Browsing Theses by Subject "Nanoparticles"
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In vitro chemically-induced DNA damage in cancer patients and healthy individuals. The effect of genotoxic compounds in cells from polyposis coli, colon cancer patients and healthy individuals.In the present study DNA damage was measured in peripheral blood lymphocytes from polyposis coli and colorectal cancer patients, treated with different dietary and environmental compounds and compared with lymphocytes from healthy individuals. In addition, confounding factors such as age, gender, alcohol intake and smoking habits were taken into consideration. The assays used in this study included the Comet assay, the Micronucleus assay, the Micronucleus ¿ FISH assay and the sister chromatid exchange assay. The food mutagens, PhIP and IQ, as well as titanium dioxide nanoparticles (TiO2 NPs) induced a dose dependent increase in the DNA damage and chromosomal abnormalities in all tested groups regardless of confounding factors. Prior to experiments physicochemical characterisation of nanoparticles was conducted. In the presence of the flavonoids, quercetin and rutin that were acting in an antioxidant manner, the DNA damage resulting from the highest doses of food mutagens was significantly reduced. Thus, dietary supplementation with flavonoid-rich vegetables and fruits may prove very effective in protection against oxidative stress. The polyposis coli and colon cancer patients were more susceptible to food mutagens, PhIP and IQ, as well as TiO2 NPs, and in the majority of cases had a higher level of DNA damage in the Comet assay and higher cytogenetic damage in the Micronucleus assay. In the final project, twelve frequently encountered (NewGeneris) chemical compounds were evaluated to establish their damaging potential in lymphocytes and spermatozoa from healthy donors. The highest damage was produced by DNA reactive aldehydes, food mutagens and benzo[a]pyrene when assessed with the neutral and alkaline Comet assay with and without metabolic activation.
An investigation into the mechanism of toxicity of zinc oxide nanoparticles.The wide scale use of ZnO nanoparticles (NPs) in the world consumer market has resulted in likelihood of exposure to human beings. The present study was aimed to assess the in vitro and in vivo interactions of ZnO NPs in the mammalian system and to elucidate the possible mechanism of their toxicity. Our in vitro results using human epidermal cells (A431), primary human epidermal keratinocytes and human liver cells (HepG2) demonstrated that cells exposed to ZnO NPs exhibit a decrease in cell viability which was independent of NP dissolution. ZnO NPs also induced oxidative DNA damage as evidenced by an increase in the Fpg sensitive sites. The reactive oxygen species triggered a decrease in mitochondrial membrane potential and an increase in the ratio of Bax/Bcl2 leading to apoptosis through the intrinsic pathway. In addition, ZnO NPs induced phosphorylation of JNK, P38 and P53ser15. The results from our in vivo studies using a mouse model showed that ZnO NPs induce lipid peroxidation, oxidative DNA damage and apoptosis in liver which further confirmed our in vitro findings. The data from the present study provide valuable insights into the cellular interactions of ZnO NPs and the underlying molecular mechanism of their toxicity. The results also stress the need for a comprehensive environmental health and safety assessment of engineered nanomaterials to ensure safer nanotechnology based products.
The physical chemistry of corticosteroid-cyclodextrin complexes: The Host-guest Chemistry of Corticosteroid and Cyclodextrin Systems Elucidated with NMR and Applied to Novel Surface-decorated Surface Enhanced Raman Spectroscopic ProbesInhaled corticosteroids (ICS) are used to address inflammatory illnesses including asthma and COPD, with delivery commonly achieved using pressurised metered dose inhalers (pMDI). Hydrofluoroalkanes (HFAs) have been introduced as an alternative propellant to chlorofluorocarbons (CFCs) to reduce their environmental impact. However, the thermodynamic properties of HFAs are poorly understood and are different to those of CFCs. It is essential, therefore, to characterise the drugs and excipients used in HFA inhalers in order to obtain a comprehensive understanding of the device performance and the therapeutic efficacy. This work has developed different analytical methods to study the complexation between ICS and CD which are added to enhance the solubility of inhaled drugs in pMDI propellant systems providing rational control of suspension vs. solution formulations and hence their dose uniformity and stability. The Nuclear Magnetic Resonance (NMR) method developed has shown weaker complexation between budesonide and the derivatised CDs DIMEB and TRIMEB in organic solvents compared to D2O with the strength of the complex formed being ranked as D2O > MeOD > CDCl3 > CD3CN. The derivatisation of the CD also shows a marked difference in complexation with budesonide with the strength of the association being ranked as DIMEB > βCD > TRIMEB. Studies of various ICS compounds with TRIMEB in the fluorinated propellant HPFP showed the association to be greatest in budesonide, followed by beclomethasone dipropionate, momestasone furoate and fluticasone propionate. Surface-enhanced Raman scattering (SERS) has been used for the detection of corticosteroids in water using thiol functionalised βCD as a complementary study to NMR. This has been utilised to evaluate the host-guest complexes formed and provides further insight into the complexation of the compounds by their inclusion into the CD cavity. The structural data obtained using the NMR and SERS approaches developed have provided a fundamental insight into the physical chemistry of these interactions at a molecular level.