Anthropogenic activities like chemical industries are releasing chlorinated species, such as perchlorate (ClO4-) or chlorite (ClO2-), into the environment. These substances are toxic and difficult to treat in the wastewater. However, nature offers a way to solve this problem. Perchlorate-respiring bacteria possess an enzyme, namely called Chlorite dismutase (Cld). It can detoxify chlorite (ClO2-) - a by-product of the perchlorate respiration - to chloride (Cl-) and molecular oxygen (O2). Therefore, it is interesting to characterise Clds in more detail to resolve its reaction mechanism and to investigate its potential for wastewater treatment. This work presents new and direct evidence for transient high valent heme species during the reaction mechanism of an interesting enzyme, which can be applied for the bioremediation of chlorite.

Water addition reactions to (un)-activated double bonds are very rewarding reactions as they elegantly introduce a hydroxyl-group thereby often adding value to the generated product by establishing a novel stereocentre in tertiary, chiral alcohols. However, performing selective water addition reactions is an extremely challenging task using classical, chemical approaches. Next to overall unfavourable reaction equilibria, the unreactive water molecule is a poor nucleophile and therefore requires activation. Furthermore, due to its small size, a controlled, stereo- and regioselective addition is difficult to achieve. Consequently, establishing straightforward processes with a preferably high selectivity under reaction conditions as environmentally benign as possible is of high interest to both industry and academia...@en

Iron deficiency is considered the most significant nutritional deficiency worldwide, affecting billions of people. Iron deficiency leads to a higher prevalence of iron deficiency anaemia; a condition responsible for over 50,000 deaths annually. Since anaemia is considered a global health problem, various countermeasures have been implemented to battle this disease. One of these countermeasures is the supplementation of iron. Different iron compounds are employed for supplementation, including ferrous sulphate and ferrous fumarate. However, since only 15% of the supplemented iron is absorbed by the human body, the remaining 85% can cause various health-related issues. Due to heightened amounts of iron present in the duodenum, a disbalance in the human gut is induced, leading to e.g. excessive growth of Escherichia coli (E.coli). This study investigates the influence of 3 and 30 µM iron supplementation of ferric chloride and ferric sulphate; radiolabelled with Fe-55. These results have been reported in the form of growth curves, and the remaining amount of Fe-55 in the growth medium has been used to estimate iron uptakeby E.coli. No significant differences were observed between 3 and 30 µM iron supplementation of both compounds, indicating that iron concentration may not be considered as the main limiting growth factor of E.coli. Therefore, further research is recommended where the medium is analysed for the presence of other nutrients. Additionally, adjustments in the growth environment are recommended, to determine which growth conditions influence E.coli the most.

The use of material properties to guide cell behaviour is often utilised in the field of regenerative medicine. Regarding this, surface topography has been shown to control different cellular processes. In nature, topographies exist in a wide variety of shapes, including hierarchical structures with a great degree of surface roughness. Here, inspired by nature, the potential of such surface characteristics in guiding cell behaviour was investigated via replication of 32 natural surfaces onto polystyrene using hot embossing techniques. Fluorescent image analysis of bone marrow-derived human mesenchymal stem cells cultured on these surfaces showed that cell shape was greatly affected by the distinct topographical features compared to a flat surface. Cluster analysis identified groups showing similar effect on nuclear and cell morphological parameter such as size, orientation and compactness. Related to this, focal adhesion formation and organisation was highly dependent on surface topography. Namely, focal adhesion maturation was promoted on the natural topographies. Furthermore, mouse embryonic stem cell pluripotency and colony morphology was influenced by natural topographies. Finally, natural topographies modulated in vitro mesenchymal stem cell differentiation. This study shows the capability of natural topographies to regulate cell behaviour useful for regenerative applications.

BACKGROUND.Implant-associated infection (IAI) is a rising complication in bone-related medical treatments using metal implants. Preventive measures, such as implant surfaces with integrated antibacterial properties, are hence required. The emergence of antibiotic-resistant pathogens has led to a growing interest in inorganic nanoparticles as antibacterial agents. In addition, implants should simultaneously stimulate bone tissue regeneration and integration to improve implant longevity. Additive manufacturing (AM) of orthopedic implants has attracted interest as improved bone tissue regeneration and integration was demonstrated by AM porous implants. AM porous implants, however, are at enhanced risks of IAIs; these porous implants require integrated antibacterial properties. This study focused on a systematic comparison of the antibacterial properties of AM porous Ti6Al4V implant surfaces with silver nanoparticles (Ag NPs), copper nanoparticles (Cu NPs) and/or zinc nanoparticles (Zn NPs) against methicillin resistant Staphylococcus aureus (MRSA). METHODS.Medical grade porous Ti6Al4V implants were additively manufactured using selective laser melting (SLM). Subsequently, the SLM Ti6Al4V implants were biofunctionalized by plasma electrolytic oxidation (PEO) using an electrolyte that consisted of Ca/P-based species and ratios of Ag NPs, Cu NPs and/or Zn NPs. Implants with 0, 25, 75 and 100% of Ag NPs, Cu NPs and/or Zn NPs were synthesized. After biofunctionalization, the surface morphology, structure and chemistry of the implants were investigated using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The antibacterial properties of the implants against MRSA were studied in vitro as well as ex vivo. The leachable antibacterial activity was studied in an agar diffusion assay, the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of Ag+, Cu2+ and Zn2+ ions was determined by a micro-dilution assay and the bactericidal activity of the implants was quantified by a colony-forming unit (CFU) count in vitro against surface-adherent and non-adherent MRSA. Furthermore, ex vivo antibacterial properties were determined using a femoral murine infection model mimicking the in vivo environment. RESULTS.Biofunctionalization of the porous SLM Ti6Al4V implants by PEO resulted in a uniform and homogeneous micro-/nano-porous oxide layer that covered the entire surface of the implants. SEM and EDS analysis demonstrated the presence of Ag NPs, Cu NPs and Zn NPs in the TiO2 surface layer. The agar diffusion assay demonstrated a strong leachable antibacterial activity for the implants with Ag NPs and Cu NPs or Zn NPs, while no leachable antibacterial activity was observed for implants without Ag NPs. Antibacterial testing showed that Ag+, Cu2+ and Zn2+ ions, as well the combinations of the ions, were growth inhibitory and bactericidal to MRSA. In addition, implants with ≥ 50% of Ag NPs and combinations of ≥ 75% of Ag NPs and Cu NPs or Zn NPs, fully eradicated surface-adherent and non-adherent MRSA within 24 h and prevented biofilm formation up to 24 h. Moreover, strong ex vivo bactericidal properties against MRSA were demonstrated for these implants within 24 h. CONCLUSION. Biofunctionalized surfaces with Ag NPs and Cu NPs or Zn NPs on porous SLM Ti6Al4V implants showed strong in vitro and ex vivo antibacterial properties against MRSA. The implants with 50% of Ag NPs and combinations of 75% of Ag NPs and 25% of Cu NPs or Zn NPs are promising for further development, to prevent IAIs and improve the longevity of the implants in clinical applications.