Rational Design of Polymethine Dyes with NIR-II Emission and High Photothermal Conversion Efficiency for Multimodal Imaging-Guided Photo-immunotherapy.

Phototheranostics have emerged and flourished as a promising pattern for cancer theranostics owing to their precise photoinduced diagnosis and therapeutic to meet the demands of precision medicine. The diagnosis information and therapeutic effect are directly determined by the fluorescence imaging ability and photothermal conversion efficiency (PCE) of phototheranostic agents. Hence, how to balance the competitive radiative and nonradiative processes of phototheranostic agents is the key factor to evaluate the phototheranostic effect. Herein, we rationally designed molecules named ICRs with fluorescence emission in the second near-infrared (NIR-II, 1000-1700 nm), exhibiting high photostability and high PCE. The optimized D-A interaction and reorganization energy of ICRs were considered to be the key factors for their high PCE. Noteworthily, ICR-Qu with stronger D-A interaction and large-sized conjugated unit encapsulated in nanoparticles exhibited high PCE (81.1%). Besides, ICR-QuNPs were used for fluorescence imaging (FLI), photoacoustic imaging (PAI), and photothermal imaging (PTI) to guide deep-tissue photonic hyperthermia, achieving precise removal and inhibition of breast cancer. Furthermore, combined with α-PD-1, ICR-QuNPs showed huge potential to be a facile and efficient tool for photo-immunotherapy. More importantly, this study not only reported an "all-in-one" polymethine-based phototheranostic agent but also shed light on the exploration of versatile organic molecules for future practical applications. This article is protected by copyright. All rights reserved.