Effect of the nature of the spacer on gene transfer efficacies of novel thiocholesterol derived gemini lipids in different cell lines: A structure-activity investigation

A structure-activity investigation was undertaken to see the effect of the nature of the spacer on the gene transfection efficacies of thiocholesterol -derived cationic gemini lipids possessing disulfide linkage between the cationic headgroup and the thiocholesterol moiety. Three gemini cationic lipids possessing hydrophobic flexible (-(CH2)(5)-; 1), hydrophobic rigid (-C6H4-; 2), and hydrophilic flexible (-CH2-CH2-O-CH2-CH2-; 3) spacer segments were synthesized. In HeLa cells, lipid formulations 1 and 2 were found to be more effective as compared to lipid 3 formulation. In HT1080 cell line, the order of transfectability was 3 > 1 > 2. Transfection studies in HeLa and HT 1080 cell line also showed 40-50% transfection efficacy in the presence of 10% serum conditions. These formulations were also able to transfect gene across difficult cells like HaCaT. Cytotoxic studies showed the nontoxic nature of these lipid-DNA complexes at different N/P ratios used for transfection studies.