An Overview of the Historical Development, Synthesis and Characterization Techniques of Nanoparticles Also Used as Radiosensitizers

Today, nanotechnology is widely used in a wide range of areas, from medical applications such as targeted drug delivery, cancer treatment, and tissue engineering to energy solutions such as solar panels, fuel cells, and batteries, and environmental applications such as the detection and treatment of air, water, and soil pollution. The use of nanoparticles as radiosensitizer agents in cancer treatment has increased significantly in recent years due to their properties such as high surface area/volume ratio, biocompatibility and targetability. Nanoparticles can enhance the biological effects of ionizing radiation during radiotherapy, thereby aggravating DNA damage in tumor cells and thus increasing treatment efficacy. Metal nanoparticles, especially those with high atomic numbers (e.g., gold, silver, gadolinium), increase photon absorption, increasing local dose density and providing selective radiosensitization at the tumor site. In addition, thanks to surface modifications, targeted delivery, extension of circulation time and protection of healthy tissues are possible. With these aspects, nanoparticle-based radiosensitizers carry significant potential in oncological treatments by contributing to achieving high therapeutic efficacy with lower radiation doses and reducing treatment-related side effects. This review aims to provide a comprehensive overview of the scientific development of nanoparticles used as radiosensitizers, from a historical perspective, and to explain how these structures are classified, synthesized, and characterized. The evolution of nanoparticles is presented in chronological order, starting from prehistoric traces to modern nanotechnology. In the classification section, the grouping of nanoparticles according to their origin, morphology and chemical composition is discussed, while the synthesis approaches are examined on the basis of top-down, bottom-up and hybrid methods. Finally, modern characterization techniques used to determine the structural and surface properties of nanoparticles are included. The compilation aims to provide an up-to-date and systematic resource for researchers working in the field of nanotechnology within the framework of these four main headings.