Nanotechnology of fluorescent proteins in a lipid/polymer matrix: soft thin film materials for artificial photosynthesis

Solar generation of electricity has rapidly increased in recent years from 19 TWh in 2009 to 724 TWh globally in 2019, suggesting that it will be a critical part of our future energy supply. As we are reaching the efficiency limits of traditional photovoltaics, there has been renewed interest in bio-inspired nanotechnologies, including the possibility of "artificial photosynthesis". Nature has evolved a suite of photo-active nano-machines, the so-called "light-harvesting" (LH) proteins found in chloroplasts which contain high concentrations of chlorophyll pigments. This project will apply a "bio-inspired" approach where we incorporate synthetic dye molecules with LH proteins extracted from spinach and place them within carefully designed soft thin films.

Lipids are an ideal soft material for thin-films: they readily self-assemble into stable nanoscale bilayers and have tunable physical and chemical properties. However, lipid are essentially "fat" molecules, and prone to rapid oxidative degradation. By mixing different types of lipid with amphiphilic synthetic polymers of lipid, we will design a film which has a pre-determined viscosity, charge and specific reactive groups, and importantly increased robustness and extended membrane lifetime. A short diblock copolymer comprised of poly(ethylene oxide) and poly(butadiene) has been shown to stabilize membrane proteins so that the proteins keep their activity for many months rather than a few days. Preliminary data suggests that Light Harvesting proteins are also stable in these polymers, therefore, this could become a more stable platform for artificial photosynthesis.

The objectives of this project are to develop lipid/polymer membranes that increase the stability of photosynthetic proteins under various physical stresses. The film properties will be varied by systematically testing the effect of the lipid saturation and chain length, the ratio of polymer-to-lipid and protein-to-lipid. Stability will be assessed across a range of temperatures and pH and to guide the optimization process. We will also exploit our knowledge of more exotic lipid behaviour to design a lipid system that will spontaneously self-assemble into a stacked multi-layer arrangement, thereby increasing protein density and light harvesting efficiency. The lipid-polymer-protein nanocomposites will be characterized using a world-class suite of techniques, including advanced spectroscopy and microscopy. Atomic Force Microscopy (AFM) will be used to map the 3-D topography and mechanical properties of the thin films at the micro- to nanoscale and fluorescence microscopy to visualize the dynamic rearrangements of membranes at scales from millimetres to nanometres. Differential Scanning Calorimetry and/or Fluorescence Correlation Spectroscopy will quantify the phase transitions against temperature. Single-molecule fluorescence spectroscopy such as FLIM-FRET will be used to measure the rates of diffusion and specific interactions between lipids/polymers and proteins to assess their mixing behaviours. The success of this project will provide new nanomaterials which could be applied in future artificial photosynthesis devices, e.g., as coating in bio-photo-electrochemical cells.

This project would support the future development of solar nanotechnologies which use biological components or bio-inspired design principles. What we do now to understand biophysical mechanisms could allow us to interface biomolecules or inorganic materials with devices (e.g. photo-active thin films). Engagement with industry will be initiated to understand the needs of the solar technologies sector and make contacts at trade-focused events (e.g. Solar Trade Association). This will prepare the ground for the future project and partnerships with industry, e.g. assessing the economic feasibility of dye-sensitized solar cells exploiting biological or bio-inspired components.

1. PEOPLE. The SOFI2 CDT will have varied economic and societal impacts, the greatest of which will be the students themselves. They will graduate with a broad and deep scientific education as well as an entrepreneurial mind-set combined with business awareness and communication skills. The training programme reflects the knowledge and skills identified by industry partners, the EPSRC, recent graduates and national strategies. Partners will facilitate impact through their engagement in the extensive training programme and through the co-supervision of PhD projects. Responsible Innovation is embedded throughout the training programme to instil an attitude towards research and innovation in which societal concerns and environmental impact are always to the fore. The team-working and leadership skills developed in SOFI2 (including an appreciation of the benefits that diversity brings to an organisation and how to foster an atmosphere of equality and inclusion) will enable our graduates to take on leadership roles in industry where they can, in turn, influence the thinking of their teams.

2. PROJECTS. The PhD research projects themselves are impact pathways. Approximately half the projects will be co-sponsored by external partners and will be aligned to scientific challenges faced by the partner. Even projects funded entirely by the EPSRC/Universities will have an industrial co-supervisor who can provide advice on development of impact. The impact workshops and Entrepreneur in Residence will additionally help students to develop impact from their research, while at the same time developing the mind-set that sees innovation in invention.

3. PUBLIC. The public benefits from innovation that comes from the research in the CDT. It also benefits from the training of a generation of researchers trained in RI who seek out the input of stakeholders in the development of products and processes. The public benefits from the outreach activities that enable them to understand better the science behind contemporary technological developments - and hence to make more informed decisions about how they lead their lives. The younger generations benefit from the excitement of science that might attract them to higher education and careers in STEM subjects.

4. PARTNERSHIPS. SOFI2 involves collaborative research with >25 external partners from large multinationals to small start-ups. In addition to the results of sponsored projects and the possibility of recruiting SOFI2 students, companies benefit from access to training resources, sharing of best practice in RI and EDI, access to the knowledge of the SOFI2 academics and sharing of expertise with other partners in the SOFI2 network. This networking is of particular benefit to SMEs and we have an SME strategy to facilitate engagement of SMEs with SOFI2. SME representation on the Management and Strategic Advisory Boards will support the SME strategy.

CPI/NFC is a key partner both for delivery of training and to connect SOFI2 research, students and staff to a wide network of companies in the formulated products sector.

The unusual partnership with the Leverhulme Research Centre on Forensic Science may lead to a stronger scientific underpinning of forensic evidence with positive impacts on the legal process and the pursuit of justice.

5. PRODUCTS. Partner companies identify areas of fundamental and applied science of interest to them with the knowledge that advances in these areas will help them to overcome technological challenges that will lead to better products or new markets. It is an expectation that scientific discoveries made within the CDT will drive new products, new markets and potentially new companies. SOFI2 CDT seeks also to develop innovative training materials, for example, in RI and in data analytics and AI (in collaboration with the Alan Turing Institute), from which other CDTs and training organisations can benefit.