Abstract: A nongaseous, ligand-targeted perfluorocarbon nanoparticle emulsion has been developed which can acoustically enhance the presence of molecular epitopes on tissue surfaces. We demonstrate the impact of incorporating perfluorocarbons with specific phase velocities into the emulsions on the acoustic reflectivity of plasma clots targeted using these nanoparticles. Porcine plasma clots were targeted in vitro with specific perfluorocarbon emulsions using anti-fibrin antibody solution (NIB 5F3). Five perfluorocarbons were investigated: perfluorohexane, perfluorooctyl-bromide, perfluorooctane, perfluorodichlorooctane, and perfluorodecalin. Ultrasonic backscatter (17 - 35 MHz) was measured at the front surface of the clots. Backscatter enhancement was determined by comparison with untreated clots. The magnitude of enhancement depended on the perfluorocarbon emulsion used. Perfluorohexane and perfluorooctane exhibited the greatest enhancement relative to untreated clots (23 dB) and perfluorodecalin the least (18 dB), consistent with predictions from a simple acoustic transmission-line model. We conclude that targeted, nongaseous perfluorocarbon contrast agents can significantly increase the sensitivity of ultrasonic detection of low-scattering biological media, and that further optimization of these contrast agents can be realized by judicious choice of the emulsified perfluorocarbon. !7
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