A review on composites based on upconversion nanoparticles and graphene oxide: development and theranostic applications centered at solid tumors

Upconversion nanoparticles (UCNPs) have attracted considerable interest for the imaging of solid tumors because of their unique optical features. These applications can be expanded towards anticancer therapeutics by developing UCNP-graphene oxide (GO) composites. This strategy addresses low loading capacity and poor dispersibility of UCNPs in physiological media. These aspects have been covered in this article. We begin by discussing the synthesis methods and challenges associated with UCNPs, along with their surface modification strategies. Next, we describe the approaches of designing UCNP-GO composites and their applications in imaging, biosensing, and different therapeutic platforms.