In Vitro Studies of Gold Nanoparticles in Cancer Radiotherapy

Gold nanoparticles as radiosensitisers in radiotherapy are a new and promising area of research, and are especially beneficial for cancers located in areas very sensitive to damage from radiation, such as the head and neck. However, the mechanisms that occur within the cell after irradiation and the characteristics (e.g. size, shape, surface composition) of the nanoparticles that provide the greatest radiosensitization effect is still not understood. Previous research has shown that biocompatible surface stabilisers and higher concentrations of nanoparticles leads to a greater radiosensitization effect. However, it is difficult to directly compare research from different studies due to the differing experimental parameters, such as cancer cell lines, incubation times, sizes and concentrations. Therefore, this research seeks to improve upon this by keeping experimental factors consistent and only changing one parameter at a time, with a focus on the study of the material property effects on radiosensitization enhancement. This will allow better comparisons and rational design of individual experiments to improve the determination of factors that have the greatest influence on radiosensitization.<br/>Spherical gold nanoparticles were synthesised through either a reduction of gold (III) chloride trihydrate or a seeded growth method with trisodium citrate to obtain citrate stabilised nanoparticles with varying diameters. Ligand exchanges were then performed with a range of polymers of different chain lengths and functionalities to produce a large library of gold nanoparticles of differing size and surface chemistries. Clonogenic assays were then performed using the head and neck cancer cell lines of FaDu (hypopharynx), A253 (submaxillary salivary gland) and UMSCC6 (tongue), which were incubated with the same number of gold nanoparticles per cell. X-ray irradiation was then applied at different doses before the surviving fractions were calculated through colony counting. It was found that the diameter of gold nanoparticles had a significant effect on radiosensitization, with larger particles showing greater promise over their smaller analogues.