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Scientists have chemically imprinted polymer particles with DNA strands—a technique that could lead to new materials for applications like biomedicine and “soft robotics.”

In Nature Chemistry, the researchers describe a method to create asymmetrical polymer particles that bind together in a spatially defined manner, the way that atoms come together to make molecules.

Although polymers are used in clothing, food packaging, 3D printing, and electronics, most self-assembled polymer structures have been only symmetrical forms such as spherical or cylindrical shapes. Recently, however, scientists have focused on creating non-symmetrical polymer structures—for example “Janus” particles with two different “faces”—and they are starting to discover exciting new applications for these materials. One example: robotics made with soft, flexible structures that can change shape in response to external stimuli.

The new method “introduces a programmable level of organization that is currently difficult to attain in polymer chemistry,” says Hanadi Sleiman, professor of chemistry at McGill University and senior author of the study. “Chemically copying the information contained in DNA nanostructures offers a powerful solution to the problem of size, shape, and directional control for polymeric materials.”

Balls in ‘cages’

The new study builds on a technique developed in 2013 by Sleiman’s research group to make nanoscale “cages” from strands of DNA, and stuff them with lipid-like polymer chains that fold together into a ball-shaped particle that can contain cargo such as drug molecules.

To take that nanoengineering feat a step further, Sleiman and her PhD student Tuan Trinh teamed up with colleagues at the University of Vermont and Texas A&M University at Qatar. Together, the researchers developed a method to imprint the polymer ball with DNA strands arranged in pre-designed orientations. The cages can then be undone, leaving behind DNA-imprinted polymer particles capable of self-assembling—much like DNA, itself—in pre-designed patterns.

Because the DNA cages are like a “mold” to build the polymer particle, the particle size and number of molecular units in the polymer are precisely controllable, says Sleiman.

Drug delivery

One potential use for the asymmetrical polymer structures: multi-compartment polymer particles, with each compartment encapsulating a different drug that could be delivered using different stimuli at different times. Another possibility: porous membranes that are asymmetric, so they direct molecules along specific paths to separate then.

Funding for the research came from the Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes for Health Research, the Centre for Self-Assembled Chemical Structures, the Qatar Research Foundation, and the Canada Research Chairs Program.

Source: McGill University