Interstitial Optical Fiber‐Mediated Multimodal Phototheranostics Based on an Aggregation‐Induced NIR‐II Emission Luminogen for Orthotopic Breast Cancer Treatment

Abstract One‐for‐all phototheranostics based on a single molecule is recognized as a convenient approach for cancer treatment, whose efficacy relies on precise lesion localization through multimodal imaging, coupled with the efficient exertion of phototherapy. To unleash the full potential of phototheranostics, advancement in both phototheranostic agents and light delivery methods is essential. Herein, an integrated strategy combining a versatile molecule featuring aggregation‐induced emission, namely tBuTTBD, with a modified optical fiber to realize comprehensive tumor diagnosis and “inside‐out” irradiation in the orthotopic breast tumor, is proposed for the first time. Attributed to the intense donor‐acceptor interaction, highly distorted conformation, abundant molecular rotors, and loose intermolecular packing upon aggregation, tBuTTBD can synchronously undergo second near‐infrared (NIR‐II) fluorescence emission, photothermal and photodynamic generation under laser irradiation, contributing to a trimodal NIR‐II fluorescence‐photoacoustic (PA)‐photothermal imaging‐guided phototherapy. The tumor treatment is further carried out following the insertion of a modified optical fiber, which is fabricated by splicing a flat‐end fiber with an air‐core fiber. This configuration aims to enable effective in situ phototherapy by maximizing energy utilization for therapeutic benefits. This work not only enriches the palette of NIR‐II phototheranostic agents but also provides valuable insight for exploring an integrated phototheranostic protocol for practical cancer treatment.