ИСТИНА

In recent years, heightened interest has been shown to biosensors based on semiconductor nanowire field-effect transistors (NWFETs). The aim of study was to develop NWFETs for the detection of prostate specific antigen (PSA), a molecular marker of prostate cancer, with a focus on chemical functionalization of Si NW surface. A new method for immobilization of antibody fragments on the silicon modified with 3-glycidopropyl-triethoxysilane with thiol groups (GOPS-SH) and small-diameter (5 nm) gold nanoparticles (GNPs) was established to provide the high density of active sites with favorable orientation. Si NWFETs were fabricated from SOI wafers (Soitec). The nanowire channel had a length of 3 μm and a width about 150 nm. A high-resolution electron microscope with lithographic attachment was used to define the NW body in the positive PMMA resist. Ti contact pads and SiO2 isolation layers were prepared by photo and electron lithography. Si NWFETs were applied for label-free and real-time quantitative detection of PSA. An analytical signal represented a change in conductivity in response to variations in electric field near the NW surface as a result of antigen binding. The sensitivity of the detection was characterized by a value of 59 mV per pH unit. Signal inversion was registered at pH range of 7.0-7.5. Binding of PSA with antibodies on the NWs was registered at pH 7.8. Response time was 15 sec, and the signal for each sample was measured for 1 minute. The limit of PSA detection was of 23fg/mL, concentration range of 45fg/mL - 300 ng/mL (6 orders of magnitude). The applicability of the method for PSA determination in human serum, diluted 100 times, was demonstrated.