Near-infrared optical and X-ray computed tomography dual-modal imaging probe based on novel lanthanide-doped K0.3Bi0.7F2.4 upconversion nanoparticles

A novel K0.3Bi0.7F2.4 upconversion (UC) matrix has been prepared successfully by a solvothermal method. K0.3Bi0.7F2.4:Yb3+/Ln3+ (Ln = Er, Ho, Tm) upconversion nanoparticles (UCNPs) show a corresponding excellent upconversion luminescence (UCL) under 980 nm laser irradiation. Especially, the strong near-infrared (NIR) UCL of K0.3Bi0.7F2.4:20% Yb3+/0.5% Tm3+ (abbreviated as BYT) UCNPs is suitable for deep tissue optical imaging. Moreover, the high X-ray absorption coefficient of Bi makes the as-prepared UCNPs favorable for computed tomography (CT) imaging. The citrate-coated BYT UCNPs show good biocompatibility through the MTT assay towards HeLa cells and low hemolytic properties by hemolysis assay, which could be applied for in vivo optical and CT imaging. After intravenous injection of citrate-coated BYT UCNPs for one month, blood biochemistry and histology analysis of mice suggest the UCNPs have a negligible toxicity in vivo, implying citrate-coated BYT could be employed as a safe bioprobe for NIR optical and CT dual-modal imaging.