Biomedical subjects

Dosi Dosev

Publications and source records attributed to Dosi Dosev.

4 recordsLinked to original sources

PubMed2006

Optical characterization of eu-doped and undoped gd(2)o(3) nanoparticles synthesized by the hydrogen flame pyrolysis method.

Rare-earth-doped nanoparticles are promising materials for fluorescent labeling, as they are characterized by a high Stokes shift, narrow emission spectra, long lifetimes, minimized photobleaching, and low toxicity. We examined the structural and optical properties of europium-doped gadolinium oxide nanoparticles synthesized by the flame pyrolysis method, with specific emphasis on full spectral characterization and fluorescence kinetics. The emission-excitation characterization revealed the presence of predominantly monoclinic but also highly luminescent cubic phases with a prominent oxygen-to-europium charge-transfer band in the 230-260 nm range. A broad emission band in the visible region, corresponding to a similar band in undoped Gd(2)O(3), related to the matrix surface defects, was observed in time-gated spectroscopy of doped nanopowders. All of the examined nanopowders showed very short decay components, on the order of 2 ns, and much longer millisecond decay times characteristic of lanthanide ions. At intermediate times, on the order of 20-100 ns, a complex behavior of the decay was observed, indicative of progressive energy transfer to the lanthanide ion, which varied with different intrashell transitions. Structural characterization data by means of XRD measurements allowed for unambiguous determination of the Eu:Gd(2)O(3) crystallographic structure and cell dimensions to be consistent with a predominantly monoclinic phase.

Journal Article↗

PubMed2006

Eu3+-doped Gd2O3 nanoparticles as reporters for optical detection and visualization of antibodies patterned by microcontact printing.

Lanthanide oxide nanoparticles are promising luminescent probes in bioanalysis, because of their unique spectral properties, photostability, and low-cost synthesis. We report for the first time the application of europium-doped gadolinium oxide (Eu:Gd2O3) nanoparticles to the optical imaging of antibody micropatterns. The nanoparticles were synthesized by spray pyrolysis and coated with antibody (IgG) molecules by physical adsorption. Our experiments showed that the Eu:Gd2O3 is a good biocompatible solid support for antibody immobilization. The antibodies (anti-rabbit IgG) immobilized on the nanoparticles had excellent biological activity in the specific recognition reaction with rabbit IgG patterned in line strips (10 micromx10 microm) on a glass substrate by use of a micro-contact printing technique. The specific immunoreaction was confirmed by two independent microscopic techniques-fluorescence and scanning electron microscopy (SEM). Both microscopic images revealed that the nanoparticles were organized into designated structures as defined by the microcontact printing process with negligible non-specific binding. The nanoparticles can be used as fluorescent markers in a variety of immunosensing applications in a microscale format.

Adsorption↗

PubMed2005

Microarray immunoassay for phenoxybenzoic acid using polymer encapsulated Eu:Gd2O3 nanoparticles as fluorescent labels.

Currently, detection in microarray bioanalysis is based mainly on the use of organic dyes. To overcome photobleaching and spectral overlaps we applied a new type of fluorophore, crystalline europium-doped gadolinium oxide (Eu:Gd2O3) nanoparticles, as labels in immunoassay microarrays. The Eu:Gd2O3 nanoparticles synthesized by spray pyrolysis offer narrow red emission, large Stokes shift, photostable laser-induced fluorescence with a long lifetime (1 ms). The amino functionalization of the particles was achieved by poly(L-lysine) (PL) encapsulation. The formation of a stable PL shell was confirmed by TEM analysis, colloidal stability studies, and quantification of the surface reactive amino groups. The PL-encapsulated particles were covalently conjugated to antibodies and successfully applied as reporters in a competitive fluorescence microimmunoassay for phenoxybenzoic acid (PBA), a generic biomarker of human exposure to pyrethroid insecticides. Microarrays were fabricated by microcontact printing of BSA-PBA in line patterns (10 x 10 microm). Confocal fluorescence microscopy combined with internal standard (fluorescein) calibration was used for quantitative measurements. The microarray immunoassay demonstrated a limit of detection of 1.4 microg L(-1) PBA. This work suggests the potential application of lanthanide oxide nanoparticles as fluorescent probes in microarray and biosensor technology, immunodiagnostics, and high-throughput screening.

Antibodies↗

PubMedDate not supplied

Application of luminescent Eu:Gd2O3 nanoparticles to the visualization of protein micropatterns.

Nanoparticle phosphors made of lanthanide oxides are a promising new class of tags in biochemistry because of their large Stokes shift, sharp emission spectra, long luminescence lifetime, and good photostability. We demonstrate the application of these nanoparticles to the visualization of protein micropatterns. Luminescent europium-doped gadolinium oxide (Eu:Gd2O3) nanoparticles are synthesized by spray pyrolysis. The size distribution is from 5 to 200 nm. The particles are characterized by means of laser-induced fluorescent spectroscopy and transmission electron microscopy (TEM). The main emission peak is at 612 nm. The nanoparticles are coated with avidin through physical adsorption. biotinylated bovine serum albumin (BSA-b) is patterned on a silicon wafer using a microcontact printing technique. The wafer is then incubated in a solution of avidin-coated nanoparticles. Fluorescent microscopic images reveal that the nanoparticles are organized onto designated area, as defined by the microcontact printing process. The luminescent nanoparticles do not suffer photobleaching during the observation, which demonstrates their suitability as luminescent labels for fluorescence microscopy studies. More detailed studies are preformed using atomic-force microscopy (AFM) at a single nanoparticle level. The specific and the nonspecific binding densities of the particles are qualitatively evaluated.

Biosensing Techniques↗