Roxanne Kieltyka first heard of supramolecular chemistry as an undergraduate studying inorganic chemistry, but she fell in love with it as a grad student.

It was then, she says, that she became captivated with the idea "that you can expeditiously make discrete structures and materials that show order, can be complex, and even be functional from self-assembling molecular precursors."

Supramolecular chemistry refers to assemblies of multiple molecules held together by noncovalent interactions. Those assemblies can have mechanical properties or bioactivity not seen in the individual components.

As a postdoc with E. W. (Bert) Meijer at Eindhoven University of Technology, Kieltyka turned her attention to the extracellular matrix in tissues and organs. This scaffolding supports cells and gives them physical and chemical cues to develop into tissue. Kieltyka wanted to use synthetic supramolecular polymers to make hydrogels as replacements for the extracellular matrix that scientists extract from mice for tissue engineering and cell cultures. She took a modular approach and found that she could make hydrogels with increased stiffness by mixing two weak ones.

In her own lab at Leiden University, Kieltyka continues to work with supramolecular materials. She makes hydrogel scaffolds for culturing induced pluripotent stem cells and plans to add chemical, biological, and environmental cues to guide them to differentiate into virtually any cell type of the human body.

"The natural extracellular matrix is the ultimate supramolecular biomaterial," Kieltyka says. She wants to mimic its ability to present the right biochemical and biophysical cues at the right place and the right time with supramolecular hydrogels.

The goal is to load the materials with cues to grow complex microtissues that can be used in applications such as drug screening. For example, a patient's own cells could be used to grow a diseased tissue to evaluate its response to potential drug treatments. These same materials could even be applied therapeutically, and she hopes to use them to deliver drugs in response to disease biomarkers or certain types of cells.

Her work is establishing design parameters that will guide others dreaming up their own supramolecular materials. John Matson, a supramolecular chemist at Virginia Tech, says: "She has a methodical approach that's helping to shape the field."