Sulfonium Polymers Deliver DNA Into Human Cells

Introducing therapeutic nucleic acids into cells is a way to potentially fix the genetic causes of diseases such as Down’s syndrome and cystic fibrosis. Scientists have designed synthetic materials to deliver nucleic acids into cells, focusing mainly on nitrogen-based polymers. Now polymer chemists report a sulfonium-based macromolecule that can package DNA and slip into human cells (ACS Macro Lett. 2013, DOI: 10.1021/mz4002172).

Cells won’t take up nucleic acids unless they’re packaged in a certain way, says Timothy E. Long, a polymer chemist at Virginia Tech. Previous delivery polymers contain positively charged ammonium or guanidinium groups so the macromolecules can wrap up with negatively charged nucleic acids and form nanoparticles that cells readily accept.

Long and his coworkers wanted to see if a positively charged sulfonium-based polymer could condense DNA into such delivery particles.

They synthesized two types of sulfonium polymers and then tested each by mixing them with a plasmid containing the gene for an enzyme that produces bioluminescent molecules. After incubating the polymer-plasmid particles with human cells for a few hours, they looked at the cells under a light microscope to see how much of the glowing enzyme the cells had made. Although cells with sulfonium polymers only expressed about one-thousandth the amount of enzyme as those with nitrogen-based polymers, Long says, the study showed that additional types of polymers can potentially be used to escort DNA into cells.