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An In-Depth Study of Nucleation and Growth Processes During Stöber Silica Synthesis
(Izmir Institute of Technology, 2019) Sop, Elif Suna; Polat, Mehmet
Silica nanoparticles (SNPs) which can be synthesized with high surface area, controllable morphology and desired particle size have gained significant interests in high-end applications such as catalysis, chemical sensors, cosmetics and drug delivery applications. The sol-gel technique is the most commonly applied method for manufacturing these particles owing to its simplicity and suitability for allowing surface modifications to the final product. Though monodisperse amorphous SNPs have been studied extensively, how their formation proceeds through nucleation and growth is still a topic of debate. Over the years, a number of mathematical models have been suggested for the nucleation and growth of SNPs; some suggesting that silica growth occurred through monomer addition while some arguing that aggregation of nuclei/subparticles were the dominant mechanism. Nevertheless, a clear understanding of the nucleation and growth sub-processes is extremely important in control on the size and shape of SNPs for those industrial applications which demand specific morphology and surface properties. The need for a simple, robust and generalized model, both conceptually and mathematically, to understand formation and growth of Stöber silica particles has been the main driving force for this thesis. In this study, silica synthesis was carried out under a wide variety of experimental conditions while determining the size distributions of the formed particles kinetically during different stages of the synthesis in-situ through SEM analysis using an image analysis software. The outcome of the extensive synthesis work was to obtain a clear understanding of how the formation and growth of the silica particles proceed during synthesis. This conceptual understanding of the nucleation and growth processes was then translated into a mathematical model to predict the size of the particles as a function of synthesis time.
The Effects of Engineered Silica Nanoparticles on the Cellular Behaviours of Human Hepatocellular Carcinoma Cell Lines
(Izmir Institute of Technology, 2018) Tüncel Çerik, Özge; Özçelik, Serdar; Atabey, Safiye Neşe
Physicochemical properties of the silica nanoparticles have vital roles in determining the physiological behaviours of the cells. Applications of nanoparticle treatments have some outcomes as a response of the cells in living systems as mitochondrial disruption, oxidative stress, reactive oxidative species (ROS) generation, altered cell cycle regulation and DNA damage. In this study 10 and 100 nm sized SiNPs were prepared and physicochemically characterized in the second part. Well characterized silica nanoparticles were used to assess the cytotoxicity and genotoxicity of the hepatocellular carcinoma cell lines as HuH-7 and SK-HEP-1 and lymphocytes. The cell cycle analysis was performed for engineered SiNPs to elucidate the DNA damage in the third part. In the fourth part mitochondrial responses of the cells were determined by real time confocal microscopy at single cell level. An image analysis method for evaluating the cellular responses by mitochondrial staining was developed. DCF stained cells were analyzed in order to assess the production of ROS in the cells. Localization of the SiNPs were determined by lysosomal and mitochondrial staining. Pearson correlation coefficients of the images were used for evaluating the colocalization of organelles with SiNPs. Lastly, diffusion coefficients of the SiNPs in the cells were determined by quantitative confocal microscopy. The SiNPs were found as non-toxic up to 200 μg/ml for 5 days. The SiNPs did not induce the formation of micronuclei in lymphocytes. The SiNPs were not cause an arrest in cell cycle progression. Mitochondrial potentials were not changed after SiNP exposure as well. They were mostly internalized at 30 minutes in both cell line in lysosomal parts without increasing ROS in the cells. It can be concluded that the SiNPs can be safely used for targeted delivery of organic compounds, biological molecules or drugs in medicine, and may be utilized as a probe system in biological studies.

Phd Degree / Doktora

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