Xanthene-Based NIR organic phototheranostics agents: Design strategies and biomedical applications

Abstract

Fluorescence imaging and phototherapy in near-infrared window (NIR, 650-1700 nm) has attracted great attention for biomedical applications due to its minimal invasiveness, ultra-low photon scattering and high spatial-temporal precision. Among NIR emitting/absorbing organic dyes, xanthene derivatives with controllable molecular structures and optical properties, excellent fluorescence quantum yields, high molar absorption coefficients and remarkable chemical stability have been extensively studied and explored in the field of biological theranostics. The present study aims to provide a comprehensive summary of the progress in the development and design strategies of xanthene derivative fluorophores tailored for advanced biological phototheranostics. Firstly, this study elucidates several representative controllable strategies, including electronic programming strategies, extension of conjugated backbones, and strategic establishment of activatable fluorophores, which enhance the NIR fluorescence of xanthene backbones. Then, the development of xanthene nanoplatforms based on NIR fluorescence for biological applications is detailed. Overall, this work outlines future efforts and directions for improving NIR xanthene derivatives to meet evolving clinical needs. It is anticipated that this contribution could provide a viable reference for the strategic design of organic NIR fluorophores, thereby enhancing their potential clinical practice in future.