Carbon dots for long-term near-infrared afterglow imaging and photodynamic therapy

Imaging-guided photodynamic therapy (PDT) has the features of precise location and non-invasiveness. However, most of the photosensitizers (PSs) for PDT are poor fluorescent emitters, and the inadequate fluorescence is usually interfered by tissue auto-fluorescence. The afterglow phosphorescence could ideally address the issues of fluorescence imaging. Therefore, it is of double benefit to design phosphorescent CDs for enhanced near-infrared (NIR) phototheranostics. Hereon, we synthesized CDs with excellent biosafety, outstanding stability, good water dispersibility and effective photodynamic activity. CDs could emit NIR luminescence with long lifetime over 2 h, which afforded large tissue penetration (10 mm) and high SNR (98.4) for deep-tissue and long-term in vivo persistent luminescent imaging. Moreover, abundant reactive oxygen species generated by CDs enabled NIR afterglow imaging-guided PDT to effectively inhibit tumor growth. This work demonstrates the enormous potential of CDs as multifunctional nanoplatforms for biomedical application.