Recent advances in NIR-II fluorescence imaging-guided type-I photodynamic therapy

Phototheranostics, which integrates tissue imaging with phototherapy, has shown considerable promise in the early diagnosis and precision treatment of cancers. However, conventional short-wavelength phototheranostic materials are often constrained by the hypoxic tumor microenvironment and limited tissue penetration, resulting in suboptimal performance for deep-seated tumors. Recently, long-wavelength-activated type-I photodynamic therapy (PDT) systems coupled with near-infrared-II (NIR-II) fluorescence have attracted attention due to their improved tissue penetration, high detection sensitivity, and less oxygen-dependent reactive oxygen species generation, positioning them as an ideal platform for treating deep-seated tumors. In this review, we summarize cutting-edge advances in NIR-II fluorescence imaging (FLI)-guided PDT materials, with an emphasis on molecular design strategies and corresponding phototheranostic performance. We also provide in-depth analysis of effective design principles and highlight key breakthroughs in the field. Finally, we discuss current challenges and future prospects for NIR-II emissive photosensitizers, with the goal of advancing the development of NIR-II FLI-guided PDT.