Characterization of Ferritin Adsorption onto Gold

Area of Science:

• Biomaterials Science
• Surface Chemistry
• Nanotechnology

Background:

• Understanding protein adsorption is crucial for developing biosensors.
• Ferritin's potential as a biological receptor layer requires characterization of its adsorption behavior on gold.

Purpose of the Study:

• To investigate the adsorption kinetics and surface properties of ferritin on gold.
• To determine the surface coverage and layer thickness of adsorbed ferritin.
• To assess the stability and suitability of ferritin layers for immunosensing applications.

Main Methods:

• Quartz Crystal Microbalance (QCM) for adsorption kinetics and isotherms.
• Surface Plasmon Resonance (SPR) for layer thickness and environmental effects.
• X-ray Photoelectron Spectroscopy (XPS) for film composition and thickness.
• Atomic Force Microscopy (AFM) for surface topography analysis.

Main Results:

• Ferritin adsorption on gold results in less than a monolayer coverage.
• Layer thickness measurements by QCM, SPR, and XPS were consistent (approx. 4.7-4.8 nm dry film).
• SPR data indicated a significant increase in layer thickness in solution (PBS) versus dry conditions, attributed to ferritin hydration.
• AFM confirmed incomplete monolayer formation and revealed nanometer-scale topography.
• Ferritin demonstrated irreversible adsorption and formed a stable layer on gold.

Conclusions:

• Ferritin forms a stable, irreversibly adsorbed layer on gold, suitable for biosensing.
• The combined use of QCM, SPR, XPS, and AFM provides comprehensive characterization of protein adsorption.
• The observed hydration-dependent thickness is critical for understanding ferritin layer behavior in biological environments.