Electroporation
[1][2][3][4] In microbiology, the process of electroporation is often used to transform bacteria, yeast, or plant protoplasts by introducing new coding DNA.
This process is approximately ten times more effective in increasing cell membrane's permeability than chemical transformation, although many laboratories lack the specialized equipment needed for electroporation.
Although bulk electroporation has many benefits over physical delivery methods such as microinjections and gene guns, it still has limitations, including low cell viability.
Miniaturization of electroporation has been studied, leading to microelectroporation and nanotransfection of tissue utilizing electroporation-based techniques via nanochannels to minimally invasively deliver cargo to the cells.
Particularly, the electroporation allows for a more efficient transfection of DNA, RNA, shRNA, and all nucleic acids into the cells of mice and rats.
Developing central nervous systems are most effective for in vivo electroporation due to the visibility of ventricles for injections of nucleic acids, as well as the increased permeability of dividing cells.
[22] Currently, a number of companies, including AngioDynamics, Inc. and VoltMed, Inc., are continuing to develop and deploy irreversible electroporation-based technologies within clinical environments.
The first group to look at electroporation for medical applications was led by Lluis M Mir at the Institute Gustave Roussy.
[29][30] Electroporation mediated delivery of a plasmid coding gene for interleukin-12 (pIL-12) was performed and safety, tolerability and therapeutic effect were monitored.
In addition partial or complete response was observed also in distant non treated metastases, suggesting the systemic treatment effect.
There are currently several ongoing clinical studies of gene electrotransfer[31] where safety, tolerability and effectiveness of immunization with DNA vaccine, which is administered by the electric pulses is monitored.
A recent technique called non-thermal irreversible electroporation (N-TIRE) has proven successful in treating many different types of tumors and other unwanted tissue.
This procedure is done using small electrodes (about 1mm in diameter), placed either inside or surrounding the target tissue to apply short, repetitive bursts of electricity at a predetermined voltage and frequency.
These bursts of electricity increase the resting transmembrane potential (TMP), so that nanopores form in the plasma membrane.
Not all tissue has the same electric field threshold; therefore careful calculations need to be made prior to a treatment to ensure safety and efficacy.
Proteins, the extracellular matrix, and critical structures such as blood vessels and nerves are all unaffected and left healthy by this treatment.
One disadvantage to using N-TIRE is that the electricity delivered from the electrodes can stimulate muscle cells to contract, which could have lethal consequences depending on the situation.
[36] Furthermore, H-FIRE has been demonstrated to produce more predictable ablations due to the lesser difference in the electrical properties of tissues at higher frequencies.
Scientists from Karolinska Institute and the University of Oxford use electroporation of exosomes to deliver siRNAs, antisense oligonucleotides, chemotherapeutic agents and proteins specifically to neurons after inject them systemically (in blood).
[38] Bacterial transformation is generally the easiest way to make large amounts of a particular protein needed for biotechnology purposes or in medicine.
Electroporation allows cellular introduction of large highly charged molecules such as DNA which would never passively diffuse across the hydrophobic bilayer core.
[46] Although electroporation and dielectric breakdown both result from application of an electric field, the mechanisms involved are fundamentally different.
In contrast, during electroporation the lipid molecules are not chemically altered but simply shift position, opening up a pore which acts as the conductive pathway through the bilayer as it is filled with water.
It is generally accepted that for a given pulse duration and shape, a specific transmembrane voltage threshold exists for the manifestation of the electroporation phenomenon (from 0.5 V to 1 V).
If this theory is correct, then the transition to a conductive state could be explained by a rearrangement at the pore edge, in which the lipid heads fold over to create a hydrophilic interface.
Application of electric pulses of sufficient strength to the cell causes an increase in the trans-membrane potential difference, which provokes the membrane destabilization.
