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Abstract
In recent years there has been a growing interest in the use of plasmonic nanostructures for color generation, a technology that dates back to ancient times. Plasmonic structural colors have several attractive features but once the structures are prepared the colors are normally fixed. Lately, several concepts have emerged for actively tuning the colors, which opens up for many new potential applications, the most obvious being novel color displays. In this review we summarize recent progress in active control of plasmonic colors and evaluate them with respect to performance criteria for color displays. It is suggested that actively controlled plasmonic colors are generally less interesting for emissive displays but could be useful for new types of electrochromic devices relying on ambient light (electronic paper). Furthermore, there are several other potential applications such as images to be revealed on demand and colorimetric sensors.
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Affiliation(s)
- Kunli Xiong
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
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2
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Aćimović SS, Šípová-Jungová H, Emilsson G, Shao L, Dahlin AB, Käll M, Antosiewicz TJ. Antibody-Antigen Interaction Dynamics Revealed by Analysis of Single-Molecule Equilibrium Fluctuations on Individual Plasmonic Nanoparticle Biosensors. ACS Nano 2018; 12:9958-9965. [PMID: 30165019 DOI: 10.1021/acsnano.8b04016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Antibody-antigen interactions are complex events central to immune response, in vivo and in vitro diagnostics, and development of therapeutic substances. We developed an ultrastable single-molecule localized surface plasmon resonance (LSPR) sensing platform optimized for studying antibody-antigen interaction kinetics over very long time scales. The setup allowed us to perform equilibrium fluctuations analysis of the PEG/anti-PEG interaction. By time and frequency domain analysis, we demonstrate that reversible adsorption of monovalently bound anti-PEG antibodies is the dominant factor affecting the LSPR fluctuations. The results suggest that equilibrium fluctuation analysis can be an alternative to established methods for determination of interaction rates. In particular, the methodology is suited to analyze molecular systems whose properties change during the initial interaction phases, for example, due to mass transport limitations or, as demonstrated here, because the effective association rate constant varies with surface concentration of adsorbed molecules.
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Affiliation(s)
- Srdjan S Aćimović
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Hana Šípová-Jungová
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Lei Shao
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Andreas B Dahlin
- Department of Chemistry and Chemical Engineering , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Mikael Käll
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
| | - Tomasz J Antosiewicz
- Department of Physics , Chalmers University of Technology , 412 96 Göteborg , Sweden
- Faculty of Physics , University of Warsaw , Pasteura 5 , 02-093 Warsaw , Poland
- Center of New Technologies , University of Warsaw , Banacha 2c , 02-097 Warsaw , Poland
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3
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Emilsson G, Sakiyama Y, Malekian B, Xiong K, Adali-Kaya Z, Lim RYH, Dahlin AB. Gating Protein Transport in Solid State Nanopores by Single Molecule Recognition. ACS Cent Sci 2018; 4:1007-1014. [PMID: 30159397 PMCID: PMC6107858 DOI: 10.1021/acscentsci.8b00268] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Indexed: 05/30/2023]
Abstract
Control of molecular translocation through nanoscale apertures is of great interest for DNA sequencing, biomolecular filters, and new platforms for single molecule analysis. However, methods for controlling the permeability of nanopores are very limited. Here, we show how nanopores functionalized with poly(ethylene glycol) brushes, which fully prevent protein translocation, can be reversibly gated to an "open" state by binding of single IgG antibodies that disrupt the macromolecular barrier. On the basis of surface plasmon resonance data we propose a two-state model describing the antibody-polymer interaction kinetics. Reversibly (weakly) bound antibodies decrease the protein exclusion height while irreversibly (strongly) bound antibodies do not. Our results are further supported by fluorescence readout from pore arrays and high-speed atomic force microscopy on single pores. This type of dynamic barrier control on the nanoscale provides new possibilities for biomolecular separation and analysis.
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Affiliation(s)
- Gustav Emilsson
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - Yusuke Sakiyama
- Biozentrum
and the Swiss Nanoscience Institute, University
of Basel, 4056 Basel, Switzerland
| | - Bita Malekian
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - Kunli Xiong
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - Zeynep Adali-Kaya
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
| | - Roderick Y. H. Lim
- Biozentrum
and the Swiss Nanoscience Institute, University
of Basel, 4056 Basel, Switzerland
| | - Andreas B. Dahlin
- Department
of Chemistry and Chemical Engineering, Chalmers
University of Technology, 41296 Göteborg, Sweden
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4
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Ferhan AR, Jackman JA, Malekian B, Xiong K, Emilsson G, Park S, Dahlin AB, Cho NJ. Nanoplasmonic Sensing Architectures for Decoding Membrane Curvature-Dependent Biomacromolecular Interactions. Anal Chem 2018; 90:7458-7466. [DOI: 10.1021/acs.analchem.8b00974] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Abdul Rahim Ferhan
- School of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore
| | - Joshua A. Jackman
- School of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore
| | - Bita Malekian
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Kunli Xiong
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Soohyun Park
- School of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore
| | - Andreas B. Dahlin
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Nam-Joon Cho
- School of Materials Science and Engineering and Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore
- School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore 637459, Singapore
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5
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Emilsson G, Xiong K, Sakiyama Y, Malekian B, Ahlberg Gagnér V, Schoch RL, Lim RYH, Dahlin AB. Polymer brushes in solid-state nanopores form an impenetrable entropic barrier for proteins. Nanoscale 2018; 10:4663-4669. [PMID: 29468241 DOI: 10.1039/c7nr09432a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Polymer brushes are widely used to prevent the adsorption of proteins, but the mechanisms by which they operate have remained heavily debated for many decades. We show conclusive evidence that a polymer brush can be a remarkably strong kinetic barrier towards proteins by using poly(ethylene glycol) grafted to the sidewalls of pores in 30 nm thin gold films. Despite consisting of about 90% water, the free coils seal apertures up to 100 nm entirely with respect to serum protein translocation, as monitored label-free through the plasmonic activity of the nanopores. The conclusions are further supported by atomic force microscopy and fluorescence microscopy. A theoretical model indicates that the brush undergoes a morphology transition to a sealing state when the ratio between the extension and the radius of curvature is approximately 0.8. The brush-sealed pores represent a new type of ultrathin filter with potential applications in bioanalytical systems.
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Affiliation(s)
- Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Göteborg, Sweden.
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6
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7
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Xiong K, Tordera D, Emilsson G, Olsson O, Linderhed U, Jonsson MP, Dahlin AB. Switchable Plasmonic Metasurfaces with High Chromaticity Containing Only Abundant Metals. Nano Lett 2017; 17:7033-7039. [PMID: 29028347 DOI: 10.1021/acs.nanolett.7b03665] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Plasmonic color generation offers several advantages but is also limited by the cost and availability of noble metals like gold. In this work, we present color-tunable metasurfaces with high chromaticity and reflectivity consisting of an aluminum mirror, a dielectric spacer, and a plasmonic nanohole array in copper. Copper is shown to be an excellent alternative to gold when properly protected from oxidation and makes it possible to generate a wide RGB gamut covering 27% of the standard RGB. By patterning the metasurfaces into microscale pixel triplets, color photos can be well reproduced with high resolution over wafer-sized areas. Further, we demonstrate active modulation of the reflected intensity using an electrochromic conductive polymer deposited on top of the nanostructures by screen printing. This technology opens up for ultrathin and flexible reflective displays in full color, that is, plasmonic electronic paper, compatible with large-scale sustainable production.
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Affiliation(s)
- Kunli Xiong
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , 41296 Göteborg, Sweden
| | - Daniel Tordera
- Department of Science and Technology, Laboratory for Organic Electronics, Linköping University , 60174 Norrköping, Sweden
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , 41296 Göteborg, Sweden
| | - Oliver Olsson
- rdot AB (559092-9831), Stena Center 1, 41292 Göteborg, Sweden
| | | | - Magnus P Jonsson
- Department of Science and Technology, Laboratory for Organic Electronics, Linköping University , 60174 Norrköping, Sweden
| | - Andreas B Dahlin
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology , 41296 Göteborg, Sweden
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8
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Aćimović SS, Šípová H, Emilsson G, Dahlin AB, Antosiewicz TJ, Käll M. Superior LSPR substrates based on electromagnetic decoupling for on-a-chip high-throughput label-free biosensing. Light Sci Appl 2017; 6:e17042. [PMID: 30167285 PMCID: PMC6062313 DOI: 10.1038/lsa.2017.42] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 03/02/2017] [Accepted: 03/08/2017] [Indexed: 05/09/2023]
Abstract
Localized surface plasmon resonance (LSPR) biosensing based on supported metal nanoparticles offers unparalleled possibilities for high-end miniaturization, multiplexing and high-throughput label-free molecular interaction analysis in real time when integrated within an opto-fluidic environment. However, such LSPR-sensing devices typically contain extremely large regions of dielectric materials that are open to molecular adsorption, which must be carefully blocked to avoid compromising the device readings. To address this issue, we made the support essentially invisible to the LSPR by carefully removing the dielectric material overlapping with the localized plasmonic fields through optimized wet-etching. The resulting LSPR substrate, which consists of gold nanodisks centered on narrow SiO2 pillars, exhibits markedly reduced vulnerability to nonspecific substrate adsorption, thus allowing, in an ideal case, the implementation of thicker and more efficient passivation layers. We demonstrate that this approach is effective and fully compatible with state-of-the-art multiplexed real-time biosensing technology and thus represents the ideal substrate design for high-throughput label-free biosensing systems with minimal sample consumption.
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Affiliation(s)
- Srdjan S Aćimović
- Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
- E-mail:
| | - Hana Šípová
- Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Andreas B Dahlin
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 412 96 Göteborg, Sweden
| | - Tomasz J Antosiewicz
- Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland
| | - Mikael Käll
- Department of Physics, Chalmers University of Technology, 412 96 Göteborg, Sweden
- E-mail:
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9
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Malekian B, Xiong K, Emilsson G, Andersson J, Fager C, Olsson E, Larsson-Langhammer EM, Dahlin AB. Fabrication and Characterization of Plasmonic Nanopores with Cavities in the Solid Support. Sensors (Basel) 2017. [PMID: 28632153 PMCID: PMC5492491 DOI: 10.3390/s17061444] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Plasmonic nanostructures are widely used for various sensing applications by monitoring changes in refractive index through optical spectroscopy or as substrates for surface enhanced Raman spectroscopy. However, in most practical situations conventional surface plasmon resonance is preferred for biomolecular interaction analysis because of its high resolution in surface coverage and the simple single-material planar interface. Still, plasmonic nanostructures may find unique sensing applications, for instance when the nanoscale geometry itself is of interest. This calls for new methods to prepare nanoscale particles and cavities with controllable dimensions and curvature. In this work, we present two types of plasmonic nanopores where the solid support underneath a nanohole array has been etched, thereby creating cavities denoted as ‘nanowells’ or ‘nanocaves’ depending on the degree of anisotropy (dry or wet etch). The refractometric sensitivity is shown to be enhanced upon removing the solid support because of an increased probing volume and a shift of the asymmetric plasmonic field towards the liquid side of the finite gold film. Furthermore, the structures exhibit different spectral changes upon binding inside the cavities compared to the gold surface, which means that the structures can be used for location-specific detection. Other sensing applications are also suggested.
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Affiliation(s)
- Bita Malekian
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Kunli Xiong
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Jenny Andersson
- Insplorion AB, Sahlgrenska Science Park, Medicinaregatan 8A, 41390 Gothenburg, Sweden.
| | - Cecilia Fager
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | - Eva Olsson
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| | | | - Andreas B Dahlin
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296 Gothenburg, Sweden.
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10
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Xiong K, Emilsson G, Maziz A, Yang X, Shao L, Jager EWH, Dahlin AB. Plasmonic Metasurfaces with Conjugated Polymers for Flexible Electronic Paper in Color. Adv Mater 2016; 28:9956-9960. [PMID: 27670834 DOI: 10.1002/adma.201603358] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2016] [Revised: 08/02/2016] [Indexed: 05/02/2023]
Abstract
A flexible electronic paper in full color is realized by plasmonic metasurfaces with conjugated polymers. An ultrathin large-area electrochromic material is presented which provides high polarization-independent reflection, strong contrast, fast response time, and long-term stability. This technology opens up for new electronic readers and posters with ultralow power consumption.
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Affiliation(s)
- Kunli Xiong
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Gustav Emilsson
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Ali Maziz
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183, Linköping, Sweden
| | - Xinxin Yang
- Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Lei Shao
- Department of Physics, Chalmers University of Technology, 41296, Göteborg, Sweden
| | - Edwin W H Jager
- Department of Physics, Chemistry and Biology (IFM), Linköping University, 58183, Linköping, Sweden
| | - Andreas B Dahlin
- Department of Chemistry and Chemical Engineering, Chalmers University of Technology, 41296, Göteborg, Sweden
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11
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Abstract
Plasmonic nanohole arrays are widely used for optical label-free molecular detection. An important factor for many applications is the diameter of the apertures. So far nanohole arrays with controllable diameters below 100 nm have not been demonstrated and it has not been systematically investigated how the diameter influences the optical properties. In this work we fine-tune the diameter in short range ordered nanohole arrays down to 50 nm. The experimental far field spectra show how the wavelength of maximum extinction remains unaffected while the transmission maximum blue shifts with smaller diameters. The near field is visualized by numerical simulations, showing a homogenous enhancement throughout the cylindrical void at the transmission maximum for diameters between 50 and 100 nm. For diameters below 50 nm plasmon excitation is no longer possible experimentally or by simulations. Further, we investigate the refractive index sensing capabilities of the smaller holes. As the diameter was reduced, the sensitivity in terms of resonance shift with bulk liquid refractive index was found to be unaltered. However, for the transmission maximum the sensitivity becomes more strongly localized to the hole interior. By directing molecular binding to the bottom of the holes we demonstrate how smaller holes enhance the sensitivity in terms of signal per molecule. A real-time detection limit well below one protein per nanohole is demonstrated. The smaller plasmonic nanoholes should be suitable for studies of molecules confined in small volumes and as mimics of biological nanopores.
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Affiliation(s)
- Kunli Xiong
- Dept. of Applied Physics, Chalmers University of Techology, Gothenburg, Sweden.
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12
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Junesch J, Emilsson G, Xiong K, Kumar S, Sannomiya T, Pace H, Vörös J, Oh SH, Bally M, Dahlin AB. Location-specific nanoplasmonic sensing of biomolecular binding to lipid membranes with negative curvature. Nanoscale 2015; 7:15080-15085. [PMID: 26351000 DOI: 10.1039/c5nr04208a] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The biochemical processes of cell membranes are sensitive to the geometry of the lipid bilayer. We show how plasmonic "nanowells" provide label-free real-time analysis of molecules on membranes with detection of preferential binding at negative curvature. It is demonstrated that norovirus accumulate in invaginations due to multivalent interactions with glycosphingolipids.
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Affiliation(s)
- Juliane Junesch
- Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden.
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13
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Fang Y, Jiao Y, Xiong K, Ogier R, Yang ZJ, Gao S, Dahlin AB, Käll M. Plasmon Enhanced Internal Photoemission in Antenna-Spacer-Mirror Based Au/TiO₂ Nanostructures. Nano Lett 2015; 15:4059-4065. [PMID: 25938263 DOI: 10.1021/acs.nanolett.5b01070] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Emission of photoexcited hot electrons from plasmonic metal nanostructures to semiconductors is key to a number of proposed nanophotonics technologies for solar harvesting, water splitting, photocatalysis, and a variety of optical sensing and photodetector applications. Favorable materials and catalytic properties make systems based on gold and TiO2 particularly interesting, but the internal photoemission efficiency for visible light is low because of the wide bandgap of the semiconductor. We investigated the incident photon-to-electron conversion efficiency of thin TiO2 films decorated with Au nanodisk antennas in an electrochemical circuit and found that incorporation of a Au mirror beneath the semiconductor amplified the photoresponse for light with wavelength λ = 500-950 nm by a factor 2-10 compared to identical structures lacking the mirror component. Classical electrodynamics simulations showed that the enhancement effect is caused by a favorable interplay between localized surface plasmon excitations and cavity modes that together amplify the light absorption in the Au/TiO2 interface. The experimentally determined internal quantum efficiency for hot electron transfer decreases monotonically with wavelength, similar to the probability for interband excitations with energy higher than the Schottky barrier obtained from a density functional theory band structure simulation of a thin Au/TiO2 slab.
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Affiliation(s)
- Yurui Fang
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Yang Jiao
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Kunli Xiong
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Robin Ogier
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Zhong-Jian Yang
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Shiwu Gao
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
- ‡Beijing Computational Science Research Center, Zhongguancun Software Park II, No. 10 Dongbeiwang West Road, Haidian District, Beijing 100094, China
| | - Andreas B Dahlin
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
| | - Mikael Käll
- †Department of Applied Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden
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14
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Emilsson G, Schoch RL, Feuz L, Höök F, Lim RYH, Dahlin AB. Strongly stretched protein resistant poly(ethylene glycol) brushes prepared by grafting-to. ACS Appl Mater Interfaces 2015; 7:7505-15. [PMID: 25812004 DOI: 10.1021/acsami.5b01590] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present a new grafting-to method for resistant "non-fouling" poly(ethylene glycol) brushes, which is based on grafting of polymers with reactive end groups in 0.9 M Na2SO4 at room temperature. The grafting process, the resulting brushes, and the resistance toward biomolecular adsorption are investigated by surface plasmon resonance, quartz crystal microbalance, and atomic force microscopy. We determine both grafting density and thickness independently and use narrow molecular weight distributions which result in well-defined brushes. High density (e.g., 0.4 coils per nm(2) for 10 kDa) and thick (40 nm for 20 kDa) brushes are readily achieved that suppress adsorption from complete serum (10× dilution, exposure for 50 min) by up to 99% on gold (down to 4 ng/cm(2) protein coverage). The brushes outperform oligo(ethylene glycol) monolayers prepared on the same surfaces and analyzed in the same manner. The brush heights are in agreement with calculations based on a simple model similar to the de Gennes "strongly stretched" brush, where the height is proportional to molecular weight. This result has so far generally been considered to be possible only for brushes prepared by grafting-from. Our results are consistent with the theory that the brushes act as kinetic barriers rather than efficient prevention of adsorption at equilibrium. We suggest that the free energy barrier for passing the brush depends on both monomer concentration and thickness. The extraordinary simplicity of the method and good inert properties of the brushes should make our results widely applicable in biointerface science.
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Affiliation(s)
- Gustav Emilsson
- †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Rafael L Schoch
- ‡Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | | | - Fredrik Höök
- †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
| | - Roderick Y H Lim
- ‡Biozentrum and the Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
| | - Andreas B Dahlin
- †Department of Applied Physics, Chalmers University of Technology, 41296 Göteborg, Sweden
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15
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Abstract
A review of sensing applications based on plasmonic nanopores is given. Many new types of plasmonic nanopores have recently been fabricated, including pores penetrating multilayers of thin films, using a great variety of fabrication techniques based on either serial nanolithography or self-assembly. One unique advantage with nanopores compared to other plasmonic sensors is that sample liquids can flow through the surface, which increases the rate of binding and improves the detection limit under certain conditions. Also, by utilizing the continuous metal films, electrical control can be implemented for electrochemistry, dielectrophoresis and resistive heating. Much effort is still spent on trying to improve sensor performance in various ways, but the literature uses inconsistent benchmark parameters. Recently plasmonic nanopores have been used to analyse targets of high clinical or academic interest. Although this is an important step forward, one should probably reflect upon whether the same results could have been achieved with another optical technique. Overall, this critical review suggests that the research field would benefit by focusing on applications where plasmonic nanopores truly can offer unique advantages over similar techniques.
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Affiliation(s)
- Andreas B Dahlin
- Chalmers University of Technology, Dept. of Applied Physics, Fysikgränd 3, 41296 Göteborg, Sweden.
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16
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Virk M, Xiong K, Svedendahl M, Käll M, Dahlin AB. A thermal plasmonic sensor platform: resistive heating of nanohole arrays. Nano Lett 2014; 14:3544-9. [PMID: 24807397 DOI: 10.1021/nl5011542] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
We have created a simple and efficient thermal plasmonic sensor platform by letting a DC current heat plasmonic nanohole arrays. The sensor can be used to determine thermodynamic parameters in addition to monitoring molecular reactions in real-time. As an application example, we use the thermal sensor to determine the kinetics and activation energy for desorption of thiol monolayers on gold. Further, the temperature of the metal can be measured optically by the spectral shift of the bonding surface plasmon mode (0.015 nm/K). We show that this resonance shift is caused by thermal lattice expansion, which reduces the plasma frequency of the metal. The sensor is also used to determine the thin film thermal expansion coefficient through a theoretical model for the expected resonance shift.
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Affiliation(s)
- Mudassar Virk
- Department of Applied Physics, Chalmers University of Technology , Göteborg, Sweden
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17
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Kumar K, Dahlin AB, Sannomiya T, Kaufmann S, Isa L, Reimhult E. Embedded plasmonic nanomenhirs as location-specific biosensors. Nano Lett 2013; 13:6122-6129. [PMID: 24188470 DOI: 10.1021/nl403445f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We introduce a novel optical biosensing platform that exploits the asymmetry of nanostructures embedded in nanocavities, termed nanomenhirs. Upon oblique illumination using plane polarized white light, two plasmonic resonances attributable to the bases and the axes of the nanomenhirs emerge; these are used for location-specific sensing of membrane-binding events. Numerical simulations of the near field distributions confirmed the experimental results. As a proof-of-concept, we present a model biosensing experiment that exploits the dual-sensing capability, the size selectivity offered by the sensor geometry, and the possibility to separately biochemically modify the nanomenhirs and the nanocavities for the specific binding of lipid membrane structures to the nanomenhirs.
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Affiliation(s)
- Karthik Kumar
- Department of Materials, Laboratory for Surface Science and Technology, Swiss Federal Institute of Technology (ETH Zürich) , CH-8093 Zürich, Switzerland
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18
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MacKenzie R, Fraschina C, Dielacher B, Sannomiya T, Dahlin AB, Vörös J. Simultaneous electrical and plasmonic monitoring of potential induced ion adsorption on metal nanowire arrays. Nanoscale 2013; 5:4966-4975. [PMID: 23632884 DOI: 10.1039/c3nr34172k] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Simultaneous LSPR and electronic sensing of potential induced ion adsorption onto gold nanowire arrays is presented. The formation of a Stern layer upon applying an electrochemical potential generated a complex optical response. Simulation of a lossy atomic layer on the nanowire array using the Multiple Multipole Program (MMP) corresponded very well to the experimentally observed peak position, intensity, and radius of curvature changes. Additionally, a significant voltage-dependent change in the resistance of the gold nanowire array was observed during the controlled formation of the electrical double layer. The results demonstrated that an applied electrochemical potential induces measurable changes in the optical and electrical properties of the gold nanowire surface. This is the first demonstration of combined plasmonic and nanowire resistance-based sensing of a surface process in the literature.
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Affiliation(s)
- Robert MacKenzie
- ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland
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19
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Abstract
Optical biosensors based on surface plasmon resonance (SPR) in metallic thin films are currently standard tools for measuring molecular binding kinetics and affinities - an important task for biophysical studies and pharmaceutical development. Motivated by recent progress in the design and fabrication of metallic nanostructures, such as nanoparticles or nanoholes of various shapes, researchers have been pursuing a new generation of biosensors harnessing tailored plasmonic effects in these engineered nanostructures. Nanoplasmonic devices, while demanding nanofabrication, offer tunability with respect to sensor dimension and physical properties, thereby enabling novel biological interfacing opportunities and extreme miniaturization. Here we provide an integrated overview of refractometric biosensing with nanoplasmonic devices and highlight some recent examples of nanoplasmonic sensors capable of unique functions that are difficult to accomplish with conventional SPR. For example, since the local field strength and spatial distribution can be readily tuned by varying the shape and arrangement of nanostructures, biomolecular interactions can be controlled to occur in regions of high field strength. This may improve signal-to-noise and also enable sensing a small number of molecules. Furthermore, the nanoscale plasmonic sensor elements may, in combination with nanofabrication and materials-selective surface-modifications, make it possible to merge affinity biosensing with nanofluidic liquid handling.
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Affiliation(s)
- Andreas B. Dahlin
- Chalmers University of Technology, Division of Bionanophotonics, Department of Applied Physics, Fysikgränd 3, 41296, Göteborg, Sweden
| | - Nathan J. Wittenberg
- Department of Electrical and Computer Engineering, Laboratory of Nanostructures and Biosensing, University of Minnesota, Twin Cities, 200 Union St. S.E., Minneapolis, MN 55455, U.S.A
| | - Fredrik Höök
- Chalmers University of Technology, Division of Bionanophotonics, Department of Applied Physics, Fysikgränd 3, 41296, Göteborg, Sweden
| | - Sang-Hyun Oh
- Department of Electrical and Computer Engineering, Laboratory of Nanostructures and Biosensing, University of Minnesota, Twin Cities, 200 Union St. S.E., Minneapolis, MN 55455, U.S.A
- Department of Biophysics and Chemical Biology, Seoul National University, Seoul 151-747, Korea
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20
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Junesch J, Sannomiya T, Dahlin AB. Optical properties of nanohole arrays in metal-dielectric double films prepared by mask-on-metal colloidal lithography. ACS Nano 2012; 6:10405-15. [PMID: 23098107 DOI: 10.1021/nn304662e] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We present the fabrication and optical characterization of plasmonic nanostructures consisting of nanohole arrays in two thin films, a metal and a dielectric. A novel method called mask-on-metal colloidal lithography is used to prepare high aspect ratio holes, providing efficient mass fabrication of stable structures with close to vertical walls and without the need for an adhesion layer under the metal. Our approach for understanding the transmission properties is based on solving the dispersions of the guided modes supported by the two films and calculating the influence from interference. The methodology is generic and can be extended to multilayered films. In particular, the influence from coupling to waveguide modes is discussed. We show that by rational design of structural dimensions it is possible to study only bonding surface plasmons and the associated hole transmission maximum. Further, numerical simulations with the multiple multipole program provide good agreement with experimental data and enable visualization of the asymmetric near-field distribution in the nanohole arrays, which is focused to the interior of the "nanowells". The refractometric sensitivity is evaluated experimentally both by liquid bulk changes and surface adsorption. We demonstrate how the localized mode provides reasonably good sensitivity in terms of resonance shift to molecular binding inside the voids. Importantly, high resolution sensing can be accomplished also for the surface plasmon mode, despite its extremely low figure of merit. This is accomplished by monitoring the coupling efficiency of light to plasmons instead of conventional sensing which is based on changes in plasmon energy. We suggest that these nanohole structures can be used for studying molecular transport through nanopores and the behavior of molecules confined in volumes of approximately one attoliter.
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Affiliation(s)
- Juliane Junesch
- Laboratory of Biosensors and Bioelectronics, Swiss Federal Institute of Technology, Zurich, Switzerland
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21
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Abstract
Many nanotechnological devices are based on implementing electrochemistry with plasmonic nanostructures, but these systems are challenging to understand. We present a detailed study of the influence of electrochemical potentials on plasmon resonances, in the absence of surface coatings and redox active molecules, by synchronized voltammetry and spectroscopy. The experiments are performed on gold nanodisks and nanohole arrays in thin gold films, which are fabricated by improved methods. New insights are provided by high resolution spectroscopy and variable scan rates. Furthermore, we introduce new analytical models in order to understand the spectral changes quantitatively. In contrast to most previous literature, we find that the plasmonic signal is caused almost entirely by the formation of ionic complexes on the metal surface, most likely gold chloride in this study. The refractometric sensing effect from the ions in the electric double layer can be fully neglected, and the charging of the metal gives a surprisingly small effect for these systems. Our conclusions are consistent for both localized nanoparticle plasmons and propagating surface plasmons. We consider the results in this work especially important in the context of combined electrochemical and optical sensors.
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Affiliation(s)
- Andreas B Dahlin
- Dept. of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden.
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22
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Sannomiya T, Scholder O, Jefimovs K, Hafner C, Dahlin AB. Investigation of plasmon resonances in metal films with nanohole arrays for biosensing applications. Small 2011; 7:1653-1663. [PMID: 21520499 DOI: 10.1002/smll.201002228] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Revised: 02/01/2011] [Indexed: 05/30/2023]
Abstract
Biosensing with nanoholes is one of the most promising applications of nanoplasmonic devices. The sensor properties, however, are complex due to coupled resonances through propagating and localized surface plasmons. This Full Paper demonstrates experimental and simulation studies on different plasmonic hole systems, namely various patterns of circular holes in gold films. In contrast to most previous work, here, the challenging situation of optically thin films is considered. The refractive-index-sensing properties, such as sensitive locations in the nanostructure and sensitive spectral features, are investigated. The multiple multipole program provides the complete field distribution in the nanostructure for different wavelengths. It is shown that the spectral feature most sensitive to refractive-index changes is the extinction minimum, rather than the maximum. The results are consistent with theory for perfect electrical conductors. The spectral response is investigated for molecular adsorption at different positions inside or outside a hole. Furthermore, the optical properties of nanohole arrays with long-range and short-range order are compared and found to demonstrate remarkable similarities. Our results help to predict the resonance wavelengths of nanoholes with arbitrary patterns, including short-range order. The results presented here are highly important since they extend and challenge several aspects of the current understanding of plasmon resonances in nanohole arrays. These theoretical models, simulation results, and experimental data together help provide the understanding necessary for the development of efficient biomolecular analysis tools based on metallic nanoholes.
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Affiliation(s)
- Takumi Sannomiya
- Laboratory of Biosensors & Bioelectronics, ETH Zurich, Gloriastrasse 35, 8092 Zurich, Switzerland.
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23
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Abstract
We show how gold recrystallizes when under the influence of electrochemical potentials. This "cold annealing" occurs without charge transfer reactions and preserves nanoscale structural features. By performing the process on plasmonic nanostructures, grain growth is monitored noninvasively by optical spectroscopy. In this way, the influence from crystal structure on plasmon resonances can be investigated independently. Observed spectral changes are in excellent agreement with analytical models and changes in electron relaxation time and plasma frequency are calculated.
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Affiliation(s)
- Andreas B Dahlin
- Laboratory of Biosensors and Bioelectronics, Swiss Federal Institute of Technology Zürich, Switzerland.
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24
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Abstract
The optical signal of a localized surface plasmon resonance (LSPR)-based sensor combined with electrochemistry was investigated. Gold nanoparticles were immobilized on an indium tin oxide (ITO) substrate, which functioned as working electrode. Using cyclic voltammetry synchronized with LSPR sensing, surface reactions on gold were detected both electrically and optically. In the capacitive charging regime, optical signals linear to the applied potential were detected. Gold was found to be dissolved above the oxidation potential and partially redeposited during the reduction, which changed size and conformation of the gold nanoparticles. In kinetic measurements, slower potential establishment was observed at lower salt concentrations. Simulations by multiple multipole program (MMP) suggested the formation of a lossy layer by combination of charge depletion of gold and negative ion adsorption even below the reaction potential. We consider the results presented here of importance for any future sensors based on combined plasmonics and electrochemistry.
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Affiliation(s)
- Takumi Sannomiya
- Laboratory of Biosensors and Bioelectronics, Department of Information Technology and Electrical Engineering, ETH Zürich, Zürich, Switzerland
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25
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Jonsson MP, Dahlin AB, Feuz L, Petronis S, Höök F. Locally Functionalized Short-Range Ordered Nanoplasmonic Pores for Bioanalytical Sensing. Anal Chem 2010; 82:2087-94. [DOI: 10.1021/ac902925e] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Magnus P. Jonsson
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
| | - Andreas B. Dahlin
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
| | - Laurent Feuz
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
| | - Sarunas Petronis
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
| | - Fredrik Höök
- Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
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26
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Rydell GE, Dahlin AB, Höök F, Larson G. QCM-D studies of human norovirus VLPs binding to glycosphingolipids in supported lipid bilayers reveal strain-specific characteristics. Glycobiology 2009; 19:1176-84. [PMID: 19625485 DOI: 10.1093/glycob/cwp103] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Susceptibility to norovirus infection has been linked to secretor status. Norovirus virus-like particles (VLPs; 0- 20 microg/mL) from the Norwalk (GI.1) and Dijon (GII.4) strains were assayed for binding to H type 1 and Lewis a pentaglycosylceramides, incorporated in laterally fluid supported lipid bilayers. Binding kinetics was monitored in real time in 40 microL stationary reaction chambers, using quartz crystal microbalance with dissipation (QCM-D) monitoring. Both strains displayed binding only to H type 1 and not to Lewis a glycosphingolipids, typical for epithelial cells of susceptible and resistant individuals, respectively. This binding specificity was confirmed by VLPs binding to the two glycosphingolipids chromatographed on TLC-plates. Experiments using bilayers with mixtures of H type 1 and Lewis a, with the total glycosphingolipid concentration constant at 10 wt%, showed that binding was only dependent on H type 1 concentrations and identical to experiments without additional Lewis a. Both strains showed a threshold concentration of H type 1 below which no binding was observable. The threshold was one order of magnitude higher for the Dijon strain (2 wt% versus 0.25 wt%) demonstrating that the interaction with a significantly larger number of glycosphingolipids was needed for the binding of the Dijon strain. The difference in threshold glycosphingolipid concentrations for the two strains suggests a lower affinity for the glycosphingolipid for the Dijon compared to the Norwalk strain. We propose that VLPs initially bind only a few glycosphingolipids but the binding is subsequently strengthened by lateral diffusion of additional glycosphingolipids moving into the interaction area.
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Affiliation(s)
- Gustaf E Rydell
- Department of Clinical Chemistry and Transfusion Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden
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27
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Dahlin AB, Chen S, Jonsson MP, Gunnarsson L, Käll M, Höök F. High-Resolution Microspectroscopy of Plasmonic Nanostructures for Miniaturized Biosensing. Anal Chem 2009; 81:6572-80. [DOI: 10.1021/ac901175k] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andreas B. Dahlin
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Si Chen
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Magnus P. Jonsson
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Linda Gunnarsson
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Mikael Käll
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Fredrik Höök
- Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden
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28
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Dahlin AB, Jönsson P, Jonsson MP, Schmid E, Zhou Y, Höök F. Synchronized quartz crystal microbalance and nanoplasmonic sensing of biomolecular recognition reactions. ACS Nano 2008; 2:2174-2182. [PMID: 19206465 DOI: 10.1021/nn800254h] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We present a method providing synchronized measurements using the two techniques: quartz crystal microbalance with dissipation (QCM-D) monitoring and localized surface plasmon resonance (LSPR). This was achieved by letting a thin gold film perforated with short-ranged ordered plasmon-active nanoholes act as one of the electrodes of a QCM-D crystal. This enabled transmission-mode optical spectroscopy to be used to temporally resolve colorimetric changes of the LSPR active substrate induced upon biomolecular binding events. The LSPR response could thus be compared with simultaneously obtained changes in resonance frequency, Deltaf, and energy dissipation, DeltaD, of the QCM-D device. Since the LSPR technique is preferentially sensitive to changes within the voids of the nanoholes, while the QCM-D technique is preferentially sensitive to reactions on the planar region between the holes, a surface chemistry providing the same binding kinetics on both gold and silica was used. This was achieved by coating the substrate with poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which was shown to bind in the same manner on silica and gold modified with a carboxyl-terminated thiol. In this way, the combined setup provided new information about structural changes upon PLL-g-PEG adsorption. We also demonstrate subsequent binding of NeutrAvidin and an immunoreaction utilizing biotin-modified IgG. The combined information from the synchronized measurements was also used in a new way to estimate the sensing volume of the LSPR sensor.
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Affiliation(s)
- Andreas B Dahlin
- Division of Solid State Physics, Department of Physics, Lund University, Lund, Sweden
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29
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Jonsson MP, Jönsson P, Dahlin AB, Höök F. Supported lipid bilayer formation and lipid-membrane-mediated biorecognition reactions studied with a new nanoplasmonic sensor template. Nano Lett 2007; 7:3462-8. [PMID: 17902726 DOI: 10.1021/nl072006t] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
This paper presents the use of the localized surface plasmon resonance (LSPR) sensor concept to probe the formation of macroscopic and laterally mobile supported lipid bilayers (SLBs) on SiOx-encapsulated nanohole-containing Au and Ag films. A comparison between Au- and Ag-based sensor templates demonstrates a higher sensitivity for Au-based templates with respect to both bulk and interfacial refractive index (RI) changes in aqueous solution. The lateral mobility of SLBs formed on the SiOx-encapsulated nanohole templates was analyzed using fluorescence recovery after photobleaching (FRAP), demonstrating essentially complete (>96%) recovery, but a reduction in diffusivity of about 35% compared with SLBs formed on flat SiOx substrates. Furthermore, upon SLB formation, the temporal variation in extinction peak position of the LSPR active templates display a characteristic shape, illustrating what, to the best of our knowledge, is the first example where the nanoplasmonic concept is shown capable of probing biomacromolecular structural changes without the introduction of labels. With a signal-to-noise ratio better than 5 x 10(2) upon protein binding to the cell-membrane mimics, the sensor concept is also proven competitive with state-of-the-art label-free sensors.
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Affiliation(s)
- Magnus P Jonsson
- Division of Solid State Physics, Lund University, SE-22100 Lund, Sweden
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30
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Abstract
The colorimetric variations induced upon changes in interfacial refractive index of nanoscale noble metal structures exhibiting localized surface plasmon resonance (LSPR) provides a convenient means of label-free, affinity-based detection of biomolecular recognition reactions. However, despite being similar in nature to conventional SPR, LSPR has so far suffered from significantly lower data quality in terms of its signal-to-noise ratio (S/N) in typical biomolecular recognition analysis. In this work, generic data analysis algorithms and a simple experimental setup that provide a S/N upon protein binding that is comparable to that of state-of-the art SPR systems are presented. Specifically, it is demonstrated how temporal variations (rate approximately 0.5 Hz) in parameters proportional to the resonance peak position can be recorded simultaneously, yielding a peak position precision of <5 x 10(-4) nm and an extinction noise level of <5 x 10(-6) absorbance units (Abs). This, in turn, is shown to provide a S/N of approximately 2000 (equivalent to a detection limit of <0.1 ng/cm(2)) for typical protein binding reactions. Furthermore, the importance of utilizing changes in both peak position and magnitude is highlighted by comparing different LSPR active noble metal architectures that respond differently to bulk and interfacial refractive index changes.
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