Adsorption of complement proteins on surfaces with a hydrophobicity gradient

Area of Science:

• Biomaterials Science
• Immunology
• Surface Chemistry

Background:

• Complement system activation is a key challenge for biomaterial biocompatibility.
• The alternative pathway of complement activation on biomaterials involves C3, factor B, and factor H.

Purpose of the Study:

• To investigate the adsorption of complement proteins C3, B, and H onto silica surfaces with varying hydrophobicity.
• To understand how surface hydrophobicity affects the binding interactions of C3, factor B, and factor H.

Main Methods:

• Utilized a silica surface with a hydrophobicity gradient.
• Studied the adsorption of radio-labeled C3, factor B (B), and factor H (H) using quantitative measurements.
• Assessed the displacement of adsorbed C3 by factors B and H.
• Analyzed the binding ratios of B/C3 and H/C3 as a function of surface hydrophobicity.

Main Results:

• C3 adsorption was similar on both hydrophilic and hydrophobic silica surfaces.
• Neither factor H nor factor B could displace pre-adsorbed C3.
• Binding of factors B and H to adsorbed C3 increased with surface hydrophilicity.
• The binding of factors B and H to C3 was influenced by C3 conformation/orientation, not just the amount of adsorbed C3.
• At hydrophobic surfaces, the H/C3 molar ratio was higher than the B/C3 ratio, suggesting preferential H binding.

Conclusions:

• Surface hydrophobicity significantly modulates the binding of complement factors B and H to adsorbed C3.
• Surface-induced conformational changes in C3 affect the accessibility of binding sites for factors B and H.
• Understanding these interactions is crucial for designing biomaterials with improved biocompatibility by controlling complement activation.