The expanding applications of nanotechnology seem to be a response to many technological, environmental, and medical challenges. The unique properties of nanoparticles allow for developing new technologies and therapies. Among many investigated compounds is manganese and its oxides, which in the form of nanoparticles, could be a promising alternative for gadolinium-based contrast agents used in diagnostic imaging. Manganese, which is essential for living organisms as an enzyme cofactor, under excessive exposure—for example, due to water contamination or as an occupational hazard for welders—can lead to neurological disorders, including manganism—a condition similar to Parkinson’s disease. This review attempts to summarise the available literature data on the potential applications of manganese and manganese oxide nanoparticles and their biological activity. Some of the published studies, both in vitro and in vivo, show negative effects of exposure to manganese, mainly on the nervous system, whereas other data suggest that it is possible to develop functionalised nanoparticles with negligible toxicity and novel promising properties.

Public awareness and discussion about animal experiments and replacement methods has greatly increased in recent years. The term ‘the Three Rs’, which stands for the Replacement, Reduction and Refinement of animal experiments, is inseparably linked in this context. A common goal within the Three Rs scientific community is to develop predictive non-animal models and to better integrate all available data from in vitro, in silico and omics technologies into regulatory decision-making processes regarding, for example, the toxicity of chemicals, drugs or food ingredients. In addition, it is a general concern to implement (human) non-animal methods in basic research. Toward these efforts, there has been an ever-increasing number of Three Rs centres and platforms established over recent years — not only to develop novel methods, but also to disseminate knowledge and help to implement the Three Rs principles in policies and education. The adoption of Directive 2010/63/EU on the protection of animals used for scientific purposes gave a strong impetus to the creation of Three Rs initiatives, in the form of centres and platforms. As the first of a series of papers, this article gives an overview of the European Three Rs centres and platforms, and their historical development. The subsequent articles, to be published over the course of ATLA’s 50th Anniversary year, will summarise the current focus and tasks as well as the future and the plans of the Three Rs centres and platforms. The Three Rs centres and platforms are very important points of contact and play an immense role in their respective countries as ‘on the ground’ facilitators of Directive 2010/63/EU. They are also invaluable for the widespread dissemination of information and for promoting implementation of the Three Rs in general.

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Nanoparticles of transition metal dichalcogenides, particularly of molybdenum (Mo), have gained a lot of focus due to their exceptional physicochemical properties and the growing number of technological applications. These nanoparticles are also considered as potential therapeutic tools, biosensors or drug carriers. It is crucial to thoroughly examine their biocompatibility and ensure safe usage. The aim of this review is to analyze the available data on the biological effects of different nanoforms of elemental Mo and its compounds. In the reviewed publications, different conditions were described, including different experimental models, examined nanoforms, and their used concentrations. Due to these differences, the results are rather difficult to compare. Various studies classify Mo related nanomaterials as very toxic, mildly toxic or non-toxic. Similarly, the mechanisms of toxicity proposed in some studies are different, including oxidative stress induction, physical membrane disruption or DNA damage. Quite promising, however, are the potential medical applications of MoS 2 nanoparticles in therapy of cancer and Alzheimer's disease. Further studies on biocompatibility of nanomaterials based on Mo compounds are warranted.