Protein Detection Using Quadratic Fit Analysis near the Dirac Point of Graphene Field-Effect Biosensors

Abstract

Although graphene-based biosensors provide extreme sensitivity for the detection of atoms, gases, and biomolecules, the specificity of graphene biosensors to the target molecules requires surface decoration of graphene with bifunctional linkers such as pyrene derivatives. Here, we demonstrate that the pyrene functionalization influences graphene's electrical properties by yielding partial formation of bilayer graphene, which was confirmed by the Raman 2D spectrum. Based on this observation, we introduce quadratic fit analysis of the nonlinear electrical behavior of pyrene-functionalized graphene near the Dirac point. Compared to the conventional linear fit analysis of the transconductance at a distance from the Dirac point, the quadratic fit analysis of the nonlinear transconductance near the Dirac point increased the overall protein detection sensitivity by a factor of 5. Furthermore, we show that both pyrene linkers and gating voltage near the Dirac point play critical roles in sensitive and reliable detection of proteins' biological activities with the graphene biosensors.

Different Single-Enzyme Conformational Dynamics upon Binding Hydrolyzable or Nonhydrolyzable Ligands

“…A pseudo wild-type T4 lysozyme mutant (C54T/C97A/S90C) was synthesized via site-directed mutagenesis and expressed from Escherichia coli cells, as previously described. − The single-walled carbon nanotube (SWNT) field-effect transistor fabricated by chemical vapor deposition synthesis and standard lithography techniques was soaked in a solution of a bifunctional linker molecule, N -(1pyrenyl)­maleimide in ethanol (1 mM) for 30 min, washed with 0.1% Tween-20 in ethanol and deionized water, and then incubated in the lysozyme solution (5.4 μM in PBS) for 60 min. On average, about one protein attachment in every two devices was confirmed by imaging the devices with atomic force microscopy (Figure a).…”

Biofunctionalization of Graphene‐Based FET Sensors through Heterobifunctional Nanoscaffolds: Technology Validation toward Rapid COVID‐19 Diagnostics and Monitoring

“…[18] Moreover, some models that describe the GFET sensing response were previously reported. [40,57,74] Nevertheless, for a rigorous validation of the GFET-based biosensing technology, it is still necessary to correlate the GFET response with the recognized surface mass obtained by a reference method. To achieve this goal, SPR measurements were performed, since it is the gold standard technique to study affinity systems on surfaces.…”

Dual-Gate Enhancement of the Sensitivity of miRNA Detection of a Solution-Gated Field-Effect Transistor Featuring a Graphene Oxide/Graphene Layered Structure

“…1−4 Fieldeffect transistors have attracted great interest recently for their use in the label-free detection of biological species in a fast, sensitive, simple, low-cost, and quantitative manner. 5 Graphene, a one-atom-thick material consisting of sp 2 -hybridized carbon atoms in a honeycomb structure, displays high carrier mobility, robust mechanical properties, high chemical stability, and a high surface-to-bulk ratio, 6 making it highly useful for the construction of solution-gated graphene transistors (SGGTs) for electrical transduction in biosensor applications. Never-theless, the electrical properties of graphene are very sensitive to biological analytes containing aromatic bases (e.g., proteins, nucleic acids), making its affinity toward biomolecules nonspecific.…”

“…Functionalization of the graphene surface can be performed using covalent and noncovalent approaches. Covalent functionalization can be performed by attacking the sp 2 hybridized carbon atoms of graphene with highly reactive free radicalsfor example, using oxygen plasma treatment to form carboxyl and hydroxyl groups. 7 These oxidative groups can undergo carbodiimide-mediated reactions with amino-terminated deoxyribonucleic acids (DNA) or peptide nucleic acid probes, thereby immobilizing them as biorecognition molecules on the graphene surface.…”

“…The global pandemic of COVID-19 has revealed a need to develop point-of-care biosensorsmeasuring systems that include a sensitive biological receptor, a transducer, and a signal processing elementthat allow rapid and sensitive detection for clinical diagnosis. The biological recognition of analytes and subsequent transduction into measurable signals can be performed using various approaches, including optical, electrical, electrochemical, and mechanical detection. − Field-effect transistors have attracted great interest recently for their use in the label-free detection of biological species in a fast, sensitive, simple, low-cost, and quantitative manner . Graphene, a one-atom-thick material consisting of sp 2 -hybridized carbon atoms in a honeycomb structure, displays high carrier mobility, robust mechanical properties, high chemical stability, and a high surface-to-bulk ratio, making it highly useful for the construction of solution-gated graphene transistors (SGGTs) for electrical transduction in biosensor applications.…”