# A Suspended Graphene Field-Effect Transistor for Ultra-Sensitive and Label-Free Detection of Cancer Biomarker miR-21

## TL;DR

A new graphene-based sensor detects cancer biomarker miR-21 with high sensitivity and without labels, offering promise for early cancer diagnosis.

## Contribution

A suspended graphene field-effect transistor (GFET) is introduced for ultra-sensitive, label-free detection of miR-21.

## Key findings

- The GFET sensor achieved femtomolar detection limits for miR-21.
- Binding events caused measurable changes in resistance and Dirac point shifts.
- The suspended design improved carrier mobility and reduced electrical noise.

## Abstract

The sensitive detection of microRNA-21 (miR-21), a key biomarker for various cancers, is crucial for early diagnosis, yet conventional methods often face limitations in sensitivity and operational complexity. Here, we report a label-free biosensor based on a suspended graphene field-effect transistor (GFET) for the direct electrical detection of miR-21. The suspended architecture isolates the graphene channel from substrate-induced interference, resulting in enhanced carrier mobility and reduced electrical noise. After surface functionalization with a specific probe, the GFET demonstrated a clear concentration-dependent response to target miR-21. The binding events were transduced into a monotonic increase in relative resistance (ΔR/R0) and a positive shift of the Dirac point (VDirac), achieving a detection limit in the femtomolar (fM) range. These results establish the suspended GFET as a highly sensitive and robust platform for quantifying nucleic acid biomarkers, holding significant potential for biomedical research and point-of-care diagnostics.