Biosensing with Surface-Charge-Modulated Graphene Field-Effect Transistors beyond Nonlinear Electrolytic Screening.

Area of Science:

• Biosensor technology
• Materials science
• Surface chemistry

Background:

• Field-effect transistor (FET) biosensors face sensitivity limitations due to charge screening in electrolyte solutions.
• Graphene FET (GFET) biosensors are particularly affected by the inherent negative charge of graphene, leading to nonlinear electrolytic screening and reduced sensitivity.

Purpose of the Study:

• To counteract the negative surface charge of graphene in GFET biosensors.
• To enhance the sensitivity and reliability of GFET biosensors for detecting biomarkers like C-reactive protein (CRP).

Main Methods:

• Decorating graphene surfaces with positively charged compounds to create surface-charge-modulated GFETs (SCM-GFETs).
• Integrating SCM-GFETs with anti-CRP antibodies on a chip and using differential measurements with nonfunctionalized GFETs to eliminate background noise.
• Correlating FET responses with fluorescence imaging to confirm specific CRP adsorption.

Main Results:

• SCM-GFETs demonstrated specific adsorption of CRP, with measured dissociation constants consistent with literature values.
• GFETs without surface modification showed signals obscured by noise due to nonlinear electrolytic screening.
• The developed system achieved a limit of detection of 2.9 nM for CRP.

Conclusions:

• Surface-charge modulation effectively circumvents nonlinear electrolytic screening in GFET biosensors.
• SCM-GFETs offer a promising approach for improving the sensitivity and reliability of biosensing applications.
• This strategy paves the way for advancements in graphene-based biosensor technology.