A simple and efficient liposome method for transfection of DNA into mammalian cells grown in suspension

For a highly efficient plasmid transfection into mammalian cells grown in suspension, DNA was entrapped in liposomes prepared by the phosphatidylserine calcium-induced fusion method. Employing this technique, a transfection efficiency of about 2% was achieved, with 22 tk+-transformants obtained from 10(3) of mouse mammary carcinoma FM3Atk- cells transfected with a plasmid carrying the thymidine kinase (tk+) gene of the Herpes simplex virus. As compared with a previous report [Ayusawa et al., J. Biol. Chem. 258 (1983) 48-53], this transfection method was more than four orders of magnitude higher than the calcium phosphate method used for FM3Atk- cells. It was shown that the tk+ gene was integrated into the chromosomal DNA and was expressed in all the tk+-transformant clones tested. The described method could be applied to various types of DNA and cells, including those grown as monolayers.