pH-responsive vesicles from supra-amphiphiles based on dynamic imine bond

pH-responsive vesicles have been prepared from the mixture of 1-(10-(4-formyl-phenoxy) decyl)-pyridinium (FDP) or 1-methyl-3-(10-(4-formyl-phenoxy) decyl) imidazolium (FDI) with 1-octyl amine at a molar ratio of 1:1 in alkaline aqueous solutions. Their structures and morphologies were characterized by transmission electron microscopy with sample preparations by negative staining or freeze-fracture. Basically, the spherical unilamellar vesicles were formed with the mean diameters respectively of about 71 and 107   nm for two supra-amphiphile systems, which were based on the formation of dynamic imine bonds between amine and FDP (i-FDP) or FDI (i-FDI). The loading and release studies of a fluorophore, Nile red (NR), demonstrated the capabilities of these vesicles to encapsulate NR and a rapid release at low pH environment. The vesicles from i-FDP behaved relatively more sensitive to acidic environment than those from i-FDI. The dynamic transitions of supra-amphiphiles were characterized by nuclear magnetic resonance or fluorescence emission spectroscopy measurements. A lower critical micelle concentration and a higher aldehyde conversion efficiency of i-FDI than those of i-FDP were observed. The characteristics of facile formation, fast dissociation, and switchable morphologies of studied systems should be referable for designing novel smart supra-amphiphile systems with potential applications as controlled drug delivery systems.