brain Korea 21 Plus Project for Medical Science, Department of Physiology, Yonsei University College of Medicine, Seoul 03722, Republic of Korea.
| | - Heon-Jin Choi
- Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea.
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13
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Abstract
Membrane potential is a fundamental biophysical property maintained by every cell on earth. In specialized cells like neurons, rapid changes in membrane potential drive the release of chemical neurotransmitters. Coordinated, rapid changes in neuronal membrane potential across large numbers of interconnected neurons form the basis for all of human cognition, sensory perception, and memory. Despite the importance of this highly orchestrated and distributed activity, the traditional method for recording membrane potential is through the use of highly invasive single-cell electrodes that offer only a small glimpse of the total activity within a system. Fluorescent dyes that change their optical properties in response to changes in biological voltage have the potential to provide a powerful complement to traditional electrode-based methods of inquiry. Voltage-sensitive fluorescent indicators would allow the direct observation of membrane potential changes, significantly expanding our ability to monitor membrane potential dynamics in living systems. Toward this end, we have initiated a program to design, synthesize, and apply voltage-sensitive fluorophores that report on membrane potential dynamics with high sensitivity and speed. The basis for this optical voltage sensing is membrane potential-dependent photoinduced electron transfer (PeT). Voltage-sensitive fluorophores, or VoltageFluors, possess a fluorophore, a conjugated molecular wire, and an aniline donor. At resting potentials, in which the cell has a hyperpolarized or negative potential relative to the outside of the cell, PeT from the aniline donor is enhanced and fluorescence is diminished. At depolarized potentials, the membrane potential decreases the rate of PeT, allowing an increase in fluorescence. We show that a number of different fluorophores, molecular wires, and aniline donors can be employed to generate fast and sensitive VoltageFluor dyes. Multiple lines of evidence point to a PeT-based mechanism for voltage sensing, delivering fast response kinetics (∼25 ns), good sensitivity (>60% ΔF/F), compatibility with two-photon illumination, excellent signal-to-noise, and the ability to detect neuronal and cardiac action potentials in single trials. In this Account, we provide an overview of the challenges facing the design of fluorescent voltage indicators. We trace the development of molecular wire-based fluorescent voltage indicators within our group, beginning from fluorescein-based VoltageFluor to long-wavelength indicators that use modern fluorophores like silicon rhodamine and carbofluorescein. We examine design principles for PeT-based voltage indicators, showcase the use of our recent indicators for two-photon voltage imaging in intact brains, and explore the development of hybrid indicators that can localize to genetically defined cells. Finally, we highlight outstanding challenges to and opportunities for voltage imaging.
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Affiliation(s)
- Pei Liu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Evan W. Miller
- Department of Chemistry, University of California, Berkeley, California 94720, United States
- Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States
- Department of Helen Wills Neuroscience Institute. University of California, Berkeley, California 94720, United States
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14
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Yudovich S, Shani L, Grupi A, Bar-Elli O, Steinitz D, Oron D, Weiss S. Ratiometric widefield imaging with spectrally balanced detection. BIOMEDICAL OPTICS EXPRESS 2019; 10:5385-5394. [PMID: 31646053 PMCID: PMC6788590 DOI: 10.1364/boe.10.005385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 08/12/2019] [Accepted: 08/29/2019] [Indexed: 06/10/2023]
Abstract
Ratiometric imaging is an invaluable tool for quantitative microscopy, allowing for robust detection of FRET, anisotropy, and spectral shifts of nano-scale optical probes in response to local physical and chemical variations such as local pH, ion composition, and electric potential. In this paper, we propose and demonstrate a scheme for widefield ratiometric imaging that allows for continuous tuning of the cutoff wavelength between its two spectral channels. This scheme is based on angle-tuning the image splitting dichroic beamsplitter, similar to previous works on tunable interference filters. This configuration allows for ratiometric imaging of spectrally heterogeneous samples, which require spectral tunability of the detection path in order to achieve good spectrally balanced ratiometric detection.
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Affiliation(s)
- Shimon Yudovich
- Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Lior Shani
- Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Asaf Grupi
- Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
| | - Omri Bar-Elli
- Department of Physics of Complex Systems, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dan Steinitz
- Department of Physics of Complex Systems, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dan Oron
- Department of Physics of Complex Systems, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Shimon Weiss
- Department of Physics, Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, 52900, Israel
- Department of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, CA 90095, USA
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA 90095, USA
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15
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Lazzari-Dean JR, Gest AM, Miller EW. Optical estimation of absolute membrane potential using fluorescence lifetime imaging. eLife 2019; 8:44522. [PMID: 31545164 PMCID: PMC6814365 DOI: 10.7554/elife.44522] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 09/16/2019] [Indexed: 12/29/2022] Open
Abstract
All cells maintain ionic gradients across their plasma membranes, producing transmembrane potentials (Vmem). Mounting evidence suggests a relationship between resting Vmem and the physiology of non-excitable cells with implications in diverse areas, including cancer, cellular differentiation, and body patterning. A lack of non-invasive methods to record absolute Vmem limits our understanding of this fundamental signal. To address this need, we developed a fluorescence lifetime-based approach (VF-FLIM) to visualize and optically quantify Vmem with single-cell resolution in mammalian cell culture. Using VF-FLIM, we report Vmem distributions over thousands of cells, a 100-fold improvement relative to electrophysiological approaches. In human carcinoma cells, we visualize the voltage response to growth factor stimulation, stably recording a 10-15 mV hyperpolarization over minutes. Using pharmacological inhibitors, we identify the source of the hyperpolarization as the Ca2+-activated K+ channel KCa3.1. The ability to optically quantify absolute Vmem with cellular resolution will allow a re-examination of its signaling roles.
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Affiliation(s)
- Julia R Lazzari-Dean
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Anneliese Mm Gest
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, Berkeley, United States.,Department of Molecular & Cell Biology, University of California, Berkeley, Berkeley, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, United States
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16
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Shinotsuka R, Oba T, Mitome T, Masuya T, Ito S, Murakami Y, Kagenishi T, Kodama Y, Matsuda M, Yoshida T, Wakamori M, Ohkura M, Nakai J. Synthesis of quinolyl-pyrrole derivatives as novel environment-sensitive fluorescent probes. J Photochem Photobiol A Chem 2019. [DOI: 10.1016/j.jphotochem.2019.111900] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Park J, Kuo Y, Li J, Huang YL, Miller EW, Weiss S. Improved Surface Functionalization and Characterization of Membrane-Targeted Semiconductor Voltage Nanosensors. J Phys Chem Lett 2019; 10:3906-3913. [PMID: 31241960 DOI: 10.1021/acs.jpclett.9b01258] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Type-II ZnSe/CdS voltage-sensing seeded nanorods (vsNRs) were functionalized with α-helical peptides and zwitterionic-decorated lipoic acids (zw-LAs). Specific membrane targeting with high loading efficiency and minimal nonspecific binding was achieved. These vsNRs display quantum yield (QY) modulation as a function of membrane potential (MP) changes, as demonstrated at the ensemble level for (i) vesicles treated with valinomycin and (ii) wild-type HEK cells under alternating buffers with different [K+]. ΔF/F of ∼ 1% was achieved.
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Affiliation(s)
- Joonhyuck Park
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California 90095 , United States
| | - Yung Kuo
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California 90095 , United States
| | - Jack Li
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California 90095 , United States
| | - Yi-Lin Huang
- Department of Chemistry , Department Molecular & Cell Biology , and Helen Wills Neuroscience Institute , University of California Berkeley , Berkeley , California 94720 , United States
| | - Evan W Miller
- Department of Chemistry , Department Molecular & Cell Biology , and Helen Wills Neuroscience Institute , University of California Berkeley , Berkeley , California 94720 , United States
| | - Shimon Weiss
- Department of Chemistry and Biochemistry , University of California Los Angeles , Los Angeles , California 90095 , United States
- California NanoSystems Institute , University of California Los Angeles , Los Angeles , California 90095 , United States
- Department of Physiology , University of California Los Angeles , Los Angeles , California 90095 , United States
- Department of Physics, Institute for Nanotechnology and Advanced Materials , Bar-Ilan University , Ramat-Gan 52900 , Israel
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18
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Plasma Membrane Potential of Candida albicans Measured by Di-4-ANEPPS Fluorescence Depends on Growth Phase and Regulatory Factors. Microorganisms 2019; 7:microorganisms7040110. [PMID: 31022974 PMCID: PMC6518178 DOI: 10.3390/microorganisms7040110] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Revised: 04/13/2019] [Accepted: 04/22/2019] [Indexed: 11/17/2022] Open
Abstract
The potential of the plasma membrane (Δѱ) regulates the electrochemical potential between the outer and inner sides of cell membranes. The opportunistic fungal pathogen, Candida albicans, regulates the membrane potential in response to environmental conditions, as well as the physiological state of the cell. Here we demonstrate a new method for detection of cell membrane depolarization/permeabilization in C. albicans using the potentiometric zwitterionic dye di-4-ANEPPS. Di-4-ANEPPS measures the changes in the cell Δѱ depending on the phases of growth and external factors regulating Δѱ, such as potassium or calcium chlorides, amiodarone or DM-11 (inhibitor of H+-ATPase). We also demonstrated that di-4-ANEPPS is a good tool for fast measurement of the influence of amphipathic compounds on Δѱ.
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19
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Iwata T, Nagatani H, Osakai T. Determination of the Electrostatic Potential of Oil-in-Water Emulsion Droplets by Combined Use of Two Membrane Potential-Sensitive Dyes. ANAL SCI 2018; 33:813-819. [PMID: 28690259 DOI: 10.2116/analsci.33.813] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The fluorescence behaviors of potential-sensitive dyes including anionic DiBAC4(3) (denoted by dye A), DiSBAC2(3) (dye B), and zwitterionic di-4-ANEPPS (dye C) were studied in oil-in-water (O/W) emulsions. In this study, the equilibrium Galvani potential difference (ΔOWφeq) of the O/W-emulsion droplets was controlled by changing the ratio of the concentrations of electrolytes added to the O (=1,2-dichloroethane) and W phases. When using an adequate combination of the dyes, i.e., B and C, we could observe that the ratio of their fluorescence peak intensities was changed from 1.08 to 1.38, depending on the change of (ΔOWφeq from 26 to 73 mV. It is desirable to apply this method to study the potential-dependent ion or electron-transfer reactions occurring at vesicles or liposomes, and also to biomembranes.
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Affiliation(s)
- Tomoya Iwata
- Department of Chemistry, Graduate School of Science, Kobe University
| | - Hirohisa Nagatani
- Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University
| | - Toshiyuki Osakai
- Department of Chemistry, Graduate School of Science, Kobe University
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20
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Bar-Elli O, Steinitz D, Yang G, Tenne R, Ludwig A, Kuo Y, Triller A, Weiss S, Oron D. Rapid Voltage Sensing with Single Nanorods via the Quantum Confined Stark Effect. ACS PHOTONICS 2018; 5:2860-2867. [PMID: 30042952 PMCID: PMC6053642 DOI: 10.1021/acsphotonics.8b00206] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Indexed: 05/05/2023]
Abstract
Properly designed colloidal semiconductor quantum dots (QDs) have already been shown to exhibit high sensitivity to external electric fields via the quantum confined Stark effect (QCSE). Yet, detection of the characteristic spectral shifts associated with the effect of the QCSE has traditionally been painstakingly slow, dramatically limiting the sensitivity of these QD sensors to fast transients. We experimentally demonstrate a new detection scheme designed to achieve shot-noise-limited sensitivity to emission wavelength shifts in QDs, showing feasibility for their use as local electric field sensors on the millisecond time scale. This regime of operation is already potentially suitable for detection of single action potentials in neurons at a high spatial resolution.
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Affiliation(s)
- Omri Bar-Elli
- Department of Physics
of Complex Systems, Weizmann Institute of
Science, Rehovot 76100, Israel
| | - Dan Steinitz
- Department of Physics
of Complex Systems, Weizmann Institute of
Science, Rehovot 76100, Israel
| | - Gaoling Yang
- Department of Physics
of Complex Systems, Weizmann Institute of
Science, Rehovot 76100, Israel
| | - Ron Tenne
- Department of Physics
of Complex Systems, Weizmann Institute of
Science, Rehovot 76100, Israel
| | - Anastasia Ludwig
- L’Ecole
Normale Superieure, Institute of Biologie
(IBENS), Paris Sciences et Lettres (PSL), CNRS UMR 8197, Inserm 1024, 46 Rue d’Ulm, Paris 75005, France
| | - Yung Kuo
- Department of Chemistry and Biochemistry, Department of Physiology,
and California NanoSystems Institute, University
of California Los Angeles, Los
Angeles, California 90095, United States
| | - Antoine Triller
- L’Ecole
Normale Superieure, Institute of Biologie
(IBENS), Paris Sciences et Lettres (PSL), CNRS UMR 8197, Inserm 1024, 46 Rue d’Ulm, Paris 75005, France
| | - Shimon Weiss
- Department of Chemistry and Biochemistry, Department of Physiology,
and California NanoSystems Institute, University
of California Los Angeles, Los
Angeles, California 90095, United States
- Department of Physics, Institute for Nanotechnology
and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Dan Oron
- Department of Physics
of Complex Systems, Weizmann Institute of
Science, Rehovot 76100, Israel
- E-mail:
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21
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Tsemperouli M, Sugihara K. Characterization of di-4-ANEPPS with nano-black lipid membranes. NANOSCALE 2018; 10:1090-1098. [PMID: 29271448 DOI: 10.1039/c7nr05863b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We report a platform based on lateral nano-black lipid membranes (nano-BLMs), where electrical measurements and fluorescence microscopy setup are combined, for the calibration of di-4-ANEPPS, a common voltage sensitive dye (VSD). The advantage of this setup is (1) its flexibility in the choice of lipids and applied voltages, (2) its high stability that enables a high voltage (500 mV) application and long-time measurements and (3) its fluorescence microscopy readout, which can be directly correlated with other fluorescence microscopy experiments using VSDs (e.g. membrane potential measurements in living cells). Using this setup, we observed that the calibration curve of di-4-ANEPPS is strongly dependent on the net electric charge of the lipids. The developed setup can be used to calibrate VSDs in different lipid environments in order to better understand their fundamental voltage-sensing mechanism in the future.
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Affiliation(s)
- Maria Tsemperouli
- Department of Physical Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland.
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22
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Zhang H, Iijima K, Huang J, Walcott GP, Rogers JM. Optical Mapping of Membrane Potential and Epicardial Deformation in Beating Hearts. Biophys J 2017; 111:438-451. [PMID: 27463145 DOI: 10.1016/j.bpj.2016.03.043] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 03/01/2016] [Accepted: 03/24/2016] [Indexed: 11/26/2022] Open
Abstract
Cardiac optical mapping uses potentiometric fluorescent dyes to image membrane potential (Vm). An important limitation of conventional optical mapping is that contraction is usually arrested pharmacologically to prevent motion artifacts from obscuring Vm signals. However, these agents may alter electrophysiology, and by abolishing contraction, also prevent optical mapping from being used to study coupling between electrical and mechanical function. Here, we present a method to simultaneously map Vm and epicardial contraction in the beating heart. Isolated perfused swine hearts were stained with di-4-ANEPPS and fiducial markers were glued to the epicardium for motion tracking. The heart was imaged at 750 Hz with a video camera. Fluorescence was excited with cyan or blue LEDs on alternating camera frames, thus providing a 375-Hz effective sampling rate. Marker tracking enabled the pixel(s) imaging any epicardial site within the marked region to be identified in each camera frame. Cyan- and blue-elicited fluorescence have different sensitivities to Vm, but other signal features, primarily motion artifacts, are common. Thus, taking the ratio of fluorescence emitted by a motion-tracked epicardial site in adjacent frames removes artifacts, leaving Vm (excitation ratiometry). Reconstructed Vm signals were validated by comparison to monophasic action potentials and to conventional optical mapping signals. Binocular imaging with additional video cameras enabled marker motion to be tracked in three dimensions. From these data, epicardial deformation during the cardiac cycle was quantified by computing finite strain fields. We show that the method can simultaneously map Vm and strain in a left-sided working heart preparation and can image changes in both electrical and mechanical function 5 min after the induction of regional ischemia. By allowing high-resolution optical mapping in the absence of electromechanical uncoupling agents, the method relieves a long-standing limitation of optical mapping and has potential to enhance new studies in coupled cardiac electromechanics.
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Affiliation(s)
- Hanyu Zhang
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Kenichi Iijima
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jian Huang
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Gregory P Walcott
- Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama
| | - Jack M Rogers
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, Alabama.
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23
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Klymchenko AS. Solvatochromic and Fluorogenic Dyes as Environment-Sensitive Probes: Design and Biological Applications. Acc Chem Res 2017; 50:366-375. [PMID: 28067047 DOI: 10.1021/acs.accounts.6b00517] [Citation(s) in RCA: 646] [Impact Index Per Article: 92.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fluorescent environment-sensitive probes are specially designed dyes that change their fluorescence intensity (fluorogenic dyes) or color (e.g., solvatochromic dyes) in response to change in their microenvironment polarity, viscosity, and molecular order. The studies of the past decade, including those of our group, have shown that these molecules become universal tools in fluorescence sensing and imaging. In fact, any biomolecular interaction or change in biomolecular organization results in modification of the local microenvironment, which can be directly monitored by these types of probes. In this Account, the main examples of environment-sensitive probes are summarized according to their design concepts. Solvatochromic dyes constitute a large class of environment-sensitive probes which change their color in response to polarity. Generally, they are push-pull dyes undergoing intramolecular charge transfer. Emission of their highly polarized excited state shifts to the red in more polar solvents. Excited-state intramolecular proton transfer is the second key concept to design efficient solvatochromic dyes, which respond to the microenvironment by changing relative intensity of the two emissive tautomeric forms. Due to their sensitivity to polarity and hydration, solvatochromic dyes have been successfully applied to biological membranes for studying lipid domains (rafts), apoptosis and endocytosis. As fluorescent labels, solvatochromic dyes can detect practically any type of biomolecular interactions, involving proteins, nucleic acids and biomembranes, because the binding event excludes local water molecules from the interaction site. On the other hand, fluorogenic probes usually exploit intramolecular rotation (conformation change) as a design concept, with molecular rotors being main representatives. These probes were particularly efficient for imaging viscosity and lipid order in biomembranes as well as to light up biomolecular targets, such as antibodies, aptamers and receptors. The emerging concepts to achieve fluorogenic response to the microenvironment include ground-state isomerization, aggregation-caused quenching, and aggregation-induced emission. The ground-state isomerization exploits, for instance, polarity-dependent spiro-lactone formation in silica-rhodamines. The aggregation-caused quenching uses disruption of the self-quenched dimers and nanoassemblies of dyes in less polar environments of lipid membranes and biomolecules. The aggregation-induced emission couples target recognition with formation of highly fluorescent dye aggregates. Overall, solvatochromic and fluorogenic probes enable background-free bioimaging in wash-free conditions as well as quantitative analysis when combined with advanced microscopy, such as fluorescence lifetime (FLIM) and ratiometric imaging. Further development of fluorescent environment-sensitive probes should address some remaining problems: (i) improving their optical properties, especially brightness, photostability, and far-red to near-infrared operating range; (ii) minimizing nonspecific interactions of the probes in biological systems; (iii) their adaptation for advanced microscopies, notably for superresolution and in vivo imaging.
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Affiliation(s)
- Andrey S. Klymchenko
- Laboratoire de Biophotonique et Pharmacologie,
UMR 7213 CNRS, Université de Strasbourg, F-67000 Strasbourg, France
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24
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Aryal GH, Huang L, Hunter KW. The donor–acceptor complexes of quantum dots and ionic perylene diimides for ratiometric detection of double-stranded DNA. RSC Adv 2016. [DOI: 10.1039/c6ra16019k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
We developed a FRET ratiometric system based on quantum dots and perylene diimides for detection of double-stranded DNAs.
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Affiliation(s)
- Gyan H. Aryal
- Department of Microbiology and Immunology
- School of Medicine
- University of Nevada
- Reno
- USA
| | - Liming Huang
- Department of Microbiology and Immunology
- School of Medicine
- University of Nevada
- Reno
- USA
| | - Kenneth W. Hunter
- Department of Microbiology and Immunology
- School of Medicine
- University of Nevada
- Reno
- USA
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25
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Mazzocchi N, De Ceglia R, Mazza D, Forti L, Muzio L, Menegon A. Fluorescence-Based Automated Screening Assay for the Study of the pH-Sensitive Channel ASIC1a. ACTA ACUST UNITED AC 2015; 21:372-80. [DOI: 10.1177/1087057115617455] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 10/26/2015] [Indexed: 11/16/2022]
Abstract
Acid-sensing ion channel 1a (ASIC1a) is involved in several pathologies, including neurodegenerative and neuroinflammatory disorders, stroke, epilepsy, and inflammatory pain. ASIC1a has been the subject of intense drug discovery programs devoted to the development of new pharmacological tools for its modulation. However, these efforts to generate new compounds have faced the lack of an efficient screening procedure. In the past decades, improvements in screening technologies and fluorescent sensors for the study of ion channels have provided new opportunities in this field. Unfortunately, ASIC1a is mainly a Na+ permeable channel and undergoes desensitization after its activation, two features that make the use of the available screening procedures problematic. We propose here a novel screening approach for the study of ASIC1a activity in full automation. Our method is based on the stimulation of ASIC1a-expressing cells by protons and the use of electrochromic fluorescent voltage sensors as a readout of ion channel activation. This method will prove to be useful for drug screening programs aimed at ASIC1a modulation.
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Affiliation(s)
- Nausicaa Mazzocchi
- Advanced Light and Electron Microscopy Bio-Imaging Centre, Experimental Imaging Centre, San Raffaele Scientific Institute, Milan, Italy
| | - Roberta De Ceglia
- Neuroimmunolgy Unit, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Davide Mazza
- Advanced Fluorescence Microscopy and Nanoscopy Research Unit, Experimental Imaging Center, San Raffaele Scientific Institute, Milan, Italy
| | - Lia Forti
- Center for Neuroscience and Dept. of Theoretical and Applied Sciences (DiSTA), Biomedical Division, University of Insubria, Busto Arsizio (VA), Italy
| | - Luca Muzio
- Neuroimmunolgy Unit, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Andrea Menegon
- Advanced Light and Electron Microscopy Bio-Imaging Centre, Experimental Imaging Centre, San Raffaele Scientific Institute, Milan, Italy
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26
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Jewell SA, Titball RW, Huyet J, Naylor CE, Basak AK, Gologan P, Winlove CP, Petrov PG. Clostridium perfringensα-toxin interaction with red cells and model membranes. SOFT MATTER 2015; 11:7748-7761. [PMID: 26303814 DOI: 10.1039/c5sm00876j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The effects of Clostridium perfringensα-toxin on host cells have previously been studied extensively but the biophysical processes associated with toxicity are poorly understood. The work reported here shows that the initial interaction between the toxin and lipid membrane leads to measurable changes in the physical properties and morphology of the membrane. A Langmuir monolayer technique was used to assess the response of different lipid species to toxin. Sphingomyelin and unsaturated phosphatidylcholine showed the highest susceptibility to toxin lypolitic action, with a two stage response to the toxin (an initial, rapid hydrolysis stage followed by the insertion and/or reorganisation of material in the monolayer). Fluorescence confocal microscopy on unsaturated phosphatidylcholine vesicles shows that the toxin initially aggregates at discrete sites followed by the formation of localised "droplets" accumulating the hydrolysis products. This process is accompanied by local increases in the membrane dipole potential by about 50 (±42) mV. In contrast, red blood cells incubated with the toxin suffered a decrease of the membrane dipole potential by 50 (±40) mV in areas of high toxin activity (equivalent to a change in electric field strength of 10(7) V m(-1)) which is sufficient to affect the functioning of the cell membrane. Changes in erythrocyte morphology caused by the toxin are presented, and the early stages of interaction between toxin and membrane are characterised using thermal shape fluctuation analysis of red cells which revealed two distinct regimes of membrane-toxin interaction.
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Affiliation(s)
- S A Jewell
- School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
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27
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Lo SQ, Koh DXP, Sng JCG, Augustine GJ. All-optical mapping of barrel cortex circuits based on simultaneous voltage-sensitive dye imaging and channelrhodopsin-mediated photostimulation. NEUROPHOTONICS 2015; 2:021013. [PMID: 26158003 PMCID: PMC4478985 DOI: 10.1117/1.nph.2.2.021013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2014] [Accepted: 03/04/2015] [Indexed: 05/25/2023]
Abstract
We describe an experimental approach that uses light to both control and detect neuronal activity in mouse barrel cortex slices: blue light patterned by a digital micromirror array system allowed us to photostimulate specific layers and columns, while a red-shifted voltage-sensitive dye was used to map out large-scale circuit activity. We demonstrate that such all-optical mapping can interrogate various circuits in somatosensory cortex by sequentially activating different layers and columns. Further, mapping in slices from whisker-deprived mice demonstrated that chronic sensory deprivation did not significantly alter feedforward inhibition driven by layer 5 pyramidal neurons. Further development of voltage-sensitive optical probes should allow this all-optical mapping approach to become an important and high-throughput tool for mapping circuit interactions in the brain.
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Affiliation(s)
- Shun Qiang Lo
- National University of Singapore, Yong Loo Lin School of Medicine, Department of Physiology, Singapore 117597, Singapore
- Nanyang Technological University, Lee Kong Chian School of Medicine, Proteos, Biopolis, Level 4, 61 Biopolis Drive, #04-06/07, Singapore 138673, Singapore
- Institute of Molecular and Cell Biology, A*STAR, Proteos, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
- Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, United States
| | - Dawn X. P. Koh
- National University of Singapore, Graduate School of Integrative Sciences and Engineering, Singapore 117456, Singapore
- National University of Singapore, Yong Loo Lin School of Medicine, Department of Pharmacology, Singapore 117599, Singapore
- Singapore Institute of Clinical Sciences (SICS), A*STAR, Brenner Centre for Molecular Medicine, 30 Medical Drive, Singapore 117609, Singapore
| | - Judy C. G. Sng
- National University of Singapore, Yong Loo Lin School of Medicine, Department of Pharmacology, Singapore 117599, Singapore
- Singapore Institute of Clinical Sciences (SICS), A*STAR, Brenner Centre for Molecular Medicine, 30 Medical Drive, Singapore 117609, Singapore
| | - George J. Augustine
- National University of Singapore, Yong Loo Lin School of Medicine, Department of Physiology, Singapore 117597, Singapore
- Nanyang Technological University, Lee Kong Chian School of Medicine, Proteos, Biopolis, Level 4, 61 Biopolis Drive, #04-06/07, Singapore 138673, Singapore
- Institute of Molecular and Cell Biology, A*STAR, Proteos, 61 Biopolis Drive, Proteos, Singapore 138673, Singapore
- Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, United States
- Korea Institute of Science and Technology, Center for Functional Connectomics, 39-1 Hawolgokdong, Seongbukgu, Seoul 136-791, Republic of Korea
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Modifiers of membrane dipole potentials as tools for investigating ion channel formation and functioning. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:245-97. [PMID: 25708465 DOI: 10.1016/bs.ircmb.2014.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electrostatic fields generated on and within biological membranes play a fundamental role in key processes in cell functions. The role of the membrane dipole potential is of particular interest because of its powerful impact on membrane permeability and lipid-protein interactions, including protein insertion, oligomerization, and function. The membrane dipole potential is defined by the orientation of electric dipoles of lipid headgroups, fatty acid carbonyl groups, and membrane-adsorbed water. As a result, the membrane interior is several hundred millivolts more positive than the external aqueous phase. This potential decrease depends on the lipid, and especially sterol, composition of the membrane. The adsorption of certain electroneutral molecules known as dipole modifiers may also lead to significant changes in the magnitude of the potential decrease. These agents are widely used to study the effects of the dipole potential on membrane transport. This review presents a critical analysis of a variety of data from studies dedicated to ion channel formation and functioning in membranes with different dipole potentials. The types of ion channels found in cellular membranes and pores formed by antimicrobial agents and toxins in artificial lipid membranes are summarized. The mechanisms underlying the influence of the membrane dipole potential on ion channel activity, including dipole-dipole and charge-dipole interactions in the pores and in membranes, are discussed. A hypothesis, in which lipid rafts in both model and cellular membranes also modulate ion channel activity by virtue of an increased or decreased dipole potential, is also considered.
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Demchenko AP, Duportail G, Oncul S, Klymchenko AS, Mély Y. Introduction to fluorescence probing of biological membranes. Methods Mol Biol 2015; 1232:19-43. [PMID: 25331125 DOI: 10.1007/978-1-4939-1752-5_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Fluorescence is one of the most powerful and commonly used tools in biophysical studies of biomembrane structure and dynamics that can be applied on different levels, from lipid monolayers and bilayers to living cells, tissues, and whole animals. Successful application of this method relies on proper design of fluorescence probes with optimized photophysical properties. These probes are efficient for studying the microscopic analogs of viscosity, polarity, and hydration, as well as the molecular order, environment relaxation, and electrostatic potentials at the sites of their location. Being smaller than the membrane width they can sense the gradients of these parameters across the membrane. We present examples of novel dyes that achieve increased spatial resolution and information content of the probe responses. In this respect, multiparametric environment-sensitive probes feature considerable promise.
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Affiliation(s)
- Alexander P Demchenko
- Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, 9 Leontovicha Street, Kiev, 01030, Ukraine,
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Loew LM. Design and Use of Organic Voltage Sensitive Dyes. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 859:27-53. [PMID: 26238048 DOI: 10.1007/978-3-319-17641-3_2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The chemistry and the physics of voltage sensitive dyes (VSDs) should be understood and appreciated as a prerequisite for their optimal application to problems in neuroscience cardiology. This chapter provides a basic understanding of the properties of the large variety of available organic VSDs. The mechanisms by which the dyes respond to voltage guides the best set up of the optics for recording or imaging electrophysiological activity. The physical and chemical properties of the dyes can be tuned to optimize delivery to and staining of the cells in different experimental preparations. The aim of this chapter is to arm the experimentalists who use the dyes with enough information and data to be able to intelligently choose the best dye for their specific requirements.
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Affiliation(s)
- Leslie M Loew
- Department of Cell Biology, R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT, 06030-6406, USA,
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31
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Chaudhuri A, Chattopadhyay A. Lipid binding specificity of bovine α-lactalbumin: A multidimensional approach. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2078-86. [DOI: 10.1016/j.bbamem.2014.04.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Revised: 04/27/2014] [Accepted: 04/28/2014] [Indexed: 10/25/2022]
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32
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Blake HL, Robinson D. QM/MM studies of contemporary and novel membrane raft fluorescent probes. Molecules 2014; 19:10230-41. [PMID: 25029071 PMCID: PMC6271554 DOI: 10.3390/molecules190710230] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/09/2014] [Accepted: 07/10/2014] [Indexed: 11/22/2022] Open
Abstract
We have studied a number of contemporary and novel membrane probes, selected for their structural similarity to membrane raft components, in order to properly anchor themselves within a sphingolipid/cholesterol rich region. A QM/MM approach was adopted in order to understand the structural and electrostatic influences of fluorescence emission shifts of the probes in different lipid and solvation environments. The proposed modifications to the membrane probes have shown encouraging data relating not only to emission shifts within the membrane, but also their ability to anchor within a membrane raft domain and the stability to internalization within a membrane system.
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Affiliation(s)
- Hannah L Blake
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
| | - David Robinson
- School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, UK.
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Combined use of two membrane-potential-sensitive dyes for determination of the Galvani potential difference across a biomimetic oil/water interface. Anal Bioanal Chem 2014; 406:3407-14. [DOI: 10.1007/s00216-014-7776-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 03/17/2014] [Accepted: 03/17/2014] [Indexed: 11/25/2022]
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Klymchenko AS, Kreder R. Fluorescent probes for lipid rafts: from model membranes to living cells. ACTA ACUST UNITED AC 2013; 21:97-113. [PMID: 24361047 DOI: 10.1016/j.chembiol.2013.11.009] [Citation(s) in RCA: 350] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 10/22/2013] [Accepted: 11/04/2013] [Indexed: 01/10/2023]
Abstract
Membrane microdomains (rafts) remain one of the controversial issues in biophysics. Fluorescent molecular probes, which make these lipid nanostructures visible through optical techniques, are one of the tools currently used to study lipid rafts. The most common are lipophilic fluorescent probes that partition specifically into liquid ordered or liquid disordered phase. Their partition depends on the lipid composition of a given phase, which complicates their use in cellular membranes. A second class of probes is based on environment-sensitive dyes, which partition into both phases, but stain them by different fluorescence color, intensity, or lifetime. These probes can directly address the properties of each separate phase, but their cellular applications are still limited. The present review focuses on summarizing the current state in the field of developing and applying fluorescent molecular probes to study lipid rafts. We highlight an urgent need to develop new probes, specifically adapted for cell plasma membranes and compatible with modern fluorescence microscopy techniques to push the understanding of membrane microdomains forward.
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Affiliation(s)
- Andrey S Klymchenko
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Université de Strasbourg, Faculté de Pharmacie, 74, Route du Rhin, 67401 ILLKIRCH, France.
| | - Rémy Kreder
- Laboratoire de Biophotonique et Pharmacologie, UMR 7213 CNRS, Université de Strasbourg, Faculté de Pharmacie, 74, Route du Rhin, 67401 ILLKIRCH, France
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Manno C, Figueroa L, Fitts R, Ríos E. Confocal imaging of transmembrane voltage by SEER of di-8-ANEPPS. ACTA ACUST UNITED AC 2013; 141:371-87. [PMID: 23440278 PMCID: PMC3581694 DOI: 10.1085/jgp.201210936] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Imaging, optical mapping, and optical multisite recording of transmembrane potential (Vm) are essential for studying excitable cells and systems. The naphthylstyryl voltage-sensitive dyes, including di-8-ANEPPS, shift both their fluorescence excitation and emission spectra upon changes in Vm. Accordingly, they have been used for monitoring Vm in nonratioing and both emission and excitation ratioing modes. Their changes in fluorescence are usually much less than 10% per 100 mV. Conventional ratioing increases sensitivity to between 3 and 15% per 100 mV. Low sensitivity limits the value of these dyes, especially when imaged with low light systems like confocal scanners. Here we demonstrate the improvement afforded by shifted excitation and emission ratioing (SEER) as applied to imaging membrane potential in flexor digitorum brevis muscle fibers of adult mice. SEER—the ratioing of two images of fluorescence, obtained with different excitation wavelengths in different emission bands—was implemented in two commercial confocal systems. A conventional pinhole scanner, affording optimal setting of emission bands but less than ideal excitation wavelengths, achieved a sensitivity of up to 27% per 100 mV, nearly doubling the value found by conventional ratioing of the same data. A better pair of excitation lights should increase the sensitivity further, to 35% per 100 mV. The maximum acquisition rate with this system was 1 kHz. A fast “slit scanner” increased the effective rate to 8 kHz, but sensitivity was lower. In its high-sensitivity implementation, the technique demonstrated progressive deterioration of action potentials upon fatiguing tetani induced by stimulation patterns at >40 Hz, thereby identifying action potential decay as a contributor to fatigue onset. Using the fast implementation, we could image for the first time an action potential simultaneously at multiple locations along the t-tubule system. These images resolved the radially varying lag associated with propagation at a finite velocity.
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Affiliation(s)
- Carlo Manno
- Section of Cellular Signaling, Department of Molecular Biophysics and Physiology, Rush University, Chicago, IL 60612, USA
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36
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Ehrenberg B, Loew LM. Absolute spectroscopic determination of cross-membrane potential. J Fluoresc 2013; 3:265-9. [PMID: 24234908 DOI: 10.1007/bf00865276] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/1993] [Indexed: 11/28/2022]
Abstract
Spectroscopic determination of the cross-membrane electric potential has been used for more than 20 years. This method, which usually employs absorption or fluorescence measurements, allows for a rapid and noninvasive study of the electrical properties of the membranes of cells and liposomes. However, the usual fluorescence techniques preferably allow monitoring changes in the potential on triggerable or excitable membranes, and not the absolute value of the potential. They also do not provide means for measuring the potential on single cells. This paper reviews three methods that solve these issues. Nernstian dyes which partition between intra-and extracompartmental volumes enable a fluorescence microscopic determination of a single cell and even a single organelle. Dual-wavelength ratiometric recording from membrane-staining dyes also provides means for measuring the field on a single cell. Resonance Raman probes provide a spectroscopic method with a natural internal standard for the absolute measurement of membrane potential.
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Affiliation(s)
- B Ehrenberg
- Department of Physics, Bar Ilan University, 52-900, Ramat Gan, Israel
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37
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Jewell SA, Petrov PG, Winlove CP. The effect of oxidative stress on the membrane dipole potential of human red blood cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:1250-8. [PMID: 23313455 DOI: 10.1016/j.bbamem.2012.12.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 12/21/2012] [Accepted: 12/31/2012] [Indexed: 02/09/2023]
Abstract
The membrane dipole potential (ψ(d)) is an important biophysical determinant of membrane function and a sensitive indicator of lipid organisation. In this study we have used the environmentally sensitive probe di-8-anepps to explore the effects of oxidative stress on the membrane dipole potential of human erythrocytes. Cells suspended in 0.15mM phosphate buffered saline containing 0.1mg/ml albumin maintained a mean value for ψ(d) of 270 (±20) mV over the course of 1hour. In the presence of 0.4mM cumene hydroperoxide there was an increase in ψ(d) of 14 (±7)%, accompanied by a decrease in cell diameter of ~14 (±2)%. Exposure of the cells to 0.4mM hydrogen peroxide caused ψ(d) to decrease by 13 (±8)% at the centre of the cell and 8 (±5)% at the edge whilst the diameter remained constant. In both cases the changes were equivalent to a change in transmembrane electric field of a magnitude of ~10MVm(-1), sufficient to influence membrane function. Raman microspectrometry supported the conclusion that cumene exerts its effect primarily on membrane lipids whilst hydrogen peroxide causes the formation of spectrin-haemoglobin complexes which stiffen the membrane.
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Affiliation(s)
- S A Jewell
- School of Physics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
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Ratiometric imaging of calcium during ischemia-reperfusion injury in isolated mouse hearts using Fura-2. Biomed Eng Online 2012; 11:39. [PMID: 22812644 PMCID: PMC3466138 DOI: 10.1186/1475-925x-11-39] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Accepted: 06/28/2012] [Indexed: 12/31/2022] Open
Abstract
Background We present an easily implementable method for measuring Fura-2 fluorescence from isolated mouse hearts using a commercially available switching light source and CCD camera. After calibration, it provides a good estimate of intracellular [Ca2+] with both high spatial and temporal resolutions, permitting study of changes in dispersion of diastolic [Ca2+], Ca2+ transient dynamics, and conduction velocities in mouse hearts. In a proof-of-principle study, we imaged isolated Langendorff-perfused mouse hearts with reversible regional myocardial infarctions. Methods Isolated mouse hearts were perfused in the Landendorff-mode and loaded with Fura-2. Hearts were then paced rapidly and subjected to 15 minutes of regional ischemia by ligation of the left anterior descending coronary artery, following which the ligation was removed to allow reperfusion for 15 minutes. Fura-2 fluorescence was recorded at regular intervals using a high-speed CCD camera. The two wavelengths of excitation light were interleaved at a rate of 1 KHz with a computer controlled switching light source to illuminate the heart. Results Fura-2 produced consistent Ca2+ transients from different hearts. Ligating the coronary artery rapidly generated a well defined region with a dramatic rise in diastolic Ca2+ without a significant change in transient amplitude; Ca2+ handling normalized during reperfusion. Conduction velocity was reduced by around 50% during ischemia, and did not recover significantly when monitored for 15 minutes following reperfusion. Conclusions Our method of imaging Fura-2 from isolated whole hearts is capable of detecting pathological changes in intracellular Ca2+ levels in cardiac tissue. The persistent change in the conduction velocities indicates that changes to tissue connectivity rather than altered intracellular Ca2+ handling may be underlying the electrical instabilities commonly seen in patients following a myocardial infarction.
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Osakai T, Yoshimura T, Kaneko D, Nagatani H, Son SH, Yamagishi Y, Yamada K. Potential-modulated fluorescence spectroscopy of zwitterionic and dicationic membrane-potential-sensitive dyes at the 1,2-dichloroethane/water interface. Anal Bioanal Chem 2012; 404:785-92. [PMID: 22744747 DOI: 10.1007/s00216-012-6199-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/10/2012] [Accepted: 06/13/2012] [Indexed: 11/25/2022]
Abstract
The previously introduced technique of potential-modulated fluorescence (PMF) spectroscopy was used to study the potential-induced fluorescence change of some different dyes at the polarized 1,2-dichloroethane (DCE)/water (W) interface. A zwitterionic dye (POLARIC 488PPS) showed a PMF response similar to that for the previously studied dye (di-4-ANEPPS) with the same ionic state, and the PMF response was likewise explained by the potential-dependent reorientation of the dye at the DCE/W interface. Though a monocationic dye (POLARIC 488PM) showed no distinct PMF signal, a dicationic dye (di-2-ANEPEQ) showed two relatively weak but detectable PMF signals at lower and higher potential. It has thus been found that the ionic state of a potential-sensitive dye strongly influences the potential-induced reorientation of the dye at the interface and consequently its PMF response. These results support the reorientation/solvatochromic mechanism proposed for "slow" dyes but do not necessarily exclude the electrochromic mechanism proposed for "fast" dyes. PMF spectroscopy would provide useful information on the design of slow dyes for the measurement of the resting potential of cell membranes.
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Affiliation(s)
- Toshiyuki Osakai
- Department of Chemistry, Graduate School of Science, Kobe University, Kobe, Japan.
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Lin Y, Wu TY, Gmitro AF. Error analysis of ratiometric imaging of extracellular pH in a window chamber model. JOURNAL OF BIOMEDICAL OPTICS 2012; 17:046004. [PMID: 22559682 PMCID: PMC4572359 DOI: 10.1117/1.jbo.17.4.046004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Revised: 01/30/2012] [Accepted: 02/01/2012] [Indexed: 05/31/2023]
Abstract
Ratiometric fluorescence-imaging technique is commonly used to measure extracellular pH in tumors and surrounding tissue within a dorsal skin-fold window chamber. Using a pH-sensitive fluorophore such as carboxy SNARF-1 one can measure pH distributions with high precision. However, it is often observed that the measured pH is lower than expected, with a bias that varies from one image to another. A comprehensive analysis of possible error sources is presented. These error sources include photon noise, estimator bias, instrument errors, temperature, and calibration errors from biological factors.
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Affiliation(s)
- Yuxiang Lin
- University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tuscon, Arizona 85721
| | - Tzu-Yu Wu
- University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tuscon, Arizona 85721
| | - Arthur F. Gmitro
- University of Arizona, College of Optical Sciences, 1630 East University Boulevard, Tuscon, Arizona 85721
- University of Arizona, College of Medicine, Department of Radiology, P.O. Box 245067, Tucson, Arizona 85724
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Abstract
There are three kinds of membrane potentials: the surface potentials, resulting from the accumulation of charges at the membrane surfaces; the transmembrane potential, determined by imbalance of charge in the aqueous solutions; and the dipole potential, a membrane-internal potential from the dipolar components of the phospholipids and interface water. The absolute value of the dipole potential has been very difficult to measure, although its value has been estimated to be in the range of 200-1,000 mV from ion translocation rates (determined by the planar lipid bilayer method), the surface potential of lipid monolayers (determined by the lipid monolayer method), molecular-dynamics calculations, and electron scattering using cryoelectron microscopy (cryo-EM). Spectroscopy methods have also been used to monitor the dipole potential changes on the basis of the observed fluorescence changes of voltage-sensitive probes. The dipole potential accounts for the much larger permeability of a bare phospholipid membrane to anions than cations and affects the conformation and function of membrane proteins.
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Affiliation(s)
- Liguo Wang
- Department of Biological Structure, University of Washington, Seattle, Washington 98195, USA.
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Baumgärtel T, v Borczyskowski C, Graaf H. Detection and stability of nanoscale space charges in local oxidation nanolithography. NANOTECHNOLOGY 2012; 23:095707. [PMID: 22327541 DOI: 10.1088/0957-4484/23/9/095707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
We report on the stability of space charges within nanoscale silicon oxide patterns generated by atomic force microscope tip-induced local anodic oxidation of alkyl-terminated silicon. Surface potentials of these structures are investigated using two different approaches: Kelvin probe force microscopy and the spectroscopy of adsorbed charge-sensitive dye molecules. Both techniques prove that there is no decay of the space charge itself at least for several days. The apparent decrease of the surface potential measured with the Kelvin probe method is known to be influenced by the ambient humidity. It is supposed to be caused by a screening effect through the formation of a water layer. This is confirmed by our investigation of the surface potential decrease kinetics, which could be well fitted with an adapted model of water condensation. The fluorescence of the charge-sensitive dye di-4-ANEPPS, which is applied to the structures, shows a spectral shift of about 270 meV compared to an uncharged silicon oxide surface. The high stability of the charges supports the use of local anodic oxidation patterns as templates for selective immobilization of cationic species.
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Affiliation(s)
- T Baumgärtel
- Center for Nanostructured Materials and Analytics, Institute of Physics, Chemnitz University of Technology, Chemnitz, Germany.
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43
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Optically monitoring voltage in neurons by photo-induced electron transfer through molecular wires. Proc Natl Acad Sci U S A 2012; 109:2114-9. [PMID: 22308458 DOI: 10.1073/pnas.1120694109] [Citation(s) in RCA: 218] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fluorescence imaging is an attractive method for monitoring neuronal activity. A key challenge for optically monitoring voltage is development of sensors that can give large and fast responses to changes in transmembrane potential. We now present fluorescent sensors that detect voltage changes in neurons by modulation of photo-induced electron transfer (PeT) from an electron donor through a synthetic molecular wire to a fluorophore. These dyes give bigger responses to voltage than electrochromic dyes, yet have much faster kinetics and much less added capacitance than existing sensors based on hydrophobic anions or voltage-sensitive ion channels. These features enable single-trial detection of synaptic and action potentials in cultured hippocampal neurons and intact leech ganglia. Voltage-dependent PeT should be amenable to much further optimization, but the existing probes are already valuable indicators of neuronal activity.
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Klymchenko AS, Duportail G, Mély Y. 3-Hydroxychromone Probes Precisely Located and Oriented in Lipid Bilayers: A Toolkit for Biomembrane Research. SPRINGER SERIES ON FLUORESCENCE 2012. [DOI: 10.1007/4243_2012_44] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Paula DMB, Valero-Lapchik VB, Paredes-Gamero EJ, Han SW. Therapeutic ultrasound promotes plasmid DNA uptake by clathrin-mediated endocytosis. J Gene Med 2011; 13:392-401. [PMID: 21721075 DOI: 10.1002/jgm.1586] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND Ultrasound (US) has been widely used to improve the efficiency of nonviral vector transfection. The mechanism of plasmid uptake is usually attributed to sonoporation, although there is not clear evidence for this attribution. Based on our previous results, we hypothesized that other mechanisms, such as endocytosis, could be involved in this process. METHODS NIH3T3 cells were transfected with plasmid vector pEGFP-N3 (4.7 kb) using a therapeutic US without microbubbles. Bioeffects such as calcium influx, reactive oxygen species (ROS) generation and membrane potential alterations were accessed with fluorescent dyes in real-time by confocal microscopy after US insonation. Localization of labeled plasmid DNA in cells was also monitored with endocytosis markers using an immunofluorescence assay. RESULTS US at 2 W/cm(2) with a duty-cycle of 20% for 30 s resulted in approximately 40% transfection efficiency but, at 1 W/cm(2) , resulted in a very low level of transfection. Both the production of ROS and calcium influx were augmented during the insonation, although they were stopped soon after turning off US, with the exception of calcium influx with 1 W/cm(2) . US also changed the cell membrane potential to the hyperpolarization state, which returned to the normal state soon after insonation. Labeled plasmids DNA could be co-localized with clathrin-mediated endocytosis marker but not with caveolin-1. CONCLUSIONS The present data indicate that plasmid DNA uptake promoted by US should occur via clathrin-mediated endocytosis.
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Bourgeois EB, Bachtel AD, Huang J, Walcott GP, Rogers JM. Simultaneous optical mapping of transmembrane potential and wall motion in isolated, perfused whole hearts. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:096020. [PMID: 21950934 PMCID: PMC3194792 DOI: 10.1117/1.3630115] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Optical mapping of cardiac propagation has traditionally been hampered by motion artifact, chiefly due to changes in photodetector-to-tissue registration as the heart moves. We have developed an optical mapping technique to simultaneously record electrical waves and mechanical contraction in isolated hearts. This allows removal of motion artifact from transmembrane potential (V(m)) recordings without the use of electromechanical uncoupling agents and allows the interplay of electrical and mechanical events to be studied at the whole organ level. Hearts are stained with the voltage-sensitive dye di-4-ANEPPS and ring-shaped markers are attached to the epicardium. Fluorescence, elicited on alternate frames by 450 and 505 nm light-emitting diodes, is recorded at 700 frames∕ per second by a camera fitted with a 605 ± 25 nm emission filter. Marker positions are tracked in software. A signal, consisting of the temporally interlaced 450 and 505 nm fluorescence, is collected from the pixels enclosed by each moving ring. After deinterlacing, the 505 nm signal consists of V(m) with motion artifact, while the 450 nm signal is minimally voltage-sensitive and contains primarily artifacts. The ratio of the two signals estimates V(m). Deformation of the tissue enclosed by each set of 3 rings is quantified using homogeneous finite strain.
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Affiliation(s)
- Elliot B Bourgeois
- University of Alabama at Birmingham, Department of Biomedical Engineering, Birmingham, Alabama 35294, USA
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Bachtel AD, Gray RA, Stohlman JM, Bourgeois EB, Pollard AE, Rogers JM. A novel approach to dual excitation ratiometric optical mapping of cardiac action potentials with di-4-ANEPPS using pulsed LED excitation. IEEE Trans Biomed Eng 2011; 58:2120-6. [PMID: 21536528 DOI: 10.1109/tbme.2011.2148719] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We developed a new method for ratiometric optical mapping of transmembrane potential (V(m)) in cardiac preparations stained with di-4-ANEPPS. V(m)-dependent shifts of excitation and emission spectra establish two excitation bands (<481 and >481 nm) that produce fluorescence changes of opposite polarity within a single emission band (575-620 nm). The ratio of these positive and negative fluorescence signals (excitation ratiometry) increases V(m) sensitivity and removes artifacts common to both signals. We pulsed blue (450 ± 10 nm) and cyan (505 ± 15 nm) light emitting diodes (LEDs) at 375 Hz in alternating phase synchronized to a camera (750 frames-per-second). Fluorescence was bandpass filtered (585 ± 20 nm). This produced signals with upright (blue) and inverted (cyan) action potentials (APs) interleaved in sequential frames. In four whole swine hearts with motion chemically arrested, fractional fluorescence for blue, cyan, and ratio signals was 1.2 ± 0.3%, 1.2 ± 0.3%, and 2.4 ± 0.6%, respectively. Signal-to-noise ratios were 4.3 ± 1.4, 4.0 ± 1.2, and 5.8 ± 1.9, respectively. After washing out the electromechanical uncoupling agent, we characterized motion artifact by cross-correlating blue, cyan, and ratio signals with a signal with normal AP morphology. Ratiometry improved cross-correlation coefficients from 0.50 ± 0.48 to 0.81 ± 0.25, but did not cancel all motion artifacts. These findings demonstrate the feasibility of pulsed LED excitation ratiometry in myocardium.
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Robinson D, Besley NA, O’Shea P, Hirst JD. Di-8-ANEPPS Emission Spectra in Phospholipid/Cholesterol Membranes: A Theoretical Study. J Phys Chem B 2011; 115:4160-7. [DOI: 10.1021/jp1111372] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- David Robinson
- School of Chemistry and ‡School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| | - Nicholas A. Besley
- School of Chemistry and ‡School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| | - Paul O’Shea
- School of Chemistry and ‡School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
| | - Jonathan D. Hirst
- School of Chemistry and ‡School of Biology, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom
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Ella SR, Yang Y, Clifford PS, Gulia J, Dora KA, Meininger GA, Davis MJ, Hill MA. Development of an image-based system for measurement of membrane potential, intracellular Ca(2+) and contraction in arteriolar smooth muscle cells. Microcirculation 2011; 17:629-40. [PMID: 21044217 DOI: 10.1111/j.1549-8719.2010.00059.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Changes in smooth muscle cell (SMC) membrane potential (Em) are critical to vasomotor responses. As a fluorescent indicator approach would lessen limitations of glass electrodes in contracting preparations, we aimed to develop a Forster (or fluorescence) resonance energy transfer (FRET)-based measurement for Em. METHODS The FRET pair used in this study (donor CC2-DMPE [excitation 405 nm] and acceptor DisBAC(4) (3)) provide rapid measurements at a sensitivity not achievable with many ratiometric indicators. The method also combined measurement of changes in Ca(2+) (i) using fluo-4 and excitation at 490 nm. RESULTS After establishing loading conditions, a linear relationship was demonstrated between Em and fluorescence signal in FRET dye-loaded HEK cells held under voltage clamp. Over the voltage range from -70 to +30 mV, slope (of FRET signal vs. voltage, m) = 0.49 ± 0.07, r(2) = 0.96 ± 0.025. Similar data were obtained in cerebral artery SMCs, slope (m) = 0.30 ± 0.02, r(2) = 0.98 ± 0.02. Change in FRET emission ratio over the holding potential of -70 to +30 mV was 41.7 ± 4.9% for HEK cells and 30.0 ± 2.3% for arterial SMCs. The FRET signal was also shown to be modulated by KCl-induced depolarization in a concentration-dependent manner. Further, in isolated arterial SMCs, KCl-induced depolarization (60 mM) measurements occurred with increased fluo-4 fluorescence emission (62 ± 9%) and contraction (-27 ± 4.2%). CONCLUSIONS The data support the FRET-based approach for measuring changes in Em in arterial SMCs. Further, image-based measurements of Em can be combined with analysis of temporal changes in Ca(2+) (i) and contraction.
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Affiliation(s)
- Srikanth R Ella
- Dalton Cardiovascular Research Center, University of Missouri, Columbia, Missouri, USA
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Huang L, Tam-Chang SW. 9-Piperazine substituted perylene-3,4-dicarboximide as a fluorescent probe in ratiometric analysis. Chem Commun (Camb) 2011; 47:2291-3. [DOI: 10.1039/c0cc04262e] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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