Alkassem, Hasan; (2018) Imaging Antimicrobial Peptides in Action by Atomic Force Microscopy. Doctoral thesis (Eng.D), UCL (University College London).

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Abstract

Antimicrobial resistance is a challenge facing the world in the twenty-first century with an estimated 10 million deaths by 2050 if no actions are taken. Microbial resistance to drugs is a natural consequence when bacteria develop and adapt genetically to face new challenges including antibiotics. Currently, this development occurs at a higher rate than drug discovery. Hence there is a need for a new generation of antibiotics that kill pathogenic bacteria. Nature itself provides inspiration for such new antibiotics. For example, our immune system secretes antimicrobial peptides (AMPs), which have been successful agents in killing pathogens with no reported bacterial resistance. Compared with conventional antibiotics, these peptides are larger and more sophisticated biological molecules, which disturb the bacterial membrane, leading to cell lysis. It is currently costly to extract AMPs from natural resources to be used for fighting infections. Alternatively, synthetic AMPs that mimic natural ones could provide a sustainable cheap weapon against such thread. This also provides a unique opportunity to understand the structure–function relationships of such molecules to optimise these effective, non-toxic antimicrobial properties. Our collaborators at National Physical Laboratory have designed and synthesised new AMPs from their essential building blocks (amino acids). This thesis describes the use of atomic force microscopy (AFM) as a nanoscale imaging technique for characterising and imaging membrane poration mechanisms of four new AMP systems. Two of these systems are helical peptides, explained in chapter 3. The third system, explained chapter 4, is a triskelion with three arms of antimicrobial β-sheet peptide that co-assemble to form a hollow antimicrobial capsules. The latter has two possible functions: gene delivery and bactericidal effects. The fourth system, explained in chapter 5, contains two peptide monomers that are designed to co-assemble and form antimicrobial hollow capsids, inspired by the natural viral capsids. Finally, chapter 6 is a plan for taking these AMPs a step closer to commercialisation, including a business plan for one potential application.

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