title: Pipette tip with integrated electrodes for gene electrotransfer of cells in suspension: a feasibility study in CHO cells.
abstract: BACKGROUND
  Gene electrotransfer is a non-viral gene delivery method that requires successful electroporation for DNA delivery into the cells. Changing the direction of the electric field during the pulse application improves the efficacy of gene delivery. In our study, we tested a pipette tip with integrated electrodes that enables changing the direction of the electric field for electroporation of cell suspension for gene electrotransfer.
  
  
  METHODS
  A new pipette tip consists of four cylindrical rod electrodes that allow the application of electric pulses in different electric field directions. The experiments were performed on cell suspension of CHO cells in phosphate buffer. Plasmid DNA encoding for green fluorescent protein (GFP) was used and the efficiency of gene electrotransfer was determined by counting cells expressing GFP 24 h after the experiment.
  
  
  RESULTS
  Experimental results showed that the percentage of cells expressing GFP increased when the electric field orientation was changed during the application. The GFP expression was almost two times higher when the pulses were applied in orthogonal directions in comparison with single direction, while cell viability was not significantly affected.
  
  
  CONCLUSIONS
  We can conclude that results obtained with the described pipette tip are comparable to previously published results on gene electrotransfer using similar electrode geometry and electric pulse parameters. The tested pipette tip, however, allows work with small volumes/samples and requires less cell manipulation.
authors.affiliation: University of Ljubljana, Faculty of Electrical Engineering, Ljubljana, Slovenia.
authors.forename: Matej
authors.initials: M
authors.lastname: Rebersek
authors.forename: Masa
authors.initials: M
authors.lastname: Kanduser
authors.forename: Damijan
authors.initials: D
authors.lastname: Miklavcic