| Now, there is great development in bioimaging and biodetection based onquantum dots(QDs) probes, and their potential application in the early sensitive andspecific diagnosis of disease has promoted the research of QDs. In this paper, wefirstly studied the different influence on the fluorescence properties of CdSe QDs,then two methods to prepare water-soluble QDs were investigated, as well as thepreparation of magnetic fluorescent nanocomposites. Finally, the QDs probes wereapplied in microfluidic biochip assays.Firstly, we prepared high crystallization and monodispersion CdSe QDs bycolloid chemistry method. The emission spectra of CdSe QDs were Gaussiansymmetric with full width at half maximum (FWHM) less than30nm. During thepreparation, the influences of the ratio of Cd and Se precursors, reactive temperature,reactive time and the materials of shell on the fluorescence properties of QDs wereinvestigated. The results indicated that when the ratio of Cd and Se precursors was1:6，we could get the highest quality QDs; As the reactive temperature or timeincreased, the absorption and emission peak of QDs were obviously red shifted.Significantly, the reactive temperature had a great influence on the quantum yield(QY) of QDs. As for the core/shell QDs, there was a marked increase in the QY with anarrow FWHM after CdSe QDs coated with inorganic shells.Secondly, in order to apply the QDs in biodetection, the oil-soluble CdSe QDsneed be transferred into aqueous phase. Two methods were employed to modify theQDs, those were polymer encapsulation method and ligand exchange method. In thefirst method, the poly(styrene-co-maleic anhydride) terminated with cumene (PSMA)was introduced to coat the oil-soluble QDs by the hydrophobic interaction, then theQDs@PSMA were transferred into aqueous phase by a ring-opening reaction andfunctionalized with Jeffamine M-1000polyetheramine (M1000). The water-solubleQDs@PSMA showed a good fluorescence and colloid stability in different pHsolution and a low protein absorption in PBS solution with10%fetal bovine serum(FBS). In addition, it also exhibited a high specificity in fluoimmunoassay. In the second method, a kind of self-synthesized multidentate polymer PGA-g-MEA wasapplied to transfer the oil-soluble QDs into aqueous phase by ligand exchange. TheQDs@PGA-g-MEA had a quite small size about10nm, and showed a high stabilityin pH2-13aqueous solution as well as in different temperature.Thirdly, the magnetic and fluorescent bifunctional nanocomposites (MNQDNCs)were prepared by a ring-opening reaction to conjugate QDs and magneticnanoparticles (MNs). And meanwhile, the MNQDNCs were functionalized withM1000by the same ring-opening reaction. The nanocomposites exhibited a highcolloidal and photochemical stability over a wide pH range (pH2-13), a low proteinadsorption in PBS with10%FBS at37°C, and showed a low nonspecific bindingincubated with Hela cells. Sandwich fluoroimmunoassay and magnetic targetingresults indicated that the nanocomposites can be successfully applied in a variety ofdiagnosis, bioimaging and delivery applications.Finally, we initially constructed microfluidic biochip detection system basedon quantum dots fluorescent probes. The system mainly included four parts, whichwere as follows:1) the sandwich reaction detection system based on quantum dotsprobes and quantum dots coded microspheres；2) the microfluidic biochip allowingencoded microspheres to pass through the interrogation region quickly in single row；3) the detection system which can read the coded microspheres signal in real time;4)information processing systems. Based on the microfluidic biochip arrays system, thereal-time decoding of encoded microspheres and sandwich immunoassay informationwere realized now. The work has laid a solid foundation for the future furtherhigh-throughput detection. |
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