Owing to the high atomic number (Z) of
gold element, the
gold nanoparticles appear as very promising
radiosensitizing agents. This character can be exploited for improving the selectivity of
radiotherapy. However, such an improvement is possible only if irradiation is performed when the
gold content is high in the
tumor and low in the surrounding healthy tissue. As a result, the beneficial action of irradiation (the eradication of the
tumor) should occur while the deleterious side effects of
radiotherapy should be limited by sparing the healthy tissue. The location of the radiosensitizers is therefore required to initiate the
radiotherapy. Designing
gold nanoparticles for monitoring their distribution by magnetic resonance imaging (MRI) is an asset due to the high resolution of MRI which permits the accurate location of particles and therefore the determination of the optimal time for the irradiation. We recently demonstrated that ultrasmall
gold nanoparticles coated by
gadolinium chelates (Au@DTDTPA-Gd) can be followed up by MRI after
intravenous injection. Herein, Au@DTDTPA and Au@DTDTPA-Gd were prepared in order to evaluate their potential for radiosensitization. Comet assays and in vivo experiments suggest that these particles appear well suited for improving the selectivity of the
radiotherapy. The dose which is used for inducing similar levels of
DNA alteration is divided by two when cells are incubated with the
gold nanoparticles prior to the irradiation. Moreover, the increase in the lifespan of
tumor bearing rats is more important when the irradiation is performed after the injection of the
gold nanoparticles. In the case of treatment of rats with a
brain tumor (9L
gliosarcoma, a radio-resistant
tumor in a radiosensitive organ), the delay between the
intravenous injection and the irradiation was determined by MRI.