Exp Mol Med.  2002 Sep;34(4):265-272.

Optimal salt concentration of vehicle for plasmid DNA enhances gene transfer mediated by electroporation

• Lee MJ
• Cho SS
• Jang HS
• Lim YS
• You JR
• Park JW
• Suh HR
• Kim JA
• Park JS
• Kim DK

Abstract

In vivo electroporation has emerged as a leading technology for developing nonviral gene therapies, and the various technical parameters governing electroporation efficiency have been optimized by both theoretical and experimental analysis. However, most electroporation parameters focused on the electric conditions and the preferred vehicle for plasmid DNA injections has been normal saline. We hypothesized that salts in vehicle for plasmid DNA must affect the efficiency of DNA transfer because cations would alter ionic atmosphere, ionic strength, and conductivity of their medium. Here, we show that half saline (71 mM) is an optimal vehicle for in vivo electroporation of naked DNA in skeletal muscle. With various salt concentrations, two reporter genes, luciferase and beta-galactosidase were injected intramuscularly under our optimal electric condition (125 V/cm, 4 pulses x 2 times, 50 ms, 1 Hz). Exact salt concentrations of DNA vehicle were measured by the inductively coupled plasma-atomic emission spectrometer (ICP-AES) and the conductivity change in the tissue induced by the salt in the medium was measured by Low-Frequency (LF) Impedance Analyzer. Luciferase expression in-creased as cation concentration of vehicle dec-reased and this result can be visualized by X-Gal staining. However, at lower salt concentration, transfection efficiency was diminished because the hypoosmotic stress and electrical injury by low conductivity induced myofiber damage. At optimal salt concentration (71 mM), we observed a 3-fold average increase in luciferase expression in comparison with the normal saline condition (p < 0.01). These results provide a valuable experimental parameter for in vivo gene therapy mediated by electroporation.

Keyword

electroporation; gene therapy; drug delivery systems; sodium chloride; electric conductivity

MeSH Terms

Animals
Comparative Study
DNA/*administration & dosage/metabolism
Drug Delivery Systems
Electric Conductivity
Electroporation/methods
Escherichia coli/genetics
Female
Gene Therapy/*methods
*Gene Transfer Techniques
Genes, Reporter
Injections, Intramuscular
Luciferase/metabolism
Mice
Mice, Inbred BALB C
Muscle, Skeletal/drug effects/*metabolism/pathology
Osmolar Concentration
Plasmids/genetics/*metabolism
Sodium Chloride/*pharmacology
Transfection
Vehicles/*administration & dosage
beta-Galactosidase/metabolism