Dynamic polymers as the latest generation of biomaterials

Supramolecular polymers are made up of building blocks that, similar to natural materials, are held together by relatively weak interactions (hydrogen bonds, ionic interactions). This enables these building blocks to be easily mixed to create a functional polymer. This is similar to constructing a very tall tower using various types of LEGO bricks, which makes it easier to incorporate functional groups into the polymers.

Another crucial aspect of supramolecular polymers is their dynamics. Due to these weaker interactions, the building blocks can come in and out of the polymer, theoretically allowing supramolecular polymers to adapt to their environment.

Creating functional supramolecular polymers

While groups led by Bert Meijer and Anja Palmans (both professors in the Department of Chemical Engineering and Chemistry) have been working with supramolecular polymers in water for a considerable amount of time, it is only recently that the first steps have been taken towards functional materials.

The objective of the PhD research of Marle Vleugels was to create functional supramolecular polymers, test these polymers in a biological environment containing cells or proteins, and explore the role of dynamics in the interaction between the functional polymers and the proteins and/or cells.

Vleugels and her collaborators began by synthesizing new functional building blocks and incorporating them with the standard building blocks to create functional supramolecular polymers. She observed that copolymerization of functional building blocks is feasible and that the functionality remains available for binding to the cell surface and for interaction with proteins. The overall polymer dynamics were not heavily affected by functionalization, so the functional material retained the desired dynamicity.

Antibiotic-resistant bacteria

One of Vleugels projects focused on developing and testing a novel type of antibiotic, given the growing problem of antibiotic-resistant bacteria. By using a charged choline group as a functional group on one of the functional building blocks, she was able to create supramolecular copolymers that were then tested as a new type of antibiotic. The actual testing on bacterial cells was conducted in collaboration with a research group in Spain. The tests on the bacteria were highly successful, as less polymer was needed to achieve the same antimicrobial effect as previously studied.

Environment testing

To further investigate whether supramolecular polymers can adapt to their environment like natural systems, Vleugels created a lipid bilayer that served as a mimic of the cell membrane. One of the functional building blocks of the polymer was labelled with a dye to track the functional group during binding to the "cell membrane."

Through super-resolution microscopy, she discovered that synthetic supramolecular polymers do indeed rearrange and cluster to strongly bind to cell-like surfaces. This demonstrated that dynamics and the ability to rearrange are essential for interaction between supramolecular polymers and cells.

In summary, the results from Vleugels thesis illustrate how functionalization affects the formation and dynamics of supramolecular systems. A foundation has also been established for studying the cell-material interface. These findings have enhanced our understanding of interactions between supramolecular polymers and biological systems, expanding their potential applications as biomaterials.

Title of PhD-thesis: Bioactive supramolecular assemblies. Supervisors: Bert Meijer and Anja Palmans.