Advances in Organic Aggregates for Biomedical Phototheranostics

Organic aggregates are emerging as versatile platforms for biomedical phototheranostics, as aggregation provides a direct means to regulate excited‐state behavior beyond the limits of isolated chromophores. Whereas conventional organic dyes often undergo aggregation‐caused quenching, uncontrolled packing, and rapid nonradiative deactivation, rationally engineered aggregates can enhance fluorescence, stabilize triplet excitons, promote reactive oxygen species generation, or channel absorbed energy into heat and photoacoustic signals. This review summarizes recent progress in the design and biomedical application of organic aggregates, with particular emphasis on the relationships among molecular structure, aggregate organization, excited‐state energy dissipation, optical output, and biological function. We discuss key aggregate‐state photophysical mechanisms, including aggregation‐induced emission, restriction of intramolecular motion, excitonic coupling, charge‐transfer interactions, and triplet‐state stabilization, and examine how these principles are implemented through molecular packing, crystallinity, supramolecular confinement, and nanostructure engineering. Representative applications in fluorescence and room‐temperature phosphorescence imaging, photoacoustic and photothermal imaging, photodynamic and photothermal therapy, and multimodal image‐guided treatment are highlighted. Finally, we outline major challenges related to structural heterogeneity, in vivo stability, biodistribution, biodegradation, biosafety, reproducible manufacturing, and clinical translation, and identify design priorities for next‐generation organic aggregate phototheranostic systems.