3D-Printed Platforms to Study and Utilise the Photoelectrochemistry of Photosynthetic Biofilms

The aim of this research, which is to be carried out at the University of Cambridge, is to 3D-print platforms for studying and utilising biofilms. The propensity for microorganisms to form biofilms on surfaces can have profoundly contrasting implications in different contexts. For example, microbial biofilms are a large problem in the medical industry since they can be highly resistant to antibiotics whilst at the same time causing up to 80% of infections, according to the US National Institutes of Health. On the other hand, there is a large community who are harnessing the metabolic power of biofilms to remediate waste water, carry out chemical synthesis, and generate electricity in an inexpensive and renewable manner. For example, photosynthetic microorganisms, including cyanobacteria and algae, have been recruited to form biofilms on conductive substrates so that it would injects charges into the substrate during light irradiation, much like solar cells, in what is known as bio-photovoltaics.
Both separate efforts to eradicate and exploit microbial biofilms are currently hindered by knowledge gaps within the complex field of biofilm biology, where the interfacial biofilm-material interactions that govern biofilm physiology are not well understood. We want to develop a platform in which the surface morphology of different materials can be precisely controlled to study and control the number of cells the scaffold can accommodate. This will be done using of 3D-printing, a powerful prototyping tool used in a wide range of applications. As a starting point, this research will focus on using 3D-printing to optimise cyanobacterial loading into a conductive scaffold. The improvement in loading is expected to improve the solar-to-power conversion efficiency of bio-photovoltaics, which is currently very inefficient. The idea is to use 3D-printing to build a library of conductive 3D scaffolds varying in dimensions, morphological features, roughness, and materials, and screen these for high cell loading, biofilm formation, and test them under light irradiation to measure solar-to-charge output.
An important parallel aim of this project is to understand the underlying mechanisms that give rise to the exchange of energy/charges between the organisms and the material during light irradiation. Currently, it is not known whether this exchange is due to a self-protective mechanism by photosynthetic organisms, a mode of cell-cell communication, or to what extent it is detrimental or beneficial to the physiology of the biofilm. To answer these questions, advanced imaging and spectroscopic techniques will be adapted to probe the distribution and chemistry of common cellular components within the biofilm during dark and light cycles. When the two parts of the project are married up, more wholistic strategies to facilitate efficient exchange between the biofilm and the conductive scaffold can be designed - either through bioengineering of the cells and/or through altering the structure/composition of the scaffold.
The most important outcome of this research is that the new platforms will open up the study and ultilisation of biofilms in a large number of applications and research fields. The 3D-printing and imaging strategies developed in this study can be adapted to improve biofilm-materials interactions in current and upcoming biofilm biotechnologies and reactors. Similarly, they can also be adapted for biomedical research to, for example, screen anti-biofilm drugs, study biofilm resistance, and study problems in the large world beyond microbial systems (such as mammalian cells). A more direct outcome of this project would be the generation of valuable lessons and benchmark systems for bio-photovoltaics, which would benefit renewable energy research. We would also unravel a little more the fascinating photobiology of cyanobacteria, which play indispensable roles in the Earth's ecology.

The overarching aim of this work is to develop new platforms for studying and exploiting the metabolic chemistry of microbial biofilms. As a starting point, the first objective of this project is to demonstrate that additive manufacturing (3D-printing) can be used to optimise solar-to-power conversion efficiency in bio-photovoltaic devices by optimising the electrode architecture for the integration of cyanobacterial biofilms. This will be achieved by using 3D-printing, either through an extrusion or inkjet printing approach, to access a library of electrode architectures varying in dimensions, pore sizes and shapes, roughness, and conductive materials, that cannot be accessed quickly and easily through other means. The new electrodes will be screened for cyanobacterial cell loading capacity, biofilm formation, photoelectrochemical response, and solar-to-power conversion efficiencies, in search of new benchmark systems.
Complementing the first objective, the second objective of this project is to develop approaches to elucidate the mechanism of electron transfer at the biofilm-electrode interface. Currently, the biological role and mechanism of photo-induced charge transfer at the cyanobacterial biofilm-electrode interface is poorly understood. Confocal fluorescence microscopy and resonance enhanced Raman imaging will be coupled to an in-house built photoelectrochemical platform to study the movement of endogenous ions (with the aid of fluorescence probes), organic and inorganic species, and exogenous mediators through a biofilm during dark and light cycles. An enhanced understanding of the interfacial electron transfer pathways will trigger more rational synthetic biology strategies to be devised in future bioengineering efforts. When this (objective 1) is coupled to the rational electrode design (objective 2), more integrated strategies for enhancing solar-to-power conversion efficiencies may become available.

There are a number of potential (non-academic) beneficiaries from the proposed research.

1) The private sector may benefit from the commercialisation of any promising electrodes or scaffolds that exhibit high loading capacity for biofilms and/or other biocatalysts. This is made more promising by the use of the additive manufacturing (3D-printing) process, which minimises waste and generates highly reproducible scaffolds. The introduction of this product into the market which will likely take several years after the completion of the project, will contribute to the nation's wealth by fostering the UK's economic competitiveness. There are many biocatalyst companies, industries and bioreactor manufacturers within the UK that may benefit from this (e.g. Biocatalysts Ltd, Cellexus, Electrolab, ACWA). The additional impact would be that such a product could be used to significantly widen the scope of biocatalysis and biotransformations possible in UK industries, increasing productivity and creating jobs. The application of this technology is likely to bestow long term benefits to the UK in terms of energy, healthcare, and sustainable manufacture processes.
The generation of promising biophotovoltaic electrodes that are suitable for commercialisation will also greatly benefit the UK economy. Such alternative forms of solar energy generation, despite low solar conversion efficiency, may have important applications in populations living off-grid (>1.5 billion on Earth), and require technology that is more resilient what the current commercial solar cells can provide (they are prone to breakdown in harsh conditions). Photosynthetic microorganisms can be very adaptive and robust against the environment, self-repair, and be assessed in any many of the world that receives sunlight. As such, the successful development of this sustainable technology will have tremendous impact for the wealth and wellbeing of many beyond that of the UK population in the long run.

2) The public sector, including educational institutions and museums, can use the biofilm electrodes developed within the Fellowship as demonstrations of how we can harness energy from natural photosynthesis to power our electronics. The impact from this will be immediate and will help to build appreciation within the community about the money that is being spent on research and also build general awareness of our energy problems.

3) There will be long term benefits to the health of the wider public, mainly due to any long term (greater than 10 years) breakthroughs made relating to biofilm formation. Biofilms are responsible for 80% of infections according to the US National Institutes of Health, and is also highly resilient to antibiotics. Building knowledge about the biofilm-material interface will greatly contribute towards finding solutions for these serious problems, and will improve the quality of life for many within the UK and around the world.

4) Researchers (post-docs and students) within this project will benefit from engaging in outreach activities, communicating and engaging with the greater community about the science being developed uniquely in the UK. They will also benefit immediately from being experience in research in such a diverse multidisciplinary field, where they will be exposed to research in biology, material science, photocatalysis, and photosynthesis, just to name a few.