NIR-II fluorescence imaging of bone using synergistic targeting nanoprobes for precise diagnosis of skeletal disorders

A synergistic nanoprobe enables precise, safe, non-radiative skeletal imaging. • Multi-targeting enables precise enrichment throughout the skeleton. • AA@TFN provides a versatile platform for bone disease diagnosis and monitoring. Early diagnosis of bone-related diseases remains a critical clinical challenge, attributable to persistent limitations in imaging accuracy and safety. While near-infrared Region II fluorescence (NIR-II FL) imaging confers substantial advantages for deep-tissue visualization, its clinical translation is hampered by the inadequate targeting specificity of conventional contrast agents. Here, we developed Au-Ag@Apo-Tf/-N 3 (AA@TFN), a synergistic targeting gold–silver nanocluster probe engineered with glutathione and azide functionalities, which achieved bone-specific enrichment via a hierarchical multi-targeting mechanism. AA@TFN first anchored to hydroxyapatite in the bone matrix through glutathione carboxyl-mediated chelation, then targeted transferrin receptors highly expressed in bone marrow, and finally endured macrophage-mediated uptake facilitated by azide-enhanced bone affinity. A synergistic targeting strategy enabled real-time, high-resolution NIR-II FL imaging across the complete skeleton, with enhanced probe enrichment at lesion sites driven by microenvironmental changes. AA@TFN enabled visualization of synovial inflammation in rheumatoid arthritis models and millimeter‑scale microlesions in multiple myeloma models. Furthermore, the probe exhibited excellent biocompatibility and favorable safety profiles, underscoring its strong translational potential. A versatile platform was established for the diagnosis of bone diseases and non-invasive monitoring of therapeutic efficacy. Download: Download high-res image (129KB) Download: Download full-size image