Graphene‐Based Electronic Immunosensor with Femtomolar Detection Limit in Whole Serum

Abstract

Purely electronic diagnostic devices that are sensitive to biomolecules' intrinsic charge present a very attractive platform for point‐of‐care (PoC) applications, since they can operate under label‐free conditions. In this report, a graphene‐based electrolyte‐gated field‐effect transistor is developed as an immunosensor capable of sensitive analyte detection, even in the complex environment of physiological samples. The coimmobilization of an antibody fragment (F(ab′)2) and polyethylene glycol on the graphene surface allows for a highly sensitive and selective detection of a protein analyte, with a limit of detection in the low femtomolar range, both in high ionic strength buffer and undiluted serum. Multiparametric analysis of the device's analyte‐dependent electronic response shows that the mechanism behind this very sensitive detection cannot be explained by a commonly reported electrostatic gating effect. Rather, the observed combination of charge neutrality point shifts and asymmetric mobility changes are attributed to the modulation of scattering by charged impurities, which seem to dominate the device's transfer characteristics. Furthermore, the reproducibility of the normalized signal response obtained from several different devices shows that this graphene‐based immunosensor is capable of direct and quantitative measurements of protein analytes in untreated serum, imperative for diagnostic tools geared toward PoC applications.

Ultrasensitive detection of nucleic acids using deformed graphene channel field effect biosensors

“…Compatibility to the conventional CMOS fabrication process is another potential advantage of using 2D materials, which carbon nanotube, Si-nanowire, nanoparticles do not have. Especially, large area graphene, which is grown through chemical vapor deposition (CVD) method, has been utilized in electrical systems, such as FET device for bio-sensing 5 including detection of pH 11 , microorganisms 12 , blood sugar 12 , and more specifically, proteins at concentrations of 10 fM 12,13 , and nucleic acids (DNA or RNA) at the 100 fM concentrations 5,14 . There are a few reports that showed DNA and RNA detection at aM level, however, had significant level of background noise and lacked robust controls 15,16 .…”

Pattern Directive Sensing Selectivity of Graphene for Wearable Multifunctional Sensors via Femtosecond Laser Fabrication

“…[ 1–4 ] It has been developed to be the core materials of flexible electronics, such as radio frequency identification device (RFID), flexible circuit, transparent electrode, and especially wearable sensors. [ 5–8 ] The graphene‐based sensors have been researched widely in recent years, including strain sensors, [ 9–15 ] gas sensors, [ 16–18 ] chemical sensors, [ 19–21 ] and biological sensors, [ 22–24 ] etc. Wherein, graphene‐based strain sensor is the most popular with the researchers, owing to its high sensibility to tactile.…”

“…Additionally, the graphene or graphene oxide has been applied to detect dopamine, glucose, deoxyribonucleic acid, heavy metal ions, toxic chemicals, and so forth. [ 22–24 ]…”

“…The main reason is that the raw materials and the material processing they reported are uniform and homogeneous. The graphene textiles [ 9–15 ] and graphene/graphene oxide powder or suspension [ 16–24 ] are the popular raw materials for sensors. To improve the sensitivity, a large quantity of active sits and defects should be introduced by weaving, [ 15 ] doping, [ 25 ] oxidating, [ 10 ] and mechanical processing.…”

Investigation of Electrical Stability and Sensitivity of Electric Double Layer Gated Field-Effect Transistors (FETs) for miRNA Detection

“…However, this requires complex actuation mechanisms and automation if FET biosensors are to be deployed for non-laboratory based applications. Some other studies have aimed to overcome the Debye screening limitations in high ionic strength media [13,14,15]. They have made use of polymer-based surface functionalization strategies to effectively increase the Debye length and facilitate protein detection, with the polymer acting as an additional capacitive layer.…”