Near-Infrared multifunctional theranostic agent with Wave-Like aggregates modulated by substituent position effect

Precise design of organic photosensitizers (PSs) promoted the technological innovation for multimodal imaging-guided synergistic therapy. Nonetheless, various group substitution could not only optimize the basic photophysical behavior, but possibly change the aggregate, which handicaps the deep understanding of the "Formula-Aggergete-Property" relationship. Bearing this in mind, herein two isomers, named 6-TDE and 7-TDE, were prepared via substituting position modification. Among them, 6-TDE exhibited the grid-like structure, while 7-TDE presented wavy-like structure. Despite the aggregates were different, 6-TDE and 7-TDE shared common features including partly twisted backbone and non-overlapped-orbit, hence resulting in similar optical physical behavior such as decent extinction coefficient, near-IR emission, large stockes shifts, etc. Meanwhile, though two PSs could both generated Type-I and Type-II ROS, 7-TDE possessed smaller singlet-triplet splitting (ΔE_ST), which exhibited favorable ROS as well as outstanding mitochondrial targeting, achieving efficient photodynamic therapy (PDT) effect. During this process, mitochondrial autophagy could be tracked and observed effectively and in real-time. Moreover, 7-TDE presented outstanding performance in multimodal imaging, including fluorescence imaging (FLI), photoacousticimaging (PAI) and photothermal imaging (PTI). This study enriches the strategy of precise molecular engineering to optimize theranostic agents.