Electric-field dependent conformations of single DNA molecules on a model biosensor surface

Area of Science:

• Biosensor technology
• Nanoscale molecular interactions
• Surface chemistry

Background:

• Current nucleic acid sensors lack definitive understanding of molecular binding, affecting sensitivity and reliability.
• Key questions remain regarding DNA probe distribution, conformation changes at surface defects, and response to electric fields.

Purpose of the Study:

• To investigate the nanoscale conformations of individual DNA molecules on a model biosensor surface.
• To understand how applied electric fields and surface chemistry influence DNA probe behavior.
• To correlate nanoscale structure with biosensor performance.

Main Methods:

• Utilized in situ electrochemical atomic force microscopy (EC-AFM) for nanoscale observation.
• Employed a model biosensor surface: thiolated DNA on gold passivated with hydroxyl-terminated alkanethiol self-assembled monolayers.
• Tailored nanoscale surface interactions to control probe behavior.

Main Results:

• Observed that DNA molecule conformations under electric fields are highly sensitive to the specific alkanethiol molecule used.
• Found that DNA molecules can adopt either highly linear or highly curved conformations depending on the monolayer and surface defects.
• Demonstrated that these nanoscale structures are challenging to detect with traditional ensemble characterization methods.

Conclusions:

• The study provides direct nanoscale visualization of individual DNA molecule conformations on biosensor surfaces.
• Findings highlight the critical role of surface chemistry and electric fields in dictating DNA probe behavior.
• Results offer a foundation for improving nucleic acid sensor design by linking probe structure to binding affinity, selectivity, and kinetics.