Functionalized upconversion nanoparticles for cancer imaging and therapy

Near infrared (NIR) light administrated fluorescence imaging and photodynamic therapy (PDT) have shown great promising in cancer diagnosis and treatment. Especially with the recent development of the rare earth ions doped upconversion nanoparticles (UCNPs), much attentions have been attracted in this field. Despite the many efforts of surface modification and functionalization done in utilizing UCNPs for biomedical applications, target labeling and/or PDT treatment of cancer cells at an early stage are still the major challenges. In this thesis we are focused on developing new strategies to construct multifunctional nanoplatforms for simultaneously cancer imaging and photodynamic therapy. The cellular uptake and cytotoxicity are systematically researched on UCNPs with different surface coatings. Target molecules like folic acids (FA) or monoclonal antibodies (mAb) are covalently functionalized onto the UCNPs so as to improving their target labeling properties in cancer cells, and both in vitro cultured cancer cells and in vivo tumor spheroids bearing chick chorioallantoic membrane (CAM) model have verified this. In order to improve upconversion luminescence intensities and singlet oxygen production, core-shell structured NaYF4:Yb,Er@NaYF4 nanoparticles are synthesized and functionalized with photosensitizers (PS) Rose Bengal, which turns out a trade-off relationship between upconversion luminescence and energy transfer efficiency. A multispectra imaging method is also put forward to accurately asserting tissue imaging depth based on the relative intensity changes of the two upconversion luminescence bands of NaYF4:Yb,Er UCNPs, which might expand the tradition 2-dimensional planar fluorescence imaging into 3-dimensional.