In this study we design and implement a novel flow chamber to assess electrostatic and streptavidin-biotin attachment mechanisms of a high-frequency ultrasound contrast agent (UCA) under high wall shear stress (WSS). The flow chamber was calibrated up to 50 Pa WSS to investigate attachment of the UCA. Attachment of the agent was assessed through measurement of the mean backscatter from targeted microbubbles attached to an agar surface within the flow chamber. The mean backscatter from microbubbles attached via a streptavidin-biotin mechanism decreased from −20 to −30 dB with increasing WSS up to 50 Pa. Mean backscatter from microbubbles attached via electrostatic attraction was indistinguishable from that of the agar surface alone beyond 0.66 Pa WSS. At 50 Pa WSS, the mean backscatter from the streptavidin-biotin attachment mechanism was 4 dB higher than from the plain agar surface. We conclude that the streptavidin-biotin attachment mechanism is ∼75 times stronger than an electrostatic mechanism. The ability of the streptavidin-biotin bond to withstand high WSS makes this attachment mechanism suitable for use as a targeted UCA for intravascular ultrasound studies and in high-resolution small animal studies, in which WSS can reach 40 Pa.
- Intravascular ultrasound
- contrast agent