Self-assembly, surface, antibacterial, and solubilization properties of phenylglycine type amino acid-based cationic surfactants

Abstract

Here, synthesis and characterization of amino acid-based chiral cationic surfactants containing phenylglycine moiety, l-phenylglycine hydrochloride octyl ester (L-PgC8E), and l-phenylglycine hydrochloride decyl ester (L-PgC10E), and their physicochemical properties such as the micellization, surface, and volumetric parameters have been reported. In addition, the structural analyses of the aggregates of these esters were also performed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. It was found that the presence of a phenyl ring in the head group promoted the micelle formation leading to a smaller critical micelle concentration (CMC) value and enhancing the adsorption efficiency with an increased hydrocarbon chain. Besides, the antibacterial activities of the synthesized surfactants have been explored against three Gram-positive (G+) and seven Gram-negative (G-) bacteria below and above their CMC values by measuring the zone of inhibition diameter. The results showed that L-PgC8E was more active than L-PgC10E against all bacteria; this was explained by the formation of smaller and less stable aggregates that could interact efficiently with the bacterial membrane. Furthermore, the solubilization power (SP) of both surfactants for Methyl Red (MR) was determined, and it was found that L-PgC10E with a longer hydrocarbon chain and forming a large hydrophobic area by its large aggregates showed a more efficient solubilizing power.