Folate-mediated macromolecule delivery across the epithelium

Moradi, Emilia (2012) Folate-mediated macromolecule delivery across the epithelium. PhD thesis, University of Nottingham.

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Folate uses the natural endocytosis pathway via the folate receptor (FR) to enter the cells. Folate conjugation to small or macromolecular therapeutics has hence been exploited for intracellular delivery to, particularly, cancerous cells. This work reports on the expression and functionality of FR in polarised cell monolayer models of respiratory and gastrointestinal mucosa with the view to assess its potential for delivery of folate-modified macromolecular therapeutics either intracellularly or across the epithelium. Four cell lines representing bronchial and intestinal epithelium; cancer-derived intestinal Caco-2 and bronchial cell line Calu-3, and noncancerous intestinal and bronchial cell lines IEC-6 and HBEC were cultured on permeable membranes to produce polarised monolayers. Expression of FR was confirmed by RT-PCR and Western blot analysis for all the tested cell types and shown to be dependent on culturing time. The functionality of the receptor for endocytosis was demonstrated by a model macromolecular folate conjugate (fluorescent ovalbumin-folate (OVA-FA)), whereby significantly higher cellular uptake of the folate-conjugate, relative to non-folate control, was clearly demonstrated. Importantly the data showed that the expressed folate receptor was capable of mediating transport of the macromolecular folate conjugate across (transcytosis) the cells in the polarised monolayers.

Preliminary studies led to investigation of the folate mediated uptake and transport of folate modified nanoparticles (NPs). It was shown that folate modified NPs traversed the Calu-3 layers and studies characterizing this transport indicated folate involvement in this process. Adsorption of OVA-FA on the surface of NPs was seen to promote their cellular uptake and transport across the cell layers.

To examine the mechanism of cellular uptake and transport of folate modified nanoparticles, various endocytic inhibitors were employed. The study demonstrated an involvement of the caveolar pathway in internalization of folate modified nanoparticles; as judged from a significant reduction of internalization in filipin (inhibitor of caveolar pathway) treated cells. Moreover, the work also showed evidence of transport of folate-modified nanoparticles via the caveolar pathway, since translocation of nanoparticles across the cell monolayer was absent when this path was inhibited.

Disruption of actin filament and microtubules caused no difference in cellular uptake of NPs but increased the transcytosis of folate modified NPs.

Confocal microscopy, Transmission Electron Microscopy (TEM), Total Internal Reflection Microscopy (TIRM) and Total Internal Reflection Florescence microscopy (TIRFM) were used to confirm and visualize quantitative data. This study also investigated the effects of surface ligand distribution pattern (ligand clustering and density) on the internalization of nanoparticles by Calu-3 cells cultured as polarised layers. The density of the displayed ligand was manipulated by controlling the conjugation level of folate-ovalbumin, while ligand clustering was achieved by co-adsorption of varying mixtures of folate-ovalbumin conjugate (at different ligand density levels) and unconjugated ovalbumin. Increasing ligand density on the nanoparticle surface resulted in increased internalization of modified nanoparticles by the cells, up to a saturation level. Surface ligand density also affected the cellular uptake pathway; from predominantly clathrin to predominantly caveolae-mediated as the ligand density was increased. It was further demonstrated that surface clustering of the folate ligand enhanced cellular internalization of nanoparticles, relative to its dispersed surface distribution.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Garnett, M.C.
Stolnik- Trenkic, S.
Keywords: Folic acid, Folate receptor, Drug delivery systems, Macromolecular systems, Epithelial cells
Subjects: R Medicine > RS Pharmacy and materia medica
Faculties/Schools: UK Campuses > Faculty of Science > School of Pharmacy
Item ID: 27899
Depositing User: Blore, Mrs Kathryn
Date Deposited: 05 Dec 2014 14:31
Last Modified: 06 May 2020 14:02

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