No abstract

We describe the fabrication, electrical and electrochemical characterization of silicon nanowire arrays, which were processed in a top‐down approach using combined nanoimprint lithography and wet chemical etching. We used the top silicon layer as contact line and observed an influence of implantation and subsequent annealing of these lines to the device performance. In addition we found a subthreshold slope dependence on wire size. When operated in a liquid environment, wires can be utilized as pH sensors. We characterized the pH sensitivity in the linear range and in the subthreshold operation regime. As a first proof‐of‐principle experiment for the later use of the sensors in bioassays, we monitored the buildup of polyelectrolyte multilayers on the wire surface. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Silicon nanowire (NW) transistors were fabricated in a top-down process. These devices were used to record the extracellular potential of the spontaneous activity of cardiac muscle HL-1 cells. Their signals were measured by direct dc sampling of the drain current. An improved signal-to-noise ratio compared to planar field-effect devices was observed. Furthermore the signal shape was evaluated and could be associated to different membrane currents. With these experiments, a qualitative description of the properties of the cell-NW contact was obtained and the suitability of these sensors for electrophysiological measurements in vitro was demonstrated.

Within an hour, as little as one disseminated tumor cell (DTC) per lymph node can be quantitatively detected using an intraoperative biosensing platform based on silicon nanowire field-effect transistors (SiNW FET). It is also demonstrated that the integrated biosensing platform is able to detect the presence of circulating tumor cells (CTCs) in the blood of colorectal cancer patients. The presence of DTCs in lymph nodes and CTCs in peripheral blood is highly significant as it is strongly associated with poor patient prognosis. The SiNW FET sensing platform out-performed in both sensitivity and rapidity not only the current standard method based on pathological examination of tissue sections but also the emerging clinical gold standard based on molecular assays. The possibility to achieve accurate and highly sensitive analysis of the presence of DTCs in the lymphatics within the surgery time frame has the potential to spare cancer patients from an unnecessary secondary surgery, leading to reduced patient morbidity, improving their psychological wellbeing and reducing time spent in hospital. This study demonstrates the potential of nanoscale field-effect technology in clinical cancer diagnostics.