Photosynthetic Black Phosphorus/Antimonene Quantum Dot/Chlorella Heterojunction-Enhanced Biohybrids for Hypoxia-Alleviated Photodynamic Immunotherapy

Abstract

Tumor hypoxia compromises oxygen-dependent photodynamic therapy (PDT) and concurrently supports an immunosuppressive tumor microenvironment. Here, a living photosynthetic biohybrid (BA-Chl) was constructed by integrating a nanoscale black phosphorus (BP)-antimonene quantum dot (AM) heterojunction with oxygen-evolving Chlorella (Chl). The heterointerface formed between BP and AM quantum dots facilitates efficient spatial separation of photogenerated charges, thereby enhancing reactive oxygen species (ROS) generation while cooperating with algal photosynthesis to sustain oxygen supply. In 4T1 tumor-bearing mice, BA-Chl mediated PDT produced marked tumor suppression and was associated with immunogenic cell death and subsequent immune activation. The treatment increased dendritic cell maturation to 20.2%, elevated tumor-infiltrating CD8+ T cells from 2.65% to 9.72%, and reduced intratumoral regulatory T cells from 12.7% to 2.06%. These coordinated changes were accompanied by more than 90% inhibition of tumor growth. Collectively, these results support interfacial charge-transfer engineering in photosynthetic biohybrids as a strategy to couple tumor oxygenation with enhanced photodynamic therapy and antitumor immune activation.