Donor-acceptor-donor small molecules for fluorescence/photoacoustic imaging and integrated photothermal therapy.

Here, a D-A-D type fluorescent conjugated molecule with a high molar absorption coefficient and emission at 1120 nm in the near-infrared region was synthesized. Conjugated molecules and two polyethylene glycol polymers with different lipophilic ends are assembled into water-soluble nanoparticles to improve their biocompatibility. Then, their physical and chemical properties were studied and compared. Compared with phospholipid-based PEG, styrene-based PEG can reduce the π-π stacking between molecules and the quenching caused by molecular aggregation. It has more advantages in particle size and fluorescence performance and can be better used in biological imaging. In addition, the Nano-particles have good photo-thermal conversion efficiency; the temperature rises to 62.8°C after 980 nm irradiation for 6 min, which can be used as a potential near-infrared II photothermal therapeutic agent. In vivo imaging experiments confirmed that nanomaterials have fluorescence, photoacoustic dual-modal imaging and good biological safety. STATEMENT OF SIGNIFICANCE: In this work, we constructed D-A-D type dual donor fluorescent molecules using BBTD, CPDT and EDOT, and used amphiphilic polymers to improve their biocompatibility. Compared with DSPE NPs, PS-NPs can reduce intermolecular π-π stacking and increase quantum yield (QY = 0.98 %). Deep penetration and low biological toxicity make it have biomedical value and realize the integration of multi-functional collaborative imaging. This work can still be further improved and supplemented, and the molecular structure can be optimized to improve its application in biomedical imaging.