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Bioconjugates of versatile β-diketonate-lanthanide complexes as probes for time-gated luminescence and magnetic resonance imaging of cancer cellsin vitroandin vivo

Abstract:

Magnetic resonance imaging (MRI) and optical imaging (OI) are attractive for constructing bimodal probes due to their complementary imaging characteristics. The combination of these two techniques could be a useful tool to simultaneously obtain both anatomical and molecular information as well as to significantly improve the accuracy of detection. In this study, we found that β-diketonate-lanthanide complexes, BHHBCB-Ln3+, could covalently bind to proteins to exhibit long-lived and intense luminescence (Ln3+= Eu3+,τ= 0.52 ms,Φ= 0.40) and remarkably high relaxivity (Ln3+= Gd3+,r1= 35.67 mM−1s−1,r2= 43.25 mM−1s−1) with excellent water solubility, stability and biocompatibility. Hence, we conjugated BHHBCB-Ln3+with a tumor-targetable biomacromolecule, transferrin (Tf), to construct the probes, Tf-BHHBCB-Ln3+, for time-gated luminescence (TGL, Ln3+= Eu3+) and MR (Ln3+= Gd3+) imaging of cancerous cellsin vitroandin vivo. As expected, the as-prepared probes showed high specificity to bind with the transferrin receptor-overexpressed cancerous cells, to enable the probe molecules to be accumulated in these cells. Using Tf-BHHBCB-Ln3+as probes, the cultured cancerous cells and the tumors in tumor-bearing mice have been clearly visualized by background-free TGL andin vivoMR imaging. The research outcomes suggested the potential of β-diketonate-lanthanide complexes for use in constructing bimodal TGL/MR imaging bioprobes.