Amino acid-based sodium n-lauroylsarcosinate as an optimised surfactant for propranolol interaction: comparative analysis of mixed micelle formation with cationic and zwitterionic surfactants

This study investigates the interactions of β-blocker drug Propranolol (PPL) with surfactants that share identical hydrophobic chains but differ in head group charges; viz, the cationic Dodecyltrimethylammonium bromide (DTAB), amino-acid based anionic Sodium N-Lauroylsarcosinate (SNLS), and zwitterionic Dodecyldimethyl (3-sulfopropyl) – ammonium Hydroxide (DDSAH). Surface tension measurements at varying mole fractions revealed mixed micelle formation, and key parameters like micellar mole fraction X₁^m, interaction parameter β^m, and activity coefficients f₁^m and f₂^m and other interfacial parameters were calculated. Theoretical models confirmed synergistic interactions with non-ideal behavior, where SNLS exhibited the strongest interaction, reflected by the lowest critical micelle concentration (cmc) and most negative interaction parameter (β^m). Cyclic voltammetry confirmed irreversible oxidation of PPL, with decreased anodic peak current (I_pa) attributed to surfactant adsorption and interactions at the electrode interface. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) and UV–Vis analyses supported the involvement of hydrogen bonding, hydrophobic, and electrostatic forces in drug-surfactant interactions. RDG and NCI analyses, along with stabilization energy calculations, further validated strong intermolecular forces in mixed micelles, with SNLS–PPL exhibiting the highest stabilization energy. These results highlight the key role of electrostatic and non-covalent forces in drug-micelle stability, relevant to drug delivery applications.