In vivo three-dimensional spectroscopic photoacoustic imaging for monitoring nanoparticle delivery.

In vivo monitoring of nanoparticle delivery is essential to better understand cellular and molecular interactions of nanoparticles with tissue and to better plan nanoparticle-mediated therapies. We developed a three-dimensional ultrasound and photoacoustic (PA) imaging system and a spectroscopic PA imaging algorithm to identify and quantify the presence of nanoparticles and other tissue constituents. Using the developed system and approach, three-dimensional in vivo imaging of a mouse with tumor was performed before and after intravenous injection of gold nanorods. The developed spectroscopic PA imaging algorithm estimated distribution of nanoparticle as well as oxygen saturation of blood. Moreover, silver staining of excised tumor tissue confirmed nanoparticle deposition, and showed good correlation with spectroscopic PA images. The results of our study suggest that three-dimensional ultrasound-guided spectroscopic PA imaging can monitor nanoparticle delivery in vivo.