Cationic conjugated macrocycles, characterized by their large hydrophobic cavities and excellent water solubility, can serve as high-performance hosts to self-assemble with hypocrellin-based guests into supramolecular photosensitizers. However, the short absorption wavelength of supramolecular photosensitizers based on natural hypocrellins severely restricts their application in deep-tissue photodynamic therapy (PDT). In this work, HCEA was selected as the guest molecule which is a hypocrellin derivative with an amino substitution at the 2-position. HCEA exhibits broad-band absorption ranging from 600 to 700 nm and acts as a type-I photosensitizer, thereby offering enhanced potential for hypoxic photodynamic therapy. Through supramolecular assembly of HCEA with two water-soluble cationic conjugated macrocycles, namely AnBox^4＋ and ExAnBox^4＋, two supramolecular photosensitizers were successfully constructed, HCEA⊂AnBox^4＋ and HCEA⊂ExAnBox^4＋. UV-vis absorption spectroscopy confirmed that these host-guest complexes retained the near-infrared (NIR) absorption characteristics of HCEA and significantly improved the water solubility, addressing a long-standing challenge associated with hypocrellin-based photosensitizers. Fluorescence titration studies confirmed a 1∶1 host-guest stoichiometry between HCEA and the conjugated macrocycles, accompanied by remarkably high binding constants on the order of 10⁶ to 10⁸ L/mol, indicating strong and stable complex formation. Reactive oxygen species detection assays confirmed that both HCEA⊂AnBox^4＋and HCEA⊂ExAnBox^4＋ function as type-I supramolecular photosensitizers and can efficiently generate hydroxyl radicals (•OH) and superoxide anions ($\text{O}_{2}^{\bullet - }$). Confocal laser scanning microscopy further validated the efficient intracellular ROS generation by these supramolecular photosensitizers. Importantly, in vitro cytotoxicity assessments combined with calcein AM and propidium iodide (AM/PI) cell viability assays revealed that the supramolecular photosensitizers not only exhibited excellent biocompatibility but also achieved remarkable photodynamic therapeutic efficacy even under hypoxic conditions. This study provides a novel strategy for constructing conjugated macrocycle-based NIR supramolecular photosensitizers and implementing photodynamic therapy against hypoxic tumors, with promising potential for future clinical translation.

Key words: hypocrellin derivative, cationic conjugated macrocycle, type Ⅰ photosensitizer, near-infrared supramolecular photosensitizer, hypoxic photodynamic therapy