Side‐Chain Engineering of Aggregation‐Induced Emission Molecules for Boosting Cancer Phototheranostics

Abstract The ingenious construction of versatile cancer phototheranostics involving fluorescence imaging (FLI) and photodynamic and photothermal therapies (PDT, PTT) concurrently has attracted great interest. By virtue of their inherent twisted structures and plentiful motion moieties, aggregation‐induced emission luminogens (AIEgens) have been proven to be perfect templates for the development of multimodal phototheranostic systems as their diverse energy consumption pathways can be flexibly regulated through tuning the intramolecular motions. Side‐chain engineering is generally accepted as a useful regulation strategy for intramolecular motions through altering the side‐chain structure of the molecule, but has rarely been reported for the construction of AIE‐active multimodal phototheranostics. Herein, by taking full advantage of the side‐chain engineering strategy, an AIE‐active multifunctional phototheranostic system (TBFT2 nanoparticles) is successfully constructed by intentionally manipulating the length of side chains. Bearing the longest alkyl chain, all of those three energy dissipation pathways including radiative decay, nonradiative thermal deactivation, and intersystem crossing process of TBFT2 are retained simultaneously and controllably in the aggregate state. In vitro and in vivo evaluations verify that TBFT2 nanoparticles perform well in terms of FLI‐guided PDT and PTT synergistic cancer therapy. This study thus provides new insight into the exploration of superior versatile phototheranostics through side‐chain engineering.