Acoustic Characterization Of Sudan Black Nanobubbles For Multimodal Ultrasound & Photoacoustic Imaging

Dyed, shelled, nanobubbles (NBs) have recently been proposed as contrast agents for multimodal ultrasound-photoacoustic (US-PA) imaging. However, changes to the shell composition due to the presence of the dye can modify the response of bubbles to ultrasound. In this work, the effects of the dye, Sudan Black B, on a formulation of lipid shelled NBs are studied. Formulations were produced with increasing concentration of Sudan Black B. The size and concentration of activated NBs were tested. The surface tension of bulk lipid solution was measured using pendant drop tensiometry and activated bubble solutions were measured for single bubble and bubble population response to incident ultrasound. While results show no statistically significant effect of Sudan Black concentration on bubble concentration or size, surface tension increased linearly with dye concentration to a maximum increase of 13%. With the addition of Sudan Black B, single bubble experiments show an increase in the contribution of bubble growth signals, a decrease in contribution of nonlinear signals, and a decrease in bubble destruction. The results presented in this work indicate that the presence of Sudan Black B in the lipid shell of a nanobubble may increase the shell permeability impacting stability of the bubble population and their potential for multimodal US-PA imaging.