Boundary Element Modeling Of Bubble-cell Interactions In Inertial Cavitation

Ultrasound-excited cavitation of microbubbles can cause sonoparation which is significant for gene delivery. A model was developed to investigate the interaction between microbubble and cell based on Boundary Element Method (BEM). A new method was proposed to describe the cell damage induced by microbubble inertial cavitation, based on the evaluation of the deformation on the cell surface at the closest point (CP) to the bubble.The BEM model was developed based on the fluid mechanics and bubble dynamics. The initial state of bubble was given by Rayleigh-Plesset equation. The cell was modeled using the Tait Equation describing the state of a water core encapsulated by a layer of thin membrane whose surface tension increases linearly with the areal expansion. First, the dynamic response of microbubble’radius and the "message" impact of cell in acoustic field were simulated separately. The results obtained by BEM simulation and conventional RP equation calculation agree well with each other. Second, the interaction between bubble and cell under ultrasound excitation was simulated. The results suggest that a jet was formed in the bubble in the last period of collapse and obvious depressed deformation can be observed at the CP in the cell membrane. Third, the impact of ultrasound parameters (frequency, acoustic pressure amplitude) and geometry parameters (bubble-cell distance, bubble radius) were thoroughly analyzed based on the BEM simulations. The results indicate that, the lower the ultrasound frequency and the higher the amplitude is, the higher the magnitude of interaction intensity is. The smaller bubble-cell distance and the greater bubble radius is, the higher the magnitude of interaction intensity is. BEM method is important for better understanding the mechanism involved in the interaction between microbubble and cell during microbubble inertial cavitation activities. It is also beneficial for standardizing the treatment dosage and controlling the sonoporation intensity in clinic.