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Enzyme-driven chemotactic synthetic vesicles

Contini, C; (2017) Enzyme-driven chemotactic synthetic vesicles. Doctoral thesis , UCL (University College London). Green open access

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Abstract

Directional locomotion or taxis is possibly one of the most important evolutionary milestones, since it has allowed many living organisms to outperform their non-motile competitors. In particular, chemotaxis is one of the most elaborated targeting processes present in Nature. By sensing a chemical gradient, uni or multicellular organisms are able to move toward or away from favourable/unfavourable stimuli, adapting to changes in environmental conditions. This phenomenon normally involves the presence of a specific chemical gradient of signaling molecules that guides cells in their orientation and movement. Chemotaxis is therefore a potent long-range directional process, extending over length scales that are several orders of magnitude larger than the motilesystem itself. Creating an artificial self-propelled object, similar to many biological micro and nano-motors present in Nature, is one of the main challenges in nanotechnology. The chemotaxis applied to an artificial nanovector could be used for a wide range of applications, including drug delivery systems and nanoreactors. Combining natural enzymes with synthetic vesicles, we propose an efficient chemotactic nano-system driven by enzymatic conversion of small water-soluble molecules. We achieve this by encapsulating enzymes into nanoscopic polymer vesicles (known as polymersomes) whose membranes are designed to contain permeable domains within an impermeable matrix. The asymmetric distribution of the permeable domains enables the localised expulsion of the entrapped enzyme reaction products. This, in turn, allows propulsion in a specific direction that is controlled by the signaling molecule concentration. We demonstrate this concept, using physiologically relevant hydrogen peroxide and glucose coupled with catalase, glucose peroxidase and their combination loaded within asymmetric polymersomes. We show that the combination of membrane topology and enzyme encapsulation produces propulsion and chemotaxis without requiring chemical modification. Finally, we propose a new diffusion mechanism whereby selective permeability across nanoscopic membrane compartments is exploited to generate locomotion.

Type: Thesis (Doctoral)
Title: Enzyme-driven chemotactic synthetic vesicles
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/1535365
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