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Multi-modality in vivo bioimaging has great renown for offering more comprehensive information in medical diagnosis and research. Incorporating different bioimaging capabilities into one biocompatible nanoprobe requires an elegant structural design. Considering optical and magnetic properties, X-ray absorption ability, and clinical safety, we prepared a water-soluble and upconverting PSIoAm-modified Sr2Yb0.3Gd0.7F7:Er3+/Tm3+ bio-probe that not only had high photostability and excellent cell membrane permeability, but could also distinguish the four types of cancer cells and normal cells tested within the scope of our study. What's more, it could realize the in vivo trimodality imaging of upconversion fluorescence, X-ray computed tomography and magnetic resonance. The histological analysis of visceral sections further demonstrated that the multifunctional bio-probe was highly safe, which could be applied to clinical diagnosis.

In this study, water-soluble PEG-modified Sr 2 YbF 7 :Tm 3+ was prepared conveniently by a one-pot solvothermal method, where the molar ratio of Sr 2+ to Yb 3+ was controlled between 3 : 2 and 1 : 1. The optimum red-light emission at 677-699 nm was modulated via 0.7% Tm 3+ doped under irradiation at 980 nm. Interestingly, biological experimental results showed that the PEG-modified Sr 2 YbF 7 :Tm 3+ with low toxicity, excellent cell membrane permeability and high photostability can not only distinguish HeLa cells from mouse embryonic fibroblasts but also target the subcellular organelle lysosome in HeLa cells; therefore it can be anticipated that the as-prepared material would be a potential tool for cancer diagnosis.