- Title
- In vivo toxicological evaluation of peptide conjugated gold nanoparticles for potential application in colorectal cancer diagnosis
- Creator
- Adewale, Olusola Bolaji
- Subject
- Nanostructured materials -- Toxicology
- Subject
- Colon (Anatomy) -- Cancer Rectum -- Cancer
- Date Issued
- 2018
- Date
- 2018
- Type
- Thesis
- Type
- Doctoral
- Type
- DPhil
- Identifier
- http://hdl.handle.net/10948/50133
- Identifier
- vital:42050
- Description
- Colorectal cancer (CRC) is among the leading cause of cancer-related deaths in South Africa and worldwide. Efforts are being made at finding improved diagnostic tools, as early detection (before metastasis) is a major factor in CRC treatment. Colonoscopy is the most reliable detection method, but is a specialised and expensive procedure, which is invasive, not readily available and not patient-friendly. There is a risk of developing interval cancers, as colonoscopies are performed every 10 years after the age of 40. The development of non-invasive, cost efficient and readily available diagnostic tools to CRC, which can be performed at more regular intervals, using tumour-targeting molecular imaging agents, is of urgent attention. Gold nanoparticles (AuNPs) possess several physicochemical properties, including ease of synthesis, biocompatibility, and the ability to be conjugated by ligands or biomolecules such as polyethylene glycol (PEG) and peptides for improved stability, tissue targeting and selectivity. These factors potentiate the role in biomedical applications, including cancer theranostics. Conjugation of AuNPs with a targeting molecule (e.g. antibody or peptide) is directed against cancer cell receptors. The peptides, p.C, p.L, and p.14, bind to CRC cells in vitro. Conjugation of AuNPs with these peptides should be investigated for CRC diagnosis in vivo, as it is hypothesised to allow examinations at shorter intervals through imaging techniques. This could reduce the risk of interval cancers, but before developing this novel tool, in vivo toxicity evaluations are essential. This study was therefore aimed at investigating the short- and long-term toxicological effects of a single intravenous injection of peptides (p.C, p.L, and p.14) conjugated to AuNPs in a healthy rat model. Citrate-capped AuNPs were synthesised by the citrate-reduction method, and conjugated with each peptide (biotinylated) using a combination of PEG (99% PEG-OH and 1% PEG-biotin) as a stabilising agent and linker, via biotin-streptavidin interaction. Healthy male Wistar rats were intravenously injected with 14 nm citrate-AuNPs, PEG-, p.C-PEG, p.L-PEG, and p.14-PEG-AuNPs (100 μg/kg body weight), and the control rats were injected with phosphate buffered saline. The animals were monitored for behavioural, physiological, biochemical, haematological and histological changes, as well as inflammatory responses. Phase 1 rats were sacrificed 2 weeks post-injection to determine the immediate or acute toxicity of the AuNPs, while phase 2 animals were sacrificed 12 weeks post-injection, to investigate the delayed or persistence toxicity of the AuNPs. Results revealed no significant toxicities with the citrate, PEG-, p.C-PEG and p.14-PEG-AuNPs over 12 weeks post-exposure, as evidenced by biochemical assays such as serum marker enzymes, liver and kidney function markers, and cholestatic indicators; haematological parameters; oxidative stress markers; and histopathological examinations. P.L-PEG-AuNPs, however, caused significant toxicity (p<0.05) to rats, as evidenced by increased relative liver weight, increased malondialdehyde levels, and total white blood cell counts 2 weeks post-exposure when compared to the control group. This was, however, reversed during the 12 weeks post-exposure. Further, there were no evidence of inflammatory responses, using pro-inflammatory markers including phospho interleukin 18 (IL-18) and interferon-γ (IFN-γ), as indicated by immunohistochemical staining of the liver, spleen, kidney and colon of rats 2 weeks post-injection of AuNPs. Citrate, PEG-, p.C-PEG, and p.14-PEG-AuNPs did not induce immediate, acute or persistent toxicity, while p.L-PEG-AuNPs induced a transient acute toxicity. It can be concluded that 14 nm spherical citrate-AuNPs at 100 μg/kg body weight is a good candidate for biomedical applications, and as a suitable carrier for diagnostic and/or therapeutic molecules. Combination of 99% PEG-OH and 1% PEG-biotin is an appropriate option for stabilising AuNPs in biological environment, and conjugating secondary diagnostic or therapeutic biomolecules or agents to citrate-capped AuNPs. Peptide-conjugated AuNPs are suitable for the development into a diagnostic tool for CRC in vivo.
- Format
- xxxiii, 251 leaves
- Format
- Publisher
- Nelson Mandela University
- Publisher
- Faculty of Science
- Language
- English
- Rights
- Nelson Mandela University
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NMU School of BioMolecular and Chemical Sciences
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | Olusola Bolaji Adewale.pdf | 6 MB | Adobe Acrobat PDF | View Details Download |