Intravascular photoacoustic imaging with gold nanoparticles

Intravascular photoacoustic (IVPA) imaging can image atherosclerotic plaques inside the artery by utilizing the differences in optical absorption between various tissue types. Combined intravascular ultrasound (TVUS) and IVPA imaging has the potential to visualize both the structure and composition of plaques. However, the molecular or cellular specific components of the plaques can be further enhanced by introducing plasmonic nanoparticles as molecularly targeted contrast agents. To demonstrate that TVPA imaging with optical contrast agents is possible, we performed TVUS and TVPA imaging of a vessel phantom containing murine macrophages with gold nanoparticles inside the cells. Several controls including gold nanoparticles suspended in gelatin and macrophages without nanoparticles were also imaged. The results of our study suggest that TVPA is capable of imaging using gold nanoparticles as contrast agents. In addition, spectroscopic TVPA imaging can be used to distinguish aggregated nanoparticles from other tissue components and nonaggregated nanoparticles thus further enhancing the contrast of targeted components in the artery.