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Biomedical Engineering Faculty Candidate Seminar
David Li, PhD
University of Washington
Abstract: Perfluorocarbon (PFC) microbubbles are FDA approved contrast agents used to enhance the vasculature for diagnostic ultrasound imaging. In recent years, there has been a growing interest in extending the use of microbubbles towards therapeutic applications. However, microbubbles suffer from relatively short recirculation times (~30 min) and are constrained to intravascular applications due to its relatively large size (~1 μm in diameter). Synthesizing nanobubbles small enough to diffuse across vessel walls and accumulate in diseased tissues remains a challenge. Moreover, reducing the size compromises acoustic performance and stability of the nanobubbles.
Liquid PFC nanodroplets are an alternative ultrasound contrast agent that can be produced with an identical chemical composition to currently FDA approved gas-based microbubbles. The difference between PFC nanodroplets and microbubbles, is that nanodroplets are synthesized, stored, and administered in its liquid phase and locally activated to form gaseous microbubbles approximately five times larger than the initial droplet. The large expansion difference means that PFC nanodroplets can be synthesized with diameters under 200 nm, allowing them to diffuse into diseased tissues, while still maintaining the ideal acoustic performance characteristics of microbubbles once activated. Until recently consistent synthesis of PFC nanodroplets remained challenging, especially when handling liquids with boiling points below 0°C. Recently, a new simple method of spontaneously nucleation PFC nanodroplets has been developed. In this presentation, we will discuss the method of spontaneous droplet nucleation in the context of medical ultrasound contrast agent design as well as discussing optical and acoustic activation methods, real-time non-linear contrast imaging, tuning contrast agent size and activation thresholds, and potential applications.
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