New findings show that gold nanoparticles with a slight positive charge work together to “unzip” DNA’s double helix. This discovery has implications for gene therapy research and the developing field of DNA-based electronics.

As the nanoparticles cluster together, they pull the strands of DNA apart. “We began this work with the goal of improving methods of packaging genetic material for use in gene therapy,” said Dr. Anatoli Melechko, an associate professor of materials science and engineering at North Carolina State University (NC State; Raleigh, USA) and coauthor of an article describing the research.

The research team introduced gold nanoparticles, approximately 1.5 nm in diameter, into a solution containing double-stranded DNA. The nanoparticles were coated with organic molecules called ligands. Some of the ligands held a positive charge, while others were hydrophobic. Because the gold nanoparticles had a slight positive charge from the ligands, and DNA is always negatively charged, the DNA and nanoparticles were pulled together into complex packages. “However, we found that the DNA was actually being unzipped by the gold nanoparticles,” stated Dr. Melechko. The positively-charged ligands on the nanoparticles attached to the DNA as predicted, but the hydrophobic ligands of the nanoparticles became tangled with each other. As this tangling pulled the nanoparticles into clusters, the nanoparticles pulled the DNA apart.

“We think gold nanoparticles still hold promise for gene therapy,” said Dr. Yaroslava Yingling, an assistant professor of materials science and engineering at NC State and co-author of the paper. “But it’s clear that we need to tailor the ligands, charge and chemistry of these materials to ensure the DNA’s structural integrity is not compromised.”

The finding is also pertinent to research on DNA-based electronics, which has the potential to utilize DNA as a template for creating nanoelectronic circuits. Because some work in that field involves placing metal nanoparticles on DNA, this finding indicates that researchers will have to pay close attention to the characteristics of those nanoparticles--or risk damaging the structural integrity of the DNA.

The study’s findings were published online June 19, 2012, in the journal Advanced Materials.

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