A fluorophore with dithienopyrrole donor for beyond 1300 nm NIR-II fluorescence/photoacoustic dual-model imaging and photothermal therapy

The fluorescence imaging in the beyond 1300 nm NIR-II window shows higher imaging depth, resolution and signal-to-noise ratio than shorter wavelength window. However, the design and synthesis of the fluorophores with such long-wavelength emission are still very challenging. Herein, we synthesized a novel NIR-II fluorophore DTP-DPTQ with dithienopyrrole (DTP) as the donor and 6,7-diphenyl- [1,2,5]thiadiazolo [3,4-g]quinoxaline (DPTQ) as the acceptor. The strong electron-donating ability of DTP enables DTP-DPTQ to be one of the longest emission fluorophores with the DPTQ acceptor. After encapsulation with F127 for hydrophilization, the emission of the formed DTP-DPTQ nanoparticles (NPs) in aqueous medium was centered at 1120 nm with a part beyond 1300 nm. By using DTP-DPTQ NPs as the contrast agent, the 86.9 μm wide vessels could be clearly seen via the in vivo imaging with 1300 nm long-pass optical filter. In addition, we also verified the good performance of the DTP-DPTQ NPs in photoacoustic imaging and photothermal therapy of tumors, signifying that the DTP-DPTQ NPs are an excellent candidate in the precise dual-modal diagnosis and efficient therapy of tumors.