In vivo performance of airway and lung ultrasound enhanced via inhalable contrast agents

Airway mucus obstruction is a hallmark of cystic fibrosis (CF) and other muco-obstructive pulmonary diseases (MOPDs), yet clinical imaging tools for assessing mucociliary clearance (MCC) remain limited. To address this gap, we developed a muco-adhesive ultrasound contrast agent by incorporating 1,2-distearoyl-3-trimethylammonium-propane (TAP) onto standard microbubbles (MBs), enabling electrostatic binding to negatively charged mucins. In mice, we compared TAP-cationic MBs to standard MBs and lipid solution via tracheal instillation and contrast-enhanced ultrasound imaging. TAP-MBs produced comparable contrast-to-noise ratio (CNR) values to standard MBs (42.3 ± 8.4 dB vs 45.1 ± 11.9 dB), both of which significantly outperformed the lipid solution (11.9 ± 7.9 dB; p < 0.05). In a porcine model, we demonstrated proof-of-concept delivery of aerosolized TAP-MBs to distal airways, visualized as “tree-in-bud” patterns consistent with MB accumulation. Together, these findings establish the feasibility of both muco-adhesive MB contrast for enhancing airway ultrasound and its aerosolized delivery to small airways. This approach supports TAP-MBs as a non-ionizing repeatable method for assessing MCC and airway obstruction in MOPDs, while laying the groundwork for future therapeutic applications based on MB cavitation. Ultimately, this technique may provide a radiation-free strategy for monitoring respiratory health and guiding treatment in patients with mucus-associated airway disease.