AbstractThe identification and measurement of biomarkers is critical to a broad range of methods that diagnose and monitor many diseases. Serum auto‐antibodies are rapidly becoming interesting targets because of their biological and medical relevance. This paper describes a highly sensitive, label‐free approach for the detection of p53‐antibodies, a prognostic indicator in ovarian cancer as well as a biomarker in the early stages of other cancers. This approach uses impedance measurements on gold microelectrodes to measure antibody concentrations at the picomolar level in undiluted serum samples. The biosensor shows high selectivity as a result of the optimization of the epitopes responsible for the detection of p53‐antibodies and was validated by several techniques including microcontact printing, self‐assembled‐monolayer desorption ionization (SAMDI) mass spectrometry, and adhesion pull‐off force by atomic force microscopy (AFM). This transduction method will lead to fast and accurate diagnostic tools for the early detection of cancer and other diseases.