Preparation and Evaluation of Immunoglobulin Free Sera for Biomaterial-Induced Complement Activation Studies

As the need for and usage of biomaterials in medicine constantly increase, so do the requirements for increased biocompatibility and hemocompatibility. Initially in blood-biomaterial interactions, the surface of an implanted biomaterial is enclosed with adsorbed host proteins and the composition of the adsorbed protein layer depends mainly on the physical-chemical properties of the biomaterial. It is known that the adsorption of proteins on the biomaterial surface may be followed by conformational changes of the adsorbed proteins and subsequent activation of the complement system. For example, binding of complement component C1q to IgG and IgM associated with biomaterial surfaces mediates complement classical pathway activation. The aim of this degree project work was to prepare and evaluate IgG and IgM free sera with functional complement activity for complement activation studies. Further complement studies necessitated IgG and IgM free sera, since two novel polymers with different compositions needed evaluation regarding their ability to induce antibody-independent complement classical pathway activation. Initially, immunoglobulin deficient fetal bovine serum was evaluated regarding complement activity, but no detectable complement activation was present. Different methods for depleting human serum of IgG and IgM were instead utilized and evaluated. From the results, it can be concluded that a close to complete IgG-depletion of human serum is achievable with serum maintaining low but functional complement activity. None of the applied methods for IgM-depletion were however successful and necessitate further optimization and evaluation