Basic Research On The Application Of Gold Nanomaterials In Radiation Oncology

The purpose of this thesis is to explore the potential of applying gold nanomaterials(gold nanoparticles and nanoclusters)to radiation oncology and the underlying mechanisms.The thesis is divided into three parts:1.The dependence of hydroxyl radical production on the concentration of 15 nm citrate-capped gold nanoparticles(Au NPs)and radiation dose using coumarin-3-carboxylic acid in phosphate buffered saline(PBS)were examined.Moreover,the radiosensitization of Au NPs of different concentration on human cervix carcinoma He La cells through clonogenic survival assay were investigated for low linear energy transfer(LET)X-rays and high-LET carbon ions.The enhancement factor of Au NPs for hydroxyl radical production reached a maximum 3.66 for X-rays at the concentration of 0.1 ?g/m L while the maximum was 5.52 for carbon ions in presence of 1.0 ?g/m L Au NPs in PBS.At 50% survival level,the sensitizer enhancement ratios of X-rays and carbon ions varied from 1.14 to 2.88 and from 1.27 to 1.44,respectively,when cells were co-cultured with 1.5-15.0 ?g/m L Au NPs.Our data indicate Au NPs showed radiosensitization in terms of hydroxyl radical production and cell killing for low-and high-LET radiations.The concentration of Au NPs in PBS and cells played an important role in radiosensitizing effect.Based on the fact-the Au NPs in PBS could improve the production of hydroxyl radical and no accumulation of cells in the G2/M phase was observed,we deduce that the increment of hydroxyl radical production with Au NPs provided a mechanism for radiosensitization.2.Cell cycle phase could affect the cellular uptake of nanoparticles.Based on the fact that ionizing radiation exposure can delay cell cycle progression including inducing G2/M phase arrest,we propose that ionizing radiation exposure is a cell cycle phase-dependent targeting approach for intracellular delivery of nano-agents in tumor cells.Luminescent gold nanoclusters(Au NCs)using a one-pot green synthetic method were synthesized.Subsequently,the as-prepared Au NCs were used as both “nano-agents” and fluorescent trafficking probes for this study using human cervical carcinoma He La cells.Estimating the cellular uptake of Au NCs and cell cycle analysis were performed following X-rays irradiation and cell synchronization.Our work showed that X-rays irradiation could delay the division of He La cells and thereby enhance the retention of Au NCs in He La cells,which is a reverse strategy compared with other studies on synergistic nano-radiotherapy.Our results demonstrated that the cell cycle synchronization influenced the cellular uptake processes of Au NCs,suggesting that dynamic cell cycle progression could affect the cellular uptake kinetics of Au NCs.We consider that the radiation-induced cell division delay might provide a possible mechanism underlying the enhanced effect for the cellular uptake of Au NCs in irradiated He La cells.3.The potential of applying gold nanomaterials to fractionated radiotherapy by employing Au NCs at the cellular level was explored.The difference of the cellular uptake between human normal heptic L02 cells and human hepatocellular carcinoma Hep G2 cells following irradiation was investigated.In addition,whether Au NCs could enhance the cell killing effect of fractionated X-ray irradiation using human cervix carcinoma He La cells while administering agents following irradiation was examined.Subsequently,the underlying mechanisms of synergistic or sensitizing effect for Au NCs were explored taking “targeted effects” as the principal line.Our data indicate there was a significant difference of the cellular uptake between human normal heptic L02 cells and human hepatocellular carcinoma Hep G2 cells following irradiation and ionizing radiation exposure could selectively increase the uptake of Au NCs for fast proliferating tumor cells.Moreover,Au NCs could enhance the cell killing effect of fractionated X-ray irradiation on He La cells while administering agents following irradiation,which might result from the complicated biological effects induced by the complex action of Au NCs and ionizing radiation exposure.