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Winkler PM, García-Parajo MF. Correlative nanophotonic approaches to enlighten the nanoscale dynamics of living cell membranes. Biochem Soc Trans 2021; 49:2357-2369. [PMID: 34495333 PMCID: PMC8589428 DOI: 10.1042/bst20210457] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 08/03/2021] [Accepted: 08/10/2021] [Indexed: 01/31/2023]
Abstract
Dynamic compartmentalization is a prevailing principle regulating the spatiotemporal organization of the living cell membrane from the nano- up to the mesoscale. This non-arbitrary organization is intricately linked to cell function. On living cell membranes, dynamic domains or 'membrane rafts' enriched with cholesterol, sphingolipids and other certain proteins exist at the nanoscale serving as signaling and sorting platforms. Moreover, it has been postulated that other local organizers of the cell membrane such as intrinsic protein interactions, the extracellular matrix and/or the actin cytoskeleton synergize with rafts to provide spatiotemporal hierarchy to the membrane. Elucidating the intricate coupling of multiple spatial and temporal scales requires the application of correlative techniques, with a particular need for simultaneous nanometer spatial precision and microsecond temporal resolution. Here, we review novel fluorescence-based techniques that readily allow to decode nanoscale membrane dynamics with unprecedented spatiotemporal resolution and single-molecule sensitivity. We particularly focus on correlative approaches from the field of nanophotonics. Notably, we introduce a versatile planar nanoantenna platform combined with fluorescence correlation spectroscopy to study spatiotemporal heterogeneities on living cell membranes at the nano- up to the mesoscale. Finally, we outline remaining future technological challenges and comment on potential directions to advance our understanding of cell membrane dynamics under the influence of the actin cytoskeleton and extracellular matrix in uttermost detail.
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Affiliation(s)
- Pamina M. Winkler
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain
| | - María F. García-Parajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, 08860 Barcelona, Spain
- ICREA, Pg. Lluis Companys 23, 08010 Barcelona, Spain
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2
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Kotnala A, Ding H, Zheng Y. Enhancing Single-Molecule Fluorescence Spectroscopy with Simple and Robust Hybrid Nanoapertures. ACS PHOTONICS 2021; 8:1673-1682. [PMID: 35445142 PMCID: PMC9017716 DOI: 10.1021/acsphotonics.1c00045] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Plasmonic nanoapertures have found exciting applications in optical sensing, spectroscopy, imaging, and nanomanipulation. The subdiffraction optical field localization, reduced detection volume (~attoliters), and background-free operation make them particularly attractive for single-particle and single-molecule studies. However, in contrast to the high field enhancements by traditional "nanoantenna"-based structures, small field enhancement in conventional nanoapertures results in weak light-matter interactions and thus small enhancement of spectroscopic signals (such as fluorescence and Raman signals) of the analytes interacting with the nanoapertures. In this work, we propose a hybrid nanoaperture design termed "gold-nanoislands-embedded nanoaperture" (AuNIs-e-NA), which provides multiple electromagnetic "hotspots" within the nanoaperture to achieve field enhancements of up to 4000. The AuNIs-e-NA was able to improve the fluorescence signals by more than 2 orders of magnitude with respect to a conventional nanoaperture. With simple design and easy fabrication, along with strong signal enhancements and operability over variable light wavelengths and polarizations, the AuNIs-e-NA will serve as a robust platform for surface-enhanced optical sensing, imaging, and spectroscopy.
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Affiliation(s)
- Abhay Kotnala
- Walker Department of Mechanical Engineering and Texas Material Institute, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Hongru Ding
- Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Yuebing Zheng
- Walker Department of Mechanical Engineering and Texas Material Institute, The University of Texas at Austin, Austin, Texas 78712, United States
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3
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Zimbone M, Contino A, Maccarrone G, Musumeci P, Lo Faro MJ, Calcagno L. Stability and morphology of Ag nanoplatelets probed by depolarized dynamic light scattering. NANOTECHNOLOGY 2018; 29:265701. [PMID: 29557787 DOI: 10.1088/1361-6528/aab82b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The stability of silver nanoplatelet (NP) suspensions prepared with different concentrations of trisodium citrate (TSC) was studied by depolarized dynamic light scattering (DDLS) and UV-vis spectrometry. The morphology of the nanoparticles, as well as the color and stability of the sols, are tuned by the concentration of the capping agent. The nanoparticles prepared with high TSC concentration (>10-4 M) are blue triangular NPs showing a slight truncation of the tips with aging. When low TSC concentrations are used, the color of the sols changes from blue to yellow with aging time and a strong modification of the morphology occurs: the nanoparticle shape changes from triangular to spherical. Remarkably, they show a high degree of anisotropy. The aging process was followed by the UV-vis spectra and by measuring the rotational diffusion coefficient by DDLS, providing information on the nanoparticle size and shape evolution. The high intensity of depolarized signal and the high value of rotational diffusion coefficient suggest that the aging process increases the thickness and the roughness of the nanoparticles.
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Affiliation(s)
- M Zimbone
- CNR-IMM, via S. Sofia 64, I-95123 Catania, Italy
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Nandi S, Parui S, Halder R, Jana B, Bhattacharyya K. Interaction of proteins with ionic liquid, alcohol and DMSO and in situ generation of gold nano-clusters in a cell. Biophys Rev 2018; 10:757-768. [PMID: 29147940 PMCID: PMC5988615 DOI: 10.1007/s12551-017-0331-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2017] [Accepted: 10/23/2017] [Indexed: 12/27/2022] Open
Abstract
In this review, we give a brief overview on how the interaction of proteins with ionic liquids, alcohols and dimethyl sulfoxide (DMSO) influences the stability, conformational dynamics and function of proteins/enzymes. We present experimental results obtained from fluorescence correlation spectroscopy on the effect of ionic liquid or alcohol or DMSO on the size (more precisely, the diffusion constant) and conformational dynamics of lysozyme, cytochrome c and human serum albumin in aqueous solution. The interaction of ionic liquid with biomolecules (e.g. protein, DNA etc.) has emerged as a current frontier. We demonstrate that ionic liquids are excellent stabilizers of protein and DNA and, in some cases, cause refolding of a protein already denatured by chemical denaturing agents. We show that in ethanol-water binary mixture, proteins undergo non-monotonic changes in size and dynamics with increasing ethanol content. We also discuss the effect of water-DMSO mixture on the stability of proteins. We demonstrate how large-scale molecular dynamics simulations have revealed the molecular origin of this observed phenomenon and provide a microscopic picture of the immediate environment of the biomolecules. Finally, we describe how favorable interactions of ionic liquids may be utilized for in situ generation of fluorescent gold nano-clusters for imaging a live cell.
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Affiliation(s)
- Somen Nandi
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Sridip Parui
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Ritaban Halder
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Biman Jana
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India.
| | - Kankan Bhattacharyya
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India.
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal, Madhya Pradesh, 462 066, India.
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5
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Huang TH, Chi XC, Xu TN, Zhang JR, Xu HY, Zhu ZY, Yu RB, Wang YH, Zhang HZ. Effect of Ag nanoparticles on the photoluminescence of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene]. J Photochem Photobiol A Chem 2018. [DOI: 10.1016/j.jphotochem.2018.01.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Winkler PM, Regmi R, Flauraud V, Brugger J, Rigneault H, Wenger J, García-Parajo MF. Optical Antenna-Based Fluorescence Correlation Spectroscopy to Probe the Nanoscale Dynamics of Biological Membranes. J Phys Chem Lett 2018; 9:110-119. [PMID: 29240442 DOI: 10.1021/acs.jpclett.7b02818] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The plasma membrane of living cells is compartmentalized at multiple spatial scales ranging from the nano- to the mesoscale. This nonrandom organization is crucial for a large number of cellular functions. At the nanoscale, cell membranes organize into dynamic nanoassemblies enriched by cholesterol, sphingolipids, and certain types of proteins. Investigating these nanoassemblies known as lipid rafts is of paramount interest in fundamental cell biology. However, this goal requires simultaneous nanometer spatial precision and microsecond temporal resolution, which is beyond the reach of common microscopes. Optical antennas based on metallic nanostructures efficiently enhance and confine light into nanometer dimensions, breaching the diffraction limit of light. In this Perspective, we discuss recent progress combining optical antennas with fluorescence correlation spectroscopy (FCS) to monitor microsecond dynamics at nanoscale spatial dimensions. These new developments offer numerous opportunities to investigate lipid and protein dynamics in both mimetic and native biological membranes.
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Affiliation(s)
- Pamina M Winkler
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Barcelona, Spain
| | - Raju Regmi
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Barcelona, Spain
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel , Marseille, France
| | - Valentin Flauraud
- Microsystems Laboratory, Institute of Microengineering, Ecole Polytechnique Fédérale de Lausanne , 1015 Lausanne, Switzerland
| | - Jürgen Brugger
- Microsystems Laboratory, Institute of Microengineering, Ecole Polytechnique Fédérale de Lausanne , 1015 Lausanne, Switzerland
| | - Hervé Rigneault
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel , Marseille, France
| | - Jérôme Wenger
- Aix Marseille Univ, CNRS, Centrale Marseille, Institut Fresnel , Marseille, France
| | - María F García-Parajo
- ICFO-Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology , 08860 Barcelona, Spain
- ICREA , Pg. Lluís Companys 23, 08010 Barcelona, Spain
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7
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Li J, Dong C, Ren J. Strategies to reduce detection volume of fluorescence correlation spectroscopy (FCS) to realize physiological concentration measurements. Trends Analyt Chem 2017. [DOI: 10.1016/j.trac.2017.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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8
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Chattoraj S, Amin MA, Mohapatra S, Ghosh S, Bhattacharyya K. Cancer Cell Imaging Using in Situ Generated Gold Nanoclusters. Chemphyschem 2015; 17:61-8. [PMID: 26437799 DOI: 10.1002/cphc.201500731] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Indexed: 12/26/2022]
Abstract
In situ generated fluorescent gold nanoclusters (Au-NCs) are used for bio-imaging of three human cancer cells, namely, lung (A549), breast (MCF7), and colon (HCT116), by confocal microscopy. The amount of Au-NCs in non-cancer cells (WI38 and MCF10A) is 20-40 times less than those in the corresponding cancer cells. The presence of a larger amount of glutathione (GSH) capped Au-NCs in the cancer cell is ascribed to a higher glutathione level in cancer cells. The Au-NCs exhibit fluorescence maxima at 490-530 nm inside the cancer cells. The fluorescence maxima and matrix-assisted laser desorption ionization (MALDI) mass spectrometry suggest that the fluorescent Au-NCs consist of GSH capped clusters with a core structure (Au8-13). Time-resolved confocal microscopy indicates a nanosecond (1-3 ns) lifetime of the Au-NCs inside the cells. This rules out the formation of aggregated Au-thiolate complexes, which typically exhibit microsecond (≈1000 ns) lifetimes. Fluorescence correlation spectroscopy (FCS) in live cells indicates that the size of the Au-NCs is ≈1-2 nm. For in situ generation, we used a conjugate consisting of a room-temperature ionic liquid (RTIL, [pmim][Br]) and HAuCl4. Cytotoxicity studies indicate that the conjugate, [pmim][AuCl4], is non-toxic for both cancer and non-cancer cells.
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Affiliation(s)
- Shyamtanu Chattoraj
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Md Asif Amin
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
| | - Saswat Mohapatra
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, 700 032, India
| | - Surajit Ghosh
- Organic & Medicinal Chemistry Division, CSIR-Indian Institute of Chemical Biology, Jadavpur, Kolkata, 700 032, India.
| | - Kankan Bhattacharyya
- Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India.
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Yin J, Zhang A, Dong C, Ren J. An aptamer-based single particle method for sensitive detection of thrombin using fluorescent quantum dots as labeling probes. Talanta 2015; 144:13-9. [PMID: 26452786 DOI: 10.1016/j.talanta.2015.05.034] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2015] [Revised: 05/10/2015] [Accepted: 05/12/2015] [Indexed: 01/28/2023]
Abstract
In this study, an aptamer-based single particle method was developed for the thrombin detection in human serum samples using fluorescence correlation spectroscopy (FCS). In this method, quantum dots (QDs) were used as the fluorescent probes and thrombin-binding aptamer (TBA) was used as molecular recognition unit. When two QDs probes labeled with TBA (QD-TBA1 and QD-TBA2) are mixed in a sample containing thrombin targets, the binding of targets will cause QDs to form dimers (or oligomers) with bigger sizes, which leads to the nearly double increase in the characteristic diffusion time of QDs in the detection volume of FCS. FCS method can detect the change in the characteristic diffusion time of QDs. Firstly, the diffusion and blinking behaviors of QD-TBA probes in the presence of thrombin were investigated by FCS and total internal reflection fluorescence microscopy (TIRFM) imaging system, and the experimental results documented that QD-TBAs were bound together with "one-by-one" structure when thrombin were added into the solution. And then, the assay conditions were optimized in order to improve the sensitivity and specificity of this method. Under the optimized conditions, the linear range of the method is from 5.0 nM to 500 nM of thrombin, and the limit of detection is about 2.6 nM. Finally, this method was applied to homogeneous determination of thrombin in human serum samples.
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Affiliation(s)
- Jinjin Yin
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
| | - Aidi Zhang
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
| | - Chaoqing Dong
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China
| | - Jicun Ren
- School of Chemistry and Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, PR China.
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10
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Dong C, Liu H, Ren J. Assessing the blinking state of fluorescent quantum dots in free solution by combining fluorescence correlation spectroscopy with ensemble spectroscopic methods. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:12969-12976. [PMID: 25290853 DOI: 10.1021/la503055v] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The current method for investigating the blinking behavior is to immobilize quantum dots (QDs) in the matrix and then apply a fluorescent technique to monitor the fluorescent trajectories of individual QDs. So far, no method can be used to directly assess the blinking state of ensemble QDs in free solution. In this study, a new method was described to characterize the blinking state of the QDs in free solution by combining single molecule fluorescence correlation spectroscopy (FCS) with ensemble spectroscopic methods. Its principle is based on the observation that the apparent concentration of bright QDs obtained by FCS is less than its actual concentration measured by ensemble spectroscopic method due to the QDs blinking. We proposed a blinking index (Kblink) for characterizing the blinking state of QDs, and Kblink is defined as the ratio of the actual concentration (Cb,actual) measured by the ensemble spectroscopic method to the apparent concentration (Cb,app) of QDs obtained by FCS. The effects of certain factors such as laser intensity, growth process, and ligands on blinking of QDs were investigated. The Kblink data of QDs obtained were successfully used to characterize the blinking state of QDs and explain certain experimental results.
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Affiliation(s)
- Chaoqing Dong
- School of Chemistry & Chemical Engineering, State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University , 800 Dongchuan Road, Shanghai 200240, P. R. China
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11
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Laurence TA, Ly S, Bourguet F, Fischer NO, Coleman MA. Fluorescence correlation spectroscopy at micromolar concentrations without optical nanoconfinement. J Phys Chem B 2014; 118:9662-7. [PMID: 25060197 DOI: 10.1021/jp505881z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fluorescence correlation spectroscopy (FCS) is an important technique for studying biochemical interactions dynamically that may be used in vitro and in cell-based studies. It is generally claimed that FCS may only be used at nM concentrations. We show that this general consensus is incorrect and that the limitation to nM concentrations is not fundamental but due to detector limits as well as laser fluctuations. With a high count rate detector system and applying laser fluctuation corrections, we demonstrate FCS measurements up to 38 μM with the same signal-to-noise as at lower concentrations. Optical nanoconfinement approaches previously used to increase the concentration range of FCS are not necessary, and further increases above 38 μM may be expected using detectors and detector arrays with higher saturation rates and better laser fluctuation corrections. This approach greatly widens the possibilities of dynamic measurements of biochemical interactions using FCS at physiological concentrations.
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Affiliation(s)
- Ted A Laurence
- Lawrence Livermore National Laboratory , Livermore, California 94550, United States
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12
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Langguth L, Femius Koenderink A. Simple model for plasmon enhanced fluorescence correlation spectroscopy. OPTICS EXPRESS 2014; 22:15397-409. [PMID: 24977800 DOI: 10.1364/oe.22.015397] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Metallic nano-antennas provide strong field confinement and intensity enhancement in hotspots and thus can ultimately enhance fluorescence detection and provide ultra small detection volumes. In solution-based fluorescence measurements, the diffraction limited focus driving the nano-antenna can outshine the fluorescence originating from the hotspot and thus render the benefits of the hotspot negligible. We introduce a model to calculate the effect of a nano-antenna, or any other object creating a nontrivial intensity distribution, for fluorescence fluctuation measurements. Approximating the local field enhancement of the nano-antenna by a 3D Gaussian profile, we show which hotspot sizes and intensities are the most beneficial for an FCS measurement and compare it to realistic antenna parameters from literature.
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Punj D, Ghenuche P, Moparthi SB, de Torres J, Grigoriev V, Rigneault H, Wenger J. Plasmonic antennas and zero-mode waveguides to enhance single molecule fluorescence detection and fluorescence correlation spectroscopy toward physiological concentrations. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2014; 6:268-82. [DOI: 10.1002/wnan.1261] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Deep Punj
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Petru Ghenuche
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Satish Babu Moparthi
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Juan de Torres
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Victor Grigoriev
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Hervé Rigneault
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
| | - Jérôme Wenger
- CNRS, Aix Marseille Université, Centrale Marseille, Institut Fresnel; UMR 7249; 13013 Marseille France
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Abstract
The structural flexibility found in human immunodeficiency virus (HIV) envelope glycoproteins creates a complex relationship between antigenicity and sensitivity to antiviral antibodies. The study of this issue in the context of viral particles is particularly problematic as conventional virus capture approaches can perturb antigenicity profiles. Here, we employed a unique analytical system based on fluorescence correlation spectroscopy (FCS), which measures antibody-virion binding with all reactants continuously in solution. Panels of nine anti-envelope monoclonal antibodies (MAbs) and five virus types were used to connect antibody binding profiles with neutralizing activities. Anti-gp120 MAbs against the 2G12 or b12 epitope, which marks functional envelope structures, neutralized viruses expressing CCR5-tropic envelopes and exhibited efficient virion binding in solution. MAbs against CD4-induced (CD4i) epitopes considered hidden on functional envelope structures poorly bound these viruses and were not neutralizing. Anti-gp41 MAb 2F5 was neutralizing despite limited virion binding. Similar antigenicity patterns occurred on CXCR4-tropic viruses, except that anti-CD4i MAbs 17b and 19e were neutralizing despite little or no virion binding. Notably, anti-gp120 MAb PG9 and anti-gp41 MAb F240 bound to both CCR5-tropic and CXCR4-tropic viruses without exerting neutralizing activity. Differences in the virus production system altered the binding efficiencies of some antibodies but did not enhance antigenicity of aberrant gp120 structures. Of all viruses tested, only JRFL pseudoviruses showed a direct relationship between MAb binding efficiency and neutralizing potency. Collectively, these data indicate that the antigenic profiles of free HIV particles generally favor the exposure of functional over aberrant gp120 structures. However, the efficiency of virion-antibody interactions in solution inconsistently predicts neutralizing activity in vitro.
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15
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Punj D, de Torres J, Rigneault H, Wenger J. Gold nanoparticles for enhanced single molecule fluorescence analysis at micromolar concentration. OPTICS EXPRESS 2013; 21:27338-27343. [PMID: 24216956 DOI: 10.1364/oe.21.027338] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Individual metal nanoparticles represent an inexpensive and versatile platform to enhance the detection of fluorescent species at biologically relevant concentrations. Here we use fluorescence correlation spectroscopy to quantify the near-field detection volume and average fluorescence enhancement factors set by a single gold nanoparticle. We demonstrate detection volumes down to 270 zeptoliters (three orders of magnitude beyond the diffraction barrier) together with 60-fold enhancement of the fluorescence brightness per molecule.
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16
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Punj D, Mivelle M, Moparthi SB, van Zanten TS, Rigneault H, van Hulst NF, García-Parajó MF, Wenger J. A plasmonic 'antenna-in-box' platform for enhanced single-molecule analysis at micromolar concentrations. NATURE NANOTECHNOLOGY 2013; 8:512-6. [PMID: 23748196 DOI: 10.1038/nnano.2013.98] [Citation(s) in RCA: 192] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2012] [Accepted: 04/26/2013] [Indexed: 05/22/2023]
Abstract
Single-molecule fluorescence techniques are key for a number of applications, including DNA sequencing, molecular and cell biology and early diagnosis. Unfortunately, observation of single molecules by diffraction-limited optics is restricted to detection volumes in the femtolitre range and requires pico- or nanomolar concentrations, far below the micromolar range where most biological reactions occur. This limitation can be overcome using plasmonic nanostructures, which enable the confinement of light down to nanoscale volumes. Although these nanoantennas enhance fluorescence brightness, large background signals and/or unspecific binding to the metallic surface have hampered the detection of individual fluorescent molecules in solution at high concentrations. Here we introduce a novel 'antenna-in-box' platform that is based on a gap-antenna inside a nanoaperture. This design combines fluorescent signal enhancement and background screening, offering high single-molecule sensitivity (fluorescence enhancement up to 1,100-fold and microsecond transit times) at micromolar sample concentrations and zeptolitre-range detection volumes. The antenna-in-box device can be optimized for single-molecule fluorescence studies at physiologically relevant concentrations, as we demonstrate using various biomolecules.
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Affiliation(s)
- Deep Punj
- CNRS, Aix-Marseille Université, Ecole Centrale Marseille, Institut Fresnel, Campus de St Jérôme, 13397 Marseille, France
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