Cationic Surfactants: Synthesis, Characterization, Micellization, Biological Behaviour and Drug Interaction

Abstract

In this study, by condensation reactions twenty three new amphiphilic surfactants were made. Out of them, 14 were n-alkyl pyridinium bromides and 9 were n-alkyl quinolinium bromides. All synthesized amphiphiles were characterized and identified by ―NMR (1H, 13C)‖and ―FT-IR‖ spectroscopic techniques. Using ―conductometry and UV/visible spectroscopic methods‖ the ―micellization process‖ of all surfactants was studied in detail. Throughout this study ethanol was selected as solvent to study the ―micellization process‖. The critical micellization concentration (CMC) values for all n-alkyl pyridinium bromides were noted to be very low, ranging from 0.27 to 0.42 mM and for n-alkyl quinolinium bromides it was found 0.38-0.51 mM.In all these ―surfactants‖ the CMC value was found to be inversely proportional to the alkyl chain length. The ―temperature effect‖ on the CMC and thermodynamics of micelle formation were thoroughly studied in the range of ―298-318 K‖. Thermodynamic parameters (ΔG, ΔH and ΔS) of the ―micellization process‖ of these surfactants were calculated. ΔG showed a negative value and ΔH was found to be positive indicating that the process of micellization was spontaneous and endothermic in nature. Biological activities like antibacterial, antifungal and antioxidant activitities of these amphiphiles were also explored. All compounds were found to be significantly bactericidal against different bacterial strains and fungicidal against different strains of fungi. These surfactants were also assessed for their potential use in a drug delivery system. For this purpose, the interactions of these surfactants with drugs (Flurbiprofen and Ketoprofen) were studied using UV- visible spectroscopic methods. It was found that both kinds of surfactants, (n-alkyl pyridinium and n-alkyl quinolinium based surfactants) bind well with the selected drugs. The ―binding constant (Kb)‖ and ―number of drug molecules incorporated per micelle (n)‖ were computed. Estimations of ―Kb‖ and ―n‖ indicated a solid collaboration of chosen drugs with the combined surfactants. A negative estimation of "Gibb's free energy (ΔG)" of the binding demonstrated the immediacy of medication surfactant associations.