Building Better Biomaterials

Research team creates polymer library to help reverse engineer biomaterials

Carnegie Mellon University chemist Krzysztof Matyjaszewski, with collaborators at the University of North Carolina at Chapel Hill and the University of Akron, have come up with a methodology that fine tunes the characteristics of brush polymers, allowing them to more closely mimic the characteristics of biological materials. Their technique is published as a letter in the Sept. 28 issue of Nature.

Synthetic chemists have tried for decades to create materials that mimic biological materials for use in medical implants, prosthetics, tissue engineering and soft robotics, but they have struggled to create materials that have the same combinations of strength, flexibility and softness as those found in biological tissue.

As a rule, when chemists make linear polymers with elastic properties called elastomers, they can make the materials stiff or stretchy, but not both. This makes producing strong, flexible materials like those needed for many biomaterials extremely difficult. In addition, linear polymers are made by trial and error and often involve mixing different chemicals and solvents, which limits chemists' ability to control the material's properties and can make the material non-biocompatible by causing inflammation.

Matyjaszewski and colleagues recommend brush polymers as a more viable candidate for creating biomaterials. Brush polymers are not limited by the strength and elasticity rules of linear polymers. Their well-defined properties can be predicted and altered across three variables: network strand length, side-chain length and grafting density. Additionally, they can be made without the inclusion of fillers or solvents.

In Nature, the group reports that they used controlled radical polymerization (CRP) methods to create a library of brush polymers. CRP techniques, such as atom transfer radical polymerization - developed by Matyjaszewski more than 20 years ago - allowed them to systematically vary the three variables for each polymer and create a well-defined reference set that researchers can use to reverse engineer a polymer architecture to closely mimic a given biological tissue.

To demonstrate the effectiveness of the library, the researchers successfully used the catalogue to create replicas of jellyfish tissue and lung and arterial tissue, and plan to expand their studies to other biological materials.