Hollow ferric-tannic acid nanocapsules with sustained O2 and ROS induction for synergistic tumor therapy

Nanoparticles presenting promoted catalytic activity, oxygen induction and loading capability are in high demand for effective synergistic tumor therapy. Herein, ferric-tannic acid complex nanocapsules with fine hollow microstructure (HFe-TA) are synthesized and loaded with a photosensitizer (indocyanine green, ICG) for synergistic tumor therapy. In acidic environment, ICG@HFe-TA decomposes and releases Fe3+ ions, TA and ICG molecules. Fe3+, with low catalytic activity, is effectively converted into highly catalytic Fe2+ by the reductant TA, enabling promoted efficacy of ˙OH induction. More importantly, the ROS (1O2) induction by ICG is significantly enhanced under 808 nm laser irradiation due to the O2 byproduct of Fe3+/Fe2+ conversion. In consequence, the ICG@HFe-TA nanoparticles exhibit considerable in vitro and in vivo tumor inhibition owing to the combined effect of ˙OH and 1O2 induced intracellularly. This study has therefore demonstrated a potential platform enabling combined photodynamic and chemodynamic therapy with high efficacy.