Characterizing the Disruption of HEK-293 Cell Membrane in AFM-based Indentation Using Energy Limiter Method

The disruption of the cell membrane is an essential stage in adherent cell microinjection. With the assistant of atomic force microscopy system, the interaction force between the cell and the AFM probe during the indentation can be measured. Mechanical response of adherent cells in AFM-based indentation were explained by different models. However, the disruption of the cell membrane has not been theoretically explained. In this study, an energy limiter method is introduced to the continuum model of the adherent cells. The strain energy density function in the continuum model is modified by involving the energy limiter. As a result, on the computational nominal stress-indentation distance curve, a global maximum value of the nominal stress on the contact boundary between the cell membrane and the AFM probe can be found. Therefore, the location of the global maximum value can be used to characterize the disruption of the cell membrane. Indentation was conducted on the human kidney embryos 293 cells, and the performance of the energy limiter method in characterizing the disruption of the cell membrane was evaluated, which shows higher consistency than the performance of the experimental criterion. These results represent a feasible approach to understand the mechanism of the disruption of the cell membrane in microinjection.