Symmetrically Fluorinated D‐π‐A Structured Cyanine Dye for Highly Efficient NIR‐II Imaging‐Guided Cancer Phototheranostics

Abstract Near‐infrared‐II (NIR‐II) fluorescence imaging‐guided photothermal therapy (PTT) represents a cutting‐edge approach for precise tumor diagnosis and treatment, providing real‐time therapeutic efficacy evaluation. However, a significant challenge lies in the creation of phototheranostic agents that provide robust imaging and efficient photothermal conversion. To address this, a donor‐ π ‐acceptor (D‐ π ‐A) structure heptamethine cyanine derivative, IR1116, that confers a strong intramolecular charge transfer effect is developed. To enhance its applicability, IR1116 is formulated with DSPE‐PEG to create a water‐dispersible NIR‐II phototheranostic nanoheater, NP IR1116 . This nanoheater benefits from the incorporation of an electron‐withdrawing group, leading to reduced photooxidation activity and significantly improved photostability. NP IR1116 exhibits strong NIR‐II absorption and fluorescence, peaking at 1004 and 1116 nm, respectively, as well as a photothermal conversion efficiency of 79% under 1064 nm lasers. In vitro and in vivo studies showed the efficacy of NP IR1116 in tumor imaging via NIR‐II fluorescence and its ability to effectively induce tumor cell apoptosis under 1064 nm laser irradiation. These findings underscore the potential of NP IR1116 in NIR‐II fluorescence imaging‐guided PTT for tumor treatment, paving the way for further advancements in NIR‐II dye development and bioimaging technologies.