AimsThe studies were aimed to contribute to the elucidation of the relationships between structure of the double-headed cationic surfactants-N,N-bis[3,3-(dimethylamine)- propyl]alkylamide dihydrochlorides and N,N-bis[3,3-(trimethylammonio)propyl]alkylamide dibromides (alkyl: n-C9H19, n-C11H23, n-C13H27, n-C15H31) and their antibacterial and biofilm preventing activity. Methods and ResultsThe minimal inhibitory and bactericidal concentrations (MIC and MBC) of dicephalic surfactants against Staphylococcus epidermidis and Pseudomonas aeruginosa were tested using standard methods. Pseudomonas aeruginosa was resistant to studied compounds but MBC values against Staph.epidermidis reached 048-001mmoll(-1). The influence of dicephalic surfactants on bacterial biofilm and adhesion to the various surfaces was investigated with crystal violet staining or colony counting. The reduction in bacterial adhesion was observed, especially in the case of glass and stainless steel. The condensation of the DNA was shown in the ethidium bromide intercalation assay. ConclusionsDicephalic surfactants exhibited antibacterial activity against Staph.epidermidis. The activity of studied compounds depended on the hydrocarbon chain length and the counterion. Surfactants deposited on different materials reduced Staph.epidermidis adhesion, dependently on the surfactant structure and the substratum. Dicephalic surfactants showed the ability of DNA compaction. Significance and Impact of the StudyThis study points the possibility of application of dicephalic surfactants as the surface-coating agents to prevent biofilm formation. These compounds efficiently condensed DNA and are potential candidates for further studies towards the transfection.