| Summary: | The formation of protein assemblies to carry out sophisticated functions is constantly gaining attention in nano-biotechnology. However protein assemblies are often linked through non-covalent interactions, limiting the stability of the complexes and the resilience to forces. Force resistance is crucial for magnetic isolation of circulating tumour cells (CTCs), when a specific protein interaction must withstand the forces pulling a captured cell in the magnetic field. CTCs are present in the blood of cancer patients at very low frequency, making their isolation extremely challenging. However, CTC isolation provides an important approach to enable cancer prognosis and personalised therapy. By optimizing the nanotechnology of the antibody-magnetic bead linkage, the membrane fluidity of the cancer cells, and the affinity of the antibody binding we developed a new approach to minimize the level of tumour markers required to immunomagnetically capture cancer cells. To improve the sensitivity of cancer cell detection even further, a peptide-peptide covalent ligation system was used to generate self-assembled polymers of affibodies (an antibody-like scaffold). Affibody polymers allowed the establishment of multivalent interactions with cell-surface tumour markers, greatly improving the recovery of tumour cells expressing low levels of cancer biomarkers. However, those polymers had a mixture of lengths and there was no control over polymer sequence. Using orthogonal sequential isopeptide bond formation, we synthesized sequence-controlled proteins chains and used these immuno-assemblies as potent inducers of apoptosis of cancer cells. The approaches presented in this thesis show the importance of generating covalent protein polymers for cell isolation and killing, potentially opening up new directions for cancer biotechnology.
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