Graphene Oxide Biosensor for Antibiotic Resistance Gene Detection — Western Kentucky University, 2021

Ha, D. T., Nguyen, V., & Kim, M. (2021). Graphene oxide-based simple and rapid detection of antibiotic resistance gene via quantum dot-labeled zinc finger proteins. *Analytical Chemistry*. https://doi.org/10.1021/acs.analchem.1c00560

Western Kentucky University · Analytical Chemistry · 2021

Researchers at Western Kentucky University used ACS Material graphene oxide dispersion to build a FRET biosensor detecting antibiotic resistance genes at 1 nM in 10 minutes.

About this research

Researchers at Western Kentucky University demonstrated a graphene oxide-based fluorescence biosensor — built around ACS Material's single-layer graphene oxide (GO) dispersion — that detects the tetracycline antibiotic resistance gene tetM directly from double-stranded DNA in only 10 minutes with a limit of detection as low as 1 nM. The platform pairs engineered quantum dot-labeled zinc finger proteins (ZFPs) with 2D GO nanosheets, leveraging fluorescence resonance energy transfer (FRET) to convert specific dsDNA recognition into a turn-on optical signal. The work, published in Analytical Chemistry in 2021 by Ha, Nguyen, and Kim, establishes a simple, PCR-free route to screen for antibiotic resistance genes (ARGs).

Antibiotic resistance is one of the most pressing global health threats, with the U.S. CDC attributing more than 23,000 deaths annually to resistant infections. Antibiotic resistance genes spread between bacterial strains through horizontal gene transfer and accumulate in hospital effluent, agricultural runoff, and municipal water systems. Conventional ARG detection relies on PCR-based amplification, which requires DNA denaturation, primer design, thermal cycling, and trained personnel. There is a clear unmet need for rapid, point-of-need assays that can identify specific resistance genes directly in their native dsDNA form. The combination of sequence-specific DNA-binding protein domains with nanomaterial transducers offers a promising path, but most graphene oxide biosensors to date have been limited to ssDNA or protein targets because dsDNA adsorbs weakly to GO surfaces.

The ACS Material GO dispersion served as the central sensing platform of the assay. According to the experimental section, the GO dispersion (ACS Material, Pasadena, CA) was vortexed for homogeneity and serially diluted from a 5 mg/mL stock down to 1 μg/mL working concentrations. The material is characterized as having a single-layer ratio greater than 80%, lateral sheet sizes of 0.5–2.0 μm, and a thickness of 0–2 nm — properties confirmed by the authors using TEM (JEOL JEM-1400plus) and contact-mode AFM (Agilent 5500). In the working assay, CdSe/ZnS carboxyl-PEG quantum dots (emission 520 nm) were covalently conjugated to engineered six-finger ZFPs targeting either the tetM resistance gene or the Shiga-toxin gene stx2 using EDC/NHS chemistry at an optimized 1:4000:8000 QD:EDC:NHS molar ratio. The QD-ZFP conjugates adsorb onto GO via π-stacking between aromatic protein residues and the GO basal plane plus hydrogen bonding through hydroxyl and carboxyl edges, placing the QDs close enough to GO for FRET quenching.

In the absence of target dsDNA, QD-ZFPs sit on the GO surface and their 520 nm fluorescence is quenched. When the cognate tetM dsDNA is introduced, ZFP binding induces a conformational change that dissociates the QD-ZFP complex from GO, restoring QD emission. The recovered fluorescence intensity scales directly with target DNA concentration, enabling quantitative readout. The authors report specific detection of dsDNA tetM after only 10 minutes of incubation, with a working limit of detection of 1 nM. Specificity was confirmed against non-cognate sequences and through parallel use of stx2-targeting ZFPs, where each engineered ZFP selectively responds to its matching 18-bp recognition site sufficient to uniquely identify a sequence within bacterial genomes. The single-step format eliminates the DNA denaturation and hybridization workflow required in PCR-based ARG assays, while the GO surface efficiently suppresses background fluorescence from unbound QD-ZFP conjugates.

The demonstrated assay points toward practical screening tools for clinical microbiology, environmental water monitoring, food safety, and veterinary diagnostics — all settings where rapid identification of resistance genes informs antibiotic stewardship decisions. Because the ZFP modular assembly approach allows engineering of new six-finger proteins for arbitrary 18-bp targets, the same GO-FRET architecture can be redirected toward other ARGs (mecA, blaNDM, vanA) or pathogen virulence markers such as stx2. The authors also note that integrating the platform into multiplexed or paper-based formats could further reduce assay cost and turnaround time. Compared with PCR or sequencing, the method trades some absolute sensitivity for speed, simplicity, and direct dsDNA recognition without thermal cycling — a useful trade-off for high-throughput screening pipelines.

For researchers developing nucleic acid biosensors, FRET-based assays, or 2D-material transducers, the consistency and well-defined sheet dimensions of ACS Material's single-layer graphene oxide dispersion are practical advantages: the >80% monolayer content and sub-2 nm thickness reported here translate directly into reliable fluorescence quenching efficiency. The graphene oxide dispersions and related GO products used in this study are available through ACS Material's graphene catalog for laboratories working on biosensing, drug delivery, and other interfacial bionanotechnology applications.

How ACS Material products were used

• Single Layer Graphene Oxide Dispersion (Graphene Series)  — “GO dispersion (ACS Material, Pasadena, CA) was vortexed to ensure a homogeneous solution before diluting with deionized water... The single layer ratio is >80% with the size of GO sheets ranging from 0.5 to 2.0 μm and the thickness of 0−2 nm.”

Product Performance in this Study

The ACS Material GO dispersion served as the central 2D nanosheet sensing platform, providing efficient FRET-based fluorescence quenching of QD-labeled zinc finger proteins and enabling rapid (10 min) detection of the tetM antibiotic resistance gene with a limit of detection of 1 nM.

Related product categories

• Graphene Series

Frequently asked questions

How does graphene oxide quench quantum dot fluorescence in biosensors?

Graphene oxide quenches quantum dot fluorescence through fluorescence resonance energy transfer (FRET) when QDs are brought into close proximity with the GO basal plane. The aromatic, electron-rich surface of GO accepts excited-state energy from nearby fluorophores, suppressing their emission. In this study, QD-labeled zinc finger proteins adsorbed onto GO via π-stacking and hydrogen bonding, quenching the 520 nm QD signal until target dsDNA binding pulled the complex away from the surface.

What is the limit of detection for antibiotic resistance genes using graphene oxide FRET sensors?

The Western Kentucky University team reported a limit of detection of 1 nM for the tetracycline resistance gene tetM using their graphene oxide and zinc finger protein FRET biosensor. Detection was achieved in just 10 minutes of incubation, without any DNA denaturation or PCR amplification step. The signal recovery scales linearly with target dsDNA concentration, enabling quantitative analysis of resistance gene levels.

Why is single-layer graphene oxide preferred for FRET-based DNA detection?

Single-layer graphene oxide maximizes the surface area available for QD-protein adsorption and provides uniform fluorescence quenching across the sensing platform. The ACS Material GO used here has a single-layer ratio above 80%, lateral sheet sizes of 0.5–2.0 μm, and thickness of 0–2 nm. These well-defined dimensions ensure reproducible FRET efficiency and consistent signal-to-noise performance in nucleic acid biosensing assays.