Anti-adhesive and biocidal properties of newly synthesized dicephalic amine- containing cationic surfactants

<title>Abstract</title> <p> Due to their characteristic amphiphilic structure, cationic surfactants have a broad spectrum of antimicrobial activity. Novel pH-sensitive cationic surfactants have been developed, synthesized and characterized for their biological evaluation. Thus, a series of dicephalic cationic surfactants comprising a tertiary amine linker in their structure, i.e., 2,2’-(alkylmino)bis( <italic>N,N,N</italic> -trimethyletanammonium) dibromindes (abbreviated as C _n -D _N NMe ₃ Br; n = 12, 14, 16) were evaluated for their ability to modify the surface properties of polystyrene and stainless steel, antimicrobial, anti-adhesive and biofilm-eradicating potential. Wettability of the bare polystyrene and stainless steel was investigated via contact angles measurements of three probe liquids, whereas after surfactant adsorption only for water. The contact angles allowed evaluation of the total surface free energy and its components of these solids. It was found that polystyrene has hydrophobic properties, while stainless steel is a weakly bi-polar solid. Adsorption of dicephalic cationic surfactants changes the hydrophobic-hydrophilic properties of substrates depending on the surfactant concentration and the alkyl chain length in the molecule. The biggest changes were observed for the longest-chain surfactant (C ₁₆ -D _N NMe ₃ Br). Minimal inhibitory concentration (MIC) and minimal bactericidal/fungicidal concentration (MBC/MFC) were determined to evaluate the antimicrobial activity of the C _n -D _N NMe ₃ Br surfactants. Their activity was analyzed against Gram-positive strains <italic>S. epidermidis</italic> and Gram-negative <italic>P. aeruginosa</italic> and the fungus <italic>C. albicans</italic> according to generally known protocols. It was shown that with increasing alkyl chain length of the compound, its antimicrobial activity increased. The <italic>S. epidermidis</italic> strain was most sensitive to the tested compounds; moreover, the filamentation process of <italic>C. albicans</italic> cells was strongly inhibited by C ₁₆ -D _N NMe ₃ Br. The tested compounds significantly reduced the adhesion of <italic>C. albicans</italic> and <italic>S. epidermidis</italic> cells to stainless steel surfaces, while <italic>P. aeruginosa</italic> showed no sensitivity to the tested surfactant group. The BOAT method demonstrated that the tested compounds were able to penetrate the biofilm structure, where they reduced the survival of <italic>S. epidermidis</italic> and <italic>C. albicans</italic> cells. This activity was also shown to lead to the loosening and eradication of the biofilm structure. </p>