Multi-Domain Self-Assembled Gels: From Multi-Component Materials to Spatial and Temporal Control of Multi-Component Biology

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Stem cells - cells which are precursor cells to all other types of cells - open up radical new possibilities for the future of medicine as they can be encouraged to convert into different types of useful growing tissue. In particular, stem cell technology offers potential to encourage joint restoration, nerve tissue regeneration, bone reconstruction and cardiovascular repair in vivo. More complex, and potentially valuable, is the use of stem cells to grow whole organs ex vivo, suitable for transplantation into patients. This would potentially satisfy the unmet need for organs faced by many patients, who die waiting. Further, this would provide organs which, because of the use of stem cells, will be tailored to the patient's immune system preventing organ rejection, and hence avoiding the massive cost associated with anti-rejection medication. This project explores a new class of soft gel-phase materials which will be able to direct and control tissue growth in more precise and sophisticated ways than can currently be achieved. We will create multi-domain gels in which different regions of the material have different chemical compositions and hence different properties. As a result, growing biological tissue will behave differently in different domains of the material. Although creating simple gels which are compatible with tissue growth is relatively straightforward, patterning multiple components in order to direct stem cells to do different things in different regions of the material is much harder. Progress has been made towards the goal of patterning gels for tissue growth using polymer gels, but our approach makes use of self-assembling small-molecule gelators, which have the potential to be much more programmable and responsive. Light will be used to pattern gel assembly, combining our technology with established polymer gels to create coherent patterned materials which have both rigid and soft domains. It would be expected that such materials would encourage stem cells to differentiate into different types - e.g. bone on the harder domains and fat on the softer domains. Biologically active agents, such as tissue growth factors, will then be incorporated within specific domains of our new materials. The controlled release of these agents will then be able to influence the growing tissue - in principle, this can be achieved with both spatial and temporal control. In this way, the growing cells are exposed to specific stimuli at chosen times in specific locations. Conducting units will also be embedded into specific gel domains, so that conducting pathways can be assembled only in specific regions of the gel. We anticipate that these conducting pathways will enable parts of growing tissue culture to be electrically stimulated in a selective manner at a chosen time point - potentially encouraging cells to develop in unique and controllable ways.The development of multi-domain gels is highly innovative and a number of important challenges will need to be solved in this project. Fundamental understanding will develop and control over multiple components within a single material will be achieved. Incoporating active agents into multi-domain gels for spatially and temporally controlled release, and the development of conducting pathways within such gels have never previously been achieved. As such, this project constitutes a step-change in multi-domain gel technology. We believe this approach may revolutionise approaches to tissue engineering and we will demonstrate its potential. Employing a supramolecular understanding of soft materials in order to control the ways in which they interact both with active agents, and biological organisms growing in their direct environment, moves the EPSRC Chemistry 'Grand Challenge' of Directed Assembly well beyond its current chemical state-of-the art by using the principles of supramolecular chemistry to interface with living systems biology.