2.3. Gel retardation of lipoplexes

The DNA binding ability of the cationic lipids were assessed by gel retardation assay on a 1% agarose gel. 0.3 μg of pCMV- SPORT-β-gal was complexed with cationic lipids (1:1:0.75, molar ratios were mixed with DNA at final charge ratios of 8:1, 4:1, 2:1 and 1:1) in a total volume of 25 μL in Hepes buffer, pH 7.4 and incubated at room temperature for 20–25 min. 4 μL of 6X loading buffer (0.25% bromo phenol blue, 40% sucrose) was added to it and 20 μL of the resultant solution was loaded in each well. The lipoplexes were run on 1% agarose gel, electrophoresed at 80 V for approximately 2 h and the DNA bands were visualized by ultraviolet illumination. To check the stability at different time points, lipoplexes were run on 1% agarose gel after 4 h and 24 h of complex formation (^{Fig. S2}).