Electroporation: Gene Delivery by Electric Pulse

Pulse Parameters

Field strength E 800 V/cm

Pulse duration 300 µs

Cell radius 8.0 µm

Membrane at rest — no field applied

Live Readout

Peak ΔV_m (pole)

0.00 V

Membrane porated

Plasmids delivered

0 / 42 (0%)

How it works

A uniform external field E induces a transmembrane potential on a spherical cell that is not uniform — it is largest at the two poles facing the electrodes and zero at the equator. For a spherical cell this is the steady-state Schwan equation:

ΔVm(θ) = 1.5 · r · E · cosθ · (1 − e^(−t/τ))

where r is the cell radius, θ is the angle from the field axis, and τ (~1 µs) is the membrane charging time constant — effectively instant compared with a typical pulse.

Poration threshold — once |ΔVm| exceeds a critical voltage (≈1 V for a lipid bilayer), the membrane's electrostatic energy overcomes the bilayer's line tension and aqueous pores nucleate, concentrated at the two poles where |ΔVm| peaks.
Electrophoretic delivery — DNA's phosphate backbone is negatively charged, so the same field that opens the pores also drags plasmids toward the electrode of opposite sign (exactly as in gel electrophoresis), threading them through the open pores and into the cytoplasm.
Resealing — after the pulse the field collapses, ΔVm relaxes, and pores reseal over roughly a second in this animation (minutes in a real cell) — the transfected DNA is left trapped inside.

This is the working principle of electroporation-based transfection and bacterial transformation (Neumann, 1982) — one of the core delivery methods in genetic engineering, used everywhere from inserting plasmids into E. coli to CAR‑T cell manufacturing. The animation compresses microsecond membrane charging and second-scale resealing into a few watchable seconds; the field, radius and threshold physics driving it are real.

Depolarized membrane (+ΔVm) Hyperpolarized membrane (−ΔVm) DNA plasmid

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