Application Of CdTe Quantum Dots (QDs) And QDs Labeled Fluorescent Microspheres In Biological Analysis

Semiconductor nanoparticles (Quantum QDs) are a specific kind of nanocrystal from one to one hundred nanometers in diameter that have recently found their way into medical and biological applications. Because of their unique optical and electronic spectrum, ability to be tuned, and neglectable optical bleach phenomenon, they provide an extremely good fluorescent signal, allowing them to be used not only for more effective fluorescent labeling, but also as an ideal bioconjugated fluorescent probe for bioanalysis. In this work, Application of QDs and QDs labeled microspheres in biological analysis were studied.In the first part of the work, Fluorescence resonance energy transfer (FRET) occured between two quantum dots with immunocomplexes of antigen and antibody as a bridge. FRET often occurs when the electronic excitation energy of donor chromophore is transferred to nearby acceptor molecule via a through—space dipole—dipole interaction between the donor—acceptor pair, and the FRET process will be efficient if there is an appreciable overlap between the emission spectrum of the donor and the absorption spectrum of the acceptor. In this work, QDs (573nm)/rabbit IgG—goat-anti-rabbit IgG/QDs(638nm) immunocomplexes were prepared utilizing antigen—antibody interaction. 573nm—emitting QDs was conjugated to antigen (rabbit IgG) and 638nm—emitting QDs was conjugated to antibody (goat-anti-rabbit IgG) via electrostatic/hydrophilic self-assembly, respectively. The mutual affinity of the antigen and antibody brought two kinds of QDs close enough to result in fluorescence resonance energy transfer (FRET) between them, the luminescence emission of QDs (573nm) was quenched while that of QDs (638nm) was enhanced. In addition, the fluorescence characteristics of the QDs - IgG conjugates were strongly related to pH value and ionic strength.In the second part in this paper, a method for preparing hydrophilic CdTe quantum dots (QDs) labeled fluorescent polystyrene (PS) microspheres and its application in immunoassay has been described in this paper. PS microspheres of 3μm diameter were used as templates for the deposition of CdTe QDs /polyelectrolyte (PE) multilayers, followed by an outermost layer of avidin. All the depositions were carried out via the layer-by-layer (LbL) electrostatic self-assembly technique. Fluorescence assays showed that the fluorescent microspheres retain their specific biorecognition. Based on the optical characteristics of the fluorescent microspheres, a fluoroimmunoassay method employing bioconjugation of antibody and antigens was carried out in this paper, and the competitive immunoassay was adopted for the quantitative analysis of rabbit IgG, the range from 3.13.-31.3 mg/L, and the correlation coefficient can reach 0.998.