Photostability Highly Improved Nanoparticles Based on IR-780 and Negative Charged Copolymer for Enhanced Photothermal Therapy

The development of near-infrared (NIR) dyes with desirable photophysical characteristics for tumor therapy is highly expected at present. In this report, IR-780 iodide was loaded by the mercaptopropionic acid grafted poly(ethylene glycol)-block-poly(ε-caprolactone)-block-poly(allyl glycidyl ether) [mPEG5K-PCL10K-PAGE6 (MPA)] copolymer to form nanomicelles (IR-780@TBMPA) in aqueous solution. On account of the hydrophobic and electrostatic interaction between mPEG5K-PCL10K-PAGE6 (MPA) and IR-780, the IR-780@TBMPA micelle was structurally stable with improved solubility, light stability and biocompatibility. The encapsulation of IR-780 indicated no influence on its original physicochemical property, showing good optical and thermal characteristics. The drug-loaded micelles had appropriate microscopic size for endocytosis, displaying significant cytotoxicity to HeLa cells under NIR laser irradiation. In addition, the phototoxicity generated by photothermal and photodynamic effect of IR-780@TBMPA under 808 nm laser irradiation was also investigated by reactive oxygen species (ROS) detection and flow cytometry. Furthermore, the superior accumulation of IR-780@TBMPA in tumor tissues provided sufficient hyperthermia to kill tumor cells, indicating its potential in cancer clinical therapy.