Characterisation and Functionalisation of Ultrabithorax Materials for Biosensing

Ultrabithorax (Ubx) is a Hox transcription factor, which self-assembles into protein films and fibres at the air-water interface. Ubx materials are bio- and cyto-compatible, and can be functionalised with DNA, proteins, and growth factors to benefit from functions such as supporting cell proliferation. This thesis investigated the optical, electrical, and mechanical properties of Ubx fusion fibres in conditions relevant to applications in biosensing and tissue engineering. The steady-state and time-resolved spectra of the fibres were measured using an ultrafast laser source. The dityrosine emission peak red-shifted by 50nm in fibres compared to Ubx fusion solutions, and resonance energy transfer between dityrosine and enhanced green fluorescent protein (EGFP) was observed in the EGFP-Ubxprotein fusion. The electrical properties of Ubx fusion fibres were tested, and anincrease in their electrical conductivity by 3 orders of magnitude was measuredwith rising relative humidity. Tensile tests of Ubx fusion fibres revealed that thefibres were less extensible but stronger after prolonged storage and rehydration,which could influence the design of Ubx materials for tissue engineering. Significant binding of DNA aptamers to Ubx in solution and in fibres was observed. A fluorescence-based method to assess binding eciency of bacteria and the SARSCoV-2 spike RBD protein was developed. Some indication of increased specific pathogen binding was observed using long oligonucleotide sequences bound to Ubx fusion fibres, and improvements to this system were suggested. Alginate and collagen are biomaterials widely used in tissue engineering. Preliminary experiments were conducted that showed the feasibility of production of composite materials made of Ubx and alginate or collagen, which could be applied to createfunctional tissue scaffolds. Ubx-based platforms and composite materials couldbenefit from the intrinsic properties of Ubx, and Ubx functionalisation with proteins,growth factors and DNA aptamers for applications in biosensing and tissueengineering.