Interactions between amphiphiles and polyelectrolyte complexes (PECs) have attracted significant attention in recent years due to their potential applications in biotechnology and medicine. Among amphiphilic systems, lipid-based assemblies such as liposomes are of special interest because they serve as model membranes and versatile carriers for bioactive molecules.
The interaction between liposomes and PECs is mainly governed by electrostatic forces, while hydrophobic interactions can additionally influence the formation and structure of the resulting complexes. Furthermore, the physicochemical properties of the polyelectrolytes contained, including their chemical constitution, charge density, distribution of charged groups, and backbone flexibility, strongly affect the structure of the PECs and affects the interaction with lipid bilayers and therefore the stability and morphology of the formed assemblies.
In this work, the interaction between PECs and lipid membranes is studied using liposomes composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) as a model liposomal system. The PECs consist of the polycation poly(diallyldimethylammonium chloride) (PDADMAC) and the polyanion sodium poly(acrylate) (NaPAA), which are hydrophobically modified with dodecylamine to different degrees. Special attention is given to the role of the degree of hydrophobic modification, as it determines the balance between electrostatic and hydrophobic interactions.
The influence of the degree of hydrophobic modification, the mixing ratio between PECs and DOPC liposomes, and the solution pH is investigated using static and dynamic light scattering (SLS/DLS), cryogenic transmission electron microscopy (cryo-TEM), and stopped-flow techniques to gain information about the temporal evolution after mixing of PECs and liposomes. The results provide insight into the mechanisms governing PEC–lipid interactions, which is a fundamental step of importance for the potential use of PECs as delivery system. In addition, they shed light on how to design more complexly built hierarchically structure colloidal assemblies.