Prospects of an engineered tumor-targeted nanotheranostic platform based on NIR-responsive upconversion nanoparticles

Abstract

Theranostics, which affords both therapeutic and diagnostic functions within a single entity, has emerged as a cutting-edge technology for the development of personalized nanomedicine. Nanoparticles also offer the potential to unlock new avenues in cancer theranostics, attributed to their capacity for multifunctionality and multivalency. Lanthanide-doped upconversion nanoparticles (UCNPs) constitute a promising nano-scale platform notable for its unique ability to convert near-infrared (NIR) light into higher-energy luminescence. In addition to the large anti-Stokes shift, UCNPs also feature multiple sharp emission peaks varying from the ultraviolet (UV) to the NIR region, long luminescence lifespan, and high stability against photobleaching. By using NIR irradiation as an excition source, UCNPs enable deep-tissue bioimaging, controlled cargo release and subsequent therapeutic actions with high spatial and temporal resolution. On the other hand, to accomplish site-specific targetability to maximize theranostic outcomes, active targeting directed by specific tumor-homing ligands has been proven to be efficacious in improving tumor accumulation and reducing side effects. The choice of targeting ligands falls into several general classes including small molecules, peptides, proteins, antibodies, carbohydrates, or nucleic acid aptamers. Ligand-mediated targeting of functionalized UCNPs tailored with cancer-specific recognition moieties will lead to enhanced cellular uptake and permeability in tumor tissues, thus achieving effective theranostic treatments and long-term prognosis. In this perspective, we discuss the provision and prospects of specific ligand functionalized UCNPs for targeted delivery and theranostic application in various types of tumor therapies.