The biological effects of engineered nanoparticles are presently a focus of interest in chemistry, biology, pharmacology, clinical medicine, and toxicology due to the enormous therapeutic and diagnostic potential that the particulate nature of nanoparticles offers for selective drug delivery and controlled release. This raises unprecedented safety issues, calling for novel paradigms to face the biocompatibility analysis of particulate (as opposed to molecular) bioactive agents that vary in shape, surface, and charge, in addition to chemical structure. This issue of MRS Bulletin focuses on the bioeffects of metal oxide nanostructures, whose high bioactivity can be exploited to design novel multifunctional devices for nanomedical applications, some of which are already undergoing testing in anticancer and antioxidant clinical trials. The ubiquitous application in research and technology of these non-biodegradable structures has evoked concerns regarding their potential hazards, due to the same chemical activities that promise nanomedical developments. A Janus-type scenario is emerging, pointing to intricate networks of beneficial and detrimental effects following the biological interactions of metal oxide nanoparticles.

Fast and significant progress has been achieved in the development of new biomarkers in recent years providing promising approaches for the reliable detection of diseases at an early stage. Yet, the disadvantages of commonly used markers, including photobleaching, autofluorescence, phototoxicity, and scattering, when ultraviolet or visible light is used for excitation, need to be overcome. Lanthanide-doped host materials are well known for their excellent optical properties, such as their ability to (up)convert near-infrared excitation to higher energies spanning the ultraviolet, visible, and near-infrared regions or to undergo strong near-infrared luminescence following near-infrared excitation. Their application as biomarkers may overcome the aforementioned drawbacks of conventional dyes. Thus, lanthanide-based nanostructures are highly promising candidates for cellular and small animal imaging, while the assessment of their cytotoxicity remains a crucial issue. Recent developments in the field of upconversion and near-infrared bioimaging focusing on some of the latest results obtained in in vitro and in vivo studies assessing the toxicity of lanthanide-based nanophosphors are highlighted in this review.

Neurological pathologies and nerve damage are two problems of significant medical and economic impact because of the hurdles of losing nerve functionality in addition to significant mortality and morbidity, and demanding rehabilitation. There are currently a number of examples of how nanotechnology can provide new solutions for biomedical problems. Current strategies for nerve repair rely on the use of functionalized scaffolds working as “nerve guidance channels” to improve axonal regeneration and to direct axonal re-growth across the nerve lesion site. Since low invasiveness and high selectivity of the growth stimulation are usually conflicting requirements, new approaches are being pursued in order to overcome such limitations. Engineered magnetic nanoparticles (MNPs) have emerged from this need for noninvasive therapies for both positioning and guiding neural cells in response to an external magnetic field. Here, we review the current state of the use of MNPs for neuroprotective and magnetically guided therapies. We discuss some conceivable outcomes of current magnetically driven strategies seeking integrated platforms for regenerative action on damaged tissues.

Metal and metal oxide nanoparticles are an important class of materials with numerous applications. Understanding how such nanoparticles interact with living systems is of considerable relevance both from a toxicological and biomedical perspective. The physicochemical features of nanoparticles are sometimes referred to as the synthetic identity, while the acquired properties of nanoparticles in a biological milieu resulting from the adsorption of biomolecules on the surface of the particles can be considered the biological identity. In this article, we explore the dynamic changes in the identity of nanoparticles resulting either from acquisition of a so-called bio-corona or through the process of biotransformation and how this impacts cellular recognition of nanoparticles and toxicological outcomes, with an emphasis on inflammation—an orchestrated host response against harmful stimuli, including pathogens as well as particles.

Tissue engineering and regenerative medicine aim to achieve functional restoration of tissue or cells damaged through disease, aging, or trauma. Advancement of tissue engineering requires innovation in the field of three-dimensional scaffolding and functionalization with bioactive molecules. Nanotechnology offers advanced materials with patterned nano-morphologies for cell growth and different molecular substrates that can support cell survival and functions. Cerium oxide nanoparticles (nanoceria) can control intracellular as well as extracellular reactive oxygen and nitrogen species. Recent findings suggest that nanoceria can enhance long-term cell survival, enable cell migration and proliferation, and promote stem cell differentiation. Moreover, the self-regenerative property of nanoceria permits a small dose to remain catalytically active for an extended time. This review summarizes the possibilities and applications of nanoceria in the field of tissue engineering and regenerative medicine.

Engineered nanoparticles, in particular metal oxide nanoparticles, with their unique and novel properties, enable a plethora of new applications in various fields of research. These new properties have raised concerns about potential adverse effects for the environment and human health and are nowadays very controversial. A reliable, cost- and time-effective, rapid and mechanistic-based testing strategy is needed to replace current conventional phenomenological assessments. Today’s in vitro technology, providing human-based advanced cellular models representing different organ barriers such as skin, lung, placenta, or liver, may cover this need. The aim of this article is to present the current changes in (nano) toxicology strategies, the extent to which in vitro models have achieved general acceptance, and how the relevance of these models can further be improved using examples of selected metal oxide nanoparticles.

Engineered nanomaterials (ENMs) strongly interact with biomolecules and cells due to their similar size scales. Consequently, ENMs are beginning to emerge as new medical diagnostic tools, probes in cell biology, and delivery vehicles, compelling us to understand the interactions at the nano-bio interface. Optical spectroscopic tools are excellent probes to characterize ENMs and investigate their interactions with complex biological systems, including biomolecules, cells, and even whole animals alike. Here, we discuss the role of many optical spectroscopic techniques such as fluorescence, Raman, surface plasmon, and infrared spectroscopy in elucidating nano-bio interactions. While these spectroscopic tools have the ability to provide valuable information on ENM distribution in biosystems, ENM interaction with proteins, and the mechanisms by which ENMs elicit an adverse physiological response, there are many challenges that remain to be addressed to improve their scope, resolution, and throughput.

In my Von Hippel Award talk, I emphasized my connection to Arthur von Hippel since our meeting in 1960, when Arthur von Hippel was 62 years of age, but still spanning the last 40 years of his life. He was a Renaissance man with many broad interests. I also spoke about the work that was cited in my award and our overlapping activities. Professor von Hippel was a mentor to me in my early career, and he worked to advance my career behind the scenes. Even after his passing a decade before my selection for the Von Hippel Award, I continue to be influenced by his teachings about science, as well as about his enjoyment of the practice of science and the life of a scientist. Professor von Hippel’s views on the foundations of materials research have strongly influenced the Materials Research Society, and this viewpoint is also emphasized in my article and by my own research career, which has been recognized by the Von Hippel Award.