Synthetic oligonucleotides: AFM characterisation and electroanalytical studies

Area of Science:

• Electrochemistry
• Biosensor Technology
• Surface Science

Background:

• Effective immobilization of nucleic acid probes is crucial for DNA biosensor sensitivity and stability.
• Maintaining probe conformational flexibility during immobilization is essential for biosensor function.
• Spontaneous adsorption of oligonucleotides on electrode surfaces can lead to porous layers and non-specific adsorption.

Purpose of the Study:

• To investigate the electrostatic immobilization of oligonucleotide sequences on a glassy carbon electrode.
• To analyze the impact of hybridization with complementary and non-complementary sequences on electrochemical signals.
• To evaluate the formation of mixed multilayers due to specific and non-specific adsorption.

Main Methods:

• Macroscopic Mode Atomic Force Microscopy (MAC Mode AFM) for surface morphology analysis.
• Differential Pulse Voltammetry (DPV) to measure changes in oxidation currents.
• Electrochemical Impedance Spectroscopy (EIS) to study modifications in double-layer capacitance.

Main Results:

• Oligonucleotide sequences spontaneously adsorb on the electrode, forming porous layers.
• Hybridization events and control experiments induced changes in guanosine and adenosine oxidation currents.
• Modifications in double-layer capacitance indicated non-specific adsorption, leading to mixed multilayer formation.

Conclusions:

• Spontaneous adsorption of nucleic acid probes on electrodes is feasible but prone to non-specific binding.
• Electrochemical techniques can detect hybridization and non-specific adsorption events.
• Understanding adsorption behavior is key to designing more stable and sensitive DNA biosensors.