Preparation of Lipid-Conjugated siRNA Oligonucleotides for Enhanced Gene Inhibition in Mammalian Cells.

Nucleic acid conjugates are promising drugs for treating gene-related diseases. Conjugating specific units like lipids, cell-penetrating peptides, polymers, antibodies, and aptamers either at the 3'- or 5'-termini of a siRNA duplex molecule has resulted in a plethora of siRNA bioconjugates with improved stabilities in bloodstream and better pharmacokinetic values than unmodified siRNAs. In this sense, lipid-siRNA conjugates have attracted a remarkable interest for their potential value in facilitating cellular uptake. In this chapter, we describe a series of protocols involving the synthesis of siRNA oligonucleotides carrying either neutral or cationic lipids at the 3'- and 5'-termini. The resulting lipid-siRNA conjugates are aimed to be used as exogenous effectors for inhibiting gene expression by RNA interference. A protocol for the formulation of lipid siRNA using sonication in the presence of serum is described yielding interesting transfection properties for cell culture without the use of transfecting agents.