The Synthesis, Characterization Of Multifunctional Silica Nanoparticles And Its Application For Bioseparation And Bioanalysis

There is no doubt that instant and sensitive detection of pathogens such as bacteria,viruses offers obvious clinical benefit.However,there is,to date,no general assay that could detect bacteria at very love concentrations without incubation or amplification by polymerase chain reaction(PCR).The presence of the impurities in a Complex sample may suppress or interfere the signal of the target microogrnaism. Separation of target pathogen from the samples can lead to Pre-enriching and decreasing the interference from the matrix samples.The magnetic nanoparticles(NPs) have the superparamagnetic property which makes the heterogeneous separation easily under the external magnetic field without centrifugation and filtration.However, most of the magnetic NPs prepared by the existing method are hydrophobic and difficult to be functionalized,which restrict they application in biochemistry.Using the silica(SiO₂) to coat the magnetic NPs will improve their dispersion without changing their characteristic,and the SiO₂ will also afford a good template for further functionalization.This magnetic controlled system will has potential application in the bacteria separation and detection.Combining with fluorescent dye will lead to a controllable fluorescent system which was not only controllable but also detectable, and offer great help to the researching of many mechanism problems in biology.This dissertation has using various methods to prepare the composite SiO₂ NPs with multi-functions including biotargetting,fluorescent and superparamagnetic.The NPs were used to the V.alginolyticus' magnetic separation and detection.This dissertation consists of four chapters.In chapter one,the conception and the characteristic of nanomaterials were summarized.And then some nanomaterials which relate to bioanalytical chemistry such as Au NPs,quantum dots(QDs),polymer NPs and SiO₂ NPs,and their applications were introduced simply.Last especially discussed SiO₂ and its composite materials' synthesis methods,and their applications in bioanalytical chemistry,based on that the research conceives were put forward. In chapter two,the mesoporous SiO₂ NPs were synthesized using reverse micelle method and characterized by SEM,TEM and N₂ absorption experiments.The research work focused on the effects of the ratio of ethanol to water,the amounts of ammonia and CTAB,the temperature and the stirring speed on the diameter and monodispersion property of mesoporous SiO₂ NPs.Furthermore,the TEM and N₂ absorption experiment demonstrated the prepared SiO₂ NPs were mesoporous.The specific surface area was calculated to be 952.4 m²/g and the diameter was 2.0 nm. The results give the optimal conditions for synthesis of mesoporous SiO₂ NPs with monodispersion and controlled diameter.In this chapter,fluorescent mesoporous SiO₂ NPs with a diameter of 400 nm were also be prepared by co-hydrolyzation of TEOS with another silylane precedesor modified with fluorescent dye.In chapter three,magnetic Fe₃O₄ NPs and MnFe₂O₄ NPs were prepared by solvothermal and thermal decomposition method respectively,and were characterized by SEM,TEM,XRD and SQUID to obtain their characteristic properties.According to the experimental results of chapter two,proper methods were chose to prepare composite magnetic SiO₂ NPs with core-shell structure,including using the St(o|¨)ber method to embed the magnetic Fe₃O₄ NPs which prepared by solvothermal with a large diameter.And this method successfully prepared the composite SiO₂ NPs with a 100 nm Fe₃O₄ NPs as core and a 20 nm SiO₂ as shell.The reverse micelle method was used to embed the magnetic MnFe₂O₄ NPs prepared by thermal decomposition method.The hydrophobic MnFe₂O₄ NPs were modified with CTAB to be transfered into water.The core-shell MnFe₂O₄@SiO₂ composite NPs and nanorods were successfully prepared via changing the experimental conditions,and the formation mechanism was proposed.The microemulsion method was also used to embed the magnetic MnFe₂O₄ NPs prepared by thermal decomposition method.The received NPs are core-shell structure with good morphology and momodispersion.In chapter four,two core-shell composite SiO₂ NPs embedding magnetic NPs and fluorescent dye simultaneous were prepared using microemulsion method based on the conclusion of the experiments in chapter three.The NP-1 and NP-2 were embed CdTe QDs and FITC as fluorescent probe,respectively.Dueing to its high and stable fluorescence,the NP-2 was chose to modify with antibody of V.alginolyticus to achieve the biotargetting function.The special interaction between antibody and antigen makes the NP-2 adsorb to the surface of V.alginolyticus while they are in mixture.Then the NP-2-V.alginolyticus composite were magnetic separated driven by the external magnetic filed and characterized by TEM and fluorescence confocal microscopy.