Impact of stabiliser selection on the uptake of polyester nanoparticles by hepatic cells

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Ünal, İlay Sema ORCID: https://orcid.org/0000-0001-5054-9606 (2024). Impact of stabiliser selection on the uptake of polyester nanoparticles by hepatic cells. University of Birmingham. Ph.D.

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Abstract

The development of new nanomedicines remains a priority for formulation scientists everywhere. It is also becoming increasingly apparent that a clear framework is needed to inform nanocarrier design and assessment to aid translation to the clinic. This seems particularly important for polymeric nanomaterials, where many factors need to be considered, including the impact of the stabiliser used in nanoparticle (NP) manufacture, which is the focus of this project.
This study will examine how polyester nanoparticles are taken up by hepatic cells. These cells were chosen as NPs are known to accumulate in the liver after intravenous (i.v.) administration, but little is known about the specific cells responsible for uptake. To this end, polyester NPs made from either poly(D,L-lactic acid) (PDLLA) or poly(lactic-co-glycolic acid) (PLGA), and using either polyvinyl alcohol (PVA) and Poloxamer 407 (PXM) as stabilisers were produced, characterised and tested in vitro. The NPs were synthesised by nanoprecipitation and met the stated quality attributes in terms of size (150-200 nm) and size distribution (PdI<0.2). The nature of the stabiliser had an impact on zeta potential (PVA<PXM), surface hydrophobicity (PVA>PXM) but this did not impact stability or protein adsorption (tested using BCA kit) after exposure to foetal bovine or human serum. NPs were loaded with Nile Red as a hydrophobic fluorescent dye and their uptake by immortalised cells representative of the different hepatic cells was studied. No clear trend between cell types could be detected using flow cytometry and fluorescent microscopy, but this might result from difficulties in analysing uptake data because of the fluorescence difference between NPs and requires further investigation.
Lactoferrin (LCF) is one of the ligands of asialoglycoprotein receptor (ASGP-R). LCF-targeted NPs were prepared and tested in a co-culture system involving HEP-G2 hepatomas, HMEC-1 endothelial cells and DTHP-1 macrophages to assess the feasibility of targeting hepatocytes and determine whether NP’s properties such as size, charge, and surface hydrophobicity were a barrier to achieving this. Modification with LCF did not significantly affect NP properties, though hydrophilicity did increase afterwards. Results showed increased uptake of LCF-coated PLGA-PVA NPs by HEP-G2 cells (2.6-fold, p<0.01) which was attributed to the ASGP-R since it is found in higher levels on hepatocytes than other hepatic cell types, while uptake by macrophages was not affected as expected since it is known that macrophages do not express ASGP-R.
To further investigate NP-cell interactions, bovine serum albumin (BSA) NPs were synthesised to compare the BSA NPs uptake behaviours of different hepatic cell lines. Here, citric acid was selected as the cross-linker. NPs, with a similar size and hydrophobicity as polyester NPs were produced. Uptake studies showed increased internalisation by THP-1 monocytes and DTHP-1 macrophage cells compared to HEP-G2 and HMEC-1 cell lines because of the higher phagocytic activity of the monocytes and macrophages than endothelial and epithelial cells. The overall findings provide an insight to importance on NP surface modification on the cellular uptake behaviour of hepatic cells.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):