Engineered design of theranostic upconversion nanoparticles for tri-modal upconversion luminescence/magnetic resonance/X-ray computed tomography imaging and targeted delivery of combined anticancer drugs

Upconversion nanoparticles (UCNPs) are ideal building blocks for fabricating multifunctional theranostic agents for simultaneous diagnosis and therapy. We develop multifunctional nanoparticles based on NaGdF4:Yb/Er@NaGdF4 core–shell UCNPs, which are not only endowed with upconversion luminescence (UCL), magnetic resonance (MR) and X-ray computed tomography (CT) imaging ability, but also could be applied as nanocarriers for targeted drug delivery. We systematically investigate their upconversion luminescent, magnetic and X-ray attenuation properties. Importantly, for the first time, we report the controlled loading and delivery of a mixture of chemotherapeutic anticancer drugs, camptothecin (CPT) and doxorubicin (DOX), through UCNPs-based nanocarriers considering that the combined use of two or more drugs usually exhibits much better therapeutic efficacy than that of a single drug. By conjugating nanoparticles with folic acid (FA), which targets folate receptors over expressed on various types of cancer cells, we further demonstrate targeted tri-modal UCL/MR/CT cell imaging and drug delivery with UCNPs. Our results suggest the as-prepared nanocomposites are highly versatile and could potentially be used for simultaneous imaging and therapeutic applications.