Complement activation by alginate-polylysine microcapsules used for islet transplantation

Area of Science:

• Biomaterials Science
• Immunology
• Cell Biology

Background:

• Foreign body reactions commonly occur around implanted alginate-polylysine microcapsules.
• Complement activation is a potential contributor to these foreign body reactions.

Purpose of the Study:

• To investigate the in vitro capacity of empty alginate-polylysine microcapsules to activate the complement system.
• To assess the protective effect of the microcapsule membrane against complement-mediated cytotoxicity.

Main Methods:

• Incubation of human serum with alginate-polylysine microcapsules.
• Evaluation of complement activation using complement hemolytic activity (CH50) assays.
• Measurement of C3adesArg fragment levels to confirm complement activation.
• Testing microcapsule membrane protection using sensitized sheep erythrocytes and activated complement.

Main Results:

• Alginate-polylysine microcapsules induced complement activation, indicated by decreased CH50 and elevated C3adesArg levels.
• C3adesArg fragments adsorbed to the microcapsule membrane.
• No hemolysis was observed when encapsulated erythrocytes were exposed to activated complement, demonstrating membrane protection.

Conclusions:

• Alginate-polylysine microcapsules activate the complement system.
• The microcapsule membrane provides a protective barrier against complement-mediated cell damage.
• The complement-activating potential of these microcapsules must be considered for their application as biomedical implants.