Ag Nanorods for Label-Free Surface-Enhanced Raman Scattering Analysis of Cancer Cells from Cell Lysates

The identification of cancer cells and tumors significantly advances the accurate diagnosis of cancer and improves the patient survivor rates. However, it remains challenging to achieve the rapid and label-free differentiation of cancer cells from their normal counterparts. Herein, we developed a rapid and effective method for the synthesis of Ag nanorods (NRs) with high uniformity and yield. The surface-enhanced Raman scattering (SERS) substrates demonstrated uniformity and reliability, with a low relative standard deviation (RSD) of 10% and an enhancement factor (EF) of 3.32 × 105. The optimized AgNR SERS substrates were then applied in the quantitative analysis of creatinine and furthermore the bioanalysis of cell lysates for cell classification. Specifically, a high sensitivity with a low detection limit (LOD) of 5.3 μM and a limit of quantification (LOQ) of 17.68 μM was achieved for the detection of creatinine. More importantly, label-free SERS analysis showed the distinct spectral features of the cell lysates for normal breast cell strains (MCF-10A) and breast cancer cell strains (MCF-7, MDA-MB-231). Statistical analysis, such as t-test, principal component analysis (PCA), and orthogonal partial least-squares discriminant analysis (OPLS-DA) aided in the clear discrimination between the normal and cancer groups and further in differentiating the two cancer groups. These results demonstrate the great potential of the combination of a high-quality AgNR SERS substrate and statistical analysis for the identification of cancers.