Copper sulfide nanoparticles as a new class of photoacoustic contrast agent for deep tissue imaging at 1064 nm.

Photoacoustic tomography (PAT) is an emerging molecular imaging modality. Here, we demonstrate use of semiconductor copper sulfide nanoparticles (CuS NPs) for PAT with an Nd:YAG laser at a wavelength of 1064 nm. CuS NPs allowed visualization of mouse brain after intracranial injection, rat lymph nodes 12 mm below the skin after interstitial injection, and CuS NP-containing agarose gel embedded in chicken breast muscle at a depth of ~5 cm. This imaging approach has great potential for molecular imaging of breast cancer.