Biosurface and Biotribology最新文献

Inspired by the excellent wear resistance and lubrication of articular joints, a novel bionic interfacial system was proposed by combining thixotropic hydrogel with surface porous Ultrahigh Molecular Weight Polyethylene (UHMWPE). Thixotropic hydrogel, synthesised by gelatin, alginate sodium, tannic acid and weak crosslinking by Ca²⁺ (Gel-TA-Alg@Ca²⁺), was used as a lubricant due to its shear-thinning when loaded, then the recovery viscosity to be benefitted for reserving in surface pores on UHMWPE when unloaded. Surface porous UHMWPE was fabricated by using hydroxyapatite particles as porogen to control its porosity, pore size, surface roughness and surface energy (PE-HA). Gel-TA-Alg@Ca²⁺ significantly reduced average coefficients of friction and wear factors compared to those under normal saline and calf serum solution lubricating after reciprocating tribological testing. Notably, Gel-TA-Alg@Ca²⁺ still maintained thixotropy and was stored in surface pores of UHMWPE even after tribological testing for 7200 min. Thus, durable lubrication could be realised due to the synergistic effect of surface porous structure and thixotropy. Stribeck curves showed the characterisations of mixed, elastohydrodynamic and hydrodynamic, but without boundary lubrications for PE-30HA under three lubricants. The present results might provide the potential application to construct the durable lubrication bionic articular joint interfacial system for artificial joints.

Experimental in vitro simulation can be used to predict the wear performance of total knee replacements. The in vitro simulation should aim to replicate the in vivo loading, motion and environment experienced by the joint, predicting wear and potential failure whilst minimising test artefacts. Experimental wear simulation can be sensitive to environmental conditions; the environment temperature is one variable which should be controlled and was the focus of this investigation. In this study, the wear of an all-polymer (PEEK-OPTIMA™ polymer-on-UHMWPE) total knee replacement and a conventional cobalt chrome-on-UHMWPE implant of similar initial surface topography and geometry were investigated under elevated temperature conditions. The wear was compared to a previous study of the same implants under simulator running temperature (i.e. without heating the test environment). Under elevated temperature conditions, the wear rate of the UHMWPE tibial inserts was low against both femoral component materials (mean <2 mm³/million cycles) and significantly lower (p < 0.05) than for investigations at simulator running temperature. Protein precipitation from the lubricant onto the component articulating surfaces is a possible explanation for the lower wear. This study highlights the need to understand the influence of different variables including environmental temperature to minimise the test artefacts during wear simulation which may affect the wear rates.

The authors previously developed a scaffold-free tissue-engineered construct (TEC) from mesenchymal stem cells (MSCs). Although the TEC exhibited even cell distribution and was successfully applied for cartilage repair in animal models, it is unsuitable for relatively large-scale cartilage defects due to its small size. To solve the problem, the authors recently developed a novel biomaterial, a centrifugally compressed cell-collagen combined construct (C⁶) from a mixture of MSCs and atelocollagen, both of which are subjected to centrifugation. The results of the previous study indicated that C⁶ exhibited high cell viability (70 %) and sufficient cell distribution similar to that of the TEC. In the present study, the morphology and gene expression of C⁶ were investigated. Histological examination indicated that C⁶ is six times thicker (approximately 1 mm) than the TEC after a 7-day culture. The C⁶ remained unchanged in scale with increased cell density after a 21-day culture. Scanning electron microscopic observation indicated that C⁶ exhibited interconnected and porous microstructures, while the TEC had close-knit microstructures. Reverse transcriptase-polymerase chain reaction analysis indicated that the expression of sex-determining region Y-box 9 and runt-related transcription factor 2 was significantly higher in C⁶ than that in TEC.