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The service conditions of rubber seals are primarily in the dynamic sliding state, with a high coefficient of friction, which can seriously compromise the equipment’s safety and the services’ lifespan. Diamond-like carbon (DLC) films have been the ideal candidate for tribological modification of rubber surfaces due to their excellent tribological properties over the last two decades. This field can be widely discussed as a hard film on soft substrates, where the challenge is the mismatch of mechanical properties, leading to the exfoliation of DLC films in friction. Early work developed the DLC films with a segment structure to solve this critical issue, illustrating the possibility of wear-resistant rubber. In recent years, researchers have paid attention to further increasing the coated rubber’s lifetime in friction, focusing on adhesion. These research achievements were reviewed on the aspects of structurization, adhesion, and doping in this article. It proposed an alternative direction of understanding the surface wear mechanism for designing wear-resistant DLC films on rubber.

Nanomaterials with unique nanotube arrays have attracted extensive attention in the field of blood-contacting biomaterials. In this study, the regular titanium dioxide nanotube arrays were first prepared on the pure titanium surface by anodic oxidation. Subsequently, copper ions (Cu2+) and strontium ions (Sr2+) were incorporated into the nanotubes by the chelation of dopamine to improve biocompatibility. The as-prepared TiO2 nanotubes had an inner diameter of about 60 nm and an outer diameter of 90–110 nm, as well as a tube length of 4–6 µm. The following annealing treatment and the incorporation of Cu2+ and Sr2+ had little effect on the morphology and dimensions of the nanotubes, but can significantly improve the hydrophilicity, and promote the adsorption of bovine serum albumin concurrently inhibit the adsorption of fibrinogen, showing the effect of selective protein adsorption. At the same time, loading Cu2+ and Sr2+ can also effectively inhibit platelet adhesion and activation, promote endothelial cell growth, and upregulate the expression of vascular endothelial growth factor and nitric oxide. Therefore, the results of this study showed that the incorporation of Cu2+ and Sr2+ into the TiO2 nanotubes can simultaneously improve the hemocompatibility and cytocompatibility of endothelial cells, which can enlarge the application of titanium-based biomaterials in cardiovascular devices such as a stent.

As biodegradable orthopedic implant materials, magnesium alloys have been attracted enough attentions recently. However, too fast degradation in vivo, limited biocompatibilities, and insufficient antibacterial properties are three main challenges at present. In order to solve these problems, a multifunctional composite coating of Chi(Zn/BMP2)/HA was constructed on AZ31B magnesium alloy surface, successively by the alkali heating treatment, self-assembly of 16-phosphonyl-hexadecanoic acid, in situ immobilization of Chi(Zn/BMP2) (chitosan, zinc ions, and bone morphogenetic protein 2), and the deposition of HA (hydroxyapatite). The results of ATR-FTIR (attenuated total reflection Fourier transform infrared spectrum) spectra and elemental compositions confirmed that 16-phosphonyl-hexadecanoic acid, Chi(Zn/BMP2), and HA were successfully immobilized on the surface. Compared with Mg, Mg-OH, Mg-16, and Mg-Chi(Zn/BMP2), Mg-Chi(Zn/BMP2)/HA with the concave–convex structure surface significantly enhanced the hydrophilicity and corrosion resistance. On the other hand, Mg-Chi(Zn/BMP2)/HA coating also showed excellent biocompatibilities, which not only significantly promoted the osteoblast adhesion and proliferation, but also upregulated ALP and OCN expression of osteoblasts. Furthermore, due to the synergistic antibacterial effect of zinc ions and chitosan, Mg-Chi(Zn/BMP2)/HA showed a good antibacterial property against Escherichia coli (E. coli). Therefore, it can be said that the method used in this work has a good application prospect in improving the corrosion resistance, biocompatibility of magnesium alloys, and inhibiting infections against E. coli.

In this study, inspired by the adhesion protein of mussels, a Zn2+-loaded polydopamine (PDA/Zn2+) coating was prepared on an alkali–heat-treated magnesium alloy surface, through the chelating effect of PDA with metal ions, to improve anticorrosion and biocompatibility. The results of water contact angles show that the PDA/Zn2+ coatings with different Zn2+ contents had excellent wettability, which contributed to the selective promotion of the albumin adsorption. The corrosion degradation behaviors of the modified magnesium alloys were characterized using potentiodynamic scanning polarization curves, electrochemical impedance spectroscopy (EIS), and an immersion test, the results indicate that anticorrosion was significantly improved with the increase of Zn2+ content in the coating. Meanwhile, the PDA/Zn2+ coatings with different Zn2+ concentrations demonstrated improved hemocompatibility, confirmed by assays of the hemolysis rate and platelet adhesion behaviors. In addition, the results regarding the growth behaviors of endothelial cells (ECs) suggest that, due to the sustained release of Zn2+ from the coatings, the modified magnesium alloys could enhance the adhesion, proliferation, and upregulated expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in endothelial cells, and that better cytocompatibility to ECs could be achieved as the Zn2+ concentration increased. Therefore, the PDA/Zn2+ coatings developed in this study could be utilized to modify magnesium alloy surfaces, to simultaneously impart better anticorrosion, hemocompatibility, and endothelialization. [ABSTRACT FROM AUTHOR]