6-Color/1-Target Immuno-SERS Microscopy on the Same Single Cancer Cell.

There is an urgent clinical need for multicolor imaging of single cancer cells (no ensemble averaging) for identifying heterogenous expression of predictive biomarkers. Specifically, the comprehensive characterization of single disseminated tumor cells (sDTCs) responsible for metastatic relapse is the key to personalized therapy for patients. Current bioimaging methods lack the necessary multicolor capacity and suffer from background/autofluorescence. Both these central limitations can be overcome by immuno-SERS microscopy using SERS nanotags conjugated to antibodies. Here, we demonstrate the proof of concept for 6-color iSERS microscopy on the same single cancer cell. Human epidermal growth factor receptor 2 (HER2), the most prominent breast cancer marker, is localized on the membrane of single SkBr-3 cells, which overexpress HER2 and are an accepted model for sDTCs in breast cancer. This work paves the way for future multicolor/multitarget imaging for characterizing heterogeneous protein expression at the single-cell level.