P4E-5 Theoretical Analysis of Oscillations of Cells in the High Frequency Ultrasonic Field

For ultrasound applications of drug delivery and sonoporation, a more comprehensive understanding of the interaction of an individual cell in an acoustic field with cavitation bubbles of close vicinity is needed. The underlying mechanisms which cause enhanced cellular transport are not well understood; moreover, few analytical theories examine the mechanics of cell-bubble interactions. Method: In this work, we examine the cell´s response and deformation induced from a nearby oscillating bubble using a shell model of the cell following an approach previously outlined. Within the shell model, the motion of the cell is composed of the motion of three components: the internal viscous fluid, the thin elastic shell and the surrounding viscous fluid. It has been demonstrated that for dipole oscillations the cell´s shell is deformed due to a change in the shell area. For the quadrupole and higher order mode oscillations, the movement of the cell is determined by both moduli of the shell: shear modulus of the shell, mu, and area deformation modulus K_s. The induced deformation of the cell´s membrane from a bubble´s oscillation can be calculated and directly related to the membrane transport behavior. The influence of linear radial bubble oscillations are examined in detail for this initial study and potential extensions to the nonlinear regime are discussed. The relative change in the area has a maximum at frequency f_K ap radicK_s/(rhoa³) where a is the radius of the cell, and rho is its density.