Adsorption-associated orientational changes of immunoglobulin G and regulated phagocytosis of Staphylococcus epidermidis.

Understanding the adsorption of immunoglobulin G (IgG) on biomaterials surfaces is crucial for design and modification of the surfaces to alleviate inflammatory responses after implantation. Here, we report direct visualization and two-dimensional (2D) image interpretation of the IgG molecule adsorbed on simplified surfaces by single particle electron microscopy and atomic force microscopy. Influence of the orientational changes in adsorbed IgG on phagocytosis of macrophages against Staphylococcus epidermidis is further examined. Untreated amorphous carbon film and -COOH and -NH2 grafted carbon films are employed as the model surfaces for the adsorption testing. Results show that IgG displays flat orientation lying on the untreated surface, while forms vertical orientations standing on the functionalized surfaces. These specific spatial alignments are associated with altered unfolding extent and structure rearrangement of IgG domains, which are influenced synergistically by surface charge and wettability of the substrata. The changes in interdomain distance of IgG molecules subsequently regulate immune behaviors of macrophages and phagocytosis of S. epidermidis. The results would give insight into appropriate design of biomaterial surfaces in nanoscales for desired inflammatory responses. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2838-2849, 2018.