Characterizing Mixed Polyethylene Glycol Monolayers with Surface-Bound Ferrocene for Label-Free Immunosensing

Area of Science:

• Electrochemistry
• Biosensing
• Surface Chemistry

Background:

• Label-free electrochemical immunosensors offer direct biomolecular detection but often lack sensitivity for low-abundance analytes.
• Current strategies to boost sensitivity typically involve nanomaterial-based electrode modifications.

Purpose of the Study:

• To develop a multifunctional monolayer for label-free electrochemical immunosensors to enhance sensitivity.
• To incorporate ferrocene for improved electron transfer and biotin for antibody immobilization.

Main Methods:

• Assembled a mixed monolayer on thermoplastic electrodes (TPEs) using copper-catalyzed azide-alkyne cycloaddition (CuAAC).
• Utilized polyethylene glycol (PEG)-based spacers with ferrocene (Fc) and biotin functionalities.
• Characterized monolayer formation using electrochemical methods and X-ray photoelectron spectroscopy (XPS).
• Detected inactivated SARS-CoV-2 virus nucleocapsid (N) protein using square wave voltammetry (SWV).

Main Results:

• Confirmed successful monolayer formation, ferrocene integration, biotin functionality, and minimized nonspecific adsorption (NSA).
• Achieved limits of detection (LOD) of 21.1 ± 10.6 ng/mL (PEG11) and 21.6 ± 10.8 ng/mL (PEG24) using ferrocyanide as the redox probe.
• Demonstrated sensor performance was independent of PEG chain length for electron transfer but influenced detection sensitivity.

Conclusions:

• Strategic surface chemistry design and redox property integration significantly enhance label-free electrochemical immunosensor sensitivity.
• The developed multifunctional monolayer provides a promising platform for sensitive detection of low-abundance analytes.