Large Laser Spot-Swift Mapping Surface-Enhanced Raman Scattering on Ag Nanoparticle Substrates for Liquid Analysis in Serum-Based Cancer Diagnosis

We propose a label-free method to analyze bodily fluids based on surface-enhanced Raman scattering (SERS) with large laser spot-swift mapping and involving the electrochemistry preparation of silver nanoparticle substrates. This method can analyze the overall properties of multicomponent liquid and identify the low-concentration components. A large laser spot formed by a scanning galvanometer is used to obtain an average spectrum from different samples, whereas swift mapping detects low-concentration components such as tumor biomarkers. The silver nanoparticle substrates used exhibit strong SERS activity and wettability, improving adsorption and avoiding sample cluster formation. We applied this method to serum-based cancer diagnosis. Accuracy of the large spot method was tested by comparison with mass spectrometry results, whereas sensitivity of swift mapping was verified by detection of carcinoembryonic antigen in early colorectal cancer serum. Several cancer-related Raman peaks may be used as predictors, like a peak at 710 cm–1 which may represent an increase of circulating tumor DNA and metabolism disorder. We assess the potential application of this method for pan-cancer detection and staging. This method has advantage in sensitivity and reproducibility and is expected to play an important role in the analysis of complex component liquids that experience subtle changes that form on mechanism.