N-doped carbon nanodots for non-invasive photoacoustic imaging and photothermal therapy

Abstract

We synthesized nitrogen-doped carbon nanodots (N-CNDs) for photoacoustic (PA) imaging and photothermal therapy (PTT) by controlling the nitrogen source and carbonizing organic acids. The N-CNDs showed strong optical absorbance in the near-infrared region, with great photostability and biodegradability. Thanks to the strong optical absorbance of N-CNDs, the PA signals from N-CNDs were high enough to detect inside living animals and enabled minimally invasive PTT using N-CND. To evaluate the biodegradability and potential application of N-CNDs as a PA imaging contrast agent, we performed time-resolved PA imaging of sentinel lymph nodes (SLNs) and assessed renal clearance after hypodermic injection. SLN and vascular networks were photoacoustically visualized by an acoustic-resolution reflection-mode PA imaging system at a 680-nm optical wavelength. Furthermore, we performed whole-body PA imaging after subcutaneous injection of N-CNDs to assess their body distribution and clearance. Finally, we further investigated the use of N-CNDs for in vivo photothermal therapy in Balb/c nude xenograft HepG2-tumor model mice.