Label-Free Aptasensor for Lysozyme Detection Using Electrochemical Impedance Spectroscopy.

Area of Science:

• Biosensor Technology
• Electrochemical Analysis
• Biomolecular Detection

Background:

• Lysozyme is a key protein in various biological and food applications.
• Label-free detection methods are crucial for simplifying biosensing procedures.
• Electrochemical Impedance Spectroscopy (EIS) offers sensitive analysis of biomolecular interactions.

Purpose of the Study:

• To develop a label-free aptamer biosensor (aptasensor) for lysozyme detection.
• To utilize graphite-epoxy composite electrodes (GECs) for enhanced sensor performance.
• To validate the aptasensor's efficacy in real-world sample analysis, such as wine.

Main Methods:

• Fabrication of GECs with electrochemically grafted carboxylic moieties.
• Immobilization of aptamers via covalent bonding using carbodiimide chemistry.
• Detection of lysozyme using Electrochemical Impedance Spectroscopy (EIS) with a [Fe(CN)₆]^3-/[Fe(CN)₆]^4- redox probe.

Main Results:

• The aptasensor exhibited a linear response for lysozyme detection up to 5 µM.
• A low limit of detection (LOD) of 1.67 µM was achieved for lysozyme.
• The method demonstrated a sensitivity of 0.090 µM^-1 and characterized interference from other proteins.

Conclusions:

• The developed label-free aptasensor on GECs is effective for lysozyme quantification.
• The aptasensor shows promising performance for practical applications, including wine analysis.
• Covalent immobilization via electrochemical grafting provides a robust platform for aptasensor development.