Early diagnosis of oral cancer based on the surface plasmon resonance of gold nanoparticles

James Chen Yong Kah¹, Kiang Wei Kho², Caroline Guat Leng Lee², Colin James Richard Sheppard¹, Ze Xiang Shen³, Khee Chee Soo², Malini Carolene Olivo²

¹Division of Bioengineering, National University of Singapore, Singapore; ²Division of Medical Sciences, National Cancer Centre Singapore, Singapore; ³School of Physical and Mathematical Sciences, NanyangnTechnological University, Singapore

Abstract: The high mortality rate in cancer such as oral squamous cell carcinoma is commonly attributed to the difficulties in detecting the disease at an early treatable stage. In this study, we exploited the ability of gold nanoparticles to undergo coupled surface plasmon resonance and set up strong electric fields when closely-spaced to improve the molecular contrast signal in reflectance-based imaging and also to enhance the Raman signal of bioanalytes in cancer. Colloidal gold nanoparticles were synthesized and conjugated to anti-epidermal growth factor receptor (EGFR) for imaging. A self-assembled surface enhanced Raman scattering (SERS)-active gold nanoparticle monolayer film was also developed as a biosensing surface using a simple drop-dry approach. We have shown that gold nanoparticles could elicit an optical contrast to discriminate between cancerous and normal cells and their conjugation with antibodies allowed them to map the expression of relevant biomarkers for molecular imaging under confocal reflectance microscopy. We have also shown that the SERS spectra of saliva from the closely-packed gold nanoparticles films was differentiable between those acquired from normal individuals and oral cancer patients, thus showing promise of a simple SERS-based saliva assay for early diagnosis of oral cancer.

Keywords: Gold nanoparticles, reflectance imaging, confocal microscopy, epithelial carcinoma, epidermal growth factor receptor, coupled surface plasmon resonance, oral cancer, surface enhanced Raman scattering