Glycan Mimetics for Cell Glycocalyx Reconstitution: a polymer chemist’s approach to fight infection

Project Information

GLYMCE

Grant agreement ID: 101088228

DOI

10.3030/101088228

EC signature date 20 March 2023

Start date 1 February 2024

End date 31 January 2029

Funded under

• European Research Council (ERC)

Total cost

€ 1 994 024,00

EU contribution

€ 1 994 024,00

Coordinated by

ALBERT-LUDWIGS-UNIVERSITAET FREIBURG
Germany

Periodic Reporting for period 1 - GLYMCE (Glycan Mimetics for Cell Glycocalyx Reconstitution: a polymer chemist’s approach to fight infection)

Reporting period: 2024-02-01 to 2026-07-31

Summary of the context and overall objectives of the project

The overall aim of GLYMCE is to understand how carbohydrates and their assemblies are recognized by pathogens to drive infections. The identified molecular patterns will be transferred to biomimetic glycopolymer materials to extend the arsenal for the fight against infections.
Carbohydrates are not just sweet, they are crucial in various biological interactions: Cell surfaces are covered in carbohydrates, the glycocalyx, that governs contact with pathogens such as viruses and bacteria. A class of carbohydrates critical for pathogen attachment and infections are sulfated glycosaminoglycans (sGAGs) that hold a great potential for the development of new antiinfection strategies. However, a key limitation is our insufficient knowledge about the mode of action of sGAGs within the complex ensemble of the glycocalyx:
How does the display of sGAGs within the glycocalyx affect their pathogen interactions?
GLYMCE will tackle this question from a polymer chemist’s point-of-view: taking a bottom-up approach to prepare sGAG mimetics (level 1); assembling glycocalyx mimetics and studying the spatial organization of sGAGs upon pathogen binding (level 2); reengineering the glycocalyx of living cells to understand the factors governing infection (level 3). This is only now possible through recently developed synthetic tools enabling sGAG mimetics with controlled sequence, molecular weight, chain conformation, architecture and sulfation patterns – all parameters known to critically impact the affinity and selectivity of sGAGs.
Overall, by taking a radically different approach informed by chemical biology and brought to life by polymer chemistry, mechanisms for sGAG-mediated pathogen attachment will be derived and applied to develop new materials and strategies to detect, prevent and treat infections.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main objective of GLYMCE is the bottom-up design of glycocalyx models specifically using sGAG mimetic macromolecules to systematically study their role in infection processes and to potentially use this knowledge as well as the derived molecules and materials to derive new strategies in the fight against infections. Along this concept, the project is divided into three major aims: 1) The synthesis of sGAG mimetics, 2) The assembly of glycocalyx models using sGAG-mimetics and 3) Glycocalyx engineering using sGAG-mimetics.

Aim 1: In the first phase of the project, solid phase polymer synthesis protocols to enable the sequence-defined synthesis of both, sulfated and non-sulfated glycomacromolecules were consolidated to now give access to sGAG mimetics with possible variations in a) the carbohydrate motif, b) the number and density of carbohydrate motifs, c) the number and density of sulfate groups and d) the introduction of oligoproline segments to alter main chain flexibility. Since solid phase protocols are limited in terms of the achievable molecular weights, polymeric sGAG-mimetics have been derived by controlled radical polymer synthesis (linear GAG mimetic polymers) and by combining solid phase and polymer synthesis (brushed GAG mimetic polymers).

Aim 2: In order to make the GAG mimetic macromolecules and polymers developed in Aim 1 accessible for the development of glycocalyx models, these need to be equipped with a so-called membrane anchor. Solid phase synthesis protocols are now established that allow for the controlled installation of different types of membrane anchors in glycomacromolecules. The same protocols also give access to macroinitiators/ -chain transfer agents that are used to then derive the according glycopolymer systems. Both, glycomacromolecules and glycopolymers are then successfully incorporated into giant unilamellar vesicles (GUVs) to derive glycocalyx models. Importantly, glycomacromolecules as well as glycopolymers are fluorescently labelled and thus can be readily used for analysis of membrane incorporation, dynamics and interactions. A key driver of multivalent glycan-mediated binding on cell surfaces is the formation of clusters. Two strategies were already successfully established: 1) Formation of phase-separated GUVs and installation of glycan mimetics selectively in either the ordered or non-ordered membrane phase to create clustered presentation (Blawitzki et al, doi.org/10.1002/anie.202414847) and 2) Incorporation of post-polymerizable diacetylene units to induce cluster formation through receptor interaction and fixation from UV-induced polymerization (Blawitzki et al, doi.org/10.1002/marc.202500567) Currently, both strategies are being extended towards sulfated GAG mimetic macromolecules and polymers.

Aim 3: While the glycocalyx models developed in Aim 2 enable systematic studies into GAG-mediated interactions, these systems are highly simplified and can intrinsically only mimic parts of the complexity of the natural cell surfaces and binding processes. Therefore, in an additional top-down approach, membrane-anchored GAG mimetics are now successfully applied for so-called glycocalyx engineering.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

One of the key questions of GLYMCE is how clustering of sGAGs drives infection processes, namely pathogen attachment in the first step. However, experimentally we only have limited access so far to build and study defined glycan clusters. A beyond the state-of-the-art development of our work therefore was the design of two distinct membrane anchors that allow positioning of glycan-mimetic ligands in either ordered or non-ordered membrane domains and thereby to imitate one of the cellular clustering strategies. A breakthrough result obtained from this methodology was a higher apparent lectin binding affinity to glycan-mimetics placed in the ordered phase of the model membrane (Blawitzki et al., 2025). We are now employing this methodology for sGAG mimetic systems and in glycocalyx engineering approaches and thereby drive our knowledge on the potential role of such glycan clusters or membrane rafts in pathogen attachment.