Organic electrochemical transistors (OECTs) are recently developed high-efficient transducers not only for electrochemical biosensor but also for cell electrophysiological recording due to the separation of gate electrode from the transistor device. al. (2018) combined the molecularly imprinted polymers (MIP) with OECT-based sensor to detect ascorbic acid (AA) (Figure 7). The selectivity of the MIP films on the gate was conducted by the preparation of the polymer with AA removal and rebinding on the surface, then the polymer film acted as the recognition unit of the sensor. They found various species, such as H2O2, Gly, GSH, UA, Glu, Na+, K+, Fe2+, Mg2+, Ca2+, and ASP, that has almost no interferences for AA detection. The sensors could be used for the AA AKT inhibitor VIII (AKTI-1/2) analysis of vitamin C beverages. Open in a separate window Figure 7 (A) Schematic diagram of an AA sensor based on the MIP modified OECT. (B) Potential drop between the channel and gate of the OECT. (C) Schematic for the sensing of AA by MIP film modified gate (Zhang et al., 2018). Reproduced with permission (Zhang et al., 2018). Copyright? 2017 Elsevier B.V. All rights reserved. OECTs Ion Sensing The OECTs can be used for ion detection due to the AKT inhibitor VIII (AKTI-1/2) ions transfer freely in the whole bulk of electrolyte, which includes not only aqueous solution but also other ionic and electronic media, such as gel and ionic liquid (Duc et al., 2017; Dai et al., 2018). Recently, Gentili et al. (2018) demonstrated a new principle of current-driven inverter-like, low-voltage, high-sensitivity ion detection OECT. Differently with the voltage-driven OECTs, the current-driven OECT configuration provides, low-voltage operation and high sensitivity, where the sensitivity depends on the large gm and load resistor. However, the applied voltage should consistent with the physiological environment. So that the trade-off among sensitivity, operating range, and applied voltage are needed. The current-driven OECT configuration is based on the recording of the changing voltage generated by the ions concentration, differentiating it from the usual ion sensors where the changing of ion concentration transferred as the output voltage. Consequently, the current-driven OECT study take advantage of the large gm of OECTs in an absolutely different way in relative to regular voltage amplifier structures, which introduce a new kind of trade-off between sensitivity and working voltage. While (Del Agua et al., 2018) introduced a PEG-based Na+ conducting hydrogel as OECT electrolyte. The hydrogel is prepared by fast photopolymerization with commercial monomer. And the hydrogel has high ionic conductivity and can be contained during the fabrication of photolithography device. With the high performances at room temperature, this hydrogel has the possibility to replace liquid electrolytes in versatile OECTs and accomplish print integrated into flexible OECT devices. OECTs Cell Monitoring The coupling of OECTs with live mammalian cells for monitoring toxicology/diagnostics and other properties was developed in the past decade. Bolin et al. (2009) firstly coupled the OECTs with cells and detected the gradients of cells on the OECT channel. They seeded Madin Darby canine kidney (MDCK) epithelial cells on an OECT channel and the channel bias added and produced a potential gradient. The gate potential controls and modulates the potential gradient of channel. Therefore, the MDCK cell quantity gradient on the channel depended on the gate and source voltages. Lin et al. (2010) reported sensors based on OECTs combined with cancer AKT inhibitor VIII (AKTI-1/2) cells and fibroblasts for Rapgef5 sensing cell activities. The sensing principle is the electrostatic actions on the interfaces of the cells and the OECT reactive layer. Since the device is sensitive to the surface charge changes induced by the adhesion of cells, it’s applicable for solution processing to miniature and integrate cell-based sensors can further promote the cell relevant testing, such as screening drugs and testing toxic substances. The potential can predict the adhesion of cell and formation of epithelium (Gu et al., 2019). Ramuz et al. (2015) found that barrier tissue cells adhered on the polymer surface can be deprived of function in calcium switch assay, AKT inhibitor VIII (AKTI-1/2) and re-addition of calcium lead to improvement of the cells function. The process is monitored both electronically and optically, AKT inhibitor VIII (AKTI-1/2) enabling the capture of cells images while simultaneously recording electronic information (Figure 8). Open in a separate window Figure 8 The OECT device for monitoring adherent cells. (A) Measurement platform consisting of 24 OECTs divided between four glass wells. (B) MDCK II cells transfected with RFP actin construct seeded on device for fluorescence imaging. (C) Schematic diagram of the cell coverage with low ion flow through barrier (right) or high ion flow through non-barrier (left) (Ramuz et al., 2015). Reproduced with permission (Ramuz et al., 2015). Copyright? 2015 The Royal Society of Chemistry. Wei et.