From sensing interactions to controlling the interactions: a novel approach to obtain biological transistors for specific and label-free immunosensing.

Antibody-antigen interactions are shaped by the solution pH level, ionic strength, and electric fields, if present. In biological field-effect transistors (BioFETs), the interactions take place at the sensing area in which the pH level, ionic strength and electric fields are determined by the Poisson-Boltzmann equation and the boundary conditions at the solid-solution interface and the potential applied at the solution electrode. The present study demonstrates how a BioFET solution electrode potential affects the sensing area double layer pH level, ionic strength, and electric fields and in this way shapes the biological interactions at the sensing area. We refer to this as 'active sensing'. To this end, we employed the meta-nano-channel (MNC) BioFET and demonstrate how the solution electrode can determine the antibody-antigen equilibrium constant and allows the control and tuning of the sensing performance in terms of the dynamic range and limit-of-detection. In the current work, we employed this method to demonstrate the specific and label-free sensing of Alpha-Fetoprotein (AFP) molecules from 0.5 µL drops of 1 : 100 diluted serum. AFP was measured during pregnancy as part of the prenatal screening program for fetal anomalies, chromosomal abnormalities, and abnormal placentation. We demonstrate AFP sensing with a limit-of-detection of 10.5 aM and a dynamic range of 6 orders of magnitude in concentration. Extensive control measurements are reported.

High-Sensitivity CMOS-Integrated Floating Gate-Based UVC Sensors.

We report on novel UVC sensors based on the floating gate (FG) discharge principle. The device operation is similar to that of EPROM non-volatile memories UV erasure, but the sensitivity to ultraviolet light is strongly increased by using single polysilicon devices of special design with low FG capacitance and long gate periphery (grilled cells). The devices were integrated without additional masks into a standard CMOS process flow featuring a UV-transparent back end. Low-cost integrated UVC solar blind sensors were optimized for implementation in UVC sterilization systems, where they provided feedback on the radiation dose sufficient for disinfection. Doses of ~10 µJ/cm2 at 220 nm could be measured in less than a second. The device can be reprogrammed up to 10,000 times and used to control ~10-50 mJ/cm2 UVC radiation doses typically employed for surface or air disinfection. Demonstrators of integrated solutions comprising UV sources, sensors, logics, and communication means were fabricated. Compared with the existing silicon-based UVC sensing devices, no degradation effects that limit the targeted applications were observed. Other applications of the developed sensors, such as UVC imaging, are also discussed.