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Evgenia Matveeva

Publications and source records attributed to Evgenia Matveeva.

9 recordsLinked to original sources
PubMed2005

Plasmonic technology: novel approach to ultrasensitive immunoassays.

At the Center for Fluorescence Spectroscopy, we have taken advantage of the favorable properties of surface plasmon-coupled emission (SPCE) to improve fluorescence-based immunoassays. SPCE occurs when excited fluorophores near conducting metallic structures efficiently couple to surface plasmons. These surface plasmons, appearing as free electron oscillations in the metallic layer, produce electromagnetic radiation that preserves the spectral properties of fluorophores but is highly polarized and directional. SPCE immunoassays provide several advantages over other fluorescence-based methods. This review explains new approaches to fluorescence immunoassays, including our own use of SPCE for simultaneous detection of more than one fluorescent marker and performance of immunoassays in the presence of an optically dense medium, such as whole blood.

Humans↗
PubMed2005

Metal-enhanced fluoroimmunoassay on a silver film by vapor deposition.

We studied a fluoroimmunoassay using metal-enhanced fluorescence (MEF) detection on silver film generated by vapor deposition method. The morphology of the silver film was controlled through the thickness of the film. A silica layer was coated on the silver film to protect the film and separate the fluorophore from the metal surface. Rabbit immunoglobulin G (IgG) was adsorbed on the silica by physiosorption and then dye-labeled anti-rabbit IgG was bound to the immobilized rabbit IgG. It was observed that the fluorophore was quenched on a thin silver film (2 nm), enhanced on a thick film (>5 nm), and reached saturation (ca. 10 times enhancement) at 20 nm. The MEF was also dependent on the thickness of the silica with a maximum at 10 nm. The lowest lifetime was observed on the 20 nm silver film, which was consistent with the saturation of MEF. These results showed the properties of a silver film needed for a maximum increase of fluorescence intensity in a fluoroimmunoassay. Dependence of the MEF on the emission wavelength was also studied using different dye-labeled anti-rabbit IgGs.

Clinical Laboratory Techniques↗
PubMed2005

Metal-enhanced fluorescence: an emerging tool in biotechnology.

Over the past 15 years, fluorescence has become the dominant detection/sensing technology in medical diagnostics and biotechnology. Although fluorescence is a highly sensitive technique, where single molecules can readily be detected, there is still a drive for reduced detection limits. The detection of a fluorophore is usually limited by its quantum yield, autofluorescence of the samples and/or the photostability of the fluorophores; however, there has been a recent explosion in the use of metallic nanostructures to favorably modify the spectral properties of fluorophores and to alleviate some of these fluorophore photophysical constraints. The use of fluorophore-metal interactions has been termed radiative decay engineering, metal-enhanced fluorescence or surface-enhanced fluorescence.

Biotechnology↗
PubMed2004

Metal-enhanced fluorescence immunoassays using total internal reflection and silver island-coated surfaces.

We present a generic immunoassay platform that uses enhanced total internal reflection fluorescence in the proximity of silver island films (SIFs), a surface coating consisting of metal (silver) particles. This platform is used with a model immunoassay where a protein antigen, rabbit immunoglobulin G, was immobilized on the SIF-coated glass surface. The signal from a fluorescent dye-labeled anti-rabbit antibody binding to the surface antigen was detected; different color dyes have been tested. Close placement of the fluorophore to surface-bound silver nanostructures results in dramatic signal enhancement (up to 40-fold) on the SIFs as compared with the glass slides. Use of the total internal reflection mode of excitation has significant advantages (over classic front-face excitation) for practical assay development. The limited evanescent wave excitation volume makes it possible to minimize the background signal and use the immunoassay with no need for any washing steps.

Antibodies↗
PubMed2004

Myoglobin immunoassay utilizing directional surface plasmon-coupled emission.

We described an immunoassay for the cardiac marker myoglobin on a thin silver mirror surface using surface plasmon-coupled emission (SPCE). SPCE occurs for fluorophores in proximity (within approximately 200 nm) of a thin metal film (in our case, silver) and results in a highly directional radiation through a glass substrate at a well-defined angle from the normal axis. We used the effect of SPCE to develop a myoglobin immunoassay on the silver mirror surface deposited on a glass substrate. Binding of the labeled anti-myoglobin antibodies led to the enhanced fluorescence emission at a specific angle of 72 degrees . The directional and enhanced directional fluorescence emission enables detection of myoglobin over a wide range of concentrations from subnormal to the elevated level of this cardiac marker. Utilizing SPCE allowed us also to demonstrate significant background suppression (from serum or whole blood) in the myoglobin immunoassay. We expect SPCE to become a powerful technique for performing immunoassays for many biomarkers in surface-bound assays.

Immunoassay↗
PubMed2004

Multi-wavelength immunoassays using surface plasmon-coupled emission.

We describe a new method for multi-wavelength immunoassays using surface plasmon-coupled emission (SPCE). This phenomenon is coupling of excited fluorophores with a nearby thin metal film, in our case silver, resulting in strongly directional emission into the underlying glass substrate. The angle at which the radiation propagate through the prism depends on the surface plasmon angle for the relevant wavelength. These angles depend on emission wavelength, allowing measurement of multiple analytes using multiple emission wavelengths. We demonstrated this possibility using antibodies labeled with either Rhodamine Red-X or AlexaFluor 647. These antibodies were directed against an antigen protein bound to the silver surface. The emission from each labeled antibody occurred at a different angle on the glass prism, allowing independent measurement of surface binding of each antibody. This method of SPCE immunoassays can be readily extended to 4 or more wavelengths.

Animals↗
PubMed2004

Immunoassays based on directional surface plasmon-coupled emission.

We described a new approach to immunoassays using surface plasmon-coupled emission (SPCE). Fluorescence is visually isotropic in space, so that the sensitivity is limited in part by the light collection efficiency. By the use of SPCE, we can efficiently collect the emission and convert it to a cone-like directional beam in a glass substrate. SPCE is the coupling of excited fluorophores with a thin metal film, resulting in radiation of surface plasmons into the higher refractive index media. We used SPCE to develop a model affinity assay using labeled goat anti-rabbit immunoglobulin G (IgG) antibodies against rabbit IgG bound to a 50-nm-thick silver film. Binding of labeled IgG to the surface resulted in increased intensity observed at an angle of 75 degrees from the normal in the glass substrate. The SPCE intensity depends on proximity of the fluorophore to the silver film and does not require a change in quantum yield upon binding. The use of SPCE is shown to provide background suppression because excited fluorophores distant from the silver film do not result in SPCE. Sensitivity and selectivity can be further increased by excitation under conditions of surface plasmon resonance (SPR) because the evanescent field is enhanced by the resonance interaction and excitation is limited to the region near the metal. We believe SPCE will provide a new technology for high sensitivity and selectivity in surface-bound assays and microfluidic systems.

Animals↗
PubMed2004

Advances in surface-enhanced fluorescence.

We report recent achievements in metal-enhanced fluorescence from our laboratory. Several fluorophore systems have been studied on metal particle-coated surfaces and in colloid suspensions. In particular, we describe a distance dependent enhancement on silver island films (SIFs), release of self-quenching of fluorescence near silver particles, and the applications of fluorescence enhancement near metalized surfaces to bioassays. We discuss a number of methods for various shaped silver particle deposition on surfaces.

Algorithms↗