Thesis Defense: Combined cancer therapy using gold nanoparticles

Event Date/Time: 
Fri, 07/14/2017 - 8:00am
Location: 
KHE 321B

Presenter: Celina Yang
Doctor of Philosophy, Biomedical Physics
Ryerson University, 2017

Supervisor: Dr. Devika Chithrani and Dr. Michael Kolios

This dissertation presents the effect of peptide-modified 10 nm colloidal gold nanoparticles (GNPs) with chemotherapeutic drugs, bleomycin and cisplatin, and 6 MV X-ray irradiation in a breast cancer cell-line, MDA-MB-231, in vitro. The GNPs were stabilized with a pentapeptide (Cys-Ala-Lys-Asp-Asp) and modified with a peptide sequence containing a ‘RGD’ amino acid motif (H-Cys-Lys-Lys-Lys-Lys-Lys-Lys-Gly-Gly-Arg-Gly-Asp-Met-Phe-Gly-OH). Bleomycin binds to the surface of the GNPs through a thiol bond and cisplatin has no significant interaction with the GNP surface.

Gold nanoparticle concentration used in studies throughout this dissertation was 0.3 nM. No significant toxicity was induced by introducing GNPs to MDA-MB-231 cells at this concentration. To examine the variability of accumulation of GNP constructs with the presence of chemotherapeutics, the amount of gold (Au) atoms were measured with Inductive Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES). There was no significant difference in the accumulation of GNPs in the presence of cisplatin. There was a 5 % decrease in accumulation of GNPs in cells with bleomycin. However, the 5 % decrease with bleomycin was still a 6-fold increase compared to the accumulation of unmodified GNPs in cells. These results suggest that with the peptide modification, the presence of chemotherapeutics do not significantly affect the accumulation of GNPs into cells.

The effect of having GNPs with chemotherapeutics (either bleomycin or cisplatin) was examined through clonogenic and immuofluorscence assays. The conjugation of bleomycin onto peptide modified GNPs decreased the survival of MDA-MB-231 cells by 22.5 % (P < 0.05) compared to treatment with the same concentration of free bleomycin (without GNPs). On the contrary, treating cells with GNPs and cisplatin did not have a significant difference in survival compared to the same concentration of free cisplatin treatment (p = 0.078). This suggests that conjugating chemotherapeutics onto the GNPs can result in a more efficient delivery of the drug. If the drug does not bind to the GNP surface, having GNPs in the media does not interfere with the uptake of the drug.

The effect of radiosensitization in the presence of peptide modified GNPs was studied using 6 MV X-rays. The MDA-MB-231 cells were incubated with 0.3 nM peptide modified GNPs 16 hours prior to irradiation with 2 Gy of 6 MV X-rays. The survival fraction decreased by 23 % (p < 0.05) compared to the cells treated with same volume of phosphate buffed saline (PBS) solution prior to radiation. This confirms radiosensitization from the modified GNPs at a low concentration (0.3 nM) with clinically relevant energies (6 MV).

Lastly, the triple combined effect of modified GNPs, chemotherapeutics, and irradiation was investigated. The MDA-MB-231 cells were treated with modified GNPs, a chemotherapeutic (either bleomycin or cisplatin) and 2 Gy of 6 MV radiation to investigate the effect of triple combined therapy. The presence of GNPs had an advantage to the combined chemotherapy and radiation therapy. Based on results from these studies, peptide-modified GNPs can be used in addition to combined chemotherapy and radiation therapy for improved outcomes in cancer treatment.