Nonspecific protein adsorption at the single molecule level studied by atomic force microscopy

Area of Science:

• Biophysics
• Surface Science
• Nanotechnology

Background:

• Understanding protein adsorption is crucial for biomaterial development and biosensor design.
• Nonspecific protein adsorption can lead to fouling or altered functionality.

Purpose of the Study:

• To investigate the adsorption behavior of horse spleen ferritin on gold surfaces at the single-molecule level.
• To analyze the adsorption mechanism and identify deviations from established models.

Main Methods:

• Liquid tapping atomic force microscopy (LT-AFM) was employed for high-resolution imaging.
• Real-time observation of ferritin molecules interacting with a bare gold surface.

Main Results:

• The majority of ferritin molecules exhibited irreversible adsorption, consistent with the random sequential adsorption (RSA) model.
• Deviations from RSA were observed, including lateral mobility, desorption, chain formation, and subunit dissociation.
• Atomic force microscopy (AFM) tip scanning effects led to reduced protein coverage in scanned regions.

Conclusions:

• Ferritin adsorption on gold is predominantly irreversible but exhibits complex dynamics beyond simple RSA.
• Molecular fragility and interactions influence adsorption outcomes, including dissociation and aggregation.
• AFM scanning methodology can impact observed protein surface coverage.