One-Step Label-Free Electrochemical Lateral Flow Immunosensor for SARS-CoV‑2 Antigen Detection

Area of Science:

• Electrochemistry
• Biosensing
• Infectious Disease Diagnostics

Background:

• Conventional COVID-19 antigen tests struggle with sensitivity at low viral loads due to reliance on labeled probes.
• There is a need for rapid, ultrasensitive, and simplified diagnostic platforms for early infectious disease detection.

Purpose of the Study:

• To develop and validate a label-free electrochemical antigen test kit (free-EATK) for sensitive SARS-CoV-2 N protein detection.
• To demonstrate the efficacy of free-EATK as a robust and reproducible diagnostic alternative.

Main Methods:

• Integration of a nitrocellulose-coated electrode and a preloaded redox pad for one-step detection.
• Utilizing direct anodic square wave voltammetry for signal generation without conjugate pads or labeled probes.
• Direct immunocomplex formation at the sensing zone followed by redox mediator diffusion.

Main Results:

• Achieved a low detection limit of 0.69 pg/mL for SARS-CoV-2 N protein.
• Demonstrated high reproducibility (RSD < 10%) and excellent specificity (100%).
• Clinical validation showed a sensitivity of 91.7% across 24 samples.

Conclusions:

• The free-EATK provides a simple, robust, and reproducible method for ultrasensitive antigen detection.
• This label-free electrochemical approach is suitable for early-stage infectious disease screening, especially in resource-limited settings.
• The technology bypasses limitations of conventional labeled assays, offering a practical alternative.