Organic molecules with propeller structures for efficient photoacoustic imaging and photothermal ablation of cancer cells

Photoacoustic (PA) imaging has recently attracted great attention due to its noninvasive and nonionizing properties and high penetration depth. This technique is particularly attractive for sentinel lymph node (SLN) imaging, which is highly desirable during sentinel lymph node biopsy for the detection of breast cancer metastasis. In this work, we report the design and synthesis of BTPETTQ with a propeller structure and a donor-acceptor-donor configuration, which exhibits strong NIR absorption, extremely weak fluorescence and a high PA signal in solution as molecular species. After being encapsulated into a polymeric matrix, BTPETTQ nanoparticles (NPs) also show excellent PA signal output, which is superior to the widely used gold nanorods based on the same mass and is also better than that from the NPs based on the core molecule of TTQ without tetraphenylethene modification. High-resolution PA imaging of SLN is achieved after injection of BTPETTQ NPs into the left paw of rats. The good photothermal conversion efficiency (40%) of BTPETTQ NPs also ensures their good performance in photothermal therapy, which is validated by the effective killing of HeLa cells upon 808 nm laser irradiation. This work demonstrates the great potential of compounds with propeller structures for PA imaging and photothermal therapy applications.