Fluorometric immunoassay for human serum albumin based on its inhibitory effect on the immunoaggregation of quantum dots with silver nanoparticles

• Competitive sensitive immunoassay for detection of human albumin based on resonance energy transfer between CdSe quantum dots and anisotropic silver nanoparticles was developed
• Changes in fluorescence intensity as a result of interaction of nanoparticles correlate with albumin concentration in media.

Quantitative determination of HSA was conducted by competitive immunoassay. Inhibition of aggregation of antibody conjugated quantum dots (QD) with albumin conjugated silver nanoparticles (AgNPs) in the presence of HSA was conducted. If antibody-loaded CdSe QDs aggregate with HSA-coated silver nanoparticles the distance between the two kinds of nanoparticles will be reduced enough to cause fluorescence resonance energy transfer (FRET). In this case the yellow fluorescence of the Ab-QDs is quenched. However if HSA (antigen) is added to the Ab-QDs their surface will be blocked and they cannot aggregate any longer with the HSA-AgNPs. Hence, fluorescence will not be quenched. The drop of the intensity of fluorescence (peaking at 570 nm) is inversely correlated with the concentration of HSA in the sample. The method allows to determine HSA in the 30–600 ng·mL−1 concentration range.

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