KLK3 and cancer: ISE biosensors are widely available for determining the pH of a clinical specimen, as well as the Na+, K+, Ca2+ and Cl− concentrations, enzyme-based potentiometric biosensors are commonly use for the detection of urea, creatinine, cholesterol, MIP biosensors are used for identifying dopamine, histamine, cortisol and Prostate-Specific Antigen (PSA), and photoelectrochemical biosensors can be used for DNA hybridization and the detection of heavy metal ions and cancer biomarkers [131,132,133].