DNA Hydrogels

In a paper published in the latest Nature Materials, researchers from Cornell report creating a sponge-like hydrogel made entirely from branched synthetic DNAs. Such material has a wide range of possible biomed applications:

Hydrogels are liquid or semisolid materials composed of long-chain molecules cross-linked to one another to create many small empty spaces that can absorb water or other liquids like a sponge. If the spaces are filled with a drug, the hydrogel can dispense the drug gradually as the structure biodegrades. Widespread research also is under way on using hydrogels as scaffolds for tissue engineering and tissue repair, where the spaces in the gel might be filled with stem cells, tissue-growth factors or a combination of both…
The new process, developed in the laboratory of Dan Luo, Cornell assistant professor of biological and environmental engineering, uses no high temperatures or harsh chemicals, so the material to be encapsulated in the gel can be introduced before the gel is formed. Because the gel is made of only synthetic DNA, no immune response should be triggered, the researchers said, so the material encapsulated can include proteins and even live mammalian cells…
To create hydrogels, they made branched DNA that formed itself into crosses, Y’s and T’s with “sticky” ends that could link to each other with the help of enzymes known as ligases. The cross-shaped branched DNA forms a gel by linking together into sheets of tiny squares that tangle in three dimensions; Y shapes form hexagonal structures like a chain link fence that combine into a fibrous three-dimensional form, while T shapes create random, disorganized patterns that look like an assembly of scales.
The researchers found that they could easily alter certain properties of the resulting gelatinous materials, including rigidity and absorbency, by adjusting the types of branched DNA used and the concentration of DNA in the mix. To demonstrate the ability of some of the materials to hold their shape, the researchers created them in a variety of different molds, including some that spelled out “CORNELL” at centimeter and nanoscales.
To test the use of the DNA hydrogels for delivering drugs, the researchers encapsulated porcine insulin and the anticancer drug Camptothecin and observed that the drugs were released in a controlled manner over time. When they encapsulated live cells in a gel, they found that the cells were still alive three days later. It is possible, the researchers said, that live cells encapsulated in a DNA hydrogel could be recovered, still alive, by breaking down the DNA structure with enzymes.

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