Characterization of the interaction of nanobubble ultrasound contrast agents with human blood components

Michaela B Cooley; Eric C Abenojar; Dana Wegierak; Anirban Sen Gupta; Michael C Kolios; Agata A Exner

doi:10.1016/j.bioactmat.2022.05.001

Characterization of the interaction of nanobubble ultrasound contrast agents with human blood components

Bioact Mater. 2022 May 11:19:642-652. doi: 10.1016/j.bioactmat.2022.05.001. eCollection 2023 Jan.

Authors

Michaela B Cooley¹, Eric C Abenojar², Dana Wegierak¹, Anirban Sen Gupta¹, Michael C Kolios^{3

4}, Agata A Exner^{1

2}

Affiliations

¹ Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44106, United States.
² Department of Radiology, Case Western Reserve University, Cleveland, OH, 44106, United States.
³ Department of Physics, Ryerson University, Toronto, Ontario, M5B 2K3, Canada.
⁴ Institute for Biomedical Engineering and Science Technology, A Partnership Between Ryerson University and St. Michael's Hospital, Toronto, Ontario, M5B 1T8, Canada.

Abstract

Nanoscale ultrasound contrast agents, or nanobubbles, are being explored in preclinical applications ranging from vascular and cardiac imaging to targeted drug delivery in cancer. These sub-micron particles are approximately 10x smaller than clinically available microbubbles. This allows them to effectively traverse compromised physiological barriers and circulate for extended periods of time. While various aspects of nanobubble behavior have been previously examined, their behavior in human whole blood has not yet been explored. Accordingly, herein we examined, for the first time, the short and long-term effects of blood components on nanobubble acoustic response. We observed differences in the kinetics of backscatter from nanobubble suspensions in whole blood compared to bubbles in phosphate buffered saline (PBS), plasma, or red blood cell solutions (RBCs). Specifically, after introducing nanobubbles to fresh human whole blood, signal enhancement, or the magnitude of nonlinear ultrasound signal, gradually increased by 22.8 ± 13.1% throughout our experiment, with peak intensity reached within 145 s. In contrast, nanobubbles in PBS had a stable signal with negligible change in intensity (-1.7 ± 3.2%) over 8 min. Under the same conditions, microbubbles made with the same lipid formulation showed a -56.8 ± 6.1% decrease in enhancement in whole blood. Subsequent confocal, fluorescent, and scanning electron microscopy analysis revealed attachment of the nanobubbles to the surface of RBCs, suggesting that direct interactions, or hitchhiking, of nanobubbles on RBCs in the presence of plasma may be a possible mechanism for the observed effects. This phenomenon could be key to extending nanobubble circulation time and has broad implications in drug delivery, where RBC interaction with nanoparticles could be exploited to improve delivery efficiency.

Keywords: Drug delivery; Hitchhiking; MB, Microbubble; NB, Nanobubble; Nanobubbles; PBS, Phosphate-Buffered Saline; RBC, Red Blood Cell; Red blood cells; TIC, Time-Intensity Curve; UCA, Ultrasound Contrast Agent; Ultrasound; Ultrasound contrast agents.

Abstract

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