Non-contact culturing of vascular endothelial cells on wall surface following retention using acoustic radiation force and lipid bubbles

For application in the fabrication of artificial blood vessels, we developed a method for non-contact culturing of vascular endothelial cells following a process of non-contact retention. Utilizing the propulsive force acting on cells under ultrasound exposure when the cells were surrounded by lipid bubbles, the conditions of the acoustic field were investigated. First, cells were cultured in the presence of lipids without ultrasound to derive the optimal concentration of lipids. Next, cells were retained on the inner surface of the flow path using various acoustic fields, which include single-focal, multifocal, and bar-shaped fields. After culturing the cells in the path without flow for 24 h, the cultured area of cells were measured to evaluate the series of performance. In the experiment of cell culturing without ultrasound, the cultured area decreased inversely proportional to the lipid concentration, thus deriving the optimal concentration of bubbles. When the bar-shaped fields were used for the retention process, significant cell engraftment was observed compared to other fields, even though the acoustic intensity of SATA (Spatial average temporal average) and the retained area of the cells were similar. Those results suggest that conditions of acoustic field, including the distribution and magnitude of sound pressure according to the flow direction, are dominant for non-contact culturing of cells following retention. We succeeded in culturing cells at desired position on inner wall of the path, regardless of the direction of gravity.