Nanotoxicology assessment of gold and silver nanoparticles in human lung cells

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Ibrahim, Bashiru ORCID: https://orcid.org/0000-0003-3426-4795 (2023). Nanotoxicology assessment of gold and silver nanoparticles in human lung cells. University of Birmingham. Ph.D.

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Abstract

Engineered nanomaterials such as gold (AuNPs) and silver nanoparticles (AgNPs) have shown a great potential in biomedical applications such as cancer therapy, diagnostics, and drug delivery. However, it is crucial to understand their potential cytotoxicity in vitro. In this work, it was hypothesised that cellular exposure to different nanoparticles (NPs) can elicit various biological responses in human alveolar adenocarcinoma (A549) cells depending on their size and chemical functionalisation. Initially the effects of different sizes of AuNPs on the ubiquitin proteasome system (UPS) was investigated with a particular focus on deubiquitinating enzymes (DUBs) such as ubiquitin specific proteases (USP) and ubiquitin carboxyl-terminal hydrolases (UCHL-1). Secondly, the influences of different functionalisation on their rate of cytotoxicity to UPS was studied. Thirdly, the effects of different NPs composition on the molecular chaperone heat shock proteins (HSPs) were evaluated and finally the combination of AuNPs with cisplatin (CDDP) and its effects on the efficacy of the anticancer CDDP was evaluated. It was found that the exposure of NPs to complex biological media significantly affected their physicochemical properties inducing agglomeration and dissolution, with complete culture media (CCM) having a stabilising impact because of protein corona formation. In addition, the cytotoxicity of NPs in A549 cells was found to be size-, type, concentration-, and time-dependent as assessed by several toxicity assays. The internalisation of AuNPs in A549 increased to a greater extent with the increase in particle size (80 > 10 > 5 nm) and was mediated by different endocytic mechanisms such as clathrin- and caveolae-mediated endocytosis. The cellular internalisation of the particles triggered the production of reactive oxygen species (ROS), depletion of glutathione, a decrease in mitochondrial membrane potential (MMP), and the activation of mitochondrial-related apoptosis. Moreover, the expression of DUBs (USP7, USP8, USP10, and UCHL-1) and HSPs (HSP40, HSP60, HSP70, and HSP90) was downregulated in a dose-dependent manner upon treatment with NPs. Combination of AuNP with CDDP had also shown pronounced effects on the expression of molecular chaperone HSPs. Additionally, it was found that a decrease in the expression of DUBs and HSPs proportionally affected the protein kinase B/mammalian target of rapamycin (P13K/AKT/mTOR) and wingless-related integration site (Wnt) pathways leading to the upregulation of poly-ADP ribose polymerase (PARP), caspase-3, and caspase-9. Overall, the findings of this work demonstrated a new effective strategy for reducing the proliferation of A549 cells through the inhibition of DUBs and HSPs. This thesis is presented in the “Alternative thesis format”

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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