Complement activation profile of a phosphorylcholine-containing zwitterionic polymer in CRP-containing serum

Phosphorylcholine (PC)-containing polymers are widely used as biomimetic materials because of their favorable blood compatibility and resistance to nonspecific protein adsorption. Poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC), one of the most extensively studied PC-containing polymers, has been applied to a variety of blood-contacting biomaterials. Although C-reactive protein (CRP), an acute-phase inflammatory protein, is known to interact with PC-containing structures and can activate the classical complement pathway through C1q recruitment, whether PC-containing polymers induce complement activation under inflammatory conditions remains unclear. In this study, complement activation induced by PMPC was evaluated using CRP-spiked human serum to examine whether elevated CRP levels alter the complement activation profile of PC-containing polymers. Poly(sulfobetaine methacrylate) (PSBMA) and phospholipid liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and lysophosphatidylcholine (LPC) were employed as reference materials. Complement activation was quantified by measuring the concentrations of C3a and soluble C5b-9 (sC5b-9), representing intermediate and terminal products of the complement cascade, respectively. PMPC did not induce significant increases in either C3a or sC5b-9 compared with control conditions. Similarly low complement activation was observed for PSBMA. In contrast, LPC-containing liposomes promoted substantial complement activation in CRP-spiked serum, resulting in elevated levels of both markers. These findings suggest that the presence of phosphorylcholine moieties within a polymeric architecture is not necessarily sufficient to trigger complement activation and that the molecular presentation of PC groups influences downstream complement responses. This study provides new insight into the immunological behavior of PC-containing polymer biomaterials and supports the development of PMPC-based biointerfaces with improved immunocompatibility.