Influence of environmental conditions on a new surfactant-based contrast agent: ST68

Environmental influences on the new surfactant-stabilized bubbles, ST68, we re investigated. We have developed a new surfactant-based contrast agent ST 68, which is prepared by insonating buffered mixtures of Span 60 and Tween 80 in the presence of either air, PFC, or SF, gas, The effect of dilution, shear, and sonication on size distribution of ST68 showed that PFC-containi ng bubbles (ST68-PFC) were most stable. ST68-PFC bubbles lasted more than 1 5 min with similar to 30 dB backscatter enhancement in degassed phosphate-b uffered saline, (pH 7.4), and air bubbles lasted similar to 3 s, suggesting the effects of diffusion. Additionally, it was found that the ionic streng th of the suspending medium (for example, PBS), did not have any effect on ST68 bubbles containing SF, or PFC, but had a dramatic impact on bubbles co ntaining air. (C) 2000 World Federation for Ultrasound in Medicine & Biolog y.