Gene transfer optimization with lipospermine-coated DNA.

Designed synthetic DNA carriers represent an attractive alternative to the widely used calcium phosphate gene transfer technique. In this context, we developed a class of nucleic acid binding lipids, the lipopolyamines, which spontaneously condense DNA on a cationic lipid layer. The resulting nucleolipidic particles transfect most animal cells efficiently. However, compaction depends on many experimental factors, some of which have been varied here to give optimal transfection efficiency. When plasmid condensation by the lipospermine is performed in the absence of competing polyions or serum proteins, or when the gene of interest is diluted into carrier DNA, transfection efficiency is increased by 2-3 orders of magnitude. With these improvements, chloramphenicol acetyl transferase activity resulting from transfection of as little as 25 ng could easily be detected by a nonradioactive ELISA test.