The concentration of wild-type tumour suppressor p53wt in cells and blood has a clinical significance for early diagnosis of some types of cancer. We developed a disposable, label-free, field-effect transistor-based immunosensor (BioFET), able to detect p53wt in physiological buffer solutions, over a wide concentration range. Microfabricated, high-purity gold electrodes were used as single-use extended gates (EG), which avoid direct interaction between the transistor gate and the biological solution. Debye screening, which normally hampers target charge effect on the FET gate potential and, consequently, on the registered FET drain-source current, at physiological ionic strength, was overcome by incorporating a biomolecule-permeable polymer layer on the EG electrode surface. Determination of an unknown p53wt concentration was obtained by calibrating the variation of the FET threshold voltage versus the target molecule concentration in buffer solution, with a sensitivity of 1.5 ± 0.2 mV/decade. The BioFET specificity was assessed by control experiments with proteins that may unspecifically bind at the EG surface, while 100pM p53wt concentration was established as limit of detection. This work paves the way for fast and highly sensitive tools for p53wt detection in physiological fluids, which deserve much interest in early cancer diagnosis and prognosis.

We present an immunosensor for the rapid and sensitive detection of the p53 oncosuppressor protein and of its mutated form p53R175H, which are both valuable cancer biomarkers. The sensor is based on the accurate measurement of the source-drain current variation of a metal oxide semiconductor field-effect transistor, as due to the gate potential changing arising from charge release upon the selective capture of a biomarker by the partner immobilized on a sensing surface connected to the gate electrode. A suitable microelectronic system is implemented to combine high current resolution, which is needed to be competitive with standard immunoassays, with compact dimensions of the final sensor device.