Effect of synovial fluid temperature on wear resistance of different polymer acetabular materials.

In order to investigate the effect of frictional heat on the wear resistance characteristics of polymeric acetabular materials, the tribological tests and wear numerical analysis of three common polymer acetabular materials were carried out under different synovial fluid temperatures. The study results show that XLPE and VE-XLPE exhibit superior wear resistance compared to UHMWPE in high-temperature, heavy load environments. The coefficient of friction of three materials gradually decreases as the temperature of the synovial fluid increases. The wear depth and wear volume of the three materials increased with the increase of the temperature of the synovial fluid, and the forms of wear at 46°C and 55°C were mainly adhesive wear and plastic deformation. The higher temperature of the synovial fluid accelerates the oxidative degradation of the material surface and generates oxidation functional groups, which leads to the breakage of C-C bonds in the surface molecular chains under the sliding shear effect, thus reducing the mechanical properties of the material. Specifically, the surface of the polymer material will soften at a higher ambient temperature, mainly due to the decrease of hardness, and then deteriorate in the friction property, and finally increase the wear rate. Ansys results showed that the volume wear of the three materials increased with the increase of synovial fluid temperature, and the trend could be approximately linear. Numerical calculations predict that VE-XLPE has the highest wear of 0.693 mm3 among the three materials at 37°C, followed by XLPE at 0.568 mm3 and UHMWPE with the lowest wear of 0.478 mm3. At higher synovial fluid temperatures (46°C, 55°C), VE-XLPE still has the largest wear volume among the three materials, while XLPE and UHMWPE have similar wear. The wear cloud pictures showed that the maximum wear volume occurred near the edge of the acetabulum.

Reduced graphene oxide-GelMA-PCL hybrid nanofibers for peripheral nerve regeneration.

Graphene oxide is currently used in peripheral nerve engineering but has certain limitations, such as cytotoxicity and lack of electrical conductivity, both of which are crucial in regulating nerve-associated cell behaviors. In this work, we engineered reduced graphene oxide-GelMA-PCL nanofiber nerve guidance conduits via electrospinning. rGO incorporated into the GelMA/PCL matrix significantly enhanced the electrical conductivity and biocompatibility of the hybrid materials. In addition, hybrid nanofibers with low concentrations of rGO (0.25 and 0.5 wt%) could significantly improve the proliferation of Schwann cells (RSC96). More importantly, rGO/GelMA/PCL hybrid nanofibers could activate the epithelial-mesenchymal transition (EMT)-related gene expression of Schwann cells (RSC96). From the in vivo study, it was observed that rGO/GelMA/PCL nerve guidance conduits could promote both sensory/motor nerve regeneration and functional recovery in rats. Our composite strategy of combining rGO within a biocompatible nanofiber scaffold is simple but effective in improving tissue engineering outcomes. The rGO/GelMA/PCL hybrid nanofibers have great potential in peripheral nerve tissue engineering. They will also provide an experimental basis for the development of further electrical stimulation in peripheral nerve regeneration.

Expanded 3D nanofibre sponge scaffolds by gas-foaming technique enhance peripheral nerve regeneration.

Peripheral nerve injury has troubled clinical doctors for many years. To obtain better function recovery of peripheral nerve repair at the base of hollow nerve guidance conduit (NGC), many NGCs with fillers were developed in the application of tissue-engineered nerve graft. In this study, expanded 3D nanofibre sponge scaffolds with orientation and porosity were first fabricated by electrospinning and gas-foaming technique. Polylactic acid (PLA)/silk fibroin nanofibre sponge scaffolds were prepared as filler to construct 3D nanofibre sponges containing NGC (SNGC). SNGC could promote the proliferation of Schwann cells compared with the hollow NGC in vitro. The results of animal experiments confirm that SNGC can significantly promote peripheral nerve function recovery from histology and function evaluation. In conclusion, we design a new method to construct a 3D scaffold containing NGC with orientation and porosity. The application of this 3D scaffold material has good prospects in future peripheral nerve repair.

Mechanism research on a bioactive resveratrol- PLA-gelatin porous nano-scaffold in promoting the repair of cartilage defect.

BACKGROUND: Articular cartilage defects are difficult to treat, but drug-loaded tissue engineering scaffolds provide a possible treatment option for these types of injuries. PURPOSE: In this study, we designed a bioactive resveratrol-PLA-gelatin porous nano-scaffold using electrospinning, freeze drying, and uniform dispersion techniques to repair articular cartilage defects, and then investigated the possible mechanism behind the successful repair. METHODS: We established an articular cartilage defect rat model with a 2 mm diameter wound in the middle of the knee joint femoral condyle non-weight-bearing area, with a depth reaching the full thickness of the subchondral bone. Postmodel specimens and micro computed tomography (CT) were used to observe any macroscopic morphological changes in the articular cartilage and subchondral bone, whereas multiple staining methods were used to observe all microcosmic morphological changes. Gross scores and Mankin scores were used to evaluate the repair condition. Immunohistochemical staining was employed to detect protein expression. RESULTS: When the repair included the resveratrol-PLA-gelatin porous nano-scaffold, the repaired cartilage and subchondral bone were in better condition. The expression levels of SIRT1, type II collagen, and PI3K/AKT signaling pathway-related proteins (AKT, VEGF, PTEN, Caspase 9, and MMP13) changed significantly. The expression levels of SIRT1,AKT and type II collagen proteins increased significantly, while the expression levels of VEGF, PTEN, Caspase9 and MMP13 proteins decreased significantly compared with the repair included blank porous PLA-gelatin nano-scaffold and without scaffold. CONCLUSION: We designed a bioactive resveratrol-PLA-gelatin porous nano-scaffold with better performance, which promoted the repair of cartilage injury as a whole, and explained its possible mechanism in accelerating cartilage repair via the PI3K/AKT signaling pathway.

Layer-by-layer paper-stacking nanofibrous membranes to deliver adipose-derived stem cells for bone regeneration.

Bone tissue engineering through seeding of stem cells in three-dimensional scaffolds has greatly improved bone regeneration technology, which historically has been a constant challenge. In this study, we researched the use of adipose-derived stem cell (ADSC)-laden layer-by-layer paper-stacking polycaprolactone/gelatin electrospinning nanofibrous membranes for bone regeneration. Using this novel paper-stacking method makes oxygen distribution, nutrition, and waste transportation work more efficiently. ADSCs can also secrete multiple growth factors required for osteogenesis. After the characterization of ADSC surface markers CD29, CD90, and CD49d using flow cytometry, we seeded ADSCs on the membranes and found cells differentiated, with significant expression of the osteogenic-related proteins osteopontin, osteocalcin, and osteoprotegerin. During 4 weeks in vitro, the ADSCs cultured on the paper-stacking membranes in the osteogenic medium exhibited the highest osteogenic-related gene expressions. In vivo, the paper-stacking scaffolds were implanted into the rat calvarial defects (5 mm diameter, one defect per parietal bone) for 12 weeks. Investigating with microcomputer tomography, the ADSC-laden paper-stacking membranes showed the most significant bone reconstruction, and from a morphological perspective, this group occupied 90% of the surface area of the defect, produced the highest bone regeneration volume, and showed the highest bone mineral density of 823.06 mg/cm(3). From hematoxylin and eosin and Masson staining, the new bone tissue was most evident in the ADSC-laden scaffold group. Using quantitative polymerase chain reaction analysis from collected tissues, we found that the ADSC-laden paper-stacking membrane group presented the highest osteogenic-related gene expressions of osteocalcin, osteopontin, osteoprotegerin, bone sialoprotein, runt-related transcription factor 2, and osterix (two to three times higher than the control group, and 1.5 times higher than the paper-stacking membrane group in all the genes). It is proposed that ADSC-laden layer-by-layer paper-stacking scaffolds could be used as a way of promoting bone defect treatment.