UC San Diego

Photoacoustic imaging has gained significant traction as a pre-clinical imaging modality in the last few decades. Combining the spectral sensitivity of optical imaging and the spatial and temporal resolution of ultrasound, photoacoustic imaging is non-invasive and safe due to the use of non-ionizing radiation in the near-infrared range. Many strategies have been developed to improve image contrast and treatment of diseases for diagnostic and therapeutic purposes. First, a brief and surface-level overview of photoacoustic imaging, its function, theoretical considerations, and potential applications are discussed. Then, the potential of silicon carbide nanoparticles as a multimodal contrast agent for stem cell imaging is shown. It has been previously reported that silicon carbide particles are photoluminescent due to quantum confinement effects and have been reported in imaging different cell lines. However, reliance on optical methods suffers from limited penetration depth for in vivo tracking. In addition to the photoluminescent property of silicon carbide, we show for the first time that they are also capable of being applied to photoacoustic imaging. These durable particles are biocompatible with mesenchymal stem cells and are capable of long-term cell tracking through photoluminescence in vitro and through photoacoustic imaging in vivo. The improved penetration depth of photoacoustic imaging provides additional versatility to silicon carbide nanoparticles as an in vivo contrast agent.