Photoluminescent nanoparticles have evolved during the last decade to become a key component of the biomedical research. Their versatile surface functionalization and adaptable optical properties are some of the remarkable features allowing their implementation for bioimaging and theranostic purposes. This review presents the recent and relevant literature dealing with the synthesis, surface functionalization, and biomedical applications of the most promising photoluminescent nanoparticles (i.e. Au nanoparticles, QDs, Ln-UCNPs, C-dots, and persistent luminescent nanophosphors), as well as a brief summary of the origin of their photoluminescent properties. We also briefly discuss their physicochemical properties, how biocompatible properties have been achieved as well, and the role that both parameters play in the interaction with biological entities.
