Optimized Solid‐Phase‐Assisted Synthesis of Oleic Acid Containing siRNA Nanocarriers

• Published in: ChemMedChem 2017-09, Vol.12 (17), p.1464-1470
• Main Authors: Reinhard, Sören, Zhang, Wei, Wagner, Ernst
• Format: Article
• Language: English
• Subjects: Acids; Adducts; Animals; Cell Line, Tumor; Cleavage; Destabilization; endosomal escape; Gene silencing; Genes, Reporter; Hemolysis; Humans; Hydrophobicity; Mice; Oleic acid; Oleic Acid - chemical synthesis; Oleic Acid - chemistry; Oligomers; Peanuts; pH effects; polyplexes; Protecting groups; RNA Interference; RNA, Small Interfering - administration & dosage; RNA, Small Interfering - genetics; siRNA; siRNA delivery; solid-phase synthesis; Solid-Phase Synthesis Techniques - methods; Stearic acid; Synthesis; Transfection - methods; Trifluoroacetic acid; Trifluoroacetic Acid - chemical synthesis; Trifluoroacetic Acid - chemistry
• ISSN: 1860-7179; 1860-7187
• DOI: 10.1002/cmdc.201700350

Cationic lipo‐oligomers containing unsaturated oleic acid are potent siRNA carriers based on electrostatic and hydrophobic lipo‐polyplex formation and endosomal membrane destabilization. Lipo‐oligomers can be produced by solid‐phase‐supported synthesis in sequence‐defined form. However, the trifluoroacetic acid (TFA)‐mediated removal of acid‐labile protecting groups and cleavage from the resin can be accompanied by side products caused by the addition of TFA to the double bonds of oleic acid. Under aqueous conditions, these TFA adducts of oleic acid are converted into hydroxystearic acid derivatives. The cleavage protocol was optimized to decrease TFA adducts. The pure oleic acid (C18:1) containing lipo‐oligomer was compared with analogous structures containing saturated or modified hydrophobic moieties (stearic acid (C18:0), hydroxystearic acid, and 8‐nonanamidooctanoic acid). The structure containing intact oleic acid shows favorable pH dependency of lytic activity, efficient gene silencing, and excellent cell tolerability relative to its counterparts. Better carriers for RNAi: Cationic lipo‐oligomers containing cis‐unsaturated fatty acids such as oleic acid are potent siRNA carriers which can be assembled by solid‐phase‐assisted synthesis. Trifluoroacetic acid (TFA)‐mediated deprotection and cleavage of carriers from the resin may lead to side products initiated by the addition of TFA to the double bonds. The cleavage protocol was optimized to minimize TFA adducts, resulting (in comparison with the modified analogues) in beneficial siRNA delivery at low cytotoxicity.