Oxygen-evolving hollow polydopamine alleviates tumour hypoxia for enhancing photodynamic therapy in cancer treatment

Hypoxia, a characteristic hallmark of solid tumours, restricts the therapeutic effect of photodynamic therapy (PDT) for cancer treatment. To address this issue, a facile and nanosized oxygen (O(2)) bubble template is established by mixing oxygenated water and water-soluble solvents for guiding hollow polydopamine (HPDA) synthesis, and O(2) is encapsulated in the cavity of HPDA. HPDA with abundant catechol is designed as a carrier for zinc phthalocyanine (ZnPc, a boronic acid modified photosensitizer) via borate ester bonds to fabricate nanomedicine (denoted as HZNPs). The in vitro and in vivo results indicate that O(2)-evolving HZNPs could alleviate tumour hypoxia and enhance PDT-anticancer efficiency. Melanin-like HPDA with a photothermal conversion rate (η) of 38.2% shows excellent synergistic photothermal therapy (PTT) efficiency in cancer treatment.