Collective Behaviour in Synthetic Protocell Consortia

Making new materials that have small-scale structures and multiple components is expected to be of great importance in a wide range of applications such as sensing, storage and release operations, and controlled catalysis. One new area where small-scale structures could make a significant breakthrough is in the formation of artificial cell-like materials (protocells). Much of the inspiration for this approach comes from mimicking key aspects of the living cell, albeit with a large degree of simplification. Our approach to addressing the necessary simplification is to draw inspiration from imaginative scenarios that are being considered as plausible mechanisms for prebiotic organization on the early Earth. We are therefore inspired by these protolife-based models of materials organization to develop new strategies in the laboratory that will result in the design and construction of chemical micro-compartments with novel properties and functions. In a sense, we aim to abstract ideas about the past in order to develop new technologies for the future.

Although several new types of protocells are currently available, the design of synthetic protocell communities and investigation of their collective behaviour has received little attention. In this regard, the proposed work has two main themes that will help us develop guidelines for the rational design, construction and collective behaviour of new classes of integrated materials based on soft cell-like colloidal micro-compartments. One theme focuses on preparing protocells with layers of organization ("nested" structures) and capturing different components in different chambers of these hierarchical small objects. For example, we intend to trap key enzymes in different layers of the nested protocells so that controlled chemical pathways can be established within each individual protocell. Moreover, we wish to try and build a synthetic protocell that has a "nucleus" within it, which contains genetic information that can be used to synthesize proteins and enzymes (catalysts). Complementary to these studies, a second theme focuses on mixtures of single-chambered protocells that together form a "community" of small-scale objects with different properties and functions. Our goal is to develop micro-engineering methods using acoustic standing waves to place members of the protocell community in specific locations within an ordered array so that they can chemically communicate with each other. In addition, we aim to produce aqueous dispersions containing a mixed population of protocells that exhibit a simple form of predatory-prey behaviour. For this, we will design a "killer" protocell that will specifically target and chemically disassemble a second type of protocell when they come into contact. This will allow us to study complex interactions within this community of small-scale objects, and to develop new concepts such as protocell "self-defence" and "tit-for-tat" strategies in mixed populations of interacting artificial cell-like microstructures.

This application seeks funding to initiate and develop a new research portfolio focused on pioneering foundational steps towards minimal representations of synthetic cellularity as expressed through the fabrication of integrated, quasi-autonomous protocell phenotypes and communities. The overall aim is to explore higher-order behaviour (multi-compartmentalization, communication, signaling, predation, cooperation) within interacting protocell populations and communities as an unprecedented step towards synthetic protocell consortia and compartmentalized colloidal-scale objects capable of novel collective properties. For this, we will pioneer advances towards the realization of protocell consortia by developing themes concerned with collective behavior arising from two types of community organization; (a) nested (multi-compartmentalized) arrangements of discrete protocells capable of endosymbiotic functionality, and (b) dispersed mixed populations of individual protocells that exhibit exosymbiotic functions via chemical signaling, communication and surface-mediated interactions. In both cases, we will utilize chemical synthetic biology methods to establish control over the internal or external interaction networks, and develop acoustic trapping procedures for micro-engineering patterned arrangements of these protocell communities.

Impact Summary

Academic benefits (See Academic Beneficiaries).

Technological impact:
We expect to establish innovative systems based around mixed communities of protocells that can be exploited for the development of signaling pathways between chemically active micro-compartments, interactive networks of functional objects, and protocell-mediated gene-directed microscale circuits. Thus, we expect the strategies described in this research proposal to generate transformative ideas for the construction of functional materials at the interface with biology, spearhead new advances in "Protolife Technologies" focused on the ex novo synthesis of minimal life constructs, and provide novel opportunities in bioinspired micro-storage and delivery, micro-reactor technologies, and cytomimetic engineering. In terms of the specific research programmes, protocells with controllable nested architecture could have important implications in micro-reactor technologies and synthetic biology applications involving the processing of molecules in liquid media, recursive uptake and cycling of substrates and cofactors, gene-mediated switching of signals between functional colloidal constructs or between protocells and living cells, and sustained self-controlled programmed release of drug and bioactive agents. In addition, studies on acoustic standing wave patterning of functionalized coacervate droplets offers a novel potential route to high-throughput analyses of spatially addressable arrays of liquid micro-droplets over a range of timescales and chemical/physical environments.

Economic benefits:
The ability to address new technological futures by abstracting problems implicit to the deep past (protolife) is a promising and significant source of new ideas for wealth creation. In this regard, the proposed work opens up novel possibilities for new disruptive technologies based on soft, wet, chemical microsystems with adaptive, collective and emergent properties. Specifically, protocell-based technologies will be useful in areas such as microscale chemical organization, functional materials micro-ensembles, miniaturization and organization of functional droplets, and the fabrication of bioinspired constructs. In particular, the development of interacting communities of compartmentalized colloidal-scale objects will be of significant interest to industrial partners in fields such as energy storage, carbon fixation, water splitting, health and personal care, and advanced composite micro-engineering. The proposed research therefore offers benefits in diverse markets such as those currently dominated by companies such as Unilever and GSK, who require continual innovation in microscale compartmentalized materials for new delivery, storage and release systems.

Societal benefits:
The fabrication of synthetic protocells could have significant long-term impact on health care and quality of life. For example, artificial cells that are designed for specific applications in which the properties of biological systems (self-organization, nano-component efficiency, adaptability etc) are compartmentalized at a relatively low cost could give rise to new miniaturized agents for applications in DNA sequencing and protein crystallization, molecular screening, soft matter biotechnology, energy conversion in microscale bio-batteries, pharmacology and medical diagnostics. Such areas can be viewed in the context and application of synthetic biology, and should aid downstream industrialization. Significantly, in contradistinction to more radical forms of synthetic biology, the chemical construction of artificial cells provides an approach to life-like constructs with minimal evolutionary capacity, and as such would be more ethically acceptable in diverse biotechnological, environmental and medical applications.