Kieren O'Neil
- B.Sc. (Thompson Rivers University, 2024)
Topic
Linear and cyclic-peptide functionalized gold nanoparticle uptake, transport, and radiosensitization in cancer cells, and their uptake in macrophages
Department of Physics and Astronomy
Date & location
- Friday, June 26, 2026
- 10:00 A.M.
- Virtual Defence
Examining Committee
Supervisory Committee
- Dr. Devika Chithrani, Department of Physics and Astronomy, University of Victoria (Supervisor)
- Dr. Jan Schuemann, Department of Radiation Oncology, Massachusetts General Hospital (Outside Member)
External Examiner
- Dr. Mohsen Akbari, Department of Mechanical Engineering, UVic
Chair of Oral Examination
- Dr. Catherine Bachewich, Department of Biochemistry and Microbiology, UVic
Abstract
Gold nanoparticles (GNPs) are candidate radiosensitizers. If a significant amount of GNPs are inside a tumour cell they make that cell more radiosensitive. However, they have low tumour cell specificity. Surface functionalizing GNPs with targeting ligands like peptides can improve this. Peptides can contain an amino acid sequence targeted to a specific receptor. An useful sequence for this is RGD (Arginine-Glycine-Aspartic acid), for the 𝛼𝑣𝛽3 integrin. It is overexpressed in many cancer cells and attaches them to the extracellular matrix. RGD can be incorporated into peptides with different shapes and sequences to optimize their specificity. A variable is shape where a linear or cyclic peptide can be used. In-vitro, linear are common, due to simple synthesis and greater availability; cyclic are more common in-vivo due to better stability and binding kinetics.
In this thesis, peptide shape-based GNP uptake was investigated in-vitro. It was tested in Mia PaCa-2 pancreatic and LNCaP prostate cancer cells for GNP uptake and radiosensitization. Additionally, GNP uptake was tested in Raw 264.7 model macrophages. Cells were dosed at 10 ug/mL gold with 12.2 nm diameter spherical GNPs functionalized with polyethylene glycol (PEG) and an RGD containing linear or cyclic peptide of the same sequence (GNP+PEG/lRGD and GNP+PEG/cRGD respectively). Uptake was measured with confocal microscopy, darkfield microscopy, and Inductively Coupled Plasma Mass Spectrometry. Samples were irradiated at 6X (600MU/min) with a Varian TrueBeam Linear Accelerator (LINAC). Radiation damage was assessed with DNA double strand break microscopy at 2 and 4 Gy and with clonogenic survival assay at 4, 8, and 10 Gy.
Uptake of GNP+PEG/cRGD was significantly higher than GNP+PEG/lRGD in Raw 264.7 macrophages (1840%, p = 0.0035 after 4 hours). Mia PaCa-2 (7.3%, p = 0.65 after 24 hours) and LNCaP (28.0 %, p = 0.12), tumour cells showed no significant difference in uptake of GNP+PEG/cRGD compared to GNP+PEG/lRGD. No GNP-radiosensitization was seen in either cell line. With no significant difference in DNA double strand breaks with either GNP complex compared to control in Mia PaCa-2 and LNCaP. Clonogenic survival of Mia PaCa-2 cells had no significant difference with either GNP complex.
Differential uptake and radiosensitization from GNPs would be better shown in the kilovoltage x-ray range where GNPs are most effective. Increased uptake of GNP+PEG/cRGD in Raw 264.7 macrophages is a potential issue with cyclic peptides in immunocompetent models and patients. Macrophage uptake should be considered in GNP complex synthesis; modified peptides or macrophage inhibitor functionalization may reduce uptake. Thorough in-vitro investigation in model immune cells could reveal similar issues prior to clinical trials.