Development of Helicobacter pylori BabA minimal binding domain as a novel biomimetic moiety for gastric-targeted drug delivery

Mohammed, Aymen (2020) Development of Helicobacter pylori BabA minimal binding domain as a novel biomimetic moiety for gastric-targeted drug delivery. PhD thesis, University of Nottingham.

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Abstract

The need for efficient drug delivery systems / better treatment for human disorders remains a challenge in medicine. This demand could be addressed by developing a new strategy that assist the formulation to act specifically. Some drugs would benefit from targeting the gastric epithelium and retain the therapeutic in the stomach. However, drugs absorbed through the stomach or upper small intestine have a narrow absorption window. Developing a drug delivery system that can adhere to the surface of the gastric epithelial cells will significantly increase drug transit time and overcome this limitation.

The gastric bacterium Helicobacter pylori uses special proteins called adhesins to adhere to the gastric epithelium, providing a novel strategy for broadening the absorption window. Therefore, a novel drug delivery system was adapted from these adhesins to facilitate drug absorption.

The best studied adhesin is Blood group Antigen Binding Adhesin (BabA), which specifically mediates H. pylori adherence to ABO/Lewis b (Leb) blood group antigens on the gastric epithelium. Recent co-crystal structure of the extracellular region of BabA with Leb revealed a smaller binding domain which was termed the BabA-Crown. In the present study, BabA-Crown, as Leb minimal binding domain, was studied towards usage as a gastric-targeting drug delivery system. By using this biomimetic strategy, a novel cytoadhesive drug system could be developed.

In the beginning, protocols for recombinant expression of BabA-Crown had to be established. We found that addition of Chloramphenicol to the growth medium had a major beneficial effect on the yield of BabA-Crown expressed in the periplasmic space of Escherichia coli. Then, BabA-Crown protein resistance to acidity and peptic digestion were studied. It was revealed that BabA-Crown can partially resist peptic degradation. However, binding studies showed that BabA-Crown did not retain Leb-binding affinity. To tackle this issue, further adjustments were made. These included structural modifications to increase the length of the protein, incorporation of a Lysine-tag to increase the expression as well as the creation of a new binding motif.

In conclusion, binding of BabA-Crown to Leb was not achieved, however, BabA conjugated with microparticles still retained the binding ability to Leb. The data generated in this study represents a good starting point for utilization of the minimal binding region for both biomimetic-drug platform and bacteriological studies.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Falcone, Franco
Stolnik-Trenkic, Snjezana
Keywords: Drug delivery systems, Helicobacter pylori, Gastric epithelium, Gastric bacterium.
Subjects: R Medicine > RM Therapeutics. Pharmacology
Faculties/Schools: UK Campuses > Faculty of Science > School of Pharmacy
Item ID: 59344
Depositing User: Mohammed, Aymen
Date Deposited: 24 Jul 2020 04:40
Last Modified: 24 Jul 2020 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/59344

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