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<p>Organic fluorophores operating in the second near-infrared (NIR-II, 1000–1700 nm) window are highly attractive for cancer phototheranostics. Yet, the advancement of aza-BODIPY-based NIR-II dyes remains challenging due to their limited spectral tunability and diminished fluorescence quantum yields (FLQY) under physiological conditions. Herein, we propose a rational donor-acceptor (D-A) molecular engineering strategy to construct an aza-BODIPY fluorophore, TPACN, featuring intramolecular charge transfer (ICT)-enhanced NIR-II emission and balanced photothermal performance. By introducing electron-rich triphenylamine (TPA) donors and peripheral cyano (−CN) acceptors, the optimized D-A coupling significantly strengthened the ICT effect, leading to broadened NIR absorption, a markedly red-shifted fluorescence peak at 1086 nm, and an exceptional fluorescence quantum yield of 1.55% in dichloromethane (DCM). When encapsulated in F127, TPACN nanoparticles (TPACN NPs) maintained a high aqueous FLQY of 0.20%, accompanied by a notable photothermal conversion efficiency (PCE) of 39% under 808 nm irradiation. The sterically twisted TPA units effectively alleviated aggregation-caused quenching (ACQ) and fine-tuned the excited-state energy dissipation pathways, realizing a synergistic balance between radiative (fluorescence) and non-radiative (heat) relaxation. Benefiting from these optimized photophysical properties, TPACN NPs achieved high-resolution NIR-I photoacoustic and NIR-II fluorescence dual-modal imaging, enabling accurate tumor visualization and efficient photothermal ablation <i>in vivo.</i> This work introduces a general design paradigm that exploits ICT modulation and steric engineering to overcome the intrinsic fluorescence bottleneck of aza-BODIPY systems, offering new molecular insights for the advancement of high-performance NIR-II dyes for precision phototheranostics.</p>

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Donor-acceptor engineered aza-BODIPY fluorophore with intramolecular charge transfer-enhanced NIR-II emission for tumor phototheranostics

  • 期刊论文

  • 发表日期：

    2026年5月6日

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  • Leichen Wang,
  • Qing Shen,
  • Weili Wang,
  • Xu Sun,
  • Jinjun Shao,
  • Su Jing,
  • Xiaochen Dong

摘要

Organic fluorophores operating in the second near-infrared (NIR-II, 1000–1700 nm) window are highly attractive for cancer phototheranostics. Yet, the advancement of aza-BODIPY-based NIR-II dyes remains challenging due to their limited spectral tunability and diminished fluorescence quantum yields (FLQY) under physiological conditions. Herein, we propose a rational donor-acceptor (D-A) molecular engineering strategy to construct an aza-BODIPY fluorophore, TPACN, featuring intramolecular charge transfer (ICT)-enhanced NIR-II emission and balanced photothermal performance. By introducing electron-rich triphenylamine (TPA) donors and peripheral cyano (−CN) acceptors, the optimized D-A coupling significantly strengthened the ICT effect, leading to broadened NIR absorption, a markedly red-shifted fluorescence peak at 1086 nm, and an exceptional fluorescence quantum yield of 1.55% in dichloromethane (DCM). When encapsulated in F127, TPACN nanoparticles (TPACN NPs) maintained a high aqueous FLQY of 0.20%, accompanied by a notable photothermal conversion efficiency (PCE) of 39% under 808 nm irradiation. The sterically twisted TPA units effectively alleviated aggregation-caused quenching (ACQ) and fine-tuned the excited-state energy dissipation pathways, realizing a synergistic balance between radiative (fluorescence) and non-radiative (heat) relaxation. Benefiting from these optimized photophysical properties, TPACN NPs achieved high-resolution NIR-I photoacoustic and NIR-II fluorescence dual-modal imaging, enabling accurate tumor visualization and efficient photothermal ablation in vivo. This work introduces a general design paradigm that exploits ICT modulation and steric engineering to overcome the intrinsic fluorescence bottleneck of aza-BODIPY systems, offering new molecular insights for the advancement of high-performance NIR-II dyes for precision phototheranostics.