Simultaneous determination of concanavalin A and peanut agglutinin by dual-color quantum dots

In this work, we designed a novel detection strategy to realize simultaneous determination of multiplex lectin by labeling glucosamine (G1) and galactosamine (G2) with different-colored semiconductor quantum dots (QDs). On the basis of the agglutination of the aminosugar-labeled QDs induced by the exclusive binding between the lectin and sugar on the QDs surfaces, the fluorescence emission of the QDs supernatant after centrifugation decreased with relevant lectin concentration [i.e., when concanavalin A (Con A) exists alone], only green color fluorescence emission from QDs-G1 supernatant decreased, so it is peanut agglutinin (PNA) and red color fluorescence emission from QDs-G2. Moreover, since QDs can be simultaneously excited with multiple fluorescence colors and have a larger Stokes shift than organic fluorophores, when both Con A and PNA are present in the sample, both of the green and red color fluorescence emission from QDs-G1 and QDs-G2 supernatant would decrease, thus realizing the simultaneous determination of Con A and PNA. The detection limits of Con A and PNA are 0.30 and 0.18 nM (3σ), respectively. Furthermore, the present detection method not only can determine the protein/lectins by fluorescence spectral method but also can realize visualization detection by UV lamp illumination. To the best of our knowledge, this is the first report of such analytical method in multiple and simultaneous lectin detection.