Calcium-binding near-infrared fluorescent nanoprobe for bone tissue imaging

We report a self-assembled calcium-binding nanoprobe which emits a near-infrared fluorescence (NIRF) signal. We have designed a calcium-binding NIRF nanoprobe by chemically coupling alendronate (ALN), a specific targeting ligand, and NIRF-emitting Cy5.5-labeled dibenzocyclooctyne, to the two respective ends of azide-polyethylene glycol-NHS ester. Prepared ALN-PEG-Cy5.5 forms the self-assembled nanostructures and has high affinity for calcium phosphates-containing bone minerals. In addition, ALN-PEG-Cy5.5 can be employed to visualize intracellular calcium ion levels in vitro as well as normal bone tissues in vivo. These results suggest that our calcium-binding NIRF nanoprobe has a promising potential for calcium imaging in vitro and in vivo. (C) 2020 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.