Quasi-dendritic sulfonate-based organic small molecule for high-quality NIR-II bone-targeted imaging

The visualization of bone imaging in vivo is of great significance for the understanding of some bone-related diseases or physiological processes. Herein, a bone-targeted NIR-II small molecule (TTQF-SO₃), which was modified with multiple sulfonate groups, was successfully fabricated for the second near-infrared (NIR-II) bone imaging. In vitro studies revealed that TTQF-SO₃ showed high affinity for hydroxyapatite and excellent macrophage accumulation ability. In in vivo assays, TTQF-SO₃ displayed high bone uptake ability and high NIR-II bone imaging quality, demonstrating the specific bone-targeting ability of the sulfonate-containing probe. In addition, the noninvasive NIR-II imaging detection in bone calcium loss was successfully verified in osteoporosis mice models. Moreover, the negative charge characteristic of TTQF-SO₃ showed efficient lymphoid enrichment in living mice by intravenous injection. Overall, these warrant that our TTQF-SO₃ is an optimal bone-targeted diagnostic agent for high-quality NIR-II imaging, highlighting its potential promise for clinical translation.