5-3.1. Gene transfer techniques

It has been discussed earlier that due to amphipathic nature of the phospholipid bilayer of the plasma membrane, polar molecules such as DNA and protein are unable to freely pass through the membrane. Various physical or mechanical methods areemployed to overcome this and aid ingene transfer as listed below-

1. Electroporation
2. Microinjection
3. Particle Bombardment
4. Sonoporation
5. Laser induced
6. Bead transfection

5-3.1.1. Electroporation

• Electroporation is a mechanical method used for the introduction of polar molecules into a host cell through the cell membrane.
  
  
• This method was first demonstrated by Wong and Neumann in 1982 to study gene transfer in mouse cells.
  
  
• It is now a widely used method for the introduction of transgene either stably or transiently into bacterial, fungal, plant and animal cells.
  
  
• It involves use of a large electric pulse that temporarily disturbs the phospholipid bilayer, allowing the passage of molecules such as DNA.

The basis of electroporation is the relatively weak hydrophobic/hydrophilic interaction of the phospholipids bilayer and ability to spontaneously reassemble after disturbance. A quick voltage shock may cause the temporary disruption of areas of the membrane and allow the passage of polar molecules. The membrane reseals leaving the cell intact soon afterwards.