Preparation and Evaluation of Radiolabeled Porphyrin-Functionalized Lipid Nanodroplets for Cancer Theranostics

[111In]In-diethylenetriaminepentaacetic acid-5,10,15,20-tetraphenylporphyrin ([111In]In-DTPA-TPP) nanodroplets were developed for cancer theranostics, featuring ultrasound-sensitive properties. The designed nanodroplets that encapsulate the low-boiling-point liquid perfluorocarbon and IR-780 iodide, a near-infrared fluorescent dye, with surface conjugation of 111In-labeled porphyrin derivative, were synthesized and evaluated by in vitro and in vivo experiments. The cellular uptake of [111In]In-DTPA-TPP nanodroplets was significantly higher than that of control nanodroplets without TPP. Biodistribution experiments revealed greater tumor accumulation in mice injected with [111In]In-DTPA-TPP nanodroplets than in those injected with control nanodroplets lacking TPP. Additionally, the accumulation of [111In]In-DTPA-TPP nanodroplets in the tumor was visualized by single-photon emission computed tomography. Sonodynamic therapeutic experiments revealed that DTPA-TPP nanodroplets at 10 µmol total lipids/kg weight with a single ultrasound irradiation onto the tumor area significantly inhibited tumor growth. These results indicate that [111In]In-DTPA-TPP nanodroplets would be promising cancer theranostic agents.