Activation of complement C3 by different calcium phosphate powders

Area of Science:

• Biomaterials Science
• Immunology
• Materials Chemistry

Background:

• Calcium phosphates are widely used in biomedical applications.
• Understanding their interaction with the immune system is crucial for safety and efficacy.
• The complement system plays a key role in innate immunity and inflammatory responses.

Purpose of the Study:

• To investigate the complement-activating potential of different calcium phosphate materials.
• To determine the specific mechanisms underlying complement activation by these materials.

Main Methods:

• Crossed immunoelectrophoresis was used to detect C3 to C3b conversion.
• A hemolytic assay (CH50) was employed to quantify complement consumption.
• Adsorption behavior, chemical composition, and crystal lattice properties were analyzed.

Main Results:

• Sintered hydroxyapatite powders significantly induced C3 conversion and reduced CH50 values.
• Sintered tricalciumphosphate (beta-whitlockite) did not activate the complement system.
• Complement activation was independent of adsorption behavior, chemical composition, and crystal lattice structure.

Conclusions:

• Hydroxyapatite possesses complement-activating properties, while tricalciumphosphate does not.
• The mechanism of C3 conversion by hydroxyapatite is not initiated by the classical complement pathway convertase.
• Material properties like adsorption, composition, and crystal structure do not solely dictate complement activation by calcium phosphates.