Characterization and in vitro biocompatibility of catanionic assemblies formed with oppositely charged dicetyl amphiphiles

In this study, cationic dicetyldimethylammonium bromide (DCB) and anionic dicetyl phosphate (DCP) were mixed to form catanionic assemblies in water, and their colloidal morphology, size, charge characteristics, phase behavior, membrane fluidity, and in vitro biocompatibility are comprehensively investigated for the first time. Our results show that the catanionic DCB and DCP mixtures in water are capable of forming circular vesicles and this binary mixed system expresses the miscibility with deviation from the ideal mixing. Compared to the nanoscale DCB-rich vesicles, the DCP-rich vesicles have smaller size, higher negative zeta potential, higher main transition temperature, and better storage stability. The temperature and molecular cooperativity of the main transition phase for the DCP vesicles can be reduced by an addition of DCB. This work demonstrates that the head groups and the relative composition of the two considered dicetyl amphiphiles remarkably affect the phase behavior, membrane rigidity, encapsulation ability and in vitro biocompatibility of DCB/DCP vesicles. The iso-stoichiometric mixed DCB/DCP vesicle, showing low cytotoxicity, long storage time, and high drug loading, is a potential candidate for the drug delivery system.