Selectivity of polyethyleneimines on DNA nanoparticle preparation and gene transport

Polyethyleneimine (PEI) is an excellent non-viral agent to transport nucleic acids to cells. We studied the ability of 22 kDa linear, 25 kDa linear and 25 kDa branched PEIs to transfect breast cancer cells (MCF-7, T-47D and SK-BR-3), using a plasmid with luciferase reporter gene. Cells were treated with DNA center dot PEI complex at different N/P ratios. Cells were harvested, lysed and tested using luciferase assay. Among different PEIs, 22 kDa linear PEI was the most efficient, followed by 25 kDa linear and 25 kDa branched PEIs. Low molecular weight (600 Da, 1.2 kDa and 10 kDa) PEIs were not effective in transporting DNA. Biophysical studies showed no significant difference in DNA nanoparticle size. Confocal microscopy showed DNA at the edge of cellular nucleus when 25 kDa branched PEI was used in transfection. DNA was dispersed within the cell with 22 kDa linear PEI. The lower transfection efficiency of 25 kDa branched PEI might be due to its inability to dissociate DNA within the cell.