In the long search for ever more versatile polymers, researchers have always faced the same problem; new polymers have almost always been based on standard shapes, such as spheres or cylinders. Whilst this has created some amazing materials, it has limited the development of more diverse polymer materials.
However, polymer researchers have now discovered a novel approach for designing new polymers.
By chemically imprinting polymer strands with DNA, they have opened the door to a whole range of new polymer structures. It is hoped that these new materials will positively impact fields as diverse as pharmaceuticals and robotics.
The research team was based at McGill University in Canada, where they outlined the challenge as follows, “Although polymers are used in everything from clothing and food packaging to 3D printing and electronics, most self-assembled polymer structures have been limited to 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."
McGill Chemistry professor Hanadi Sleiman, senior author of the study, described the breakthrough as, “introducing a programmable level of organization that is currently difficult to attain in polymer chemistry. Chemically copying the information contained in DNA nanostructures offers a powerful solution to the problem of size, shape and directional control for polymeric materials.”
Prof Hanadi Sleiman, the Canada Research Chair in DNA Nanoscience.
The researchers have now published their study in the journal Nature, where they explain how, “Nature uses a combination of non-covalent interactions to create a hierarchy of complex systems from simple building blocks. One example is the selective association of the hydrophobic side chains that are a strong determinant of protein organization.” Adding that due to their research they can “… report a parallel mode of assembly in DNA nanotechnology.”
The process is based on a previous study by Prof Sleiman, which involved the construction of nanoscale ‘cages’ from strands of DNA. These cages are then filled with lipid-like polymer chains that fold together into ball-shaped particles.
Following on from this discovery the process was further developed. As the online scientific journal Phys.org describes, “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 used as a 'mold' to build the polymer particle, the particle size and number of molecular units in the polymer can be precisely controlled.”
You can view a computer simulation of the first step of the process on YouTube.
Although the research is still relatively new, polymer scientists are already imagining the directions the new polymers could take. For example, multi-compartmental polymer particles could be used by the pharmaceutical industry to deliver drugs. Each compartment could contain a different drug that could be delivered at different times.
The process could allow for the manufacture of asymmetrically porous membranes which can separate molecules by directing them along specific different paths. Alternatively, DNA imprinting may even prove a breakthrough in the development of ‘soft robotics’. These could be entirely flexible structures that change shape, move, and react in response to external stimuli.
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Photo credit: Sleimangroup, SleimanLab, McGillUniversity & Harvardtechnologyreview
