Background. Electropulsation is one of the non-viral methods successfully used to transfer drugs and genes into living cells in vitro as in vivo. This approach shows promise in field of gene and cellular therapies. This presentation first describes the temporal factors controlling electropermeabilization to small molecules (< 4kDa) and then the processes supporting DNA transfer in vitro. The description of in vitro events brings our attention on the processes occurring before (s), during (ms) and after electropulsation (ms to hours) ofhas the main advantages of being easy to use, fast, reproducible and safe.While during 30 years due to technological limits, pulse duration was always larger than 1 microsecond, the recent availability of high voltage (tens of kV) nanosecond long pulse generators opens the way to a new approach. Very fast perturbations under strong fields are induced in the membrane organization. 16,17 A new field of development is now present for electropermeabilization and promising results for clinical applications were reported.One of the limiting problems remains that very few is known on the physicochemical mechanisms supporting the reorganisation of the cell membrane. The molecular target of the field effect remains unclear.The present review focuses on the critical role played by the pulse duration in the electropermeabilization to small molecules (< 4kDa) and on its support to the processes associated to DNA transfer in vitro. Pulse durations are easy to adjust for an optimization of the clinical target: electrochemotherapy, irreversible electropermeabilization or gene therapy as suggested as a final conclusion. Electropermeabilization Theory of membrane potential difference modulation.An external electric field modulates the membrane potential difference. 18 From the physical point of view, a cell can be described as a spherical capacitor which is charged by the external electrical field. The transmembrane potential difference induced by the electric field, ΔΨi is a complex function g(λ) of the specific conductivities of the membrane (λ m ), the pulsing buffer (λ out ) and the cytoplasm (λ cyt ), the membrane thickness and the cell size. Thus, 1 ΔΨi = f. g (λ). r. E.cosθ [1] in which θ designates the angle between the direction of the normal to the membrane at the considered point on the cell surface and the field direction, E the field intensity, r the radius of the cell and f, which is a shape factor (a cell being a spheroid). Therefore, ΔΨi is not uniform on the cell surface. It is maximum at the positions of the cell facing the electrodes. These physical predictions were checked experimentally by videomicroscopy by using the potential difference sensitive fluorescent probes. [19][20][21] The pulse duration plays a critical role when shorter than the capacitive loading time of the membrane. In the previous part of the paper, it was considered that the pulse was long enough to bring the potential steady state value. The loading time τ load brings a limit in this description. 1 ΔΨi = f. ...

No abstract

No abstract

No abstract

No abstract