Photoacoustic properties of plasmonic nanoparticle-coated microbubbles

We present the design of a multimodality contrast agent for photoacoustic and ultrasound imaging comprised of microbubbles coated with optically absorbing gold nanorods (AuMBs). We hypothesized that coupling nanorods to the microbubble shell would drive thermal expansion of the microbubble's gaseous core and result in an amplified photoacoustic emission following excitation by nanosecond pulsed laser irradiation. We also simulated heat transfer between gold nanorods irradiated by low-energy laser pulses and the AuMB gas core to model the radial expansion of single AuMBs following laser irradiation. The simulation results predict that AuMBs exhibit radial oscillations between 10 – 100 nm at frequencies determined by their resonant frequency. Results of both in vitro and in vivo ultrasound/photoacoustic dual-modality imaging are also presented.