Reduced cytotoxicity of polyhexamethylene biguanide hydrochloride (PHMB) by egg phosphatidylcholine while maintaining antimicrobial efficacy

Liposomes or oil-in-water emulsions containing egg yolk phosphatidylcholine (EPC) were combined with aqueous polyhexamethylene biguanide hydrochloride (PHMB). The bactericidal activity of these preparations against Pseudomonas aeruginosa and Staphylococcus aureus as well as their cytotoxicity on cultured murine fibroblasts (L929 cells) was then assayed for either 30 min or 60 min in the presence of cell culture medium containing 10% fetal bovine serum as surrogate for wound fluid. We used two assay designs: in the first bactericidal activity and cytotoxicity were determined in separate experiments; in the second both were determined in one experiment. Combining PHMB and EPC containing o/w emulsions or liposomes protects mammalian cells without neutralizing the antiseptic effect. From all tested combinations the o/w emulsions containing 0.05% PHMB proved to be superior in this respect to the aqueous preparation.