Ultrahigh Molecular Weight Polyethylene/Graphene Oxide Nanocomposites: Wear characterization and Biological Response to wear particles

In the field of total joint replacements, polymer nanocomposites are being investigated as alternatives to ultra high molecular weight polyethylene (UHMWPE) for acetabular cup bearings. The objective of the present study was to investigate the wear performance and biocompatibility of UHMWPE/graphene oxide (GO) nanocomposites. This study revealed that low concentrations of GO nanoparticles (0.5 wt%) do not significantly alter the wear performance of UHMWPE. In contrast, the addition of higher concentrations (2 wt%) led to a significant reduction in wear. In terms of biocompatibility, UHMWPE/GO wear particles did not show any adverse effects on L929 fibroblast and PBMNC viability at any of the concentrations tested over time. Moreover, the addition of GO to a UHMWPE matrix did not significantly affect the inflammatory response to wear particles. Further work is required to optimise the manufacturing processes to improve the mechanical properties of the nanocomposites and additional biocompatibility testing should be performed to understand the potential clinical application of these materials

Advanced ultra-high molecular weight polyethylene/antioxidant-functionalized carbon nanotubes nanocomposites with improved thermo-oxidative resistance

Multiwalled carbon nanotubes (CNTs) functionalized with hindered phenol moieties are dispersed in ultra-high molecular weight polyethylene (UHMWPE), and the stabilizing action of the antioxidant (AO) functionalized CNTs (AO-f-CNTs) is studied through a combination of rheological and spectroscopic (FT-IR) analyses. The effectiveness of two alternative compounding methods, namely hot compaction (HC) and melt mixing (MM), is compared. The combination of high temperature and mechanical stress experienced during MM brings about noticeable degradation phenomena of the matrix already in the course of the compounding step. Differently, the milder conditions of the HC process preserve the stability of the polymer, making this method preferable when dealing with highly viscous matrices. In addition, HC guarantees a better CNT dispersion, allowing for the maximization of the stabilizing action of the AO grafted on the nanotubes. As a result, the HC samples exhibit improved thermo-oxidative resistance despite the very low amount of AO grafted onto the CNTs. Besides demonstrating the effectiveness of our AO-f-CNTs as stabilizers for polymer matrices, our results prove that CNTs can serve as a support on which grafting specific functional molecules to be dispersed in a host polymer matri

Mechanical behavior, microstructure and thermooxidation properties of sequentially crosslinked ultrahigh molecular weight polyethylenes

The aim of this study was to explore the impact of the sequential irradiation and annealing process on the microstructure, thermooxidation behavior and mechanical properties of GUR 1050 ultrahigh molecular weight polyethylene (UHMWPE) with respect to the postirradiation annealed material. For this purpose, the effects of a variety of irradiation and annealing conditions on microstructure and mechanical properties were investigated. Differential scanning calorimetry was performed to characterize melting temperature, crystalline content and crystal thickness, whereas transmission electron microscopy provided additional insights into crystal morphology. Thermogravimetric experiments in air served to assess thermooxidation resistance and changes associated to radiation-induced crosslinking. Fatigue properties were studied from three different approaches, namely short-term cyclic stress–strain tests, long-term fatigue experiments and crack propagation behavior. Likewise, three experimental techniques (uniaxial tensile test, impact experiments, and load to fracture of compact tension specimens) allowed evaluation of the fracture resistance. The present findings confirm sequentially crosslinked UHMWPE exhibited improved thermooxidation resistance and thermal stability compared to post-irradiation annealed UHMWPE. Also, the mechanical behavior, including the fatigue and fracture resistance, of these materials was generally comparable regardless of the annealing strategy. Therefore, the sequential irradiation and annealing process might provide higher oxidation resistance, but not a significant improvement in mechanical properties compared to the single radiation dose and subsequent annealing procedure.Research funded by the Comisi on Interministerial de Ciencia y Tecnología (CICYT), Spain. Project: MAT 2006-12603-C02-01.Peer reviewe

Sulfonated polysulfone/tio2(B) nanowires composite membranes as polymer electrolytes in fuel cells

New proton conducting membranes based on sulfonated polysulfone (sPSU) reinforced with TiO(B) nanowires (1, 2, 5 and 10 wt.%) were synthesized and characterized. TiO(B) nanowires were synthesized by means of a hydrothermal method by mixing TiO precursor in aqueous solution of NaOH as solvent. The presence of the TiO(B) nanowires into the polymer were confirmed by means of Field Emission Scanning Electron Microscopy, Fourier transform infrared and X-ray diffraction. The thermal study showed an increase of almost 20 °C in the maximum temperature of sPSU backbone decomposition due to the presence of 10 wt.% TiO(B) nanowires. Water uptake also is improved with the presence of hydrophilic TiO(B) nanowires. Proton conductivity of sPSU with 10 wt.% TiO(B) nanowires was 21 mS cm (at 85 °C and 100% RH). Under these experimental conditions the power density was 350 mW cm similar to the value obtained for Nafion 117. Considering all these obtained results, the composite membrane doped with 10 wt.% TiO(B) nanowires is a promising candidate as proton exchange electrolyte in fuel cells (PEMFCs), especially those operating at high temperatures.The authors would like to thank the following Institution for funding the Projects: Agencia Española de Investigación /Fondo Europeo de Desarrollo Regional (FEDER/UE): Projects PID2019-106662RBC43 and MAT2016-78362-C4-3-R. Comunidad de Madrid: Projects “Excelencia para el Profesorado Universitario”—EPUC3M04) and PEM4ENERGY-CM-UC

Genotype-Phenotype Correlation in Hypertrophic Cardiomyopathy: New Variant p.Arg652Lys in MYH7

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterised by increased left ventricle (LV) wall thickness caused by mutations in sarcomeric genes. Finding a causal mutation can help to better assess the proband’s risk, as it allows the presence of the mutation to be evaluated in relatives and the follow-up to be focused on carriers. We performed an observational study of patients with HCM due to the novel p.Arg652Lys variant in the MYH7 gene. Eight families and 59 patients are described in the follow-up for a median of 63 months, among whom 39 (66%) carry the variant. Twenty-five (64%) of carriers developed HCM. A median maximum LV wall thickness of 16.5 mm was described. The LV hypertrophy was asymmetric septal in 75% of cases, with LV outflow tract obstruction in 28%. The incidence of a composite of serious adverse cardiovascular events (sudden death, aborted sudden death, appropriate implantable cardiac defibrillator discharge, an embolic event, or admission for heart failure) was observed in five (20%) patients. Given the finding of the p.Arg652Lys variant in patients with HCM, but not in controls, with evident segregation in patients with HCM from eight families and the location in an active site of the protein, we can define this variant as likely pathogenic and associated with the development of HCM