In vivo non-ionizing photoacoustic mapping of sentinel lymph nodes and bladders with ICG-enhanced carbon nanotubes.

We demonstrate the feasibility of mapping a sentinel lymph node (SLN) and urinary bladder by using modified single-walled carbon nanotubes (SWNTs) as a nonionizing photoacoustic (PA) contrast agent. To improve the PA sensitivity, indocyanine green (ICG) was conjugated with SWNTs and the optical absorption of SWNTs-ICG was enhanced by approximately four times compared to that of plain SWNTs at a concentration of 0.3 µM. In vivo PA imaging results showed that the SLN and bladder were clearly visualized due to accumulation of SWNTs-ICG. This implies that the SWNTs-ICG could be potentially utilized to identify SLNs in breast cancer patients and tracking vesicoureteral reflux in combination with PA imaging.