Implants of materials that are typically considered inert have been shown to cause early inflammatory complications. In addition, implant wear products may also cause overproduction of proinflammatory cytokines in the long run. Among the cytokines is tumor necrosis factor alpha (TNFα), which not only participates in the inflammatory response but also in the degradation of the bone. Therefore, a lack of production of TNFα by the cells of the immune system in contact with a candidate material for implant design is an indication of the acceptance of the biomaterial, and predicts the inflammatory response responsible for implant intolerance. There is no standard laboratory test to evaluate an individual response of a patient to a possible implant, although the use of peripheral blood mononuclear cells (PBMCs) has been suggested. Here, we evaluated the biocompatibility and cytotoxicity of films made of polyhydroxybutyrate (PHB) reinforced with different concentrations of cellulose nanowhiskers (CNWs) using PBMCs from healthy donors. Cells from healthy donors were cultured in the presence of films of the biomaterial during 24 h and 7 d and the cell viability and proinflammatory cytokines TNFα and IL6 production were measured. We confirmed that PHB, CNWs and the reinforced blends (PHB/CNWs) are safe and lack cytotoxicity in human cells, which make them good candidates for implant materials.

Poly-R-hydroxyalkanoates (PHAs) are polymers produced by a vast number of bacterial species under stress conditions. PHAs exhibit different thermal and mechanical properties that depend on their molecular structure. In this work, PHAs were produced using avocado oil as the carbon source. Cupriavidus necator H16 was cultured in three-stage fermentation using fructose during the cell growth stages and avocado oil during the PHA synthesis stage. Different concentrations of avocado oil were used during the third stage to test the incorporation of various monomeric units into the PHAs. Biomass and PHA production were measured during the fermentation. DSC, FTIR, and gas chromatography analysis aided the PHA characterization. Different proportions of 3-hydroxyvalerate were present in the 3-hydroxybutyrate main chain depending on the concentration of avocado oil. The results suggest that avocado oil is a viable new substrate for PHA production.

This paper aims at encouraging the use of laser treatment as an environmentally friendly technique to improve the mechanical properties of metallic materials over conventional quenching and tempering techniques through the study of the tribological behavior of AISI 1538 MV steel subjected to surface laser quenching treatment. Sliding wear tests were carried out by the pin-on-disk method. In order to identify the wear mechanisms, the worn surfaces on the disks were evaluated by scanning electron microscopy and the wear scars on the ball were observed by optical microscopy. Results reveal that laser treatment reduces the average friction coefficient by 25% and the wear rate by 60% compared with those achieved by the conventional methods, while the depths of the wear track and hardness of the cross section and surface are maintained.

Simulations of impact events in the automotive industry are now common practice. Vehicle crashworthiness simulations on plastic components cover a wide range of strain rates from 0.01 to 500 s-1. Because plastics mechanical properties are very dependent on strain rate, developing experimental methods for generating stress-strain curves at this strain rate range is of great technological importance. In this paper, a modified Charpy machine capable of acquiring useful information to obtain the stress-strain curve is presented. Strain rates between 300 to 400 s-1 were achieved. Three thermoplastics were tested: high-density polyethylene, polypropylene-copolymer and polypropylene-homopolymer. Impact simulations using LS-DYNA were performed using the acquired high-strain rates stress-strain curves and compared with experimental data. Simulations using stress-strain curves from quasi-static tests were also performed for comparison. Very good agreement between the simulation and experimental results was found when the ASTM D1822 type S specimen was used for testing each material.