A PEGylated conjugated-BODIPY oligomer for NIR-II imaging-guided photothermal therapy†

The integration of second near-infrared (NIR-II) fluorescence imaging and photothermal therapy (PTT) achieved precise and efficient tumor treatment. BODIPY, a promising fluorescent dye, is widely used in biological fluorescence imaging due to its excellent optical properties and chemical stability. However, the excitation wavelengths of BODIPY typically range from 530 nm to 650 nm within the visible spectrum, which significantly limits tissue penetration. In this work, a self-assembled nanoparticle (BODIPY₄–PEG NP) was fabricated with a BODIPY-conjugated oligomer (BODIPY₄) bearing a hydrophilic polyethylene glycol (PEG) chain. BODIPY₄–PEG NPs exhibit excellent NIR-II emission, with a maximum fluorescence emission peak of 1123 nm. The outstanding imaging performance of BODIPY₄–PEG NPs has been evaluated in the imaging of lymph nodes and the vascular system in mice, demonstrating excellent spatial resolution. Based on the excellent imaging performance and photothermal conversion efficiency (35%) of the BODIPY₄–PEG NPs, they can be further utilized in NIR-II imaging-guided photothermal therapy. In a 4T1 tumor-bearing mouse model, BODIPY₄–PEG NPs exhibited strong fluorescence under 980 nm laser irradiation and successfully induced heat generation to eliminate the tumor. To summarize, BODIPY₄–PEG NPs contribute to the ongoing progress in the field of NIR-II fluorescence imaging-guided PTT.