EPCAM and cancer: used disulfide (SS)‐biotin doped polypyrrole nanowires (Ppy‐NWs) to construct a multifunctional system for in situ capturing, releasing, and quantifying circulating tumor cells (CTCs) (Figure 7C).[56] The surface SS‐biotin could bind with streptavidin and connect with a biotinylated anti‐epithelial cell adhesion molecule (anti‐EpCAM), showing specific recognition of EpCAM‐positive cancer cells.