A way to self-assemble complex structures out of bricks smaller than a grain of salt was found by a team of researchers at the Wyss Institute of Biologically Inspired Engineering at Harvard University. The new method could help solve one of the major challenges in tissue engineering: creating injectable components that self-assemble into intricately structured, biocompatible scaffolds at an injury site to help regrow human tissues.
The key to self-assembly was developing the world's first programmable glue. The glue is made of DNA, and it directs specific bricks of a water-filled gel to stick only to each other, the scientists report in the September 9 online issue of Nature Communications
"By using DNA glue to guide gel bricks to self-assemble, we're creating sophisticated programmable architecture," says Peng Yin, Ph.D., a Core Faculty member at the Wyss Institute and senior coauthor of the study. Yin is also an Assistant Professor of Systems Biology at Harvard Medical School. This novel self-assembly method worked for gel cubes as small as a tiny piece of silt (30 microns diameter) to as large as a grain of sand (1 millimeter diameter), underscoring the method's versatility.
The programmable DNA glue could also be used with other materials to create a variety of small, self-assembling devices, including lenses and reconfigurable microchips as well as surgical glue that could knit together only the desired tissues, said Ali Khademhosseini, Ph.D., an Associate Faculty member at the Wyss Institute who is the other senior coauthor of the study.
"It could work for anything where you'd want a programmable glue to induce assembly of higher-order structures, with great control over their final architecture -- and that's very exciting," said Khademhosseini, who is also an Associate Professor at Harvard-MIT's Division of Health Sciences and Technology, Brigham and Women's Hospital and Harvard Medical School.
To fabricate devices or their component parts, manufacturers often start with a single piece of material, then modify it until it has the desired properties. In other cases, they employ the same strategy as auto manufacturers, making components with the desired properties, then assembling them to produce the final device. Living organisms fabricate their tissues using a similar strategy, in which different types of cells assemble into functional building blocks that generate the appropriate tissue function. In the liver, for example, the functional building blocks are small tissue units called lobules. In muscle tissue, the functional building blocks are muscle fibers.