Lipothioureas as Lipids for Gene Transfection: A Review

Non-viral gene therapy requires innovative strategies to achieve higher transfection efficacy. A few years ago, our group proposed bioinspired lipids whoseinteraction with DNA was not based on ionic interactions, but on hydrogen bonds. We thusdeveloped lipids bearing a thiourea head which allowed an interaction with DNAphosphates through hydrogen bonds. After a proof of concept with a lipid bearing threethiourea functions, a molecular and cellular screening was performed by varying all partsof the lipids: the hydrophobic anchor, the spacer, the linker, and the thiourea head. Twolipothiourea-based structures were identified as highly efficient in vitro transfecting agents.The lipothioureas were shown to reduce non specific interactions with cell membranes anddeliver their DNA content intracellularly more efficiently, as compared to cationiclipoplexes. These lipids could deliver siRNA efficiently and allowed specific cell targetingin vitro. In vivo, thiourea lipoplexes presented a longer retention time in the blood and lessaccumulation in the lungs after an intravenous injection in mice. They also inducedluciferase gene expression in muscle and tumor after local administration in mice.Therefore, these novel lipoplexes represent an excellent alternative to cationic lipoplexes astransfecting agents. In this review we will focus on the structure activity studies thatpermitted the identification of the two most efficient thiourea lipids.