The synthesis of boron enriched core-shell nanoparticles for neutron capture therapy & The synthesis and biological impact of model plastic nanoparticles

Abstract

Nanoparticles, with their unique properties at the nanoscale, have garnered significant interest. Their potential in medicine, catalysis, and other fields is tremendous. However, it is crucial to acknowledge the potential detrimental effects of nanoparticles, particularly plastic nanoparticles and the largely unknown effect on human health through plastic degradation in the environment. This thesis is structured around two pivotal research topics. The first explores the synthesis of nanoparticles for a groundbreaking purpose - treating glioblastomas with a new radiotherapy, neutron capture therapy. The second topic delves into the environmental impact of plastic waste, particularly its breakdown and the toxicity of plastic nanoparticles to cell lines. Within the first two research chapters [chapters 3 and 4], a deep study on the synthesis of iron-boron core and gold shell (FeB-Au) nanoparticles for neutron capture therapy. Patients diagnosed with GBM have a very short life expectancy, with 17.7 % of patients having a survival rate of one year. Two essential methods were trialled to synthesise the trimetallic nanoparticles: non-aqueous conditions using redox-transmetalation and aqueous conditions using reverse micelles. When using an Fe3+ salt (FeCl3) in non-aqeuous conditions led to a significant incorporation of boron into the core when compared to using an Fe2+ salt (FeCl2), with a B/Fe atomic ratio of 0.92 compared to 0.32, respectively. Redox-transmetalation helped overcome the lattice mismatch between the Fe-B core and Au shell, with Fe being used as the reducing agent for gold, which promotes seeding at the surface of the core. From this method, high importance around the temperature drop of the core solution to minimise homonucleation of the gold and promote hetronucleation was essential for forming a gold shell and partial core-shell nanoparticles were formed. The reverse micelle method was not reproducible compared to the literature and was ineffective at forming core-shell nanoparticles. It was challenging to confirm whether there was micelle stability which led to a significant challenge in forming a shell around the core material. There was no clear core-shell structure formation using reverse micelles and the method proved to be less effective compared to the redox-transmetalation method. Within the plastic nanoparticle toxicity test [chapter 5], different common petroleum-based waste plastics [PS, PMMA, PE, PP] were synthesised and used for cell testing on MRC-5 cells. Several analysis techniques (EDX, XRF, XPS TGA, XRD, FTIR), were used to compare raw polystyrene and a polystyrene coffee lid to identify the differences and additives in processed commercial coffee lids. In this case, it was found that the coffee lid had CaCO3 and TiO2 added as a colourant and TiO2 as an antimicrobial. The average sizes of all plastic nanoparticle solutions (PS, PMMA, PP, PE, PS coffee lid) were between 50-200 nm at high concentrations between 2 x 1012 and 2 x 1014 particles per ml. It was found that the coffee lid was highly toxic towards MRC-5 cells, with cell viability of less than 10 %. However, the concerning information found in this chapter was that all the plastics indicate that DNA damage is caused by double-strand breaks in the DNA and a delay in the cells progressing through the cell cycle due to damage being caused.