Photostability enhancement of silica-coated gold nanostars for photoacoustic imaging guided photothermal therapy

Gold nanostars (GNSs) are promising contrast agents for simultaneous photothermal therapy and photoacoustic imaging (PAI) owing to their excellent photothermal conversion efficiency. However, GNSs are easily reshaped under transient high-intensity laser pulses, which can cause a rapid shift in the light absorption peak, resulting in a decrease in both therapeutic and monitoring effects. In this work, we synthesized GNSs without toxic surfactants and coated them with a silica shell to retain their shape, thus maintaining their photostability. The excellent performance of these silica-coated GNSs was verified through both in vitro and in vivo PAI experiments. The silica-coated GNSs exhibited a threefold improvement in photoacoustic stability, as compared with the noncoated GNSs. The proposed silica coating method for GNSs was found to improve the photostability of GNSs, making them efficient, safe, and reliable nanoparticles for PAI.