Singzyme: A Single–Molecule Enzyme–Like Photocatalyst Powered by the Super Cage Effect

Photodynamic therapy (PDT) represents a powerful approach for treating cancers through light-induced reactive oxygen species (ROS) generation; however, its efficacy is often constrained by limitations in photosensitivity, ROS yield, and tumor microenvironment adaptation. Addressing these challenges requires highly engineered photosensitizers capable of enhanced light absorption, stable catalytic performance, and selective redox modulation. Herein, we introduce a structurally and functionally single-molecule enzyme-like photocatalyst (superphane <b>1</b>), a supramolecular photosensitizer based singzyme designed through a "super cage effect" or "superphane effect" that promotes enhanced photosensitivity, superior ROS generation, photocatalytic oxidation and multi-enzyme mimetic activities. Its unique structure, featuring precisely and densely arranged phenothiazine units, maximizes light absorption and optimizes electron transfer dynamics, resulting in an excellent singlet oxygen (¹O₂) yield of 70% under 450 nm irradiation, significantly surpassing the yields of 42% for cage <b>2</b>, 39% for macrocycle <b>3</b>, and 24% for monomer <b>4</b>. Functionally, singzyme <b>1</b> exhibits excellent catalytic efficiency to NADH (<i>K</i> _cat/<i>K</i> _m = 2.43 × 10⁴ L mol^-1 min^-1) and catalyzes oxidation of NADH and GSH, mimicking NADH oxidase and GSH oxidase activity. This selectively depletes NADH and GSH, inducing an intracellular "oxygen burst" effect. This redox imbalance inhibits mitochondrial oxidative phosphorylation (OXPHOS), reduces ATP production, and promotes apoptosis and ferroptosis pathways. With stable activity across acidic and neutral pH environments typical of tumors, singzyme <b>1</b> provides a versatile, biocompatible platform for precision cancer therapy. This study establishes a superphane-based singzyme with precise structure and multi-enzyme mimetic functionality, paving the way for single-molecule enzyme mimicry.