Nanobiophotonics for molecular imaging of cancer: Au- and Ag-based Epidermal Growth Factor receptor (EGFR) specific nanoprobes

Leanne J. Lucas; Kevin C. Hewitt

doi:10.1117/12.906794

8 February 2012 Nanobiophotonics for molecular imaging of cancer: Au- and Ag-based Epidermal Growth Factor receptor (EGFR) specific nanoprobes

Leanne J. Lucas, Kevin C. Hewitt

Author Affiliations +

Proceedings Volume 8234, Plasmonics in Biology and Medicine IX; 82340C (2012) https://doi.org/10.1117/12.906794
Event: SPIE BiOS, 2012, San Francisco, California, United States

Abstract

Our aim is to create and validate a novel SERS-based nanoprobe for optical imaging of the epidermal growth factor receptor (EGFR). Gold and silver nanoparticles (Au/AgNPs) of various sizes were synthesized and coupled to epidermal growth factor (EGF) via a short ligand, α-lipoic acid (206 g/mol), which binds strongly to both Au and Ag nanoparticles via its disulfide end group. We used carbodiimide chemistry to couple EGF to α-lipoic acid. These nanoprobes were tested for binding affinity using Enzyme Linked ImmunoSorbent Assay (ELISA) and, in-vitro, using EGFRoverexpressing A431 cells. The nanoprobes show excellent EGFR-specific binding. Time of Flight Mass Spectrometry demonstrate the carbodiimide based linking of the carboxylic acid end-group of α-lipoic acid to one or more of the three (terminal, or 2 lysine) amine groups on EGF. ELISA confirms that the linked EGF is active by itself, and following conjugation with gold or silver nanoparticles. Compared with bare nanoparticles, UV-Vis spectroscopy of Ag-based nanoprobes exhibit significant plasmon red-shift, while there was no discernable shift for Au-based ones. 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 in the dark field images, supporting the notion that these nanoprobes should provide excellent SERS signals at all nanoprobe sizes. In summary, novel EGFR-specific nanoprobes have been synthesized and validated by standard assay and in cell culture for use as SERS optical imaging probes.

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Leanne J. Lucas and Kevin C. Hewitt "Nanobiophotonics for molecular imaging of cancer: Au- and Ag-based Epidermal Growth Factor receptor (EGFR) specific nanoprobes", Proc. SPIE 8234, Plasmonics in Biology and Medicine IX, 82340C (8 February 2012); https://doi.org/10.1117/12.906794

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