Computational Modelling of Radiosensitising Properties of Nanoparticles

Haume, Kaspar (2018). Computational Modelling of Radiosensitising Properties of Nanoparticles. PhD thesis The Open University.



Metal nanoparticles (NPs) are currently under intense investigation due to their potential application in radiotherapy treatment of cancerous tumors by acting as radiosensitizing agents which may potentially lead to a reduction of side-effects caused by radiotherapy.

This theses presents a framework to accurately explore a number of important parameters of coated NPs using computational and theoretical methods which may be applied to any coated NP system.

The detailed structure of poly(ethylene glycol) (PEG)-coated gold nanoparticles (AuNPs) was studied using atomistic classical molecular dynamics simulations. By varying the number of attached PEG molecules it was demonstrated that the thickness of the coating, and therefore the size of the overall NP, was independent of the coating molecule surface density. On the other hand, the water content of the coating was observed to decrease with increased coating surface density. In particular, it was found that the region immediately outside the NP core was devoid of water for high coating densities.

The energetics of the coating formation was investigated by calculating the free energy change associated with the binding of a PEG molecule to a gold surface. The binding was demonstrated to be energetically favourable with a dominating contribution coming from a decrease in potential energy associated with the binding. This methodology may be be extended to provide estimates for the lifetime on NP coatings in vivo where they have been shown to degraded by exchange with biological proteins post administration.

The transport of low-energy secondary electrons emitted by carbon ion-irradiated AuNP was calculated as a diffusion process and the radical production, due to inelastic collisions of the electrons inside the coating medium, was quantified. By varying the ion energy and coating water content we demonstrated that the presence of water near NP surface is crucial in order to achieve radical production enhancement compared to pure water.

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