Combined pulse electroporation--a novel strategy for highly efficient transfection of human and mouse cells

The type of a nucleic acid and the type of the cell to be transfected generally affect the efficiency of electroporation, the versatile method of choice for gene regulation studies or for recombinant protein expression. We here present a combined square pulse electroporation strategy to reproducibly and efficiently transfect eukaryotic cells. Cells suspended in a universal buffer system received an initial high voltage pulse that was continuously combined with a subsequent low voltage pulse with independently defined electric parameters of the effective field and the duration of each pulse. At comparable viable cell recoveries and transfection efficiencies of up to 95% of all cells, a wide variety of cells especially profited from this combined pulse strategy by high protein expression levels of individual cells after transfection. Long-term silencing of gene expression by transfected small interfering RNA was most likely due to the uptake of large nucleic acid amounts as shown by direct detection of fluorochromated small interfering RNA. The highly efficient combined pulse electroporation strategy enables for external regulation of the number of naked nucleic acid molecules taken up and can be easily adapted for cells considered difficult to transfect.