Cobalt-base alloys (Co-Cr-Mo) are widely employed in dentistry and orthopedic implants due to their biocompatibility, high mechanical strength and wear resistance. The osseointegration of implants can be improved by surface modification techniques. However, complex geometries obtained by additive manufacturing (AM) limits the efficiency of mechanical-based surface modification techniques. Therefore, plasma immersion ion implantation (PIII) is the best alternative, creating nanotopography even in complex structures. In the present study, we report the osseointegration results in three conditions of the additively manufactured Co-Cr-Mo alloy: (i) as-built, (ii) after PIII, and (iii) coated with titanium (Ti) followed by PIII. The metallic samples were designed with a solid half and a porous half to observe the bone ingrowth in different surfaces. Our results revealed that all conditions presented cortical bone formation. The titanium-coated sample exhibited the best biomechanical results, which was attributed to the higher bone ingrowth percentage with almost all medullary canals filled with neoformed bone and the pores of the implant filled and surrounded by bone ingrowth. It was concluded that the metal alloys produced for AM are biocompatible and stimulate bone neoformation, especially when the Co-28Cr-6Mo alloy with a Ti-coated surface, nanostructured and anodized by PIII is used, whose technology has been shown to increase the osseointegration capacity of this implant.

Silver nanoparticle (AgNPs) toxicity is related to nanoparticle interaction with the cell wall of microorganisms and plants. This interaction alters cell wall conformation with increased reactive oxygen species (ROS) in the cell. With the increase of ROS in the cell, the dissolution of zero silver (Ag0) to ionic silver (Ag+) occurs, which is a strong oxidant agent to the cellular wall. AgNP interaction was evaluated by transmission electron microscopy (TEM) on Lactuca sativa roots, and the mechanism of passage through the outer cell wall (OCW) was also proposed. The results suggest that Ag+ binds to the hydroxyls (OH) present in the cellulose structure, thus causing the breakdown of the hydrogen bonds. Changes in cell wall structure facilitate the passage of AgNPs, reaching the plasma membrane. According to the literature, silver nanoparticles with an average diameter of 15 nm are transported across the membrane into the cells by caveolines. This work describes the interaction between AgNPs and the cell wall and proposes a transport model through the outer cell wall.

The advancement of nanotechnology has increased use of nanoparticles in industrial scale. Among the most used nanoparticles are those silver-based. Large-scale use can raise levels of these nanoparticles in aquatic environments, which, in turn, presents potential risks to aquatic organisms and ecosystems, causing undesired environmental impacts. To evaluate the potential risk of the silver nanoparticles (AgNPs) interaction with plants, seeds of Lactuca sativa L. (Asteraceae) were exposed to different concentrations of AgNPs (12.5, 25, 50, 100 ppm), using the percentage of germinated seeds and morphological changes in the root as toxicity criterion. Only at the maximum concentration of AgNPs (100 ppm), there is a negative effect on root growth in relation to the positive control (distilled water). These negative effects may be related to the production of reactive oxygen species (ROS) caused by the dissolution of Ag0 in Ag+. Other concentrations had a positive effect on root growth, although not significant. Scanning electron microscopy (SEM) images showed morphological changes in the root surface exposed to the concentration of 100 ppm of AgNPs, resulting in root deformation. The accumulation of silver nanoparticles (AgNPs) was observed using transmission electron microscopy (TEM). AgNPs were found in the vacuoles, cell wall, middle lamella and cytoplasm, individualised or forming agglomerates. These results broaden our understanding of the safe levels of nanoparticle use and its impact on the environment. In addition, the nanoparticles used in this study can be used in new product development, since the observed maximum safe amount.