Preparation of colloidal polydopamine/Au hollow spheres for enhanced ultrasound contrast imaging and photothermal therapy.

Development of functional theranostic platform for systemic contrast-enhanced diagnostic imaging and therapy is of great necessity in nanomedicine. However, synthesizing the biocompatible theranostic agents with enhanced merits in imaging and therapy via a facile and green way is still highly challenged. Here, we report a novel theranostic agent based on colloidal polydopamine/Au (PDA/Au) hollow spheres, which are synthesized with combined use of PDA chemistry and sacrificial template techniques. Colloidal polystyrene (PS) spheres serve as the templates with coatings of a PDA shell and Au nanoparticles in sequence, which are subsequently removed with trichloromethane, giving rise to colloidal PDA/Au hollow spheres. Colloidal PDA/Au hollow spheres exhibit excellent contrast enhancement for ultrasound imaging, and can serve as the near-infrared (NIR) photoabsorbers for the effective photothermal ablation of 4 T1 breast cancer cells in vitro with minor cytotoxicity to living cells. This method suggests a novel avenue for theranostic treatment in oncology.