Graphene-Based Electrolyte-Gated Field-Effect Transistors for Potentiometrically Sensing Neuropeptide Y in Physiologically Relevant Environments

Abstract

Wearable electronics with real-time biosensing capabilities are very important for future applications in monitoring and augmenting human health and performance. Graphene-based potentiometric sensing offers a route for developing wearable sensors that can selectively sense biomarkers in biofluids such as sweat and saliva. This manuscript studies the sensitivity of potentiometric sensors made with graphene-based electrolyte-gated field-effect transistors (GFETs). Selectivity in the sensor toward a nanoscale biomarker, neuropeptide Y (NPY), was achieved by functionalizing graphene with a peptide-based biorecognition element. The sensors were then characterized extensively by varying concentrations of NPY in a complex medium containing artificial sweat with varying ionic concentrations and pH. This medium, therefore, emulated the response of the sensor to biomarkers in a physiologically relevant condition approaching a real-world scenario. Analysis using Gouy−Chapman−Stern theory for the liquid−solid interface at nanoscale highlighted important features of potentiometric sensing such as log-linear response and charge screening effects in GFET sensors.

Wearable electrochemical biosensors to measure biomarkers with complex blood-to-sweat partition such as proteins and hormones

“…Similarly, the electrostatic gated effect predicts that if the recognition elements capture a positive-charged target, it will tend to attract negative carriers, i.e., electron trapping, leading to an n-doping, and vice versa (Fig. 3h ) [ 111 , 119 ].…”

“…A recent work uses short 12-mer peptide as biological recognition element (BRE) called PN1 (HSSYWYAFNNKT) (Fig. 10 ) (Table 1 ) [ 111 ]. Interestingly, the use of liquid cell transmission electron microscopy (LC-TEM) variation enabled researchers to study the interaction of the graphene chemisorbed PN1 and the NYP at the same time of measurements [ 112 ].…”

“…It partially explains the screening effect by direct observation. It recalls the importance of basic research to ameliorate limitations associated with the charge screening, for future WEB-FETs devices, especially for the real-time sensing of small charged biomarkers like NPY [ 111 ].

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“…Optical microscope image of the chip (b) and its magnification (c) shows a proper distribution of TiAu S and D electrodes to alter the current I SD at the channel when the customized voltage V GS was applied to generate the transfer curve (d) after immersion into the artificial sweat picked with cortisol. Reprinted with permission from [ 111 ] …”

COVID-19 Biomarkers and Advanced Sensing Technologies for Point-of-Care (POC) Diagnosis

“…The drawback of this technology is the baseline drift in an aqueous environment. This limits their ability to respond to target molecules [156][157][158]. Figure 8 presents the COVID-19 biomarker sensors.…”