EGF conjugated gold and silver nanoparticles for imaging EGFR over-expressing cells

L.J. Lucas, K.C. Hewitt
Dalhousie University, CA

Keywords: surface enhanced Raman spectroscopy (SERS), epidermal growth factor (EGF), cancer imaging, gold nanoparticles, silver nanoparticles, A431 cells, dark field microscopy


Purpose: To create and validate a novel SERS-based nanoprobe for optical imaging of the epidermal growth factor receptor (EGFR). Experimental Design: Gold and silver nanoparticles (Au/AgNPs) were synthesized and coupled to epidermal growth factor (EGF) through carbodiimide chemistry via a short α-lipoic acid ligand, which binds strongly to both Au and Ag nanoparticles via its disulfide. These nanoprobes were tested for binding affinity using ELISA and, in-vitro, using EGFR-overexpressing A431 cells. Results: The nanoprobes show excellent EGFR-specific binding. Time-of-Flight Mass Spectrometry demonstrates the carbodiimide based linking of the carboxylic acid group of α-lipoic acid to one or more of the three amine groups on EGF. ELISA confirms the linked EGF is active by itself, and following conjugation with gold or silver nanoparticles. Dark field microscopy shows abundant uptake by EGFR overexpressing A431 cells, and serves to further confirm the excellent binding affinity. Nanoprobe internalization and consequent aggregation is thought to be the basis of enhanced light scattering, supporting the notion that these should be an excellent SERS platform at all nanoprobe sizes. Conclusion: Novel EGFR-specific gold and silver nanoprobes have been synthesized and validated by standard assay and in cell culture as SERS optical imaging probes.