Multiple emulsion microbubbles for ultrasound imaging

In order to improve the sensitivity of ultrasound imaging, the contrast agents, a powerful non-invasive and real-time medical imaging technique, are used. However, air or N₂ or perfluorocarbon only encapsulated microbubbles which are currently used have lower efficiency and short imaging time. So the novel contrast agents with a higher efficiency are required. To achieve this objective, the strategy that we have explored involves the use of superparamagnetic iron oxide (SPIO) Fe₃O₄ nanoparticles multilayer emulsion microbubbles. This multilayer structure consists of three layers. The core is poly-d, l-lactide (PLA) encapsulated N₂ nanobubble with the SPIO nanoparticles forming oil-in-water (W/O) layer. The outermost is water-in-oil-in-water ((W/O)/W) emulsion layer with PVA solution. Herein we describe the synthesis and characterization of ultrasound imaging microstructure with an overall diameter of around 2μm-8μm. On the one hand, the stable gas encapsulated microstructure can provide a high scattering intensity resulting in high echogenicity, On the other hand, SPIO nanoparticles have shown the potential of high-resolution sonography. So the multiple emulsion microbubbles with SPIO can have double action to enhance the ultrasound imaging. Besides, because SPIO can also serve as magnetic resonance imaging (MRI) contrast agents, such microstructure may be useful for multimodality imaging studies in ultrasound imaging and MRI.