Antibody-functionalized nanoparticles for imaging cancer: influence of conjugation to gold nanoparticles on the biodistribution of 89Zr-labeled cetuximab in mice

Antibody-labeled gold nanoparticles represent a promising novel tool regarding cancer imaging and therapy. Nevertheless, the characterization of biodistribution of such immunonanocarriers has been poorly documented. In this study, the biodistribution of 89Zr-labeled cetuximab before and after the coupling reaction to gold nanoparticles (AuNPs) was compared and the quantitative imaging performance of 89Zr immuno-PET was evaluated. Cetuximab was functionalized with the desferal moiety and labeled with 89Zr (89Zr-Df-Bz-NCS-cetuximab). AuNPs with a mean diameter of 5 nm were synthesized according a new method developed in the laboratory, and conjugated to 89Zr-Df-Bz-NCS-cetuximab using carbodiimide chemistry (AuNPs-PPAA-cetuximab-89Zr). The two tracers were injected in A431 xenograft-bearing mice. Tumor and liver uptakes were assessed at different times after injection using quantitative PET imaging. The in vivo specificity of the binding was investigated using a saturating dose of unlabeled cetuximab. Radiolabeled cetuximab was conjugated to AuNPs with a coupling reaction yield >75%. All conjugates were stablein vitro and to a lesser extent in plasma. In vivo distribution studies revealed no significant difference in tumor uptake for cetuximab conjugated to nanoparticles up to 72 h after injection, compared with unconjugated cetuximab. Immuno-PET studies showed that AuNPs-PPAA-cetuximab-89Zr provided high tumor-to-background ratio. The liver uptake of AuNPs-PPAA-cetuximab-89Zr was higher, compared with 89Zr-Df-Bz-NCS-cetuximab. In vivo blocking experiments demonstrated selective tumor targeting after coupling reaction. This study showed that the conjugation of AuNPs to cetuximab did not affect its tumor accumulation and that the efficacy of EGFR-targeted nanoparticles was unaltered. The 89Zr-labeled cetuximab-targeted gold nanoparticles could be a valuable tool for theranostic purposes. Copyright (c) 2013 John Wiley & Sons, Ltd.