Patients with heart problems may one day get an injection of tiny bubbles as part of ultrasound technology for imaging blood flow. No ordinary bubbles, these microspheres exist as protein envelopes that encase the air bubbles as they bounce through the heart's turbulent channels, says Kenneth S. Suslick, a chemist at the University of Illinois at Urbana-Champaign.
Different materials reflect sound differently, but the similar acoustic properties of blood and muscle make them difficult to distinguish. "It's just not that easy to see anything," says Suslick.
Years ago, however, other researchers demonstrated that adding bubbles to blood makes its flow stand out because air reflects ultrasound so strongly. They also discovered that albumin-coated bubbles -- made by zapping dissolved albumin with long pulses of low-frequency, high-intensity sound -- worked well for this purpose.
Now, Suslick and Mark W. Grinstaff have learned how these sound blasts make albumin, a common body protein, encircle air to form tough microbubbles. They first found that the process requires oxygen and involves chemical modification of the albumin. The blast of sound draws air into the albumin solution and disperses it, like a milkshake, Suslick explains. …