Ultrasound imaging is a safe modality that can achieve excellent penetration depths using inexpensive, ubiquitous equipment. The most effective contrast agents for improving ultrasound performance are microbubbles, which are FDA approved for cardiac imaging. Microbubbles improve signal generation either through either reflection of incident sound waves through acoustic impedance mismatch, or through generation of harmonic sound waves caused by insonation of the microbubble at its resonance frequency. Acoustic theory states that the microbubble’s response to ultrasound depends on the properties of the bubble, including diameter and shell rigidity and thickness. The most common contrast agents are perfluorocarbon microbubbles stabilized by either phospholipids3 or crosslinked denatured albumin. These agents in turn exhibit strong differences in behavior in an ultrasound field. Thus by modulating the properties of the microbubble, the ability of the microbubble to reflect ultrasound can be changed as well, opening the possibility for stimulus- respsonsive contrast agents. We report the synthesis of microbubbles that change their ability to reflect ultrasound upon addition of chemical reagents.
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