ConfocAl Microscopy and real-time Rheology of dynamIc hyroGels

Project Information

CAM-RIG

Grant agreement ID: 726470

DOI

10.3030/726470

Project closed

EC signature date 27 April 2017

Start date 1 May 2017

End date 30 June 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 038 120,00

EU contribution

€ 2 038 120,00

Coordinated by

THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
United Kingdom

Periodic Reporting for period 5 - CAM-RIG (ConfocAl Microscopy and real-time Rheology of dynamIc hyroGels)

Reporting period: 2023-05-01 to 2024-06-30

Summary of the context and overall objectives of the project

Supramolecular hydrogels have become an important research area in the last decade due to their unique properties including easy preparation, self-healing and stimuli-responsiveness for applications such as sensing, biomaterials, biomedicine, energy conversion, catalysis, etc. Nonetheless, the rational design of the current state-of-the-art of supramolecular hydrogels is limited due to a lack of quantitatively systematic studies of structure-property relationships between microscopic supramolecular motifs and the macroscopic mechanical behaviour. In order to overcome this limitation, the direct visualization and resolution of single molecules by super-resolution microscopy (SRM) can enable in-depth investigations into the structure-property relationships of supramolecular hydrogels with unprecedented temporal and spatial resolution. Through the deep understanding of structure-property relationships, the rational design of supramolecular hydrogels with controlled architecture and function will become possible, bringing new potential for the development of supramolecular materials with desirable applications in many different fields.

This project represents a new research strategy at the frontier of supramolecular chemistry, polymer chemistry and material science, aiming to develop an innovative methodology to probe dynamic host-guest complexation as individual entities and within hydrogels at the molecular level with temporal and spatial resolution; design of supramolecular hydrogels with tuneable dynamics, morphologies and optical properties; gain fundamental knowledge that will serve to the development of technologies in sensing, biomedical and pharmaceutical sector. In this way, the ability to create desirable supramolecular hydrogels with tuneable properties and functions will draw enormous attention from scientists in different fields of chemistry, materials science, engineering and biomedicine, and will also inspire new collaboration within our scientific community. It is also noteworthy that the profound knowledge that we will acquire by studying the rheological behaviour of a range of supramolecular hydrogels will contribute fundamental knowledge to the field of polymer rheology, especially for the class of supramolecular polymers formed from noncovalent interactions.

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

1. Development and validation of the CAM-RIG experimental setup
One of the primary achievements of the project was the successful sourcing, custom design, and assembly of a bespoke setup that integrates optical and mechanical characterisation methods. CAM-RIG enables simultaneous visualisation of dynamic supramolecular interactions at the nanoscale and measurement of macroscopic material properties. This dual capability is, to the best of our knowledge, unprecedented. The platform opens new possibilities for studying stimuli-responsive and adaptive materials in real time.

2. Development of novel fluorophores and host–guest systems
During the project period several novel fluorophore guest molecules were designed, synthesised, and characterised, including bispyridinium-based structures capable of forming quaternary 2:2 complexes with CB[8]. These guest molecules serve dual functions: (1) as cross-linkers within hydrogels via supramolecular complexation, and (2) as optical reporters whose emission properties change upon binding. Single molecule total internal reflection fluorescence (TIRF) microscopy was established to enable characterisation of these interactions at nanomolar concentrations — the first demonstration of stable CB[n]-based host–guest interactions at such low dilutions. This significant finding led to our first publication on the CAM-RIG set up (J. Am. Chem. Soc., 2024, 146, 12877-12882).

3. Supramolecular hydrogel formation and dynamic imaging
Building on fluorophore development, we began to incorporate fluorophores as crosslinks within supramolecular hydrogels. These materials exploit CB[8]-mediated host-guest complexation as dynamic crosslinkers within the polymer network. The resultant hydrogels exhibit switchable optical states - “on” when crosslinks are intact and “off” when disrupted - enabling direct imaging of crosslink dynamics within the material using CAM-RIG. Preliminary studies reveal a significant difference between the dynamics of host–guest complexation in solution and when attached to the polymer network. This real-time comparison across length scales is one of the central breakthroughs of the project.

4. Super-resolution imaging of hydrogel pore structure
The CAM-RIG platform was also extended to the structural characterisation of hydrogels. Using advanced SRM techniques, we are developing a method to "trace" the pore network of hydrogels, with the potential to quantify internal structure and connectivity at nanometre resolution. We hope that this will provide crucial insight for materials design — particularly for applications in tissue scaffolding, drug delivery, and other biomedical systems where pore size and architecture influence performance.

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)

Discovering a new binding mode for CB[8] based on polar-pi interactions was not planned. This finding resulted in a new class of supramolecular polymeric materials where we could access glass-like networks for the first time through slow dissociative CB[8] host-guest crosslinks. This was unprecedented and represented a significant advance in the field. The work was published in Nature Materials and attracted significant media attention.

The work on insulin stabilisation stemmed from the new polar-pi interaction finding and again, was not planned but the technology has been patented, and we have applied for an ERC Proof of Concept to help commercialise this technology.

The bispyridinium fluorophores that were developed as self-reporting guest molecules to understanding the dynamics within CB[n] crosslinked polymer networks proved to have a much broader applicability than initially planned. The broader exploitation of these molecules included exploring their use as electrolytes in redox flow batteries. This work showcased a route to metal-free electrolytes that offered minimal capacity fade and tolerance to oxygen – a landmark achievement in the field. The findings were published in Nature and have resulted in an ERC Proof of Concept grant to help commercialise the technology through a spin out company Kodiaq Technologies.

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