Figure 4

Comparison of biolistic transfection efficiencies in HEK293 cells using micro and nano particles under different conditions. DNA encoding YFP was routinely precipitated onto gold projectiles using spermidine and CaCl₂. Removal of one of these components resulted in a significant loss of protein expressed, as measured by the numbers of fluorescent HEK 293 cells recorded by confocal microscopy 24 h after transfection with gold particles coated with 1 μg DNA. In the absence of spermidine, transfection efficiency was reduced to 6.1 ± 2.2 and 4.6 ± 1.7 for 1 µm and 40 nm gold particles respectively (n = 12; significantly different, Students t-test, p < 0.05), and in the absence of only CaCl₂ transfection efficiency was reduced to 17.2 ± 3.2 and 16.6 ± 2.5 respectively (n = 12; significantly different, Students t-test, p < 0.05). Cells transfected with projectiles containing no DNA, or that had been prepared with neither spermidine nor CaCl₂, resulted in no fluorescent cells (data not shown, n = 12).