Cationic amphiphile in phospholipid bilayer or oil-water interface of nanocarriers affects planktonic and biofilm bacteria killing.

A cationic amphiphile, soyaethyl morpholinium ethosulfate (SME), immobilized in liposomes or nanoemulsions, was prepared in an attempt to compare the antibacterial activity between SME intercalated in the phospholipid bilayer and oil-water interface. Before antibacterial assessment, the size of the liposomes and nanoemulsions was respectively recorded as 75 and 214 nm. The data of minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) and live/dead cell count demonstrated a superior antimicrobial activity of nanoemulsions compared to liposomes against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), and Staphylococcus epidermidis. Nanoemulsion incubation reduced biofilm thickness by 2.4-fold, whereas liposomes showed a 1.6-fold decrease in thickness. SME insertion in the oil-water phase was found to induce bacterial membrane disruption. SME nanosystems were nontoxic to keratinocytes. In vivo topical application of the cationic nanosystems reduced skin infection, MRSA load, and inflammation in mice. The deteriorated skin barrier function evoked by MRSA was recovered by nanoemulsion treatment.