A reagentless DNA biosensor based on cathodic electrochemiluminescence at a C/C(x)O(1-x) electrode

Area of Science:

• Electrochemistry
• Biosensor Technology
• Molecular Diagnostics

Background:

• Electrochemical biosensors offer sensitive detection platforms.
• Molecular beacons (MBs) are effective tools for nucleic acid detection.
• Ferrocene (Fc) can be used to modulate electrochemical signals.

Purpose of the Study:

• To develop a reagentless, signal-on electrochemiluminescence (ECL) biosensor for DNA hybridization.
• To utilize the quenching effect of ferrocene on cathodic ECL for sensitive detection.
• To enable cost-effective and simple DNA detection without external luminophores.

Main Methods:

• Fabrication of a DNA biosensor using ferrocene-modified molecular beacons (3'-Fc-MB) on carbon/carbon oxide (C/C(x)O(1-x)) electrodes.
• Covalent immobilization of 5'-amino-labeled MBs onto the electrode surface.
• Detection of complementary target DNA (cDNA) via hybridization-induced conformational change of MB and restoration of ECL signal.

Main Results:

• The immobilization efficiency of the probe depended on the surface carbonyl moiety.
• Hybridization with cDNA caused Fc to move away from the electrode, restoring cathodic ECL.
• The ECL intensity showed a linear response with the logarithm of cDNA concentration (1.0x10(-11) to 7.0x10(-8)M).
• A low detection limit of approximately 5.0 pM (S/N=3) was achieved.
• Effective discrimination of single-base mismatched DNA was demonstrated.

Conclusions:

• A simple, cost-effective, and reagentless ECL biosensor for DNA hybridization detection was successfully developed.
• The biosensor offers high sensitivity and specificity, with potential for clinical diagnostics.
• The intrinsic ECL generation from the electrode eliminates the need for external luminophores.