Carbon dots deposition in adult bones reveal areas of growth, injury and regeneration

C-dots synthesized from carbon nanopowder (oxidation, hydrothermal) are particularly attractive theragnostic agents for bone-related injuries and disease due to their bright fluorescence and high binding affinity and specificity for bones, as demonstrated in a larval animal model. Larval bone development, however, is significantly different from the bone growth, repair and regeneration processes occurring in adults. Using adult zebrafish, we investigated C-dots interactions with adult skeletal structures. Upon injection, C-dots were observed at the surface of bones, at sites of appositional growth. In regenerating bones, C-dots were observed at the core and on the surface of the bones depending on the age of the tissue. C-dots deposition occurred within 30 min of delivery and it was highly selective. Importantly, their deposition did not interfere with bone regeneration or the animals health. Together, these properties establish C-dots as novel tools for the diagnostic and treatment of adult bone-related injuries and diseases.