Machine parts made of nickel-based alloys usually work in high-temperature service environments such as aircraft turbines. The mechanical properties and antioxidant properties of materials tend to be reduced at high temperatures. Therefore, it is of great practical significance to reveal the wear mechanisms of materials at different temperatures. In the present investigation, the tribological behaviour of an Inconel 718 superalloy at different temperatures was investigated. First, the coefficient of friction curves obtained under different test conditions were analysed in detail to illustrate the dynamic change process of friction at high temperature. Next, the morphology of the wear surface, surface morphology of friction pairs and material transfer during friction were analysed via scanning electron microscopy 3D morphology and energy dispersive spectroscopy measurements to reveal the wear mechanisms of materials in a high-temperature environment. Finally, the microstructure of the cross section of the wear tracks was analysed by using optical microscopy electron back-scattered diffraction etc., to clarify the mechanisms of crack initiation and material removal. The results show that the friction properties of the Inconel 718 superalloy have differences at different test temperatures. Although increasing the test temperature does not necessarily aggravate the wear of the material, the oxidation of the wear surface during the friction process significantly increases. In addition, when the contact load increases, the thickness of the oxide layer and wear of the material simultaneously increase.

Biomaterials employed in the articular joint cavity, such as polycarbonate urethane (PCU) for meniscus replacement, lack of lubrication ability, leading to pain and tissue degradation. We present a nanostructured adhesive coating based on dopamine-modified hyaluronan (HADN) and poly-lysine (PLL), which can reestablish boundary lubrication between the cartilage and biomaterial. Lubrication restoration takes place without the need of exogenous lubricious molecules but through a novel strategy of recruitment of native lubricious molecules present in the surrounding milieu. The biomimetic adhesive coating PLL–HADN (78 nm thickness) shows a high adhesive strength (0.51 MPa) to PCU and a high synovial fluid responsiveness. The quartz crystal microbalance with dissipation monitoring shows the formation of a thick and softer layer when these coatings are brought in contact with the synovial fluid. X-ray photoelectron spectroscopy and ConA-Alexa staining show clear signs of lubricious protein (PRG4) recruitment on the PLL–HADN surface. Effective recruitment of a lubricious protein by PLL–HADN caused it to dissipate only one-third of the frictional energy as compared to bare PCU when rubbed against the cartilage. Histology shows that this reduction makes the PLL–HADN highly chondroprotective, whereas PLL–HA coatings still show signs of cartilage wear. Shear forces in the range of 0.07–0.1 N were able to remove ∼80% of the PRG4 from the PCU–PLL–HA but only 27% from the PCU–PLL–HADN. Thus, in this study, we have shown that surface recruitment and strong adsorption of biomacromolecules from the surrounding milieu is an effective biomaterial lubrication strategy. This opens up new possibilities for lubrication system reconstruction for medical devices.

Osteosarcoma remains a worldwide concern due to the poor effectiveness of available therapies in the clinic. Therefore, it is necessary to find a safe and effective therapy to realize the complete resection of osteosarcoma and reconstruction of the bone defect. Magnetic hyperthermia based on magnetic nanoparticles can kill tumor cells by raising the temperature without causing the side effects of conventional cancer treatments. This research aims to design a high-performance magnetic hydrogel composed of gelatin methacrylate and highly magnetic cobalt ferrite (CFO) nanoparticles for osteosarcoma treatment. Specifically, CFO is surface functionalized with methacrylate groups (MeCFO). The surface modified CFO has good biocompatibility and stable solution dispersion ability. Afterward, MeCFO nanoparticles are incorporated into GelMA to fabricate a three-dimensional (3D) printable MeCFO/GelMA magnetic hydrogel and then photocross-linked by UV radiation. MeCFO/GelMA hydrogel has high porosity and swelling ability, indicating that the hydrogel possesses more space and good hydrophily for cell survival. The rheological results showed that the hydrogel has shear thinning property, which is suitable as a bioprinting ink to produce desired structures by a 3D printer. Furthermore, 50 μg/mL MeCFO not only decreases the cell activity of osteosarcoma cells but also promotes the osteogenic differentiation of mBMSCs. The results of the CCK-8 assay and live/dead staining showed that MeCFO/GelMA hydrogel had good cytocompatibility. These results indicated that MeCFO/GelMA hydrogel with potential antitumor and bone reconstruction functions is a promising therapeutic strategy after osteosarcoma resection.