Ultrasmall-in-Nano

This chapter offers an in-depth exploration of ultrasmall-in-nano constructs, with a primary focus on sub-5 nm gold nanoparticles (AuNPs) assembled into nanostructures. These constructs present a unique amalgamation of properties, encompassing extended circulation times, heightened tumour accumulation, and the potential for phototherapeutic applications. A central theme addressed is the crucial necessity for excretion, underscoring the pivotal role of nanoparticles being smaller than 5 nm to enable efficient elimination from the body. This chapter delves comprehensively into size-dependent properties of nanoparticles, employing AuNPs as an exemplary model with precise control over size, shape, and surface chemistry. It also showcases notable achievements in the field, including the attainment of absorbance within the phototherapeutic window and the demonstrations of controlled excretion. Concluding with a forward-looking perspective, this chapter envisions a promising future for ultrasmall-in-nano constructs, highlighting their dynamic approach to harnessing the advantages of both small and large nanoparticles across a wide spectrum of biomedical applications.