The Preparation Of Composite FITC/SiO₂Nanoparticles And Its Application In Biological Analysis

Luminescent nanoparticles have become an attractive research area in recent years. It has been known that they can be used as luminescence probes for various bioassays. Compared to conventional organic dye, advantages of the nano-sized luminescence nanoparticles mainly include their higher luminescence and stability. Nanoparticles were usually prepared into core-shell nanoparticles in order to modifie them easily, while silica-shell nanoparticles was one of them that have been widely used, because they have shown several advantages such as high water solubility, easy preparation, separation and surface modification. They were proposed to be a new class of biological labeling agents, which have the potentiality and ability to overcome a number of problems associated with the commonly used biological labeling agents, such as they could improve the detection sensitivity of biological molecules.In this work, the FITC/SiO2composite nanoparticles (FITC/SiO2NPs) were synthesized by reverse microemulsion method and the best volume of precursor was investigated. The best proportion of tetraethoxysilane, hexamethylene, n-hexanol, TritonX-100was0.1:10:4:4at room temperature. The FITC/SiO2composite nanoparticles remained about90%of fluorescence intensity after a week. The prepared nanoparticles were charactered. TEM photo showed the average particle size of nanoparticles was about80nm. The result of TEM and particle size distribution experiment could be consistence with each other. IR spectrum showed fluorescent nanoparticles were wraped by amino.It was not the shell thickness but the electrical property of the shell and core that determines whether to form stable composite fluorescent nanoparticles. As a result, it was not all the hydrophilic materials were suitable to make silicon shell nanoparticles with core-shell structure by microemulsion method, but the experiment conditions could be changed to adjust the electrical property of certain materials in order to form composite nanoparticles.The FITC/SiO2composite nanoparticles can label BSA by electrostatic and covalence interaction, and the optimized experimental conditions were obtained. The flourescence intensity of the fluorescent nanoparticles was proportional to the concentration of BSA in the range of0.050-0.55μg/mL, the linear equation was y=578.42c+10.99, with the correlation coefficient of0.9789and detection limit of14μg/L under optimal conditions. The relative standard deviation (n=11) was2.5%at0.40mg/L BSA concentration level.In the phosphate-buffered solution of pH8.50, the FITC/SiO2composite nanoparticles can label avidin by electrostatic interaction successfully. Moreover, avidin still kept their activity so that they reacted with D-biotin specifically. Using filter membrane as carrier, the flourescence intensity at512nm of different concentrations of avidin could be quantified with good linear range of0.20-1.4μg/mL. The linear equation was y=355.91c+107.58, with the correlation coefficient of0.9821. The experimental results showed that the FITC/SiO2composite nanoparticles can be used as a common fluorescent markers for the application of BAS.