Cr-Free Bismuth-Based Persistent Luminescence Nanoparticle Composite for Cancer Theranostics

Near-infrared (NIR) persistent luminescence nanoparticles (PLNPs) showed great potential for bioimaging due to their integration of non-in situ excitation and deep tissue penetration. However, PLNPs are often introduced with Cr3+ ions as the NIR emission centers. Herein, we report Cr-free Bi2Ga3.985O9:1.5% Fe3+ (BGF), with Fe3+ ions as the NIR emission centers. BGF under 310 nm excitation exhibited NIR afterglow emission at 794 nm in the first biological imaging window (650–950 nm), with the afterglow duration of 3 h. BGF was grafted with hydroxyl groups and then polydopamine (PDA) for the integration of indocyanine green (ICG) through π–π stacking and hydrophobic interactions, as the PLNP–PDA–ICG composite. Bi in the composite, as a heavy atom element, exhibits computed tomography (CT) contrast capacity, while PDA is a photothermal agent, and ICG is excited to produce reactive oxide species for photodynamic therapy. The afterglow/CT dual-modality imaging-guided photothermal/photodynamic combination therapy was validated with in vitro/vivo imaging and therapeutic applications. This work provides the Cr-free PLNP composite for drug-free theranostics with a low toxicity.