A physical approach to reduce nonspecific adhesion in molecular recognition atomic force microscopy

Area of Science:

• Biophysics
• Surface Science
• Nanotechnology

Background:

• Atomic force microscopy (AFM) enables single-molecule analysis of biological interactions.
• Nonspecific interactions between the AFM tip and substrate limit measurement accuracy.
• Understanding and mitigating these nonspecific forces is crucial for precise biological sensing.

Purpose of the Study:

• To model and experimentally validate a method for reducing nonspecific interactions in AFM.
• To develop a novel AFM measurement approach in the repulsive regime for enhanced specificity.
• To improve the analysis of biological recognition processes at the single-molecule level.

Main Methods:

• Utilized Derjaguin, Landau, Verwey, Overbeek (DLVO) theory and numerical calculations to model tip-sample interaction potentials.
• Simulated AFM cantilever approach-retract cycles to analyze force-distance curves.
• Experimentally observed tip hopping behavior due to thermal fluctuations at low salt concentrations.
• Functionalized AFM tips with antibodies for specific molecular imaging.

Main Results:

• Simulations predicted and experiments confirmed discrete tip hopping in the repulsive regime.
• This novel approach significantly minimized nonspecific interactions between the tip and mica substrate.
• Imaging of intercellular adhesion molecule 1 (ICAM-1) demonstrated high topographical image quality and specific binding.
• The functionalized tip's specific bonding capability remained unaffected.

Conclusions:

• A new AFM measurement strategy operating in the repulsive regime effectively reduces nonspecific binding.
• This method enhances the accuracy of single-molecule biological recognition studies.
• The validated physical model provides a pathway for more precise AFM-based biosensing applications.