Towards switchable biological surfaces for on-demand biosensing in cell therapy bioprocessing

Carroll, Daniel (2024). Towards switchable biological surfaces for on-demand biosensing in cell therapy bioprocessing. University of Birmingham. Ph.D.

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Abstract

Over the past two decades advancements in our understanding of biological processes has opened the door to new and effective therapeutic products. In particular, cell and gene therapies have established themselves as pillars of modern medicine, which are often used to respond to diseases not effectively treated by other methods. However, therapies derived from biological sources have a higher degree of natural variability compared to small drug molecules obtained through traditional chemical synthesis. Manufacturing of such therapeutics requires constant monitoring to ensure product yield and efficacy. However, current bioprocesses used for the manufacturing of cell therapy products rely on off-line or end-point diagnostics. This results in long feedback loops limiting the capacity to react to needs of the cell culture in real time. Therefore, the need for integrated biosensing platforms has never been higher. To this end, this research explores combining nanobodies (Nbs), electropolymerised films, and stimuli response surfaces for the robust, sensitive, and on-demand detection of key cellular biomarkers. The capacity of oligopeptides to modulate surface Nb-antigen interactions was successfully confirmed using electrochemical surface plasmon resonance. Furthermore, surface characterisation techniques including X-ray photoelectron spectroscopy, ellipsometry, and electrochemical impedance spectroscopy highlighted the need for better insulation of the gold surface to prevent non-specific interactions. This led to the fabrication and optimisation of different electropolymerised films which also facilitated the covalent attachment of the biomolecules at the interface. Gold arrays were successfully fabricated in-house through clean-room manufacturing processes including thermal evaporation, spin coating, photolithography, and wet-etching. This platform was integrated with pre-existing potentiostats and the capacity of the working electrodes to be individually electrically addressed was demonstrated. This would allow the detection of multiple analytes from the same sample in an on-demand fashion. Different surface activation and receptor coupling strategies were then adopted from the literature, along with a tailored strategy being developed for the site-specific coupling of Nbs in a controlled orientation. This led to the development of a robust label-free biosensing platform by utilising changes in surface capacitance.

Overall, this works provides a solid foundation and outlines a road map to develop a sensitive biosensing platform with the capacity to modulate receptor-antigen interactions.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):