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Considering both cancer's serious impact on public health and the side effects of cancer treatments, strategies towards targeted cancer therapy have lately gained considerable interest. Employment of gold nanoparticles (GNPs), in combination with ionizing and non-ionizing radiations, has been shown to improve the effect of radiation treatment significantly. GNPs, as high-Z particles, possess the ability to absorb ionizing radiation and enhance the deposited dose within the targeted tumors. Furthermore, they can convert non-ionizing radiation into heat, due to plasmon resonance, leading to hyperthermic damage to cancer cells. These observations, also supported by experimental evidence both in vitro and in vivo systems, reveal the capacity of GNPs to act as radiosensitizers for different types of radiation. In addition, they can be chemically modified to selectively target tumors, which renders them suitable for future cancer treatment therapies. Herein, a current review of the latest data on the physical properties of GNPs and their effects on GNP circulation time, biodistribution and clearance, as well as their interactions with plasma proteins and the immune system, is presented. Emphasis is also given with an in depth discussion on the underlying physical and biological mechanisms of radiosensitization. Furthermore, simulation data are provided on the use of GNPs in photothermal therapy upon non-ionizing laser irradiation treatment. Finally, the results obtained from the application of GNPs at clinical trials and pre-clinical experiments in vivo are reported.

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The current article presents the photobleaching properties of a group of pyrylium salts under ultrashort pulsed illumination. These pyrylium salts have the same basic chemical structure and differ only by a specific substituent. It is proven experimentally that two different mechanisms are simultaneously present to the photobleaching of all molecules studied (independently of their specific chemical structure). However, the particular parameters of each mechanism are influenced significantly by the substituent change. The experimental investigation of these parameters showed the presence of multiphoton interactions in the photobleaching of pyrylium salts depending essentially on the specific substituent.