Discrimination of DNA hybridization using chemical force microscopy

Area of Science:

• Biophysics
• Surface Science
• Nanotechnology

Background:

• Atomic force microscopy (AFM) enables probing molecular interactions.
• Chemical force microscopy (CFM) uses chemically modified AFM tips to detect molecular recognition.
• AFM tips can be functionalized with ligands to identify specific binding partners on surfaces.

Purpose of the Study:

• To investigate the use of CFM for probing sequence-specific interactions between DNA oligonucleotides.
• To measure the mechanical forces, specifically friction and adhesion, during DNA hybridization.
• To correlate measured forces with the molecular affinity and hydrogen bonding between complementary DNA strands.

Main Methods:

• Functionalizing an AFM cantilever with a DNA oligonucleotide (3 omino-CAGTTCTACGATGGCAAGTC).
• Scanning patterned substrates containing complementary and noncomplementary DNA sequences with the functionalized AFM tip.
• Measuring friction and adhesion forces between the DNA-modified tip and the surface-bound DNA.

Main Results:

• A strong friction interaction was observed between the DNA-modified tip and surface-bound DNA.
• Complementary DNA sequences exhibited significantly stronger friction and adhesion (rupture force) compared to noncomplementary sequences.
• Friction forces correlated directly with adhesion forces, suggesting a common origin in molecular interactions.

Conclusions:

• CFM can effectively detect sequence-specific hybridization between surface-bound DNA and a DNA-modified AFM tip.
• The observed friction and adhesion forces are indicative of DNA hybridization, driven by hydrogen bond formation.
• This study demonstrates CFM as a powerful tool for analyzing molecular recognition and mechanical properties of DNA at the nanoscale.