Recent advances of upconversion nanoparticles in theranostics and bioimaging applications

In recent years, upconversion nanoparticles (UCNPs) have attracted considerable research interest because of their unique optical merits (unique optical merits: sharp emissions, large anti-Stokes shifts, long lifetimes, and negligible photobleaching) that make them as ideal candidates for unified applications in biomedical fields including drug delivery, bioimaging, and cancer therapy. In this review, we illustrate the recent efforts on fabrication of UCNPs with organic, inorganic and biomolecules that create UCNPs as the next generation biomedical agents for drug delivery and cancer therapy. The introduction summarizes the recent developments and uses of UCNPs in analytical and biomedical research areas. We discuss the optical properties and the surface modifications of UCNPs and their synergistic theranostic applications in cancer therapies (chemo and photothermal) in vivo and in vitro studies. Further, we also discuss the cytotoxicity of UCNPs. Finally, the prospects and future challenges of UCNPs in drug delivery, bioimaging and cancer therapy are described. (c) 2019 Elsevier B.V. All rights reserved.