Low-background, highly sensitive DNA biosensor by using an electrically neutral cobalt(II) complex as the redox...

Area of Science:

• Electrochemistry
• Bioinorganic Chemistry
• Molecular Recognition

Background:

• Cobalt complexes offer unique electrochemical properties for biomolecular interactions.
• DNA intercalation is a key mechanism for binding small molecules to DNA.
• Developing selective and sensitive DNA detection methods is crucial for diagnostics.

Purpose of the Study:

• To synthesize and characterize a cobalt complex, [Co(GA)2(phen)], for DNA interaction studies.
• To investigate the binding mechanism and affinity of the cobalt complex with double-stranded DNA (dsDNA).
• To develop a novel electrochemical biosensor for detecting specific DNA sequences using the cobalt complex as a hybridization indicator.

Main Methods:

• Synthesis and electrochemical characterization of the cobalt complex [Co(GA)2(phen)].
• Electrochemical studies using glassy carbon electrode (GCE) to analyze dsDNA-complex interactions.
• Application of the complex as a redox-active indicator for oligonucleotide hybridization detection.

Main Results:

• The cobalt complex [Co(GA)2(phen)] was synthesized and demonstrated intercalation into dsDNA via the phen ligand with a high binding constant (6.2×10^5 M⁻¹).
• The complex selectively accumulated on dsDNA, not single-stranded DNA (ssDNA), enabling its use as a hybridization indicator.
• The developed biosensor achieved a wide detection range (1.0×10⁻¹⁴ to 1.0×10⁻⁸ M) and a low limit of detection (2.0 fM) for target oligonucleotides.
• High selectivity was observed, distinguishing complementary, one-base-mismatched, and non-complementary DNA sequences.

Conclusions:

• The synthesized cobalt complex exhibits strong intercalation into dsDNA.
• The complex serves as an effective redox-active hybridization indicator for electrochemical DNA biosensing.
• This biosensor offers high sensitivity, selectivity, and a broad detection range for oligonucleotide detection.