Cancer protein biomarker identification and quantification using nanoforest substrate and hand-held Raman spectrometer

Abstract

Cancer biomarkers, an indication of cancer cells in the body, can play an important role in diagnosis, prognosis, and the prediction of treatment efficacy as well as recurrence. Here, we developed a simple Raman spectroscopic method that utilized a silver nanoforest (SNF) substrate and a hand-held Raman spectrometer for identifying cancer protein biomarkers with very high sensitivity. First, various concentrations of ethanol solutions were analyzed using the hand-held Raman spectrometer to confirm its performance. Next, the functionality of the SNF substrate, in other words, the effect of the surface enhanced Raman scattering was characterized by measuring varying, known concentrations of rhodamine 6G. The novel structure of the SNF substrate can provide the enhancement factor of 1.13 × 107. Following the characterization, the Raman spectra of cancer biomarkers, epithelial cell adhesion molecule (EpCAM) and carcinoembryonic antigen (CEA), were examined using the hand-held Raman spectrometer with the SNF substrate. As low as 0.2 picomoles of the protein were successfully detected with very tiny amount of sample solutions (~2 µl) containing cancer biomarkers. The developed technique allows for the simple, convenient measurement of cancer protein biomarkers using the SNF substrate and hand-held Raman spectrometer. We believe these findings will motivate the creation of Raman libraries for cancer biomarkers.