Preparation, radiolabeling, and conjugation of an Aurora Kinase B Inhibitor to 198Au-activated nanoparticles for cancer imaging and therapy

Abstract

When targeting cancer, it is often necessary to attack the disease on multiple fronts. This work proposes the development of multifunctional nanoparticles (NPs) to deliver both a therapeutic radiation dose and a cancer-targeting (Aurora Kinase Inhibitor) chemotherapeutic directly to the tumour. Additionally, the incorporation of a diagnostic agent to the NP allows for a theranostic approach. The progression of the therapeutic agent can be subsequently monitored via the NPs as delivery vehicles, with the diagnostic agent allowing assessment of tumour dosage. The presence of leaky vasculature in many tumours facilitates the infiltration and accumulation of NPs in these tissues. The preparation of polyethylene-glycol (PEG)-stabilized gold NPs (AuNPs) has been achieved and enables the targeted delivery of both therapeutic and diagnostic agents directly to the tumour. In a CCK-8 cytotoxicity assay, the AuNPs were found to have an IC50 of 0.06  0.04 (n=10) mg/mL on the SiHa cell line, 0.08  0.07 (n=4) mg/mL on the CaSki cell line, and 0.041  0.002 (n=2) mg/mL on the C33A cell line. The subsequent use of cyclotron-based neutron activation to convert the AuNP into gold-198 NP (198AuNP) can be used to provide a therapeutic radiation dose. This conversion of gold into 198Au has been demonstrated and can facilitate the delivery of beta radiation directly to the tumour. The IC₅₀ of the ¹⁹⁸AuNPs decreased with increasing radioactivity, indicating an increase in cytotoxicity. At lower activity levels (111 and 278 Bq/mL), only a minor increase in toxicity was observed; however, further increases in activity (1,145 and 2,290 Bq/mL) resulted in a continued decrease in IC50, indicating enhanced cytotoxicity. The AuNP has been labelled with an aurora kinase inhibitor (AKI) as a chemotherapeutic and a cancer-targeting moiety. The Aurora Kinase B inhibitor of interest was found to have an IC50 of (1.0  1.2) x 10-3 (n=3) mg/mL on the SiHa cell line, (6.3  1.8) x 10-5 (n=3) mg/mL on the CaSki cell line, and (3.5  2.4) x 10-3 (n=3) mg/mL on the C33A cell line. Conjugating this inhibitor enhances both specific cancer cell targeting in addition to the enhanced permeability and retention (EPR) effect that allows for the AuNPs to enter the tumour tissue, and the killing capacity of the 198AuNP. The PEG chain used for the peptide linkage that connects the inhibitor to the AuNP has been synthesized, as well as the AuNP-AKI conjugate. The IC50 for the AuNP-AKI conjugate was determined to be 0.0298  0.0008 (n=2) mg/mL with a 30:1 ratio of PEG:PEG-AKI on SiHa. This work uniquely employs the use of a medical cyclotron for the simultaneous preparation of [18F]-fluoride for PET labelling and the neutron activation of the prepared AuNPs via the 197Au(n,γ)198Au reaction. A model system for the PET-radiolabelling of the AuNPs has been investigated and a method has been proposed to achieve 18F-labelling.