Individual plasma proteins detected on rough biomaterials by phase imaging AFM

Area of Science:

• Biomaterials Science
• Surface Science
• Biophysics

Background:

• Atomic Force Microscopy (AFM) provides high-resolution topographic imaging of adsorbed plasma proteins.
• Previous AFM imaging was limited to smooth model substrates, hindering protein observation on rough biomaterials.
• Biomaterial surface roughness complicates the visualization of adsorbed proteins.

Purpose of the Study:

• To investigate the utility of phase imaging AFM for visualizing adsorbed fibrinogen on rough biomaterial surfaces.
• To characterize fibrinogen adsorption on National Heart Lung and Blood Institute (NHLBI) reference materials.
• To assess the capabilities and limitations of phase imaging for protein adsorption studies.

Main Methods:

• Utilized tapping mode AFM with phase imaging to study fibrinogen adsorbed from dilute solution onto polydimethylsiloxane and low-density polyethylene.
• Compared topographic imaging with phase imaging for protein visualization on different surface topographies.
• Investigated protein adsorption on expanded polytetrafluoroethylene to further evaluate phase imaging limitations.

Main Results:

• Phase imaging AFM successfully distinguished adsorbed fibrinogen from the polydimethylsiloxane surface, even when topographic imaging was limited.
• On low-density polyethylene, phase imaging located and characterized protein distribution where topography failed.
• Phase imaging could not distinguish fibrinogen on expanded polytetrafluoroethylene, highlighting technique limitations.

Conclusions:

• Phase imaging AFM is a valuable tool for characterizing protein adsorption on certain rough biomaterial surfaces.
• The technique's success depends on the relative scales of surface features and adsorbed molecules.
• Further development is needed to overcome limitations in visualizing proteins on highly complex or similar-material surfaces.