Pure dark red emission (650-670 nm) of NaYF(4):Yb/Er upconversion nanoparticles (UCNPs) is achieved by manganese ions (Mn(2+)) doping. In addition, the Mn(2+)-doping can also control the crystalline phase and size of the resulting UCNPs simultaneously. Drug delivery studies suggest the promise of these UCNPs as drug carriers for intracellular drug delivery and eventually as a multifunctional nanoplatform for simultaneous diagnosis and therapy.

Upconverting nanoparticles (UCNPs) have attracted considerable attention as potential photosensitizer carriers for photodynamic therapy (PDT) in deep tissues. In this work, a new and efficient NIR photosensitizing nanoplatform for PDT based on red-emitting UCNPs is designed. The red emission band matches well with the efficient absorption bands of the widely used commercially available photosensitizers (Ps), benefiting the fluorescence resonance energy transfer (FRET) from UCNPs to the attached photosensitizers and thus efficiently activating them to generate cytotoxic singlet oxygen. Three commonly used photosensitizers, including chlorine e6 (Ce6), zinc phthalocyanine (ZnPc) and methylene blue (MB), are loaded onto the alpha-cyclodextrin-modified UCNPs to form Ps@UCNPs complexes that efficiently produce singlet oxygen to kill cancer cells under 980 nm near-infrared excitation. Moreover, two different kinds of drugs are co-loaded onto these nanoparticles: chemotherapy drug doxorubicin and PDT agent Ce6. The combinational therapy based on doxorubicin (DOX)-induced chemotherapy and Ce6-triggered PDT exhibits higher therapeutic efficacy relative to the individual means for cancer therapy in vitro.

Rare-earth (RE)-doped gadolinium oxide (Gd2O3) hollow nanospheres have been successfully prepared on a large scale via a template-directed method using hydrothermal carbon spheres as sacrificed templates. Scanning electron microscope and transmission electron microscope images reveal that these hollow-structured nanospheres have the mesoporous shells that are composed of a large amount of uniform nanoparticles. By doping the RE ions (Yb/Er) into the Gd2O3 host matrix, these NPs emitted bright multicolored upconversion emissions that can be fine-tuned from green to red by adjusting the codoped Yb/Er ratio under 980 nm NIR laser excitation. The possibility of using these upconversion nanoparticles for optical imaging in vivo has been demonstrated. It was also shown that these Gd2O3 nanospheres brightened the T 1-weighted images and enhanced the r 1 relaxivity of water protons, which suggested that they could act as T 1 contrast agents for magnetic resonance (MR) imaging. Moreover, these hollow spheres can be used as drug delivery host carriers, and drug storage/release properties were investigated using ibuprofen as the model drug. As a result, the so-prepared nanoscaled Gd2O3 hollow spheres bearing upconversion luminescence, MR imaging, and drug delivery capabilities could be potentially employed for simultaneous MR/fluorescent imaging and therapeutic applications.