Biopharmaceuticals represent a variety of biological products for diagnostic and therapeutic purposes, of which developments are driven by the recent advances in biotechnology. However, oral administration of biopharmaceuticals is challenging due to the low absorption of macromolecules and the potential degradation that occurs in the harsh environment of the gastrointestinal tract. Various strategies have been explored to improve the bioavailability of these therapeutic agents, and some strategies have the potential to protect these fragile proteins from the harsh environment. The low permeability of these macromolecules across the intestinal epithelium remains the main challenge. This work focuses on providing a strategy to increase the intestinal epithelium permeability of biopharmaceuticals. In nature, bacterial toxins, such as Pseudomonas aeruginosa exotoxin A (PE), are able to travel across the intestinal epithelium and target the immune cells underneath. The hypothesis of this study is that these toxins can facilitate the trans-epithelial transport of toxin-conjugated nanoparticles. Two biodegradable and mucoadhesive polymers, alginate and chitosan, were selected for the preparation of nanoparticles. Alginate-chitosan nanoparticles had a diameter of 179 ± 3 nm and a zeta potential of 17 ± 5 mV. After the conjugation with ntPE, the size and zeta potential changed to 202 ± 20 nm and -6 ± 5 mV, respectively. Transcytosis of ntPE-coupled nanoparticles was evaluated on Caco-2 cell monolayers in vitro. The transport rate was 4.36 ± 2.24 %, compared to 4.18 ± 2.05 % for nanoparticles conjugated with bovine serum albumin (BSA) and 2.83 ± 1.29 % for unmodified ones. The trans-epithelial transport of ntPE-coupled nanoparticles was then examined in the living rat small intestine. Nanoparticles coupled with ntPE were found to accumulate in the lamina propria of the rat small intestine, while no BSA-coupled nanoparticles or unmodified nanoparticles were found in the tissue sections. Finally, green fluorescent protein served as a model for biopharmaceuticals, and was loaded into alginate-chitosan nanoparticles to study the trans-epithelial delivery ability of these nano-carriers. Overall, this thesis tests the feasibility of using a bacterial toxin to facilitate the trans-epithelial transport of nano-carriers loaded with biopharmaceuticals. Results support this hypothesis and suggest these alginate-chitosan nanoparticles are worthy of continued work to develop into nano-carriers for oral administration of biopharmaceuticals.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:720658 |
| Date | January 2017 |
| Creators | Li, Ruiying |
| Contributors | Mrsny, Randall ; De Bank, Paul |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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