Volume 7, Issue 3

In this essay, we offer the opinion that engineered nanomaterials are, by definition, materials that can interact with biological systems at the nanoscale, and that this very fact underlies both the promise and the peril of this multifaceted class of materials. Furthermore, nanomaterials are cloaked in host-derived proteins, lipids, or other biomolecules as they enter into a living organism and this so-called bio-corona may impact on subsequent interactions with biological structures. We will explore some examples of nanoscale effects of engineered nanomaterials, and discuss how such interactions may underpin toxicity, and, conversely, how nanoscale interactions may be harnessed for clinical applications, including the use of nanoparticles as drugs per se.

The rapidly growing application of nano-sized materials and nano-scaled processes will result in increased exposure of humans and the environment. The small size of nanomaterials (NM) comparable with molecular building blocks of cells raises concerns that their toxic potential cannot be extrapolated from studies of larger particles due to their unique physico-chemical properties. These properties are also responsible that NM rapidly adsorb various (bio)molecules when introduced into complex physiological or natural environments. As the thus formed protein/biomolecule ‘corona’ seems to affect the NM’ in situ identity, an understanding of its toxicological relevance and the biophysical forces regulating corona formation is needed but not yet achieved. This review introduces our current concept of corona formation and evolution and present analytical methods for corona profiling. We discuss toxicity mechanisms potentially affected by the biomolecule corona, including NM cellular uptake and impact on components of the blood system. Further, we comment on pending knowledge gaps and challenges, which need to be resolved by the field. We conclude by presenting a tiered systems biology-driven approach recommended to mechanistically understand the coronas’ nanotoxicological relevance and predictive potential.

Engineered nanomaterials have unique and novel properties enabling wide-ranging new applications in nearly all fields of research. As these new properties have raised concerns about potential adverse effects for the environment and human health, extensive efforts are underway to define reliable, cost- and time-effective, as well as mechanistic-based testing strategies to replace the current method of animal testing, which is still the most prevalent model used for the risk assessment of chemicals. Current approaches for nanomaterials follow this line. The aim of this review is to explore and qualify the relevance of new in vitro and ex vivo models in (nano)material safety assessment, a crucial prerequisite for translation into applications.

In October of 2014, a meeting jointly organized by the EU Nanosafety Cluster and the COST Action TD 1204, was held on the beautiful island of Ortygia in Syracuse (Sicily). The meeting was specifically conceived to give the opportunity to young researchers in the field of nanotoxicology to present and discuss the results of their research. Presentations were divided into eight sessions over 2 days, reflecting the eight working groups of the Nanosafety Cluster. This report gives a description of the meeting activities and a summary of the data presented there.

In 2013, the World Health Organisation (WHO) released an update of the report on “Priority Medicines for Europe and the World” with the aim to bridge the gap between public health needs and the current research and development priorities. A number of emerging technologies are currently explored for their potential to respond to the identified unmet medical needs. Nanotechnology has the potential to offer scientific/technical solutions for some of these pharmaceutical gaps. The present report investigates to what extent projects funded by the European Commission will lead to innovative formulations as well as new therapeutic concepts, if clinical studies in European Member States investigating nanomedicines and finally if nanotech based products authorised in the European Union will contribute to identified public health needs.

Exosomes are nature’s nanocarriers that transport biological information in humans. Their structural properties, origin and functions are making them interesting objects for the diagnosis of diseases, such as cancer, and also, as innovative tools for drug delivery. The interaction of exosomes with the immune system has been one of the focal points of interest; nevertheless their “stealth” properties helping to avoid adverse immune reactions are still not fully understood. In this review, after giving an overview of recent findings on the role of exosomes in disease pathogenesis and physiological functions, we focused on their interaction with the immune system and possibilities for clinical applications. The potential of exosomes of creating stealth nanoparticles that are better tolerated by the immune system than the presently available synthetic drug delivery systems represent a promising new approach in nanomedicine.

Pigs provide a sensitive and quantitative animal model of complement (C) activation-related pseudoallergy (CARPA) caused by liposomes and a wide range of nanoparticulate drugs or drug nanocarriers (nanomedicines). The tetrad of symptoms (hemodynamic, hematological, laboratory and skin changes) that arise within minutes after i.v. injection of reactogenic nanomedicines (RNMs) are highly reproducible among different pigs but the presence, direction and relative severity of symptoms are very different with different RNMs and their administration schedule. Bolus administration of RNMs usually trigger pulmonary hypertension with or without various degrees of systemic hyper- or hypotension, tachy-or bradycardia, arrhythmia, blood cell and inflammatory mediator changes and skin rash. These reactions can be rapid or protracted, and fully tachyphylactic, semi-tachyphylactic or non-tachyphylactic. Slow infusion usually diminishes the reactions and/or entail delayed, protracted and less severe hemodynamic and other changes. The goal of this review is to present some technical details of the porcine CARPA model, point out its constant and variable parameters, show examples of different reactions, highlight the unique features and capabilities of the model and evaluate its utility in preclinical safety assessment. The information obtained in this model enables the understanding of the complex pathomechanism of CARPA involving simultaneous anaphylatoxin and inflammatory mediator actions at multiple sites in different organs.

The characteristic physiological changes in complement (C) activation-related pseudoallergy (CARPA) include thrombocytopenia, leukocytosis and leukopenia with or without compensatory leukocytosis. In the background of these phenomena it is known that anaphylatoxins, the triggers of CARPA, can activate white blood cells (WBCs) and platelets, and that this activation can lead to the binding of these cells to each other and also to capillary endothelial cells, entailing microthrombus formation and circulatory blockage mainly in the pulmonary and coronary microcirculation. These changes are key contributors to the hemodynamic alterations in CARPA, and can lead to anaphylactic shock. The goal of this review was to catalogue the blood cell changes in man and different animals undergoing CARPA and focus on some details of the molecular and cellular interactions among anaphylatoxins, other C activation byproducts, platelets, WBCs (mainly monocytes), macrophages and endothelial cells and these cells’ secretory products during CARPA. By discussing the inhibitors of different steps of the complex interplay between reaction mediators and cell surface receptors, the review might help in identifying possible novel drugs candidates against CARPA.

The rapid advance of nanomedicines and biologicals in pharmacotherapy gives increasing importance to a common adverse effect of these modern therapeutics: complement (C) activation-related pseudoallergy (CARPA). CARPA is a relatively frequent and potentially lethal acute immune toxicity of many intravenous drugs that contain nanoparticles or proteins, whose prediction by laboratory or in vivo testing has not yet been solved. Preliminary studies suggest that proneness of the drug to cause C activation in the blood of patients may predict the individual risk of CARPA, thus, a sensitive and rapid bedside assay for individualized assessment of a drug’s C activating potential could alleviate the CARPA problem. The goal of the present study was to lay down the foundations of a novel approach for real-time sensing of C activation on a supported lipid bilayer platform. We utilized the quartz crystal microbalance with dissipation (QCM-D) monitoring technique to measure the self-assembly of C terminal complex (or membrane attack complex [MAC]) on supported lipid bilayers rapidly assembled by the solvent-assisted lipid bilayer (SALB) formation method, as an immediate measure of C activation. By measuring the changes in frequency and energy dissipation of deposited protein, the technique allows extremely sensitive real-time quantification of the sequential assembly of MAC from its molecular components (C5b-6, C7, C8 and C9) and hence, measure C activation in the ambient medium. The present paper delineates the technique and our initial evidence with purified C proteins that the approach enables sensitive and rapid (real-time) quantification of MAC formation on a silicon-supported planar (phospho) lipid bilayer, which can be used as an endpoint in a clinically useful bedside C activation assay.

The complement (C) activating effect of zymosan and liposomal drugs (AmBisome, Caelyx) leads to significant C consumption in rats, dogs, pigs and other species in vivo, as reflected by a fall in hemolytic complement activity (HCA) of their plasma. However, the acute C activating effect of zymosan and liposomal drugs is unclear in the mouse. Therefore, using sheep red blood cells, we assayed the HCA of plasma obtained from apolipoprotein E-deficient (ApoE) as well as from background C57BL/6 (BL6) mice. Intravenous (i.v.) administration of C activators led to a significant rise (up to 40%) in HCA of the plasma. The HCA steadily rose up to 30 min in ApoE mice, while it peaked at 3 min in BL6 mice, returning to baseline thereafter. The elevated HCA after IV injection of C activators is “paradoxical” in mice, since it implies an increase rather than a decrease in C levels in the blood. One possible explanation of the phenomenon is hemoconcentration due to anaphylatoxin-induced capillary leakage, resulting in an apparent rise of HCA. In conclusion, these preliminary observations highlight, for the first time, a species-dependent opposing impact of C activation and the resulting anaphylatoxin actions on hemolytic complement activity.

The lectin pathway of the complement system is an integral component of the innate immune system recognizing pathogens through patterns of sugar moieties displayed on their surfaces and neutralizing them through an antibody-independent reaction cascade. Many engineered nanoparticles incite complement through the lectin pathway, but these nanoparticles inherently do not express surface-exposed sugars. However, the projected polymeric surface architecture of nanoparticles may transiently resemble structural motifs of peptidoglycan constituents of pathogens and trigger the lectin pathway. We discuss these issues in relation to nanomedicine design and immune safety.