Thesis

Fabrication of mesoporous silica using novel templating agents

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Awarding institution
  • University of Strathclyde
Date of award
  • 2012
Thesis identifier
  • T13391
Qualification Level
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Department, School or Faculty
Abstract
  • The formulation of silica nanoparticles was developed from silica hydrogel and compared with those from conventional sol-gel process. Tetramethoxysilane (TMOS) and sodium silicate were employed in the silica formulation. The particle size was in nanoscale (< 250nm) by calcining silica hydrogel from alkaline silica source and inorganic salt, while the particle originating from sodium silicate had a micro size of 2-5 [u]m. The chemical composition of silica particles was confirmed by FT-IR and sufficient condensation of silica was observed by longer calcination. Zeta potential revealed the negatively charged silica surface and the values were in good agreement with previously published papers. The particle size and morphology were further studied using AFM. Release profiles were investigated from a series of model drug: methylene blue hydrate (MBH), Nile red (NR), calcein blue (CB) and carbamazepine (CBZ). Silica particles showed high loading efficiency towards most model drugs by a simple post-diffusion route and loading can be improved by heating or evaporation methods. The highest loading content can be > 100 [u]g/mg (drug/silica, w/w) for MBH and NR. A successive long-term release was obtained in MBH, NR and CBZ. By fitting into mathematical models, a diffusion-controlled release ws suggested, yet NR might have a unique dissolution-controlled release. On the other hand, different release profiles were observed by modifying release conditions. Therefore, more attention needs to be paid to mimc a sink condition, as solubility can be enhanced at the cost of inferior diffusion. The instability of MBH loaded in silica particles was first proposed in our study and the change of the structure was confirmed by UV, FT-IR and Raman. The interaction was time and temperature-dependent. Particles were successfully functionalised with 3-amino-propyltriethoxysilane (APTES) and 3-glycidoxy-propytrimethoxysilane (GPTMS) afterwards and the grafted content can be quantitatively measured by TGA and qualitatively observed by zeta potential and its influence towards different dye molecules. Unfortunately, there was a question as to how APTES reacted with silica surface during functionalisation. This question was further explored by using different order to incorporate fluorescein (FLU) and APTES in silica. The FLU loading efficiency was much increased by first connecting FLU with APTES and then functionalising with silica. In conclusion, by combining the advantages of both hydrogel and silica particles, smaller size of silica can be achieved and they have promising application in drug delivery.
Resource Type
DOI
Date Created
  • 2012
Former identifier
  • 989282

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