From polyoxometalate-based protocells to protocellular materials

: protocells join forces to perform photoinduced water oxidation

Abstract

Despite the advances that the field of bottom-up synthetic biology has made towards the development and optimisation of synthetic protocells in recent years, the idea of combining organic elements with inorganic materials for the construction of hybrid protocells is still relatively unexplored. Furthermore, little progress has been achieved towards building higher order hierarchical structures. The assembly of protocells into spatially interlinked 3-dimensional networks that display emergent properties remains a considerable challenge.

This work focuses on a hybrid protocell model, polyoxometalate coacervate vesicles (PCVs) that incorporates Ru₄POM, an inorganic, ruthenium-based synzyme capable of photoinduced water oxidation. In Chapter 3, Ru₄POM-containing PCVs (Ru₄PCVs) are assembled, and their structure characterised. Their ability to perform photoinduced water oxidation is thoroughly explored and compared to the performance of Ru4POM in homogeneous conditions. Chapter 4 explores the interactions between the components of the photocatalytic cycle and seeks to understand where each reagent is during the reaction.

Chapter 5 demonstrates that PCVs can be assembled via electrostatic interactions into protocellular materials (PCMs), and that a range of morphologies can be achieved. Significantly, these 3-dimensional tissues are able to act cooperatively and display an enhanced performance when compared to the same amount of free PCVs under the same conditions, as demonstrated in chapter 6.

Finally, Chapter 7 shows that both Ru₄PCVs and Ru₄PCV based PCMs are capable of protocell-protocell communication. This is achieved with the use of an oxygen-dependent enzyme cascade, using the glucose oxidase (GOx) and horseradish peroxidase (HRP) enzymes.

Chapter 8 provides a summary of the work presented in this thesis and discusses the outlook and future work.

Overall, the results presented in this thesis help to bridge an important gap in bottom-up synthetic biology. This work presents a novel use of Ru₄PCVs and provides a different alternative to the generation of PCMs that display emergent properties.

Date of Award	21 Mar 2023
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Stephen Mann (Supervisor) & M C Galan (Supervisor)