Controllable assembly of a novel cationic gemini surfactant containing a naphthalene and amide spacer with β-cyclodextrin

Abstract

A novel cationic gemini surfactant (C₁₂NDDA) with a spacer containing naphthalene and amides was successfully synthesized. The assembly of C₁₂NDDA with β-cyclodextrin (β-CD) was investigated using various techniques including transmission electron microscopy, proton nuclear magnetic resonance (¹H NMR), and scanning electron microscopy. Tuning the C₁₂NDDA concentration and the C₁₂NDDA/β-CD molar ratio allowed the production of different assembled aggregate morphologies such as micelles, vesicles, nanowires, nanorods, and hydrogels. Investigation of the inclusion mechanisms of C₁₂NDDA and β-CD by ¹H NMR revealed that hydrophobic interactions, hydrogen bonding, π–π stacking, and electrostatic forces play key roles in the assembly process. The antimicrobial activities of the C₁₂NDDA/xβ-CD (x = 0–4) inclusion complexes were tested against Gram-negative bacteria (Escherichia coli and Salmonella) and Gram-positive bacteria (Staphylococcus aureus and Streptococcus), and very low minimum inhibitory concentrations of 0.078–0.31 μg mL⁻¹ were observed. Thus, this newly synthesized gemini surfactant and its inclusion complexes exhibit potential as superior broad-spectrum disinfectants for various biomedical and biotechnological applications.