3D measurement of fouling in membrane filtration: towards model based investigation and design

Bioprocess challenge the project seeks to address
Fouling of membrane filtration systems is an ever-increasing issue due to upstream titre and associated burden increases [1]. These complex feeds contain a large array of unwanted material that can detrimentally affect performance through several fouling mechanisms that can reduce permeation through membrane structure and change sieving coefficients [2]. Here we aim to develop a better understanding of these mechanisms using a measurement and visualisation approach that will inform modelling and simulation efforts core the CoE vision of enabling improved membrane design and operation.

Objectives
- To advance imaging approaches to measure foulant locations within membrane and feed types representative of current bioprocessing challenges
- To combine confocal microscopy and x-ray CT techniques to determine at new levels of resolution the location and species of foulant within membranes.
- Use these methods at multiple length scales, from small samples initially up to pleated sheet cartridges and single pass TFF systems to determine the impact of scale-up approach.
- Interface the three dimensional data acquired with modelling approaches.

Project Description
Fouling during filtration is a commonplace issue for industrial bioprocesses [1, 2], with a variety of target product sizes to consider and impurities that must be removed. At UCL and within the CoE various high-resolution imaging techniques have been applied to visualise and characterise Pall separation media, including x-ray CT, confocal microscopy, electron microscopy and focused ion beam microscopy [3-5]. This has shown that utilising multiple techniques in a complementary manner can overcome the shortcomings of individual methods and maximise the data gathered about a sample. In this project confocal and super-fluorescence microscopy, will enable optical slicing and large field of view imaging respectively on tagged feeds to identify the location and composition of entrapped material within Pall filtration membranes of varying characteristics such as pore size and asymmetry.

The research would build upon a CoE MSc project that investigated the location liposome entrapment within Pall membranes using confocal microscopy applied to dual layer membrane systems. It would further this by using liposome material with differing sizes and compositions in order to mimic products such as lentivirus and potential foulants e.g. extracellular vesicles that could be individually labelled prior to imaging. These mimics will be designed to align with other CoE EngD projects such as in lentivirus manufacture, and the data generated will support the CoE vision.
[1] Gronemeyer et al. (2014), [2], Fallahianbijan et al. (2019) [3], Johnson et al. (2017)
[4] Johnson et al. (2018), [5] Jackson et al. (2014)

Proposed timeline
Year 1: Imaging and analysis training (e.g. confocal), initial membrane experiments with liposomes
Year 2: Expand media (including dual layer) and formulation (move to liposome mimic of lentivirus)
Year 3: Combine results with other imaging data in the CoE, investigate multi-length scale imaging
Year 4: Complete studies, compare lenti mimic to actual, CoE imaging collaboration, submit thesis

The CDT has a proven track record of delivering impact from its research and training activities and this will continue in the new Centre. The main types of impact relate to: (i) provision of highly skilled EngD and sPhD graduates; (ii) generation of intellectual property (IP) in support of collaborating companies or for spin-out company creation; (iii) knowledge exchange to the wider bioprocess-using industries; (iv) benefits to patients in terms of new and more cost effective medicines, and (v) benefits to the wider society via involvement in public engagement activities and impacts on policy.

With regard to training, provision of future bioindustry leaders is the primary output of the CDT and some 96% of previous EngD graduates have progressed to relevant bioindustry careers. These highly skilled individuals help catalyse private sector innovation and biomanufacturing activity. This is of enormous importance to capitalise on emerging markets, such as Advanced Therapy Medicinal Products (ATMPs), and to create new jobs and a skilled labour force to underpin economic growth. The CDT will deliver new, flexible on-line training modules on complex biological products manufacture that will be made available to the wider bioprocessing community. It will also provide researchers with opportunities for international company placements and cross-cohort training between UCL and SSPC via a new annual Summer School and Conference.

In terms of IP generation, each industry-collaborative EngD project will have direct impact on the industry sponsor in terms of new technology generation and improvements to existing processes or procedures. Where substantial IP is generated in EngD or sPhD programmes, this has the potential to lead to spin-out company creation and job creation with wider economic benefit. CDT research has already led to creation of a number of successful spin-out companies and licensing agreements. Once arising IP is protected the existing UCL and NIBRT post-experience training programmes provide opportunities for wider industrial dissemination and impact of CDT research and training materials.

CDT projects will address production of new ATMPs or improvements to the manufacture of the next generation of complex biological products that will directly benefit healthcare providers and patients. Examples arising from previous EngD projects have included engineered enzymes for greener pharmaceutical synthesis, novel bioprocess operations to reduce biopharmaceutical manufacturing costs and the translation of early stem cell therapies into clinical trials. In each case the individual researchers have been important champions of knowledge exchange to their collaborating companies.

Finally, in terms of wider public engagement and society, the CDT has achieved substantial impact via involvement of staff and researchers in activities with schools (e.g. STEMnet), presentations at science fairs (Big Bang, Cheltenham), delivery of high profile public lectures (Wellcome Trust, Royal Institution) as well as TV and radio presentations. The next generation of CDT researchers will receive new training on the principles of Responsible Innovation (RI) that will be embedded in their research and help inform their public engagement activities and impact on policy.