Plate-based biochemical assay using quantum dots as a fluorescent labeling agent

A biochemical assay based on fluorescence imaging analysis by confocal laser scanning as a detection technique is specified. The method involved a glass plate coated with nitrocellulose (NC), where α-human-IgE-biotin at various concentrations was immobilized on an NC plate. Luminescent core-shell CdSe/ZnS QD–SA conjugates were then used as a fluorescent labeling agent to be captured specifically by biotinated α-human-IgE immobilized in a micro-array by affinity binding between SA and biotin in a plate-based biochemical assay. A confocal laser scanner was used to detect the fluorescence signals from the α-human-IgE-biotin–SA–QD complex. Experimental findings reveal that fluorescence intensity of QD–SA saturated at QD concentrations above 0.4 mg/ml. Moreover, a calibration curve between the fluorescence intensity and the concentration of α-human-IgE-biotin is plotted. The range of detectable concentrations of biotinlated α-human IgE was found to be between 3.3 and 100 μg/ml in the α-human-IgE-biotin–SA–QD complex. Therefore, the results were consistent with the binding specificity in a plate-based biochemical assay, as determined using luminescent QDs as a labeling agent.