Biosensors using the Si nanochannel junction-isolated from the Si bulk substrate

The biosensor using a silicon nanochannel field effect transistor has been developed on the basis of a bulk silicon substrate instead of an expensive silicon-on-insulator material, for low cost applications. "Top-down" fabricated Si nanochannels for detecting prostate specific antigen (PSA) are electrically isolated from the bulk Si substrate only by a reverse-biased p-n junction with very low reverse leakage currents. The reverse leakage current flowing through the p-n junction is small enough to be ignored, when compared with the current flowing through the p-type Si channel; roughly 100 times lower. The surface immobilization of anti-PSA has been confirmed by the specific binding test of DNA stabilized Au nanoparticles (NPs), showing 1200 NPs/mu m(2) and atomic force microscopy surface analysis. The injection of 10 ng/ml PSA solutions leads to a clear increase in the conductance of Si nanochannels, indicating the specific binding of PSA with the immobilized anti-PSA. The similar signal changes were observed on the injection of the 1 pg/ml PSA, very low concentration of PSA.