# A Graphene Field-Effect Transistor-Based Biosensor Platform for the Electrochemical Profiling of Amino Acids

## TL;DR

This paper introduces a graphene-based biosensor platform for electrochemically profiling amino acids, aiming to improve peptide and protein sequencing.

## Contribution

The novelty lies in the development of a GFET-based platform with stable surface chemistry for amino acid fingerprinting and in situ peptide synthesis.

## Key findings

- A graphene functionalization protocol enables directional amino acid attachment with surface densities of ~10^12 molecules/cm².
- In situ tripeptide synthesis on graphene demonstrates the platform's potential for peptide sequencing.
- Sensor stability is confirmed with Dirac point drift below 10 mV over 45 minutes.

## Abstract

In this work, we present the introductory methodology for a graphene field-effect transistor (GFET)-based platform for probing the electrochemical fingerprints of amino acids, designed to enable stable and controlled surface chemistry and electrochemical measurements toward peptide and protein sequencing. We begin with a focused conceptual review that motivates electrochemical fingerprinting as a strategy for amino acid and peptide identification and contextualizes this approach within recent advances in protein manipulation relevant to sequencing. We then describe a graphene functionalization protocol that facilitates the directional attachment of amino acids onto the graphene surface. This surface chemistry is quantitatively characterized through surface plasmon resonance (SPR), yielding surface densities in the order of 1012 molecules/cm2. The same functionalization protocol enables in situ peptide synthesis directly on graphene, as demonstrated by the successful synthesis of a model tripeptide. To support electrochemical interrogation, we developed three complementary platforms for sensor preconditioning, surface functionalization, and titration-based electrochemical measurements, compatible with both aqueous and organic solutions. Preliminary stability measurements indicate a Dirac point drift below 10 mV over 45 min. Altogether, this work establishes the experimental foundations for electrochemical amino acid and peptide fingerprinting using GFET sensors and provides a framework for the future development of electrochemically enabled protein sequencing technologies.