Multifunctional lipids based on a molecular switch for the improved delivery of nucleic acids

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Who could have envisaged it would be possible to use a gene as a drug 50 years ago, when the structure of DNA has just been discovered? Thanks to synergistic efforts of a whole scientific community, the concept has gone from bench to bedside, and two gene products are now available on the market. However, these new therapeutics are still in their first stages and require optimization. It is possible to improve their efficiency by the use of carefully engineered vectors, able to carry the genetic material through each of the biological barriers they need to cross. In particular, getting inside the cell is a major challenge, because these hydrophilic nucleic acids have to cross the lipid-rich plasmatic and/or endosomal membrane, before being degraded into lysosomes. Designing a lipidic vector able to destabilize the membrane upon a specific stimulus would facilitate nucleic acids to reach the cytoplasm of the targeted cell. This research program is focused on the design and evaluation of multifunctional lipids, bearing DNA binding affinity and pH-triggered membrane destabilization properties. The DNA binding affinity will be provided by variable cationic headgroups. The pH-sensitivity will be based on the use of previously developed molecular tweezer units, which have shown the suitable pH range for endosomal escape. This research program will process in three phases. In phase I, a library of 20 lipids will be synthesized and characterized. A selection process, based on their pH-triggered release and affinity for diverse nucleic acids, will be applied to select the best 6 candidates. The phase II will confirm the membrane-destabilizing properties and assess the transfection efficiency and cytotoxicity. The two best candidates will access to phase III, where the cytosolic delivery of nucleic acids will be imaged. Finally, a proof of concept in mice will evaluate the potential of these bioresponsive lipid nanoparticles to improve the efficiency of genetic material delivery in vivo.