ABSTRACT
A quantitative multianalyte immunoassay utilizing luminescent upconverting single-crystal nanoparticles as reporters on an antibody array-in-well platform was demonstrated. Upconverting nanoparticles are inorganic rare earth doped materials that have the unique feature of converting low energy infrared radiation into higher energy visible light. Autofluorescence, commonly limiting the sensitivity of fluorescence-based assays, can be completely eliminated with photon upconversion technology because the phenomenon does not occur in biological materials. Biotinylated antibodies for three analytes (prostate specific antigen, thyroid stimulating hormone, and luteinizing hormone) were printed in an array format onto the bottom of streptavidin-coated microtiter wells. Analyte dilutions were added to the wells, and the analytes were detected with antibody-coated upconverting nanoparticles. Binding of the upconverting nanoparticles was imaged with an anti-Stokes photoluminescence microwell imager, and the standard curves for each analyte were quantified from the selected spot areas of the images. Single analyte and reference assays were also carried out to compare with the results of the multianalyte assay. Multiplexing did not have an effect on the assay performance. This study demonstrates the feasibility of upconverting single-crystal nanoparticles for imaging-based detection of quantitative multianalyte assays.
Subject(s)
Immunoassay/instrumentation , Luminescent Agents/chemistry , Luteinizing Hormone/analysis , Nanoparticles/chemistry , Prostate-Specific Antigen/analysis , Thyrotropin/analysis , Animals , Antibodies, Immobilized/chemistry , Antibodies, Immobilized/immunology , Biotinylation , Female , Humans , Luminescent Measurements/instrumentation , Luteinizing Hormone/immunology , Male , Prostate-Specific Antigen/immunology , Protein Array Analysis/instrumentation , Sensitivity and Specificity , Thyrotropin/immunologyABSTRACT
According to a widely accepted idea, only the results of attentional selection reach visual awareness. A competing model postulates that awareness is independent of attentional selection: contents of subjective visual experience may also exist without the contribution of attention. We tested these competing models by tracking the independent contributions of selective attention and awareness to electrophysiological brain responses. Our results showed that the earliest effects of visual awareness emerged earlier than the effects of attention and regardless of the presence or absence of attention. The early effects of attention were elicited regardless of the presence or absence of awareness. The results suggest that visual awareness and selective attention are initially independent of each other.
