In a study for a label-free electrochemical immunosensor developed for early-stage detection of prostate cancer, the surface of the indium tin oxide electrode was firstly coated with chitosan and reduced graphene oxide, and then the specific polyclonal anti-prostate-specific antigen (PSA) antibody as a recognition element was immobilized on the surface. The gene discussed is KLK3; the disease is Familial prostate cancer.