Nanosized Field-effect Transistor Based on Germanium for Next Generation Biosensors in Scanning Ion-conductance Microscopy

The new frontiers of the investigation into biosensors based on the field effect transistor (FET) opened the way for sensing single-molecular DNA [1], for single-cell analysis [2] and early cancer diagnosis [3]. Recently Zhang et al. [1] presented a FET based on poly-pyrrole (PPy). PPy-FET is manufactured on the tip of a spear-shaped dual carbon nanoelectrode derived from carbon deposition inside double-barrel nanopipettes. This structure can measure the pH gradient in three-dimensional space, detect adenosine triphosphate and identify biochemical properties of a single living cell. However, PPy is not stable and degrades after few measurement cycles. The challenge is to create the FET structure based on inorganic semiconductor materials on a nanometric tip which is biocompatible, does not degrade over time and is capable of detecting the gradient of a few mV potential in living cells, dendrites and axons of neurons in vivo.