Squaraine nanoparticles for optoacoustic imaging-guided synergistic cancer phototherapy.

The unique optical properties of squaraine dyes make them promising for cancer phototheranostics, but the reported squaraines for treatments mainly rely on their photothermal effect, where monotherapy cannot achieve the desired therapeutic effect. Here we generated a type of squaraine capable of killing tumors through both photothermal and photodynamic effects. We optimized squaraine structure with selenium modulation and formulated it into nanoparticles that showed strong absorption of infrared light, negligible fluorescence, good photothermal conversion (66.6 %), and strong photodynamic effects even after several irradiation cycles. In addition, the nanoparticles could be tracked through their strong optoacoustic signal. In mice, the nanoparticles effectively accumulated in tumors and eliminated them upon irradiation, without causing adverse effects. Our work demonstrates the potential of selenium modulation of squaraine for precise cancer diagnosis and treatment through synergistic photothermal and photodynamic effects.