Chapter 14 - Gold nanoparticles in photodynamic and photothermal therapy

Abstract

Gold nanoparticles represent a decent model for nontoxic carriers in gene and drug delivery applications. This is due to their unique features such as the inertness of the gold core, the ease of synthesis in different shapes and sizes, the tunability of the surface properties, and the superior ability to interact with thiols, a feature that allows facile surface functionalization through thiol linkage. Loading drugs onto solid gold nanoparticles or within hollow gold nanostructures represent an interesting strategy to enhance the therapeutic effects of drugs and, consequently, decreasing their IC50 values. Gold nanoparticles have optical activity that can be easily modulated to fulfill different needs in several fields. Concerning the pharmaceutical and medical fields, the optical properties of gold nanoparticles were widely exploited to synthesize various therapeutic and diagnostic tools. In general, gold nanoparticles can conduct their photoinduced effects either directly or indirectly or both. Direct photocytotoxicity can be attributed to their inherent photothermal activity through inducing localized hyperthermia (in the cancerous tissue, for example), upon irradiation. On the other hand, indirect photoinduced cytotoxicity of gold nanoparticles may be exerted via enhancing the photothermal and/or the photodynamic effects of a conjugated photosensitizer. In addition to the previous therapeutic functions, the diagnostic value of a fluorescent photosensitizer may be greatly enhanced by conjugation to gold nanoparticles. Thus, gold nanoparticles are promising tools, from a pharmaceutical side of view, for use in photothermal and photodynamic therapy, providing the ability to design and formulate unlimited types of highly efficient, function-tailored, and targetable photoactive nanomaterials.