Fabrication And Application Of Bi-color CdTe Quantum Dots Encoding Sensor

In recent years, QDs have attracted great attention because of their unique opticaland surface properties. Especially in the biomedical field, including the detection ofthe protein, DNA sequence detection, immunofluorescence assay, biosensordevelopment, cytology, animal medicine and so on.Electrostatic self-assembly technology （LbL） has developed rapidly in recentyears. The advantages of this method is the self-assembly of membrane structure andcontrollable thickness. And the electrostatic adsorption is non-specific binding, whichmake the biological macromolecules, polymers, etc. can be easily assembly to thefilm. This technology was employed in my two parts experiments of this thesis.In this paper, CdTe QDs capped with MPA were prepared. Furthermore,multicolor quantum dots （QDs）-encoded fluorescent nanoprobe were prepared byreverse microemulsion method and Layer-by-Layer （LbL） assembly. Then they aremade into the different sensors respectively and applied to the detection of heavymetal ions and the detection of mutant DNA sequences. Specific studies are asfollows:The functional multilayer films were assembled by layer-by-layer （LbL）deposition of oppositely charged CdTe QDs and poly（dimethyldiallylemmoniumchloride）（PDDA）. Then the outermost layer of2-QDMF was cross-linked to bovineserum albumin （BSA）, polyethylene glycol （PEG） or glutathione （GSH）. It was foundthat when BSA modified quartz slides were immersed into solutions containing Hg²⁺and Cu²⁺respectively, the2-QDMF can be quenched by Hg²⁺, but not by Cu²⁺. Underthe optimization conditions, the quenched photoluminescence （PL） intensities ofmultilayer films was almost linearly proportional to the concentration of Hg²⁺in therange of1.0×10^-8 to1.0×10^-6mol/L and the detection limit was4.5×10^-9mol/L.Furthermore, Hg²⁺concentration could also be directly readout using the “Hg²⁺ruler”with bi-color quantum dots. This colorimetric method has the advantages of simplification and convenience, which will become a trend in rapid andsemi-quantitative measurement.Firstly, red emitting CdTe QDs were encapsulated in silica nanoparticles byreverse microemulsion method, and yellow emitting QDs were deposited on thesurface of silica nanoparticles to form multicolor QDs@silica beads/QDs （QSQ）nanoprobe system. The resulting QSQ nanoprobe-capture DNA conjugates showedsequence-specific hybridization with target DNA （v-raf murine sarcoma viraloncogene homolog B1，BRAF of PTC）. Under the optimization conditions, thephotoluminescence （PL） intensities of QSQ nanoprobe was almost linearly to theconcentration of BRAF DNA in the range of0.25to25nM and the detection limit was0.1nM. This method has a mild reaction, low-consuming, easy to control the accuratecoding and almost no quantum dot aggregation. We further utilized multispectralimaging system to distinguish QDs optical code in the QSQ nanoprobe, and theproposed method was used in HepG2cell imaging, which indicates that it haspractical applications in DNA detection. This method also can be extended to otherproteins, viruses, antibody-antigen immunoassay.