Rapid, quantitative therapeutic screening for Alzheimer's enzymes enabled by optimal signal transduction with transistors

Abstract

We show that simple, commercially sourced n-channel silicon field-effect transistors (nFETs) operating under closed loop control exhibit an »3-fold improvement in pH readout resolution to (7.2±0.3)´10 -3 at a bandwidth of 10 Hz when compared with the open loop operation commonly employed by integrated ion-sensitive field-effect transistors (ISFETs). We leveraged the improved nFET performance to measure the change in solution pH arising from the activity of a pathological form of the kinase Cdk5, an enzyme implicated in Alzheimer's disease, and showed quantitative agreement with previous measurements. The improved pH resolution was realized while the devices were operated in a remote sensing configuration with the pH sensing element off-chip and connected electrically to the FET gate terminal. We compared these results with those measured by using a custom-built dual-gate 2D field-effect transistor (dg2DFET) fabricated with 2D semi-conducting MoS2 channels and a moderate device gain, a=8. Under identical solution conditions the pH resolution of the nFETs was only 2-fold worse than the dg2DFETs pH resolution of (3.9±0.7)´10 -3 . Finally, using the nFETs, we demonstrated the effectiveness of a custom polypeptide, p5, as a therapeutic agent in restoring the function of Cdk5. We expect that the straight-forward modifications to commercially sourced nFETs demonstrated here will lower the barrier to widespread adoption of these remote-gate devices and enable sensitive bioanalytical measurements for high throughput screening in drug discovery and precision medicine applications.

High resolution voltammetric and field-effect transistor readout of carbon fiber microelectrode biosensors

“… 18 - 22 While FSCV offers chemical selectivity and the capability to distinguish co-released electroactive molecules, the challenge remains in integrating other customized transduction elements to improve the resolution, sensitivity, selectivity and other performance parameters needed for various applications. 4 , 12 , 23 - 25 …”

“…[18][19][20][21][22] While FSCV offers chemical selectivity and the capability to distinguish co-released electroactive molecules, the challenge remains in integrating other customized transduction elements to improve the resolution, sensitivity, selectivity and other performance parameters needed for various applications. 4,12,[23][24][25] Biosensors based on field-effect transistors (FETs) that operate in a remote configuration allow for diverse pH sensitive films to be tested. [25][26][27][28] FET sensors have been used as effective biosensors for several biomolecules 29 including dopamine, 30 phenylalanine, 7 DNA/RNA, 31 cortisol, 32 serotonin, sphingosine-1-phosphate (S1P), and glucose.…”

“…4,12,[23][24][25] Biosensors based on field-effect transistors (FETs) that operate in a remote configuration allow for diverse pH sensitive films to be tested. [25][26][27][28] FET sensors have been used as effective biosensors for several biomolecules 29 including dopamine, 30 phenylalanine, 7 DNA/RNA, 31 cortisol, 32 serotonin, sphingosine-1-phosphate (S1P), and glucose. Glass pH probes are commonly used for pH measurements, 33,34 however they suffer from drift, limited storage in a wet environment, frequent recalibration, and interference from alkali metals.…”