Exploring communication and collective behaviour between spatially organised inorganic protocell communities

A living system profoundly relies on mass, information and energy interactions through cell-cell and cell-environment networks. As a step towards understanding such interactions, it is beneficial to design and create bottom-up artificial living systems from non-living components, with a specific focus on synergistic interactivity between artificial cells (protocells) and their local environment. Although there are several routes for fabricating protocellular systems, we recognise key challenges associated with a) developing protocellular models with high levels of organisational tunability, b) achieving cell-environment bilateral communication, and c) realising autonomous self-assembly and regulation of protocell systems. The aim of this thesis is thus to review some matrix-based and matrix-free methods of inorganic protocell (colloidosome) 3D-spatial organisation, as judicious system designs capable of cell-cell and cell-environment communication, collective behaviours, and dynamic self-assembly, in close relation with local environments.The first experimental chapter details assembly of colloidosomes within hydrogel or coacervate-based matrices. A droplet microfluidic technique is employed as a novel method for encapsulating segregated colloidosome colonies within alginate hydrogel microspheres. The technique exploits high tunability for customisable size, ratio, microscale geometry, and 3D-patterning parameters. Benefiting from the versatility associated with such matrix-based systems, the second experimental chapter develops 3D-organised colloidosomes for collective signalling and emergent behaviours. Notably, spatially segregated colonies show proximity-mediated chemical communication with increased kinetics compared to analogous homogenous arrangements. This proximity-enhanced colloidosome signalling is exploited, alongside segregated ionic/covalent crosslinking transitions in the environment, to obtain simultaneous structural degradation and resilience of hydrogel hemispheres as a programmable mechanism for protocell ejection. Colloidosomes are also employed as simple signalling hotspots within coacervate-matrix systems. The final experimental chapter aims to re-imagine colloidosome organisation into a matrix-free system, capable of dynamic self-assembly and self-sorting via electrostatically-active membrane appendages. Alginate-coated and chitosan-coated colloidosomes are either co-assembled or self-sorted, in response to varied pH environments. Again, these systems are highly coordinated with their environment and as such, can be spatially pattered according to temporal pH changes through endogenous enzyme catalysis. Furthermore, a spatiotemporal effect on the rate of colloidosome communication in the presence of a hostile guest molecule is demonstrated.