Independent Roles of Molecular Mobility and Zeta Potential on Supramolecular Surfaces in the Sequence of RAW264.7 Macrophage Responses.

Surface properties of biomaterials affect the morphologies and inflammatory responses of macrophages. Recently, biomaterial design utilizing these properties has been explored to build a scaffold for balancing the immune system in vivo. In the present study, polyrotaxane surfaces with different functional groups including methyl, amino, and sulfo groups are utilized to clarify the effect of molecular mobility and zeta potential of these surfaces on RAW264.7 macrophage responses. At 24 h post-seeding, the majority of the cells adhere onto each surface, and the initial spreading is suppressed by more negatively-charged polyrotaxane surfaces. From 24 to 48 h of incubation, the spreading areas on the unmodified and methylated surfaces significantly increase, whereas those on the aminated and sulfonated surfaces remain unchanged. These results suggest that the initially cellular spreading process depends on the zeta potential, while the subsequent spreading process is governed by the molecular mobility. After lipopolysaccharide stimulation, the less mobile surfaces induce higher expression of inflammation-related genes than highly mobile surfaces, suggesting that molecular mobility is the main factor modulating the inflammatory activity in macrophages. These findings indicate that the zeta potential and molecular mobility of polyrotaxane surfaces may play independent roles in the sequence of macrophage responses.