| Quantum dots(QDs) had become ideal fluorescent marker due to their excellent fluorescence properties. Magnetic nanomaterials had been paid much attention in the field of biomedicine because of their excellent magnetic manipulation/separation abilities. However, only a single magnetic or fluorescence property had not met the requirements of biomedical. The preparation of fluorescent-magnetic composite nonmaterials had become the popular project in biomedical research. In the previous work, the fluorescent-magnetic composite nanomaterials were commonly applied to the separation and detection of a variety of target substances from mixed samples by single-component analysis mode. However, this mode has a series of flaws, such as complicated operation, time-consuming, laborious and low efficiency. In order to overcome these obstacles, fluorescent-magnetic composed nanomaterials with gradient magnetic susceptibility were constructed by our lab, which were able to complete the separation and detection of target substances in one-step, and improved work efficiency ultimately. Our previous studies have showed the successfully fabrication of fluorescent-magnetic multifunctional nanoparticles with different magnetic response by the strategies of electrostatic interaction based layer-by-layer self-assembly approach and of reverse microemulsion encapsulation. However, the fabrication of self-assembly based on electrostatic had a poor binding force which led to the multifunctional nanoparticles’ s instability. And the reverse microemulsion encapsulation had suffered from the limited loading number of QDs and maghemite in each polymer which led to a poor magnetic gradient and the fluorescent quenching that arose from the direct contact of QDs with maghemite. To overcome the drawbacks of these two methods, the layer-by-layer self-assembly based on thiol-metal interaction were studied in this work. Therefore, this thesis aimed to fabricate fluorescent- magnetic multifunctional nanospheres which have different magnetic response intensity. Then, they were expected to conjugate with biomolecule on their surface, then applied to the separation and detaction of targets. The strategy exhibits great potential to accomplish nearly simultaneous separation and analysis of multi-components from complex samples system, which are significantly benefit for disease diagnosis, food safety control, environmental monitoring and so on. Based on discussed above, the work as the following:(1) Preparation of fluorescent-magnetic multifunctional nanospheres with different magnetic response intensity.First of all, the γ-Fe2O3 were prepared through the thermolytic toutes by reacting inorganic precursors in organic solvents at high temperatures.Through the characterization of magnetic properties, particle size,it could be inferred that the γ-Fe2O3 magnetic nanoparticles with a high saturation magnetization and stability and the diameter of 10 nm were successfully prepared.Secondly, the 100 nm of MPS were fabricated. The effects of the volume of(3-mercaptopropyl) trimethoxysilane and ammonia were studied. Through the characterization of particle size, it could be inferred that the MPS with the diameter of 100 nm were successfully prepared.Most importantly, the fluorescent-magnetic multifunctional nanospheres with different magnetic response intensity were fabricatied by layer-by-layer based on the thiol-metal interaction. The different magnetic response intensity of nanospheres were achieved by contralling layers of γ-Fe2O3 in the process. At last, the fluorescent- magnetic multifunctional nanospheres with high fluorescence intensity and different magnetic response intensity were successfully prepared.(2) The preliminary application of fluorescent-magnetic multifunctional nanospheres with different magnetic response intensityMultifunctional nanospheres were respectively modified with avidin, and then conjugated with the aptamer which was labled by fluorochrome and biotin. So the fluorescent-magnetic-biotargeting multifunctional nanobioprobes were successfully prepared and then applied to recognize and separate the target substances from mixed samples. Our results showed that the multifunctional nanospheres could be achieved magnetic separation and capture under certain external magnetic field. The strategy exhibits great potential to accomplish nearly simultaneous separation and analysis of multi-components from complex samples. |
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