Ferrocene-functionalized polydopamine film timely mediates M1-to-M2 macrophage polarization through adaptive wettability.

Dynamical control of macrophage polarization from M1 (pro-inflammatory) to M2 (anti-inflammatory) at implant surfaces is essential for balancing innate immunity and tissue repair. In this aspect, the design of orthopedic implant that can response to inflammation microenvironment with transformation in surface properties has shown promising in timely driving M1-to-M2 macrophage transition. Considering excessive reactive oxygen species (ROS) contribute to macrophage M1 polarization and progression of inflammation, in this study, ferrocene modified polydopamine (PDA-Fc) films were deposited on plasma sprayed Ti coatings to endow the implants with ROS-responsive and -scavenging abilities. Plasma sprayed Ti (PST) coating and PDA modified PST coating (PST/PDA) served as control. The presence of PDA endowed PST/PDA and PST/PDA-Fc with free-radical scavenging abilities. Moreover, PST/PDA-Fc showed adaptive wettability as evidenced by increased hydrophilicity under HO treatment. With respect to PST/PDA, PST/PDA-Fc exerted greater effects on inducing lipopolysaccharides-induced M1 macrophages to adopt M2-type macrophage phenotype, characterized by higher percentage of CD206-positive cells, increased cell elongation rate and higher expression level of anti-inflammatory cytokine arginase type 1. The results obtained in our study may provide a prospective approach for manipulating an appropriate immune response at implant surfaces.