Enhancement of therapeutic drug and DNA delivery into cells by electroporation*

Abstract

The effectiveness of potentially powerful therapeutics, including DNA, is often limited by their inability to permeate the cell membrane efficiently. Electroporation (EP) also referred to as `electropermeabilization' of the outer cell membrane renders this barrier temporarily permeable by inducing `pores' across the lipid bilayer. For in vivo EP, the drug or DNA is delivered into the interstitial space of the target tissue by conventional means, followed by local EP. EP pulses of micro- to millisecond duration and field strengths of 100–1500 V cm−1 generally enhance the delivery of certain chemotherapeutic drugs by three to four orders of magnitude and intracellular delivery of DNA several hundred-fold. We have used EP in clinical studies for human cancer therapy and in animals for gene therapy and DNA vaccination. Late stage squamous cell carcinomas of the head and neck were treated with intratumoural injection of bleomycin and subsequent EP. Of the 69 tumours treated, 25% disappeared completely and another 32% were reduced in volume by more than half. Residence time of bleomycin in electroporated tumours was significantly greater than in non-electroporated lesions. Histological findings and gene expression patterns after bleomycin-EP treatment indicated rapid apoptosis of the majority of tumour cells. In animals, we demonstrated the usefulness of EP for enhanced DNA delivery by achieving normalization of blood clotting times in haemophilic dogs, and by substantially increasing transgene expression in smooth muscle cells of arterial walls using a novel porous balloon EP catheter. Finally, we have found in animal experiments that the immune response to DNA vaccines can be dramatically enhanced and accelerated by EP and co-injection of micron-sized particles. We conclude that EP represents an effective, economical and safe approach to enhance the intracellular delivery, and thus potency, of important drugs and genes for therapeutic purposes. The safety and pharmaco-economic profile of EP compares favourably with other drug and DNA delivery methods.

Ultrashort electric pulse induced changes in cellular dielectric properties

“…The mechanism behind this electropermeabilization is electroporation, or pore formation in the cell membrane, and usually occurs for PEFs with electric fields on the order of a few kV/cm and pulse durations on the order of 0.1-10 ms. With the appropriate combination of these parameters, electroporation is irreversible and the membrane breaks down, which is desirable for applications ranging from bacterial decontamination to food processing [2]. Many applications require temporarily opening the cell membrane to normally impermeant molecules, such as electrochemotherapy and gene therapy [3]. Applying pulses with higher field strength (50-300 kV/cm) and shorter duration (10-300 ns) do not fully charge the cell membrane and instead interact primarily with the membranes of intracellular organelles [4].…”

Prospects for Gold Nanorod Particles in Diagnostic and Therapeutic Applications

“…DNA-coated gold particles have been used for intradermal genetic immunization by particle bombardment (Yang and Sun, 1995). Nevertheless, there are some limitations to this approach including the relatively low DNA binding capacity of the gold nanoparticles and the shallow depth of their penetration (Rabussay et al, 2003).…”

Nanosecond pulsed electric field generators for the study of subcellular effects

“…If the amplitude and duration of the pulsed electric field is such that the energy deposited does not cause considerable heating of the suspension , no permanent damage is done to the cell and the cell recovers. During the time the pores are open, large molecules, for example drugs or DNA, can enter the cell [Neumann et al, 1999;Rabussay et al, 2003].…”