Showing papers on "Surface plasmon resonance published in 1998"
TL;DR: In this new nanoparticle-based detection system, Au particles are used to complex a 24-base polynucleotide target and exhibit characteristic, exceptionally sharp “melting transitions” which allows one to distinguish target sequences that contain one base end mismatches, deletions, or an insertion from the fully complementary target.
Abstract: Selective colorimetric polynucleotide detection based on Au nanoparticle probes which align in a “tail-to-tail” fashion onto a target polynucleotide is described. In this new nanoparticle-based detection system, Au particles (∼13 nm diameter), which are capped with 3‘- and 5‘-(alkanethiol)oligonucleotides, are used to complex a 24-base polynucleotide target. Hybridization of the target with the probes results in the formation of an extended polymeric Au nanoparticle/polynucleotide aggregate, which triggers a red to purple color change in solution. The color change is due to a red shift in the surface plasmon resonance of the Au nanoparticles. The aggregates exhibit characteristic, exceptionally sharp “melting transitions” (monitored at 260 or 700 nm), which allows one to distinguish target sequences that contain one base end mismatches, deletions, or an insertion from the fully complementary target. When test solutions are spotted onto a C18 reverse-phase thin-layer chromatography plate, color differentia...
2,244 citations
TL;DR: In this article, a simple but quantitative mathematical formalism for interpretation of surface plasmon resonance (SPR) signals from adsorbed films of a wide variety of structures is presented.
Abstract: A simple but quantitative mathematical formalism for interpretation of surface plasmon resonance (SPR) signals from adsorbed films of a wide variety of structures is presented. It can be used to estimate adsorbed film thicknesses, surface coverages, or surface concentrations from the SPR response over the entire range of film thicknesses without relying on calibration curves of response versus known thicknesses or surface concentrations. This formalism is compared to more complex optical simulations. It is further tested by (1) calibrating the response of two SPR spectrometers to changes in bulk index of refraction, (2) using these calibrations with this formalism to predict responses to several well-characterized adlayer structures (alkanethiolates and serum albumin on gold, propylamine on COOH-functionalized gold), and then (3) comparing these predictions to measured SPR responses. Methods for estimating the refractive index of the adlayer material are also discussed. Detection limits in both bulk and a...
986 citations
TL;DR: A quasi-linear relationship between particle coverage and plasmon angle shift is presented, thereby providing for a direct correlation between plAsmon shift and solution antigen concentration.
Abstract: Surface plasmon resonance (SPR) biosensing using colloidal Au enhancement is reported. Immobilization of ∼11-nm-diameter colloidal Au to an evaporated Au film results in a large shift in plasmon angle, a broadened plasmon resonance, and an increase in minimum reflectance. The incorporation of colloidal Au into SPR biosensing results in increased SPR sensitivity to protein−protein interactions when a Au film-immobilized antibody and an antigen−colloidal Au conjugate comprise the binding pair. A highly specific particle-enhanced analogue of a sandwich immunoassay is also demonstrated by complexing the Au particle to a secondary antibody. A tremendous signal amplification is observed, as addition of the antibody−Au colloid conjugate results in a 25-fold larger signal than that due to addition of a free antibody solution that is 6 orders of magnitude more concentrated. Picomolar detection of human immunoglobulin G has been realized using particle enhancement, with the theoretical limits for the technique bein...
592 citations
TL;DR: Advances in experimental design and data analysis methods are making it possible to accurately define the assembly mechanisms and rate constants associated with macromolecular interactions.
Abstract: Surface plasmon resonance based biosensors are being used to define the kinetics of a wide variety of macromolecular interactions. As the popularity of this approach grows, experimental design and data analysis methods continue to evolve. These advances are making it possible to accurately define the assembly mechanisms and rate constants associated with macromolecular interactions.
450 citations
TL;DR: A highly sensitive 27-MHz quartz-crystal microbalance was employed to detect hybridization of complementary oligonucleotides in aqueous solution and the obtained results were compared with those obtained by a surface plasmon resonance method using a BIAcore system.
Abstract: A highly sensitive 27-MHz quartz-crystal microbalance, on which a 10−30-mer oligonucleotide was immobilized as a probe molecule, was employed to detect hybridization of complementary oligonucleotides in aqueous solution. From frequency decreases (mass increases due to the hybridization) with passage of time, kinetic parameters such as association constants (Ka) and binding and dissociation rate constants (k1 and k-1) could be obtained, as well as binding (hybridization) amount at the nanogram level (Δm). Kinetic studies were carried out by changing various parameters: (i) the immobilization method of a probe oligonucleotide on Au electrode, (ii) number of mismatching bases in sequences of target oligonucleotides, (iii) length of both probe and target oligonucleotides, (iv) hybridization temperature, and (v) ionic strength in solution. The obtained results were compared with those obtained by a surface plasmon resonance method using a BIAcore system.
422 citations
TL;DR: The surface plasmon resonance (SPR) wavelength of colloidal gold particles coated with a monoclonal antibody is red-shifted when the antibody interacts with its specific ligand to monitor in real-time the association and dissociation kinetics of the interaction in solution.
Abstract: The surface plasmon resonance (SPR) wavelength of colloidal gold particles coated with a monoclonal antibody is red-shifted when the antibody interacts with its specific ligand. This shift results from the change in the refractive index of the particles as induced by ligand binding. This property is used to monitor in real-time the association and dissociation kinetics of the interaction in solution. The monitoring is perfomed in a clinical chemistry automated analyzer during a few minutes of incubation at 37 °C. Data treatment allows calculation of the affinity constant of the interaction. The SPR wavelength shift does not necessarily require agglutination or aggregation of the particles to occur since particles coated with one monoclonal antibody specific for a single epitope on the ligand can be used in the procedure. The affinity constants measured by this procedure correlate with those calculated from Scatchard plots or BIAcore data.
319 citations
TL;DR: Surfaces that promote the ligand-directed binding of cells and resist the cellular deposition of adhesive proteins are described, based on self-assembled monolayers of alkanethiolates on gold that present mixtures of arginine-glycine-aspartate, a tripeptide that promotes cell adhesion by binding to cell surface integrin receptors.
Abstract: This paper describes surfaces that promote the ligand-directed binding of cells and resist the cellular deposition of adhesive proteins. These surfaces are based on self-assembled monolayers (SAMs) of alkanethiolates on gold that present mixtures of arginine-glycine-aspartate (RGD), a tripeptide that promotes cell adhesion by binding to cell surface integrin receptors, and oligo(ethyleneglycol) moieties, groups that resist nonbiospecific adsorption of proteins and cells. Surface plasmon resonance (SPR) spectroscopy was used to measure the adsorption of carbonic anhydrase and fibrinogen to mixed SAMs comprising RGD groups ((EG)6OGRGD) and tri(ethylene glycol) groups ((EG)3OH); SAMs having values of the mole fraction of RGD (χRGD) ≤ 0.05 adsorbed nearly undetectable levels of carbonic anhydrase or fibrinogen. Bovine capillary endothelial cells attached and spread on SAMs at χRGD ≥ 0.00001, with spreading of cells reaching a maximum at χRGD ≥ 0.001. These mixed SAMs reduced the deposition of proteins by atta...
311 citations
TL;DR: It is clear that ellipsometry and related methods such as reflectometry and surface plasmon resonance (Biacore) are now being increasingly used in biomaterial research as well as in other areas of research.
292 citations
TL;DR: A convenient method to rapidly evaluate the inhibitory constants for a panel of different ligands, both monovalent and multivalent, for low-affinity receptors, such as the carbohydrate-binding protein Con A.
Abstract: The affinities of the carbohydrate-binding protein concanavalin A (Con A) for mono- and multivalent ligands were measured by surface plasmon resonance (SPR) detection Assessing protein−carbohydrate affinities is typically difficult due to weak affinities observed and the complications that arise from the importance of multivalency in these interactions We describe a convenient method to rapidly evaluate the inhibitory constants for a panel of different ligands, both monovalent and multivalent, for low-affinity receptors, such as the carbohydrate-binding protein Con A A nonnatural, mannose-substituted glycolipid was synthesized, and self-assembled monolayers of varying carbohydrate density were generated The synthetic surfaces bind Con A Competition experiments that employed monovalent ligands in solution yielded Ki values similar to equilibrium binding constants obtained in titration microcalorimetry experiments In addition, this assay could be used to examine various polymeric ligands of defined le
268 citations
TL;DR: In this article, the effect of colloidal gold clusters on surface-enhanced Raman scattering (SERS) enhancement has been investigated and it was shown that colloidal clusters can provide an enhancement level sufficient for Raman single molecule detection.
Abstract: In agreement with previous results reported for colloidal silver clusters, effective surface-enhanced Raman cross sections of about 10-16 cm2 per molecule, corresponding to enhancement factors on the order of 10 14, have also been obtained for molecules attached to colloidal gold clusters. Spatially isolated nearly spherical colloidal gold particles of about 60 nm size show maximum enhancement factors on the order of 103 at 514 nm excitation, close to the single plasmon resonance. The enhancement factor increases by eleven orders of magnitude when colloidal gold clusters are formed by aggregation of the gold colloids and when near-infrared excitation is applied. The large effective surface-enhanced Raman cross section has been estimated by a straightforward method based on steady-state population redistribution due to the pumping of molecules to the first excited vibrational state via the strongly enhanced Raman process. Our experimental finding confirms the important role of colloidal clusters for extremely large surface-enhanced Raman scattering (SERS) enhancement factors. Simultaneously, it suggests colloidal gold clusters as a substrate for high-sensitivity surface-enhanced Raman scattering, which can provide an enhancement level sufficient for Raman single molecule detection. Due to its chemical inactivity, gold might have some advantages compared to silver, particularly in biomedical spectroscopy.
260 citations
TL;DR: In this article, a gamma radiolysis method was used to synthesize capped copper nanoclusters by optimizing various conditions like metal ion concentration, polymer or surfactant concentration and pH.
TL;DR: In this paper, Azobenzene-derivatized alkanethiols have been used to form self-assembled monolayers on planar and colloidal gold substrates.
Abstract: Azobenzene-derivatized alkanethiols have been used to form self-assembled monolayers on planar and colloidal gold substrates. Five derivatives were used allowing investigation of the effects of chain length, ω-functionality and a comparison of thiol versus disulfide. Single-component monolayer films, i.e., consisting only of the “azo”-derivatized thiols (disulfides), showed no evidence of photoswitching. However, “photoswitching” was observed in “mixed monolayers”, in self-assembled multilayers, and on nanoparticles coated with mixed monolayers. The photoswitching was observed using surface plasmon resonance on the planar samples and by UV−vis spectroscopy from nanoparticle solutions.
TL;DR: In this paper, an interferometric method for the detection of the phase shifts of reflected light under surface plasmon resonance (SPR) conditions due to refractive index changes is proposed and experimentally realized.
TL;DR: This is the first demonstration of detection of conformational changes in an immobilized protein using an SPR biosensor, and has potential for developing novel sensors and/or switching devices in response to protein conformational change.
Abstract: Utilizing surface plasmon resonance (SPR), we have developed novel methodology for the detection of conformational change(s) in immobilized proteins. A genetically altered E. coli dihydrofolate reductase (DHFR-ASC) was attached to a carboxymethyldextran matrix layer covering the sensor surface of an SPR biosensor through a disulfide linkage at the engineered protein's C-terminus. The DHFR-ASC-immobilized surface exhibited a larger response to acid treatment than reference surfaces lacking immobilized proteins. The SPR signal of the tethered protein and the molar ellipticity of DHFR-ASC in solution responded similarly to pH changes, consistent with the interpretation that changes in the SPR signal reflect conformational changes occurring during acid denaturation. A pH shift observed between the SPR signal and ellipticity changes may reflect a difference between surface and bulk pH. The tethered protein sensor surface was stable to repeated acid treatment using solutions in the pH range of 0.12−7.80 and yie...
TL;DR: The feasibility of surface plasmon resonance (SPR) multisensing is demonstrated by monitoring four separate immunoreactions simultaneously in real time using a multichannel SPR instrument and results do correlate with expected immunologic specificity.
Abstract: We have demonstrated the feasibility of surface plasmon resonance (SPR) multisensing by monitoring four separate immunoreactions simultaneously in real time using a multichannel SPR instrument. A plasmon carrying gold layer, onto which a four-channel flow cell was pressed, was imaged at a fixed angle of incidence. First, the four-channels were coated with antibodies and then the flow cell was turned by 90° such that the flow channels overlapped the areas coated in the first step. In that geometry, antigens were applied to the different antibodies on the surface. Thus, all antibody−antigen combinations can be measured in a two-dimensional array of sensor surfaces in real time. Our results do correlate with expected immunologic specificity. The emphasis will be on presenting this method to obtain data on immunosystems and not as much on the assessment of biological activity.
TL;DR: It is shown that, when liposomes are used, a substantial enhancement of the detection limit is achieved and the "liposome" strategy improves the sensitivity for the IFN-gamma assay approximately 4 x 10(4) times and the detectionlimit to low picomolar.
Abstract: A recently developed liposome sandwich immunoassay for interferon-γ (IFN-γ), to be applied in microtiter plates, is tailored for surface plasmon resonance (SPR) spectrometry. The assay is performed on a thin (∼20 nm) polystyrene layer that covers a gold surface. This way, analytical data obtained from microtiter plate technology can directly be extrapolated toward SPR. For assaying the antigen IFN-γ, a 16-kDa cytokine, a capture monoclonal antibody is physically adsorbed onto the polystyrene surface. After addition of the sample containing IFN-γ, a biotinylated detecting antibody is added. Avidin is used as a bridging molecule between the biotinylated antibody and the biotinylated liposomes. All solutions are prepared with PBS buffer (10 mM, pH 7.4). This avoids additional changes in index of refraction caused by the use of various buffer solutions in immunoassays on microtiter plates for coating, binding, and washing procedures. It is shown that, when liposomes are used, a substantial enhancement of the ...
TL;DR: This combination of techniques is very promising for the investigation of the lateral diffusion of transducin, can be extended to include signalling proteins downstream of the G protein, and may be applied to functional screening of other G protein-coupled receptors.
Abstract: Rhodopsin−transducin coupling was used as an assay to investigate a laterally patterned membrane reconstituted with a receptor and its G protein. It served as a model system to show the feasibility to immobilize G protein-coupled receptors on solid supports and investigate receptor activation and interaction with G proteins by one-dimensional imaging surface plasmon resonance. Supported membranes were formed by the self-assembly of lipids and rhodopsin from detergent solution onto functionalized gold surfaces. They formed micrometer-sized alternating regions of pure fluid phospholipid bilayers separated by bilayers composed of an outer phospholipid leaflet on a gold-attached inner thiolipid. Rhodopsin was found to incorporate preferentially into the phospholipid bilayer regions, whereas transducin was uniformly distributed over the entire outer surface of the supported patterned membrane. The influence of rhodopsin on the dark binding of transducin to lipid membranes was described quantitatively and compa...
TL;DR: In this article, a metal nanoparticle system has been prepared by 200 Kev Ag+ ion implantation into perfect single crystal SiO2 at room temperature to dose: 6.7×1016/cm2.
Abstract: A metal nanoparticle system has been prepared by 200 Kev Ag+ ion implantation into perfect single crystal SiO2 at room temperature to dose: 6.7×1016/cm2. The system presents quasidual-layer structure: the shallower implanted layer containing noninteracting small Ag nanoparticles and the deeper layer containing interacting large nanoparticles, in which great red shift, about 1 eV, comparing with the plasmon resonance frequency of the noninteracting nanoparticle, can be clearly observed. The red shift is attributed to the multipoles interaction among the high density nanoparticles at external electric field. Moreover, the magnitude of red shift increases with implanted dose.
TL;DR: A model to quantitate the principal aspects of multivalent binding describes the random distribution of an immobilized component taking into account local densities, which will be helpful for understanding and designing experiments to assess avidity effects as well as for developing molecules with high avidity.
TL;DR: In this paper, a surface plasmon resonance (SPR) sensor was proposed to detect changes in refractive index of analyte by measuring changes in the intensity of the light back-reflected from a mirrored end face of the fiber.
Abstract: A novel design of surface plasmon resonance (SPR) sensor is reported which leads to a highly miniaturized optical fiber sensing element with high sensitivity A surface plasmon wave is excited on a thin metal film on a side-polished single-mode optical fiber and variations in the refractive index of analyte are detected by measuring changes in the intensity of the light back-reflected from a mirrored end face of the fiber The operation range of the sensor is tuned toward aqueous media by using a thin tantalum pentoxide overlayer It is demonstrated that the sensor is capable of detecting changes in the refractive index below 4×10 −5
TL;DR: A novel biodegradable polymer designed to present bioactive motifs at the surfaces of materials of any architecture is described, using surface plasmon resonance analysis (SPR) and confocal microscopy that surface engineering can be achieved under aqueous conditions in short time periods.
Abstract: We describe the development of a novel biodegradable polymer designed to present bioactive motifs at the surfaces of materials of any architecture. The polymer is a block copolymer of biotinylated poly(ethylene glycol) (PEG) with poly(lactic acid) (PLA); it utilizes the high-affinity coupling of the biotin-avidin system to undergo postfabrication surface engineering. We show, using surface plasmon resonance analysis (SPR) and confocal microscopy that surface engineering can be achieved under aqueous conditions in short time periods. These surfaces interact with cell surface molecules and generate beneficial responses as demonstrated by the model study of integrin-mediated spreading of endothelial cells on polymer surfaces presenting RGD peptide adhesion sequences.
TL;DR: Conditions for the formation of lipid monolayers have been optimised with respect to lipid type, chemical and buffer compatibility, ligand stability and reproducibility.
TL;DR: A surface plasmon resonance [SPR] immunosensor demonstrates an increased ability for performing sensitive and selective assay of human immunoglobulin G [hIgG] compared with a device fabricated with a physically-adsorbed IgG-silver interfacial-layer due to reduced levels of non-specific binding.
TL;DR: Highly sensitive and selective detection of morphine (MO) based on surface-plasmon-resonance (SPR) was realized by using an anti-MO monoclonal antibody and MO–bovine serum albumin (MO–BSA) conjugate (antigen).
Abstract: Highly sensitive and selective detection of morphine (MO) based on surface-plasmon-resonance (SPR) was realized by using an anti-MO monoclonal antibody and MO–bovine serum albumin (MO–BSA) conjugate (antigen). MO–BSA was immobilized on the Au thin film of the SPR sensor chip by physical adsorption. The incident angle of the SPR system using the MO–BSA immobilized chip increased almost linearly with increasing concentration of antibody up to ca. 5 μg ml−1 (ppm). The addition of MO to the antibody solution (5 ppm) was found to reduce the incident angle shift sharply because of the inhibition effect of MO. Based on this inhibiting principle, the present sensor could detect MO in the concentration range 0.1–10 ng ml−1 (ppb). The affinity constants between the antibody and the antigens (MO and MO–BSA) could be obtained by assuming a Langmuir adsorption model for the immunoreaction system.
TL;DR: A heterodyne optical measurement system for studying the phase shift of surface plasmon resonance (SPR) utilizing a frequency-stabilized Zeeman laser as a detection light source and suitable for real-time phase measurement in SPR-sensing applications.
Abstract: A heterodyne optical measurement system for studying the phase shift of surface plasmon resonance (SPR) is presented. The system utilizes a frequency-stabilized Zeeman laser as a detection light source and is suitable for real-time phase measurement in SPR-sensing applications. The phase shift in an angular dispersion SPR excitation setup was measured ranging from +180 degrees to -120 degrees around the SPR excitation region. The experimental results fit well with the theoretical analysis. Compared with the reflection coefficient variation that is widely investigated in SPR studies, phase shift is estimated to provide a higher sensitivity to sensor systems and more information about the resonance phenomenon.
TL;DR: A surface plasmon resonance (SPR) immunosensor is developed to determine concentrations of the mycotoxin, fumonisin B1 (FB1), in spiked samples and a detection limit of 50 ng/mL is obtained for the direct assay with an analysis time under 10 min.
Patent•
16 Dec 1998TL;DR: In this article, a method for detecting and analysing carrier-borne chemical compounds with Raman spectroscopy using an improved SERS substrate is presented, which can be used to detect biomolecule analytes through measuring of binding-induced changes in electrical resistance or surface plasmon resonance.
Abstract: A biosensor based on complexes between biomolecule receptors and colloidal Au nanoparticles, and more specifically, colloid layers of receptor/Au complexes that can be used to detect biomolecule analytes through measuring of binding-induced changes in electrical resistance or surface plasmon resonance. Also disclosed is a method for detecting and analysing carrier-borne chemical compounds with Raman spectroscopy using an improved SERS substrate. Further disclosed is an improved method for detecting compounds in solvents using capillary electrophoresis in conjunction with Raman spectroscopy.
TL;DR: The binding of one protein to another provokes a variety of biophysical changes that can then be used as a measure of the binding reaction, and optical spectroscopy, particularly fluorescence, is the most flexible technique.
TL;DR: In this article, the effect of Coulomb correlations on the ultrafast optical dynamics of small metal particles was studied. And they showed that a surface-induced dynamical screening of the electron-electron interactions leads to quasiparticle scattering with collective surface excitations.
Abstract: We study the effect of Coulomb correlations on the ultrafast optical dynamics of small metal particles. We demonstrate that a surface-induced dynamical screening of the electron-electron interactions leads to quasiparticle scattering with collective surface excitations. In noble-metal nanoparticles, it results in an interband resonant scattering of $d$ holes with surface plasmons. We show that this size-dependent many-body effect manifests itself in the differential absorption dynamics for frequencies close to the surface plasmon resonance. In particular, our self-consistent calculations reveal a strong frequency dependence of the relaxation, in agreement with recent femtosecond pump-probe experiments.