Characterizing the Flow and Interaction of Microbubbles in a 2D Capillary Network for Targeted Drug Delivery: A Simulation Study
Abstract
Purpose: Microbubble ultrasound contrast agents inside the bloodstream enhance the ultrasound signals of the vascular bed. In addition, microbubbles can be used for treatment. The present study assesses how air bubbles flow in a microchannel 2D capillary network. The evaluated network mimics part of a capillary system by comprising multiple bifurcations.
Materials and Methods: We designed the capillary network based on the tree pattern employed in quantitative studies per Murray’s minimum work rule and the cardiovascular network to simulate the hemodynamics of the vessels. The maximum width of the main channels in the capillary network is 1085 µm. The capillary network designed by AutoCAD software was transferred to Comsol software. We also ran fluid-structure interaction simulations in a microchannel capillary network, assuming that capillary walls were incompressible and isotropic, physiological boundary conditions were met, and non-Newtonian blood behavior occurred. After these simulations, we investigated Microbubbles’ (MBs’) capacity for targeted drug delivery through the capillary network. Specifically, we distributed four particles with 1 to 5 µm diameters and assessed the resultant performance.
Results: The greatest capillary network wall displacement is 0.225 µm. Meanwhile, the maximum velocity was 5.59 mm/s, and the minimum and maximum pressure values were 303.13 Pa and 0.42 Pa. Finally, the MB-MB interaction force exceeded the Brownian and gravitational forces. Therefore, it can be concluded that the MB-MB interaction force is crucial for MB-based targeted drug delivery. The kinetic energy of microbubbles increases while passing through the capillary bed. By increasing the amount of kinetic energy of microbubbles, the probability of adhesion to the capillary wall decreases. As the diameter of microbubbles increases, their energy increases.
Conclusion: The kinetic energy of microbubbles in the same conditions is the highest value related to Sonovue and then related to Optison, Micromarker, and Definity, respectively. The highest percentage of passing through the capillary network belongs to the Sonovue with a diameter of 2.5 µm and the lowest percentage of passing through the capillary network belongs to the Definity with a diameter of 1.1 µm.
