Mesoporous Silica Nanoparticles In Cellular Therapy

Since the development of mesoporous silica nanoparticles (MSNs) in 1992, they have been of great interest due to the multifunctionality that they afford due to their porous nature, facile surface functionalisation and chemical stability. More recently, their use as delivery vehicles for theranostic (all-in-one therapeutic delivery and disease diagnosis) drugs and nucleic acids has been increasingly investigated and the development of these biocompatible delivery vehicles could signify a great advance in therapeutic treatment of a range of diseases, including cancer. In this work, the use of MSNs as membrane-impermeable drug and gene delivery vehicles to cancer cells has been investigated. Such agents can either be chemically conjugated to particle surfaces or can exploit strong electrostatic interactions to facilitate their transport into cells. This thesis firstly aims to utilise a method of engineering nanoparticles capable of being reliably endocytosed by human cervical carcinoma (HeLa) cells and escaping subsequent entrapment in cellular endo/lysosomal compartments. Exploiting this cytosolic access, MSNs are then used to deliver theranostic drugs and nucleic acids into the cytosol of cancer cells. In this way, cytochrome c (Cyt-c), a protein heavily implicated in the apoptotic route of cell death, can be functionalised onto nanoparticles capable of accessing the cytosol, whereupon triggering of apoptotic cell death can be efficiently achieved. Gene therapy has gained a lot of interest in recent years and a very current challenge is the delivery of plasmid DNA (pDNA) into the cytosol of cancer cells. This part of the work uses electrostatic interactions between anionic pDNA and cationic MSNs to deliver pDNA to cells; green fluorescent protein (GFP) expression has been observed to monitor the successful delivery of pDNA to the cytosol. Subsequent gene modification of the plasmids could result in delivery of genetic material capable of inducing cell death, overcoming the uncontrollable cell death associated with cancerous cell growth. Overall, this thesis demonstrates that careful engineering of nanoparticle surface chemistry can be used to reliably allow cytosolic access to HeLa cells. This access has been exploited to effect apoptotic cell death through the appendage and delivery of a critical dose of Cyt-c. Delivery of a gene therapy agent (pDNA) has also been shown and confirmed through successful GFP expression.