Galactose conjugated boron dipyrromethene and hydrogen bonding promoted J-aggregates for efficiently targeted NIR-II fluorescence assistant photothermal therapy

It is essential to develop novel multifunctional and easily synthesized stable NIR-II fluorescent probes to guide photothermal therapy for tumors. Here, we propose a new strategy to construct boron dipyrromethene (BODIPY) J-aggregates by intermolecular hydrogen bonding (H-bond) and π-π stacking interactions to achieve fluorescence emission in the second near-infrared window (NIR-II, 1000-1700 nm). A novel meso-benzamide galactose hexanoate-BODIPY (Gal-OH-BDP) amphiphilic small molecular dye was synthesized and it formed nanoparticles spontaneously in aqueous solution with a maximum emission wavelength near 1060 nm, which works as a smart nanomedicine for targeting NIR-II imaging-guided photothermal therapy (PTT) of hepatocellular carcinoma. Galactose not only provided hydrogen bonds to regulate the aggregation pattern of the molecules but also effectively targeted hepatocellular carcinoma cells and promoted the formation of well-dispersed nanoparticles of dye molecules due to their hydrophilicity. Moreover, due to high photothermal conversion efficiency (PCE = 55%), Gal-OH-BDP NPs achieve galactose-targeted NIR-II imaging and PTT, which is important for the precise diagnosis and treatment of tumors (Scheme 1). In the present research work, H-bond was introduced for the first time into BODIPY for building J-aggregates to achieve the NIR-II fluorescence.