Development of Nanoparticle-Based Gold Contrast Agent for Photoacoustic Tomography

Photoacoustic tomography (PAT) utilizes non-ionizing energy to obtain structural/functional information with high spatial resolution and sensitivity. Heterogeneous absorption of optical energy in biological tissues results in differentially expressed acoustic signals yielding spatial/temporal information. A critically underdeveloped area in PAT is the development of contrast agents. Gold-containing nanoparticles can be a good choice due to their high bio-compatibility, low toxicity, and high feasibility of surface modification/conjugation. Here we present a broad evaluation of gold nanosphere with diameters 2-60nm for PAT contrast agents at similar to 550nm. The acoustic signal enhances with increasing size. Encapsulation of gold nanospheres using liposomes shifted optical absorption to >600nm with increased enhancement. The highest contrast enhancement was obtained for 5nm-Au and 30nm-Au nanosphere encapsulated in PDA. Future work focuses on modifying the liposome for in-vivo targeted delivery.