Protonation of lipids impacts the supramolecular and biological properties of their self-assembly.

We assessed in this work how a chemical structure di$ erence could in" uence a supramolecular organiza- tion and then its biological properties. In our case study, we considered two amphiphilic lipidic gene vectors. The chemical di$ erence was situated on their hydrophilic part which was eitherapureneutralthioureaheadoramixtureofthreethiourea function derivatives, thiourea, iminothiol, and charged imi- nothiol. This small di$ erence was obtained thanks to the last chemicaldeprotectionconditionsofthepolarheadhydroxylgroups.Light,neutron,andX-rayscatteringtechniqueshavebeenused to investigate the spatial structure of the liposomes and lipoplexes formed by the lipids. The chemical structure di$ erence impacts the supramolecular assemblies of the lipids and with DNA as shown by " uorescence correlation spectroscopy (FCS), X-ray, and neutron scattering. Hence the structures formed were found to be highly di$ erent in terms of liposomes to DNA ratio and size and polydispersityoftheaggregates.Finally,thetransfectionandinternalizationresultsprovedthatthedi$ erencesinthestructureofthe lipid aggregates fully a$ ect the biological properties of the lipopolythiourea compounds. The lipid containing three functions is a better gene transfection agent than the lipid which only contains one thiourea moiety. As a conclusion, we showed that the conditions ofthe last chemical step can in" uencethe lipidic supramolecular structure whichin turnstrongly impactstheir biological properties.