Upconversion nanoparticles and application in precision medicine

Rare earth elements doped upconversion nanoparticles (UCNPs) which absorb two or more near infrared (NIR) photons and emit one visible or ultraviolet (UV) photon have a significant potential for biomedical applications, e.g. imaging/diagnosis and therapy of cancers, due to the lack of an autofluorescence background, less scattering, less absorption of tissue and high penetration depth. Integrated with photosensitizers (PS), upconversion nanophotosensitizers are in principle a proper candidate for application of photodynamic therapy (PDT) with minimally invasion while retaining control over location and time. In order to meet the requirements of effective precision medicine and further reduce side effects we propose and develop in this thesis various strategies for PDT aided by upconversion nanoplatforms, including “in vivo assembly of upconversion nanophotosensitizers”, “optical imaging and pH-activated therapy” and “imaging-guided, X-ray activated synergistic radiotherapy (RT) and PDT”. In order to improve the upconversion luminescence efficiency we explore in this thesis as well quantitatively the role of OH- during the various steps of upconversion dynamics.