Direct detection of DNA with an electrocatalytic threading intercalator

Area of Science:

• Supramolecular Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Naphthalene diimides (NDIs) are known for their DNA intercalation properties.
• Functionalization of NDIs with redox-active moieties can enhance their analytical applications.
• Osmium complexes offer electrocatalytic activity valuable for biosensing.

Purpose of the Study:

• To synthesize and characterize an imidazole-substituted naphthalene diimide (PIND) functionalized with osmium redox moieties (PIND-Os).
• To investigate the DNA binding properties of PIND-Os compared to its parent compound.
• To develop and evaluate an electrochemical biosensor for DNA detection using PIND-Os.

Main Methods:

• Single-step synthesis of PIND from dianhydride.
• Ligand exchange to attach Os(bpy)2Cl2 complex to PIND via imidazole groups, forming PIND-Os.
• Gel electrophoresis to study DNA binding affinity.
• Fabrication of an electrochemical biosensor and evaluation using electrocatalytic amperometry.

Main Results:

• PIND-Os was successfully synthesized and characterized.
• PIND-Os exhibits stronger binding to double-stranded DNA (ds-DNA) than 1,4,5,8-naphthalene diimide.
• The PIND-Os intercalator enabled a 2500-fold increase in sensitivity for DNA detection via electrocatalytic amperometry.
• The biosensor detected a 50-mer target DNA in the 1.0-300 pM range with a 600 fM detection limit.

Conclusions:

• The novel PIND-Os compound effectively binds to ds-DNA through intercalation and electrostatic interactions.
• PIND-Os serves as an efficient redox-active element for electrochemical DNA biosensing.
• The developed biosensor demonstrates high sensitivity and a low detection limit for specific DNA sequences.