Genetic engineering through click chemistry

Gene therapy and many types of biological research use a process called transfection to efficiently deliver nucleic acids into cells. Many transfection approaches for mammalian cells rely on electrostatics: Cationic reagents bind to negatively charged nucleic acids and form ionic complexes that cells can pull inside via a mechanism known as endocytosis. The concentration of positive charge in the reagents can kill cells, however, and the process works poorly for some types of cells.

Now researchers report a click-chemistry-based transfection technique, dubbed SnapFect, which relies on bio-orthogonal molecules—a class of chemically reactive compounds that don’t interfere with biological systems (ACS Cent. Sci. 2017, DOI: 10.1021/acscentsci.7b00132).

The team, led by Muhammad N. Yousaf of York University, designed nanoparticle liposomes carrying a ketone ligand. When added to cultured cells, they fuse into the cell membrane within seconds, leaving the ligand exposed on the cells’ surfaces. Meanwhile, the researchers created lipid complexes decorated with oxyamines that hold nucleic acids. When these complexes were added to the cells, their oxyamines reacted with the cell surface ketones. The cells then pulled the resulting membrane-bound nucleic acid complex inside via endocytosis, and the nucleic acid could be expressed by the cells’ machinery.

Yousaf’s team compared the performance of two widely used transfection kits—Lipofectamine (Life Technologies) and ViaFect (Promega)—with SnapFect, which is now for sale via Yousaf’s company, OrganoLinX. SnapFect transfected cells with a 68% overall efficiency, while the other two did so with 19% and 29% efficiency, respectively.

“It’s an interesting step forward,” says James H. Eberwine, a molecular neurobiologist at the University of Pennsylvania. Eberwine adds that researchers often optimize transfection techniques for their particular applications and achieve much higher efficiencies than those noted in this study. “I would certainly try it,” he says, to see how the efficiency stacks up in a real-world context.