Utilising inorganic protocells in hydrogel-based prototissues

  • Joanna F Sparks

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)


A new challenge in bottom-up synthetic biology is the construction of multi-protocellular communities capable of exhibiting emergent behaviours. The aim of this thesis is to produce rudimentary synthetic prototissues by embedding colloidosome-based protocells within polysaccharide hydrogels, which mimic the natural extracellular matrix.
Colloidosome protocells are chosen due to their previously demonstrated stability and the ability to encapsulate a range of molecules. Investigations into their structure and function are presented in Chapter 3. Instead of simple aqueous-filled capsules, the colloidosomes have an internal silica network which varies with the formation conditions. As a consequence, colloidosomes sequester above equilibrium concentrations of certain molecules from solution.
Retention of proteins within the colloidosomes, which is essential to their function as protocells, is shown to be strongly facilitated by interaction with the entrapped silica rather than by physical encapsulation within the membrane.
Chapter 4 outlines the design and characterisation of prototissues formed by embedding colloidosomes in agarose hydrogels. A modular system is used to pattern colloidosomes within the hydrogel and when a substrate is homogeneously applied, chemical communication between protocell populations results in patterned enzymatic reactions. The patterning is extended to shapes in 3-dimensions and due to its transient nature forms in situ, pre-programmed chemical gradients thus opening up the possibility of creating directional gradients between protocell populations in a way which is not possible for protocells in suspension.
Chapter 5 describes a prototissue designed to exhibit chemo-mechanical transduction upon addition of chemical fuels, through the collective behaviour of the component parts. Binary colloidosome populations capable of producing pH changes due to enzymatic turnover of chemical fuels are embedded in a novel, pH responsive, photocrosslinked hydrogel bilayer. Due to the use of antagonistic enzyme-containing colloidosomes the synthetic prototissue exhibits pre-programable motion which is a promising step towards the controlled fabrication of out-of-equilibrium soft
Date of Award23 Jun 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorStephen Mann (Supervisor)

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