Lanthanide-Bisphosphonate Coordination Chemistry: Biocompatible Fluorescent Labeling Strategy for Hydrogel

Fluorescent hydrogel demonstrates great potential in biomedical field as chemo/biosensor and bioimaging agent Herein, a labeling strategy based on coordination bond between lanthanide and bisphosphonate (BP) is reported to form fluorescent hydrogel. Specifically, BP-acrylamide compound was synthesized as organic "antenna" to stabilize lanthanide fluorescent signal. The coordination chemical structure and interaction energy between lanthanide (Eu3+) and BP-acrylamide ligand were obtained using density functional theory (DFT) calculations, indicating strong binding of Eu3+ ions with phosphonic oxygen atoms. Additionally, the lanthanide center dot BP complex could be chemically incorporated through acrylamide group into poly(ethylene glycol) diacrylate network to fabricate fluorescent hydrogels. The dynamic inherent properties of lanthanide center dot BP coordination bonds imparted the presented hydrogel's multistimuli-responsive properties against pH value and metal ions. The animal experiments revealed lanthanide-BP fluorescent hydrogel of great biocompatibilities and long-term structure stabilities in vivo. Therefore, we provide a facile coordination labeling strategy to develop biocompatible fluorescent hydrogel that presents potential for biomedical sensing and imaging applications.