Synthesis Of Silica Nanoparticles And Its Applications In Bioanalysis

This thesis consists of four chapters, including introdution, preparation of tetraamino-phthalocyanine zinc loaded silica nanoparticles and its application in cytotoxicity and photodynamic therapy of cancer, synthesis of bare carboxylated silica nanoparticles and its application for the detection of DNA.In chapter one, the development course and the development trend of nanotechnology and nanomaterials were introduced. And the properties, synthesis and application on silica nanoparticles were described in detail. Moreover, the research plans for this thesis were presented.In chapter two, the preparation of tetraamino-phthalocyanine zinc loaded silica nanoparticles (SiO2 @ZnPc(NH2 )4) and its cytotoxicity experiments were reported. The positive charged silica nanoparticles, entrapping hydrophobic photosensitizer 2,9,16,23-tetraamino-phthalocyanine zinc (ZnPc(NH2 )4), have been synthesized in the nonpolar core of micelles by hydrolysis of triethoxyvinylsilane (TEVS) and 3-aminopropyltriethoxysilane (APTES). The water-soluble, stability, surface morphologies and charge were characterized using transmission electron microscopy (TEM),dynamic light scattering (DLS) and UV-visible spectrophotometer (UV/Vis) absorption spectra. The as-prepared nanoparticles are highly monodispersed spheres with uniform diameter (~ 20 nm), and stable in aqueous system. Its averageζpotential value is 28.8±2.79 mV and exhibits strong absorption peak at 714 nm. In addition, encapsulation of ZnPc(NH2 ) 4 in the silica nanoparticles prevented ZnPc(NH2 )4 from been leaked and enhanced the anti-photobleaching. The toxicity of silica nanoparticles to cells has been investigated by the incubation of the ZnPc(NH2 )4 entrapped-nanoparticles and the nanoparticles without ZnPc(NH2 )4 (SiO2 -NH2) with living cancer cells (HeLa, U251, PC-12). The experimental result reveals that both SiO2 @ZnPc(NH2 ) 4 and SiO2 -NH2 particles have no significant cytotoxicity when the concentration of the particles is below 300 mg/L. This proposed method provides a new way to synthesize photodynamic therapy (PDT) drugs. In chapter three, the as-prepared tetraamino-phthalocyanine zinc loaded silica nanoparticles (SiO2 @ZnPc(NH2 )4) were employed for photodynamic therapy of cancer. The use of silica nanoparticles increased the water-solubility of ZnPc(NH2 )4. The SiO2 @ZnPc(NH2 )4 nanoparticles can efficiently generat singlet oxygen as measured by chemical probe 1,3-diphenylisobenzofuran (DPBF). Subsequently, we investigated the effect of both SiO2 @ZnPc(NH 2 )4 nanoparticles and ZnPc(NH2 )4 on the PDT of HeLa cells. The experimental results showed that compared with ZnPc(NH2 )4, SiO2 @ZnPc(NH2 ) 4 nanoparticles could increase the cell death rate by 26% when the concentration of the particles was 2μM. Therefore, SiO2 @ZnPc(NH2 )4 nanoparticles as the carrier of drugs have potential applications in PDT of cancer.In chapter four, carboxylated silica nanoparticles were prepared and used for detection of DNA with the aid of a dynamic light scattering (DLS) technique. Based on reversible microemulsion (W/O) approach, the pure carboxylated silica nanoparticles were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) and carboxyethylsilanetriol sodium salt (CTES). The as-prepared nanoparticles were highly monodispersed spheres with uniform diameter (~ 45 nm), and had good water-solubility and biocompatibility. DNA was conjugated to the surface of silica nanoparticles by using amine coupling chemical approach. Based on the"sandwich"principle, we applied the DNA-modified silica nanoparticles as probes to detect target DNA level with the aid of dynamic light scattering technique. It was found that the linear range for the DNA biosensor was from 1 pM to 10 nM with the detection limit of around 1 pM. This technique provides a new idea for DNA detection. This assay is easy to conduct without any signal amplification process. Compared with other optical and chip-based methods, the advantage of the method lies in the simplicity, rapidness, low cost and high sensitivity.