Host–Guest Engineered Pure Organic Phosphorescent Proteins for Long-Persistent Bioimaging and Photocatalytic Controlled Radical Polymerization

Room-temperature phosphorescence (RTP) in proteins is exceptionally rare due to efficient quenching of triplet excitons in aqueous and biological environments. Here, we report a general supramolecular strategy to engineer phosphorescent proteins by embedding organic phosphors within protein scaffolds via host–guest interactions, where the confined microenvironment suppresses nonradiative decay and stabilizes triplet states, enabling bright and long-lived phosphorescence in both the solid state and aqueous media. The stabilized triplet excitons further endow these phosphorescent proteins with photocatalytic activity, allowing them to serve as efficient photosensitizers for photoinduced electron transfer-mediated reversible addition-fragmentation chain transfer polymerization in water, exhibiting excellent temporal control, predictable molecular weights, and narrow dispersities, with mechanistic studies supporting an electron-transfer pathway. Moreover, these systems enable polymerization-induced self-assembly to generate vesicular structures that encapsulate the photoactive proteins while retaining persistent afterglow emission, thereby integrating cellular-like compartmentalization with intrinsic optical traceability. This work establishes a versatile supramolecular route to RTP proteins and expands protein–phosphor assemblies toward artificial phosphorescent cells and light-driven biochemical systems.