Highly Efficient Photothermal Therapy of Tumors Using Easily Prepared Nanoparticles

The simple molecular design of small molecule-based photothermal nano-agents with high photothermal conversion efficiencies (η) remains a highly challenging obstacle in the development of new anti-tumor drugs. Although several efficient small agents have been reported, they tend to contain bulky alkyl chains and/or aromatic rings, which were introduced to enhance the photothermal effect, but result in complicated preparation procedures. Herein, we report the preparation of nano-agents from commercial reagents using a one-step organic reaction with facile purification and a subsequent simple self-assembly process in water under a flow of air overnight. The obtained nano-agents exhibited high photothermal conversion efficiencies (η) of up to 92.5%. This photothermal effect originated mainly from twisted C=N bond-induced non-radiative decay with completely inhibited radiative decay and the intersystem crossing process. In addition, the photothermal effect was enhanced by synergistic twisted intramolecular charge transfer, strong donor–acceptor interactions, various intramolecular vibrations, and the presence of rotators. The obtained nano-agents efficiently inhibited tumor growth after 10 d of photothermal therapy, and they exhibited a good biocompatibility in a mouse tumor model. This simple approach can conveniently facilitate the further development and testing of such systems.