Gold nanoparticles in radiation therapy: an old story yet mesmerizing

Radiotherapy (RT) is generally considered to be one of the most effective cancer treatments. The primary goal of RT is to accurately induce radiation damage to the tumor while limiting radiation toxicity to a level acceptable to normal tissue. This is accomplished by targeting the tumor with radiation. On the other hand, the status of RT procedures as they stand today is not substantial enough to eliminate advanced metastatic and radio-resistant hypoxic tumors. Radiologists and medical physicists all face the same fundamental challenge of improving treatment efficacy while minimizing damage to surrounding healthy tissue. Through a process called radio-sensitization, tumor cells become more sensitive to the damaging effects of radiation. Therefore, radiosensitizers are compounds that are either medicinal or inactive and boost the efficacy of radiation treatment. In the last few years, there has been a surge of interest in the use of formulations to enhance the effectiveness of radiotherapy, especially when employing metallic, primarily gold-based nanoparticles. The aim of combining NPs with radiation therapy is to enhance the differential effect of treatment between normal and malignant cells. Gold nanoparticles (AuNPs) have been the most widely investigated nanoplatforms for use in radiation therapy due to their high X-ray absorption rate and synthetic modifiability, which allows precise control over the physical properties of the particles. We only highlight the radio-sensitization characteristics of gold nanoparticles in cancer treatment in the current review article.