Traditional gas microbubbles provide excellent contrast enhancement and are well-established in clinical diagnostic ultrasound. However, microbubbles are relatively large: on the order of the size of red blood cells. This means that microbubbles are confined to vascular imaging applications. Unfortunately, most molecular targets and pathologies are extravascular, which limits microbubble-based diagnostics and treatments when applied to diseases such as cancer.
To this end, perfluorocarbon nanodroplets were developed. These nanodroplets are roughly five times smaller than microbubbles, which allows them to extravasate to extravascular regions of interest. The high Laplace pressure of the droplets keeps their perfluorocarbon cores in a liquid state at physiologic temperature, and our group uses a novel optically-triggered method to vaporize the droplets into microbubbles using near-infrared light. This allows us to create in situ, on-demand ultrasound contrast. By using a high boiling point perfluorocarbon core (e.g., perfluorohexane), we can transiently vaporize and recondense droplets in response to pulsed near-infrared light to generate robust and repeatable contrast enhancement via this “blinking” phenomenon.
Members of our group are pursuing projects with perfluorocarbon nanodroplets related to blood-brain barrier opening, mRNA delivery, and the detection of lymphatic metastases.
Current Personnel Working on Perfluorocarbon Nanodroplets:
Hannah, Alexander S., Geoffrey P. Luke, and Stanislav Y. Emelianov. “Blinking Phase-Change Nanocapsules Enable Background-Free Ultrasound Imaging.” Theranostics 6.11 (2016): 1866-1876.
Luke, Geoffrey P., Alexander S. Hannah, and Stanislav Y. Emelianov. “Super-resolution ultrasound imaging in vivo with transient laser-activated nanodroplets.” Nano letters 16.4 (2016): 2556-2559.
Hannah, Alexander, et al. “Indocyanine green-loaded photoacoustic nanodroplets: dual contrast nanoconstructs for enhanced photoacoustic and ultrasound imaging.” ACS nano 8.1 (2013): 250-259.