Development And Applications Of Gold-Silica Nanohybrids For Bioanalysis

In the first project, both non-spherical and spherical silica nanomateirals with hollow interiors were synthesized by a one-step soft-templating method. By simply changing the applied solvent from ethanol to 1-propanol, or 1-pentanol, three different shapes of nanomaterials, including nanosphere, nanowire, and nanotadpole, could be obtained, respectively. The effects of other factors on morphology were also systematically studied to propose a growth mechanism. It was found that the PVP-water droplet was the crucial factor on the formation of hollow interiors. Without the addition of PVP, only solid silica nanomaterials, such as solid nanoparticles, nanorods, and nanowires, were synthesized. This developed method showed excellent reproducibility and great potential for a large-scale synthesis. In the second project, a novel nanocomposite contained a spherical gold nanoparticle core, a silica spacer and a fluorescent dye layer in the silica matrix was designed to study the metal-enhanced fluorescence phenomenon. It was found that the size of gold nanoparticles cores and the distances between cores and fluorescent dyes had significant effects on the emitted fluorescence intensity. An enhancement factor of 9.2 was obtained when the nanocomposite contained a 13.7 ± 1.3 nm gold nanoparticle core and a 36.6 ± 4.4 nm silica spacer. In the third project, an ultrasensitive protein assay was developed by using silica nanorods decorated with gold nanoparticles (AuNPs-SiNPs) as labelsin a lateral flow platform. A large number of AuNPs on one single SiNR provided visualized dark purple color that was much darker than the pure AuNPs solution. Therefore, the detection limit was lowered 50 times compared to the traditional AuNP-based lateral flow assay. Under optimal conditions, a linear range of 0.05 - 2 ng/mL with a detection limit of 0.01 ng/mL was obtained. The lateral flow bioassay based on these composite nanomaterials thus offered an ultrasensitive method for rapid detection of trace amount of proteins and has a potential application for point-of-care screening in clinical diagnostics and biomedical research. In the fourth project, a new hyperthermia agent, Au-silica nanowire nanohybrid (Au-SiNW nanohybrid)was synthesized and applied in the photothermal therapy. Due to its strong NIR absorption ability, the Au-SiNW nanohybrid can generate significant amount of heat upon NIR irradiation and induced thermal cell death. By incubating the nanohybrids with cancer cells and irradiating with NIR laser, cancer cells were successfully killed, indicating their potential as promising hyperthermia agents