Quantitative measurement of C3 activation at polymer surfaces

Abstract

Abstract Activation of C3 by nylon 6,6 and polymethyl methacrylate (PMMA) polymers in whole canine serum was investigated using Laurell electroimmunoassay and antigen-antibody crossed immunoelectrophoresis (XAA). Canine sera were utilized because most artificial blood contact materials used in prosthetic devices are tested in dogs. The measurements were made possible by converting the polymers to microparticles, increasing the available surface area to approximately 200,000 sq cm/g. Both polymers activated C3 within a few minutes of serum contact at 39°C, the canine biologic temperature, after which no further development was seen. Nylon activation, studied in detail, increased with increasing surface area up to a saturation level of about 20% conversion reached at approximately 350 sq cm/ml polymer surface/serum volume. At saturation, XAA plates from nylon and control zymosan particles appeared identical. The nylon-induced activation was highly temperature dependent and was inhibited by at least a factor of 5 at 30°C, relative to that at 39°C. Both nylon and zymosan particles aggregated canine platelets in citrated plasma in vitro. Addition of Mg-EGTA inhibited nylon-induced C3 activation and platelet aggregation, but did not affect zymosan-induced C3 activation or platelet aggregation. Rapid activation of C3 by nylon 6,6 and PMMA suggest a role for complement activation at polymer surfaces in the early phase of the blood/surface interaction in the canine model. Results of ex vivo blood flow experiments using these same polymer surfaces are consistent with this hypothesis.