Label-free electrochemical impedimetric immunosensor for sensitive detection of IgM rheumatoid factor in human serum

Area of Science:

• Biosensor technology
• Immunosensing
• Electrochemical detection

Background:

• Rheumatoid factor Immunoglobulin M (IgM-RF) is a key biomarker for rheumatoid arthritis.
• Accurate and rapid detection of IgM-RF is crucial for early diagnosis and management.
• Existing detection methods can be time-consuming and require complex laboratory setups.

Purpose of the Study:

• To develop a label-free and direct impedimetric biosensor for sensitive detection of IgM-RF.
• To functionalize an interdigitated wave type microelectrode array (IDWμE) for antigen immobilization.
• To evaluate the performance of the developed biosensor for potential point-of-care applications.

Main Methods:

• Fabrication and characterization of thioctic acid-functionalized IDWμE.
• Covalent immobilization of IgG-Fc antigen onto the modified electrode.
• Electrochemical impedance spectroscopy (EIS) for label-free IgM-RF detection using a redox probe and human serum.
• Performance evaluation including sensitivity, selectivity, reproducibility, and stability.

Main Results:

• The biosensor demonstrated label-free and direct detection of IgM-RF.
• Impedimetric measurements showed significant changes in impedance and charge transfer resistance upon IgM-RF binding.
• Linear detection range from 1 to 200 IU mL⁻¹ with low detection limits (0.6 IU mL⁻¹ in redox probe, 0.22 IU mL⁻¹ in human serum).
• The sensor exhibited good reproducibility (RSD, 4.96%), repeatability (RSD, 2.31%), selectivity, and stability for 3 weeks.

Conclusions:

• The developed impedimetric immunosensor based on IDWμE is sensitive, stable, and specific for IgM-RF detection.
• The sensor's performance suggests its suitability for integration with miniaturized potentiostats.
• This technology holds promise for developing rapid point-of-care diagnostic systems for rheumatoid arthritis.