High-capacitance air-brushed electrodes for capacitive label-free bioassays

Area of Science:

• Biomarker Detection
• Electrochemistry
• Materials Science

Background:

• Non-invasive protein biomarker assays are crucial for early cancer diagnosis and monitoring.
• Accurate point-of-care (POC) diagnostic devices are scarce due to high costs and bulky equipment.
• HER-2/neu is a key protein biomarker for aggressive cancers and a target for therapy.

Purpose of the Study:

• To develop an accurate and economical point-of-care diagnostic device for HER-2/neu detection.
• To utilize airbrushed graphite electrodes for a capacitive electrochemical enzyme-linked aptamer-sorbent assay (e-ELASA).
• To enable sensitive and rapid monitoring of cancer biomarkers in diverse settings.

Main Methods:

• Fabrication of disposable graphite (Gr) electrodes by airbrushing graphite-powder/chitosan inks onto polyester films.
• Development of a capacitive cellulase-linked electrochemical enzyme-linked aptamer-sorbent assay (e-ELASA) on magnetic beads (MBs).
• Performance evaluation of airbrushed Gr electrodes against manually polished electrodes for HER-2/neu detection in buffer and serum.

Main Results:

• Airbrushed Gr electrodes exhibited high capacitance (3.61–8.88 mF cm⁻²).
• The developed e-ELASA achieved a limit of detection of 0.1 fM for HER-2/neu in buffer and serum.
• Five-layer airbrushed electrodes showed a three-fold increase in sensitivity compared to previous methods.

Conclusions:

• The portable and low-cost airbrushed electrode/e-ELASA system provides accurate and sensitive HER-2/neu detection.
• This technology is suitable for regular POC monitoring, particularly in low- and middle-income countries.
• The high-capacitance airbrushed electrodes have potential for adaptation to other label-free capacitive bioassays.