Synthesis Of Nanoparticles Quantum Dots And Nano Gold And Their Applications In Immunoassays

Nanotechnology and biotechnology are two key technologies of the 21st century.Herein, nanoprobe technology and nanobiosensing technology are one of the intersectant research areas of nanotechnology, biotechnolog, probe technology and sensing technology and becomes an emerging area and has attracted world-wide attention and research. Nowadays, nanomaterials, or matrices with at least one of their dimensions ranging in scale from 1 to 100 nm, display unique physical and chemical feats because of the quantum size effect,mini size effect,surface effect and macro-quantum tunnel effect. Nanomaterials are revolutionizing the development of bioprobes and biosensors. How to construct and improve the sensitivity, stability and other attributes of nanoparticles probes and sensors for better application and expand use by using nanomaterials rernain to be further studied.The immunoassay method is the use of antigen-specific antibody response to a deter- mination of trace substances in a high-sensitivity, high selectivity of the method. In recent years, nanoprobe technology and nanobiosensing technology as currently popular techniques are being developed for the detection of biomarkers. And great efforts have been made worldwide to develop and improve immunoassays for the detection of biomarkers with the aim of creating portable and affordable method. Despite of many advances in this field, it is still a challenge to exploit new nanoparticles that can improve the simplicity, selectivity, and sensitivity of clinical immunoassay, to meet the require- ments of modern medical diagnostics and biomedical research applications.We synthesized quantum dots, gold nanoparticles and applied these nanoparticles to fluorescent immunoassay, electrochemical immunoassay, the results show that the selectivity and sensitivity were greatly improvedThe major contents in this dissertation are described as follows:Chapter One In this chapter one, the immunoassay method, nanoparticles quantum dot synthesis and application in biological and chemical analysis, the gold nanoparticles application in the electrochemical immune analysis were discussed.Chapter Two In this study, the preparation of a new kind of magnetic and luminescent Fe₃O₄/CdTe nanocomposites was demonstrated. Superparamagnetic Fe₃O₄ nanoparticles were first synthesized by hydrothermal coprecipitation of ferric and ferrous ions, followed by the modification of their surfaces with tetramethylammonium hydroxide (TMAOH) and the chemical activation with aspartic acid. The surface-modified Fe₃O₄ nanoparticles were then covalently coated with CdTe quantum dots (QDs), which were modified with mercaptoacetic acid (MPA), to form the Fe₃O₄/CdTe magnetic and luminescent nanocomposites through the coordination of the amino groups on the surfaces of Fe₃O₄ and the carboxyl groups on CdTe QDs. The structure and properties of as-synthesized nanocomposites were characterized. It was indicated that the nanocomposites possessed structure with an average diameter of 40-50 nm, yellow-green emission feature and room temperature ferro-magnetism. Both the fluorescence and UV-vis absorption spectra of the nanocomposites showed a blue shift comparing with those of CdTe QDs. The mechanism of the blue shift was presented. The nanocomposites retained the ferromagnetic property with a saturation magnetization of 8.9 emu/g.In oil phase synthesis of a stable CdSe/CdS nanocrystalline, and through mercaptoacetic acid as stabilizers and modifier solubility realize water-soluble quantum dot.Chapter Three This work demonstrates the feasibility of detecting clenuterol residue in pig urine using CdSe/CdS quantum dots as fluorescent labels based magnetic core/shell Fe₃O₄/Au nanoparticles (MCFN) as solid carriers. The detection of clenbuterol is carried out by a fluoroimmunoassay-based biosensor using competitive binding between conjugated clenbuterol antigen-CdSe/CdS QDs and free clenbuterol with immobilized clenbuterol antibodies on MCFN. This assay method allows for clenbuterol determination in a linear working range of 0.5 - 20000 pg.mL^-1. It would provide a simple, rapid, and ultra-sensitive detection method for clenbuterol or other biomolecular analysis.Chapter Four This work demonstrated the feasibility of detecting hydrocor- tisone in cosmetics using a novel CdSe/CdS quantum dots-based competitive fluoroimmunoassay with magnetic core/shell Fe₃O₄/Au nanoparticles (MCFN) as solid carriers. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.5 to 15000 pg.mL^-1and a low detection limit of 0.5 pg.mL^-1. The proposed method was successfully applied to the determination of hydrocortisone in cosmetics with satisfactory results.Chapter Five This work demonstrated the feasibility of detecting estriol in cosmetics using a novel CdSe/CdS quantum dots-based competitive fluoroimmunoassay with ELISA plate as solid carriers. The proposed method was characterized by simplicity, rapidity, and high sensitivity with a wide linear working range of 0.1 pg.mL^-1to 100 ng.mL^-1and a low detection limit of 0.1 pg.mL^-1. The proposed method was successfully applied to the determination of estriol in cosmetics with satisfactory results.In this article, we have constructed several potentiometric immunosensors immobilized antigen/antibody onto substrate electrode based on nanoparticles/compound nanoparticles, poly(amidoamine) G4-dendrimer, nanogold hollow microsphereas matrixes. The detailed materials are shown as follows:Chapter Six A simple and sensitive electrochemical immunosensor was designed for the determination of ferritin (FeAg, as a model) in human serum by using a nanogold hollow- microsphere (NGHS)-functionalized interface as an immunosensingprobe. The presence of NGHSs provided a congenial microenvironment with large surface coverage for the immobilization of ferritin antibodies (FeAb). The formation of the antibody-antigen complex by a simple onestep immunoreaction between the immobilized FeAb and FeAg in sample solution introduced a change of membrane charge on the surface of the immunosensing probe. Thus, local potential variations could be detected by potentiometry. Compared to conventional gold nanoparticle probes, the NGHS-modified immunosensors exhibit wide dynamic range from 1.0 to 500 ng·mL?1 toward FeAg, with a detection limit of 0.1 ng·mL?1 (at 3?). The selectivity, reproducibility and stability of the immunosensors are acceptable. The assay was evaluated with clinical serum specimens (n = 25), and excellent correspondence with the reference enzyme-linked immunosorbent assay method wasobtained.Chapter Seven A simple and portable electrochemical immunosensor for the detection of total prostate specific antigen (t-PSA) in human serum was developed using a double-layer nanogold particles and dendrimer-functionalized polyvinyl chloride (PVC) membrane as immunosensing interface. To fabricate such a multifunctional PVC electrode, an o-phenylenediamine-doped PVC membrane was initially constructed, then nanogold particles and poly(amidoamine) G4-dendrimer with a sandwich-type format were assembled onto the PVC membrane surface, and then t-PSA antibodies(anti-PSA) were adsorbed on the nanogold surface. The detection principle of the immunosensor is based on the change in the electric potential before and after the antigen-antibody interaction. The experimental conditions and the factors influencing the performance of the immunosensor were investigated. Under optimal conditions, the proposed immunosensor exhibits good electrochemical behavior in the dynamic range of 0.5?18 ng.mL^-1relative to t-PSA concentration with a relative low detection limit of 0.1 ng.mL^-1(S/N3). The precision, reproducibility, and stability of the immunosensor are acceptable. In addition, 43 serum specimens were assayed by the as-prepared immunosensor, and consistent results were obtained in comparison with those obtained by the standard enzymelinked immunosorbent assay (ELISA). Compared with the conventional ELISAs, the developed immunoassay system was simple and rapid without labeling and separation steps. Importantly, the immobilization and detection methodologies could be extended for the immobilization and detection of other biomarker...