| In recent years, semiconductor quantum dots (QDs) have attracted great interests because of their unique optical and surface properties. As a new fluorescent probe, QDs have made great progress in bioassay, including the detection of Pharmaceuticals, biological imaging, immunoassays and virus detection.In this thesis, some biological analysis based on CdTe quantum dots and Mn-doped ZnSe quantum dots were studied. Three different methods (resonance light scattering, fluorescence quenching, and electrochemical biosensor) were used respectively in each study. The main contents and results are summarized as follows:(1) A sensitive QDs-based resonance light scattering (RLS) assay method for the detection of Newcastle disease virus (NDV) antibody had been developed. CdTe quantum dots (QDs) were conjugated with Newcastle disease virus and used as RLS-based probes to detect NDV antibody. The electrostatic interaction between CdTe QDs and NDV resulted in enhanced resonance light scattering (RLS) signal characterized at 555 nm. Upon the addition of NDV antibody, QDs-NDV formed dispersive immunocomplex that can decrease the RLS signal. The decreased RLS intensity at 555 nm (ΔIRLS) was linearly proportional to the concentration of NDV antibody (Canti-NDV) in the range of 0.5-50 ng/mL, with correlation coefficient of 0.974 and detection limit of 0.1 ng/mL under the optimization conditions. The proposed method was applied to the determination of NDV antibody in spiked samples with satisfactory results.(2) We attempted to develop a novel application of Mn-doped ZnSe quantum dots (Mn:ZnSe d-dots) as probes to detect L-tyrosine (L-Tyr). The bio-conjugates of horseradish peroxidase (HRP)-conjugated Mn:ZnSe d-dots were used in the enzyme catalyzed reaction of L-Tyr with H2O2.Compared with traditional CdTe QDs, Mn: ZnSe d-dots have better biocompatibility and less negative impact on enzyme catalyzed system. In HRP-conjugated Mn:ZnSe-L-Tyr-H2O2 system, electron transfer occurred between Mn:ZnSe d-dots and HRP. It resulted in the luminescence quenching of the Mn:ZnSe d-dots., which can be used to detect L-Tyr. The coupling of efficient photoluminescence (PL) quenching of Mn:ZnSe d-dots and the effective enzyme-catalysis can afford a simple and sensitive method for L-Tyr detection. The Mn:ZnSe d-dots-enzyme catalyzed system displays great potential in the development of enzyme-based biosensing systems for various analytes.(3) A hybrid film was fabricated by casting hemoglobin (Hb)-CdTe quantum dots-polyvinyl alcohol (PVA) suspension on a glassy carbon electrode (GCE). Then it was covered with thin Nafion film and the Nafion/Hb-CdTe-PVA/GCE was constructed. In the hybrid film, the ultraviolet visible (UV-Vis) absorption spectra of Hb kept almost unchanged. The direct electrochemistry of Hb on this surface was studied by cyclic voltammetry (CV) and different pulse voltammetry (DPV) method. The results indicated that CdTe quantum dots could effectively promote the direct electron transfer of Hb. It was also found that the modified electrode could be used as a sensor for NO2-; the linear range of detection was 0.04-0.40 mM, with a detection limit of 30μM. The sensor exhibited high sensitivity, reproducibility and stability.
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