Inhomogeneous Au₂S for Photoacoustic Imaging and Photodynamic Tumor Therapy Based on Different Forms of Energy Dissipation

Nanomaterials with unique structures and components play a crucial role in nanomedicine. In this study, we discovered that the inhomogeneous Au 2 S constructed by cation exchange and acid etching could dissipate energy in different forms after absorbing multichromatic light, which could be used to achieve the integrated diagnosis and treatment of tumors, respectively. Folic acid modified Au 2 S ringed nanoparticles (FA-Au 2 S RNs) with an assembly-like structure were demonstrated to result in better PA imaging performance and generate more reactive oxygen species (O2· –, ·OH, and 1 O 2 ) than folic acid modified Au 2 S triangular nanoparticles (FA-Au 2 S TNs). Finite element analyses determined the reason for the high absorbance properties and synergistic enhancement of plasma resonance in the assembly-like structure of Au 2 S RNs. Both FA-Au 2 S nanostructures were modified with folic acid and injected into 4T1 tumor-bearing mice via the tail vein. The best PA imaging contrast was obtained under 700 nm laser illumination, and the most effective PDT antitumor activity was achieved under 1064 nm laser illumination. The PA average of the tumor in the FA-Au 2 S RN group was approximately 2 times higher than that of the FA-Au 2 S TN group at 24 h of injection. The PA imaging results of intratumorally injected FA-Au 2 S RNs proved that they were still able to show better PA signal enhancement at 24 h postinjection. Our study demonstrates that FA-Au 2 S nanomaterials with unique structures and special properties can be reliably produced using strictly controlled chemical synthesis. It further provides a strategy for the construction of highly sensitive PA imaging platforms and efficient PDT antitumor agents that exploit wavelength-dependent energy dissipation mechanisms.