Material surfaces that provide biomimetic cues, such as nanoscale architectures, have been shown to alter cell/biomaterial interactions. Recent studies have identified titania nanotube arrays as strong candidates for use in interfaces on implantable devices due to their ability to elicit improved cellular functionality. However, limited information exists regarding the immune response of nanotube arrays. Thus, in this study, we have investigated the short- and long-term immune cell reaction of titania nanotube arrays. Whole blood lysate (containing leukocytes, thrombocytes and trace amounts of erythrocytes), isolated from human blood, were cultured on titania nanotube arrays and biomedical grade titanium (as a control) for 2 hours and 2 and 7 days. In order to determine the in vitro immune response on titania nanotube arrays, immune cell functionality was evaluated by cellular viability, adhesion, proliferation, morphology, cytokine/chemokine expression, with and without lipopolysaccharide (LPS), and nitric oxide release. The results presented in this study indicate a decrease in short- and long-term monocyte, macrophage and neutrophil functionality on titania nanotube arrays as compared to the control substrate. This work shows a reduced stimulation of the immune response on titania nanotube arrays, identifying this specific nanoarchitecture as a potentially optimal interface for implantable biomedical devices.

Due to its great amount of microstructure and property possibilities as well as its high thermodynamic stability and superior mechanical performance, the new class of material known as high-entropy alloys (HEAs) has aroused great interest in the research community over the last two decades. Recent works have investigated the potential for applying this material in several strategical conditions such as high temperature structural devices, hydrogen storage, and biological environments. Concerning the biomedical field, several papers have been recently published with the aim of overcoming the limitations of conventional alloys, such as corrosion, fracture, incompatibility with bone tissue, and bacterial infection. Due to the low number of available literature reviews, the aim of the present work is to consolidate the information related to high-entropy alloys developed for biomedical applications (bioHEAs), mainly focused on their microstructure, mechanical performance, and biocompatibility. Topics such as phases, microstructure, constituent elements, and their effect on microstructure and biocompatibility, hardness, elastic modulus, polarization resistance, and corrosion potential are presented and discussed. The works indicate that HEAs have high potential to act as candidates for complementing the materials available for biomedical applications.

Metallic biomaterials are widely used for implants and dental and orthopedic applications due to their good mechanical properties. Among all these materials, 316L stainless steel has gained special attention, because of its good characteristics as an implantable biomaterial. However, the Young’s modulus of this metal is much higher than that of human bone (~193 GPa compared to 5–30 GPa). Thus, a stress shielding effect can occur, leading the implant to fail. In addition, due to this difference, the bond between implant and surrounding tissue is weak. Already, calcium phosphate ceramics, such as beta-tricalcium phosphate, have shown excellent osteoconductive and osteoinductive properties. However, they present low mechanical strength. For this reason, this study aimed to combine 316L stainless steel with the beta-tricalcium phosphate ceramic (β-TCP), with the objective of improving the steel’s biological performance and the ceramic’s mechanical strength. The 316L stainless steel/β-TCP biocomposites were produced using powder metallurgy and functionally graded materials (FGMs) techniques. Initially, β-TCP was obtained by solid-state reaction using powders of calcium carbonate and calcium phosphate. The forerunner materials were analyzed microstructurally. Pure 316L stainless steel and β-TCP were individually submitted to temperature tests (1000 and 1100 °C) to determine the best condition. Blended compositions used to obtain the FGMs were defined as 20% to 20%. They were homogenized in a high-energy ball mill, uniaxially pressed, sintered and analyzed microstructurally and mechanically. The results indicated that 1100 °C/2 h was the best sintering condition, for both 316L stainless steel and β-TCP. For all individual compositions and the FGM composite, the parameters used for pressing and sintering were appropriate to produce samples with good microstructural and mechanical properties. Wettability and hemocompatibility were also achieved efficiently, with no presence of contaminants. All results indicated that the production of 316L stainless steel/β-TCP FGMs through PM is viable for dental and orthopedic purposes.

The inadequate disposal of household appliances by consumers and industries have annually been generating enormous amounts of polymeric waste (PW). So, the interest in reuse of PW in civil construction has increased. The production of new cementitious materials, such as concrete with PW, proves to be a promising solution to inappropriate disposal of this waste. In this study, self-compacting concrete (SCC) was developed with partial replacement of the coarse aggregates by polymeric waste (PW) from the recycling of refrigerators. In the SCC reference mixture, Portland cement, silica fume, sand, gravel and superplasticizer were used. The study also grouped the gravel as replaced by 5%, 10%, 15% and 20% of PW. In order to analyze the samples, the following tests were used: spreading, viscosity, passing ability, compressive strength, tensile strength, microstructure, modulus of elasticity, specific gravity, absorption, voids index and electrical resistivity. The SCC found showed adequate homogeneity and viscosity, staying within the normative parameters. The mechanical resistance was above 20 MPa; specific mass between 1870 to 2260 kg/m³; modulus of elasticity ranged from 34 to 14 GPa; and electrical resistivity between 319 to 420 ohm.m. Due to the mechanical resistance, the SCC with PW can be used for structural purposes and densely reinforced structures such as pillars, beams and foundation elements.