Gu et al. has reported light-addressable potentiometric sensor (LAPS) for the label-free detection of circulating tumor cells (CTCs) of prostate cancer by using mouse anti-human epithelial cell adhesion molecule (anti-EpCAM) monoclonal antibody as the capture probe which was immobilized to the sensor surface containing graphene oxide modified with carboxylic acid group (GO-COOH) [109]. The gene discussed is EPCAM; the disease is prostate cancer.