Engineering upconversion nanoparticles for multimodal biomedical imaging-guided therapeutic applications

As one of the most important branches of nanotechnology, nanotheranos-tic medicine that aims at integrating diagnostic/therapeutic functions in one system is expected to provide novel strategies for accurate imaging-guided therapy of human major diseases like cancer. Among various inorganic or organic theranostic probes, lanthanide-doped upconversion nanoparticles (UCNPs) demonstrate superior advantages in upconversion luminescent imaging by contrast with traditional luminescent probes as well as great potential in the development as multimodal imaging (e.g., magnetic resonance imaging, computed tomography imaging, etc.) probes by the selective doping of various functional ions (e.g., Gd³⁺, Yb³+, Ho³+, etc.). Furthermore, by suitable surface engineering (e.g., mesoporous silica coating, biological molecule conjugation etc.), UCNPs can simultaneously serve as delivery vehicles of drugs/photosensitizers for multimodal therapeutic applications (e.g., chemotherapy, photodynamic therapy, etc.) under the above significant multimodal imaging guidance. Herein, we summarize and discuss the very recent progresses in the engineering of UCNPs for multimodal imaging-guided therapeutic applications.