The concept of bio-corona in modulating the toxicity of engineered nanomaterials (ENM)

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Toxicological Profiling and Long-Term Effects of Bare, PEGylated- and Galacto-Oligosaccharide-Functionalized Mesoporous Silica Nanoparticles

Mesoporous silica nanoparticles (MSNs) are amongst the most used nanoparticles in biomedicine. However, the potentially toxic effects of MSNs have not yet been fully evaluated, being a controversial matter in research. In this study, bare MSNs, PEGylated MSNs (MSNs-PEG), and galacto-oligosaccharide-functionalized MSNs (MSNs-GAL) are synthesized and characterized to assess their genotoxicity and transforming ability on human lung epithelial BEAS-2B cells in short- (48 h) and long-term (8 weeks) exposure scenarios. Initial short-term treatments show a dose-dependent increase in genotoxicity for MSNs-PEG-treated cells but not oxidative DNA damage for MSNs, MSNs-PEG, or for MSNs-GAL. In addition, after 8 weeks of continuous exposure, neither induced genotoxic nor oxidative DNA is observed. Nevertheless, long-term treatment with MSNs-PEG and MSNs-GAL, but not bare MSNs, induces cell transformation features, as evidenced by the cell's enhanced ability to grow independently of anchorage, to migrate, and to invade. Further, the secretome from cells treated with MSNs and MSNs-GAL, but not MSNs-PEG, shows certain tumor-promoting abilities, increasing the number and size of HeLa cell colonies formed in the indirect soft-agar assay. These results show that MSNs, specifically the functionalized ones, provoke some measurable adverse effects linked to tumorigenesis. These effects are in the order of other nanomaterials, such as carbon nanotubes or cerium dioxide nanoparticles, but they are lower than those provoked by some approved drugs, such as doxorubicin or dexamethasone.

Exosomes in Cancer Progression and Therapy Resistance: Molecular Insights and Therapeutic Opportunities

The development of therapy resistance still represents a major hurdle in treating cancers, leading to impaired treatment success and increased patient morbidity. The establishment of minimally invasive liquid biopsies is a promising approach to improving the early diagnosis, as well as therapy monitoring, of solid tumors. Because of their manifold functions in the tumor microenvironment, tumor-associated small extracellular vesicles, referred to as exosomes, have become a subject of intense research. Besides their important roles in cancer progression, metastasis, and the immune response, it has been proposed that exosomes also contribute to the acquisition and transfer of therapy resistance, mainly by delivering functional proteins and RNAs, as well as facilitating the export of active drugs or functioning as extracellular decoys. Extensive research has focused on understanding the molecular mechanisms underlying the occurrence of resistance and translating these into strategies for early detection. With this review, we want to provide an overview of the current knowledge about the (patho-)biology of exosomes, as well as state-of-the-art methods of isolation and analysis. Furthermore, we highlight the role of exosomes in tumorigenesis and cancer treatment, where they can function as therapeutic agents, biomarkers, and/or targets. By focusing on their roles in therapy resistance, we will reveal new paths of exploiting exosomes for cancer diagnosis and treatment.

Biosafety of mesoporous silica nanoparticles; towards clinical translation

Mesoporous silica nanoparticles (MSNs) have attracted the attention of chemists, who have developed numerous systems for the encapsulation of a plethora of molecules, allowing the use of mesoporous silica nanoparticles for biomedical applications. MSNs have been extensively studied for their use in nanomedicine, in applications such as drug delivery, diagnosis, and bioimaging, demonstrating significant in vivo efficacy in different preclinical models. Nevertheless, for the transition of MSNs into clinical trials, it is imperative to understand the characteristics that make MSNs effective and safe. The biosafety properties of MSNs in vivo are greatly influenced by their physicochemical characteristics such as particle shape, size, surface modification, and silica framework. In this review, we compile the most relevant and recent progress in the literature up to the present by analyzing the contributions on biodistribution, biodegradability, and clearance of MSNs. Furthermore, the ongoing clinical trials and the potential challenges related to the administration of silica materials for advanced therapeutics are discussed. This approach aims to provide a solid overview of the state-of-the-art in this field and to encourage the translation of MSNs to the clinic.

The protein corona from nanomedicine to environmental science

The protein corona spontaneously develops and evolves on the surface of nanoscale materials when they are exposed to biological environments, altering their physiochemical properties and affecting their subsequent interactions with biosystems. In this Review, we provide an overview of the current state of protein corona research in nanomedicine. We next discuss remaining challenges in the research methodology and characterization of the protein corona that slow the development of nanoparticle therapeutics and diagnostics, and we address how artificial intelligence can advance protein corona research as a complement to experimental research efforts. We then review emerging opportunities provided by the protein corona to address major issues in healthcare and environmental sciences. This Review details how mechanistic insights into nanoparticle protein corona formation can broadly address unmet clinical and environmental needs, as well as enhance the safety and efficacy of nanobiotechnology products.

Daphnia as a model organism to probe biological responses to nanomaterials-from individual to population effects via adverse outcome pathways

The importance of the cladoceran Daphnia as a model organism for ecotoxicity testing has been well-established since the 1980s. Daphnia have been increasingly used in standardised testing of chemicals as they are well characterised and show sensitivity to pollutants, making them an essential indicator species for environmental stress. The mapping of the genomes of D. pulex in 2012 and D. magna in 2017 further consolidated their utility for ecotoxicity testing, including demonstrating the responsiveness of the Daphnia genome to environmental stressors. The short lifecycle and parthenogenetic reproduction make Daphnia useful for assessment of developmental toxicity and adaption to stress. The emergence of nanomaterials (NMs) and their safety assessment has introduced some challenges to the use of standard toxicity tests which were developed for soluble chemicals. NMs have enormous reactive surface areas resulting in dynamic interactions with dissolved organic carbon, proteins and other biomolecules in their surroundings leading to a myriad of physical, chemical, biological, and macromolecular transformations of the NMs and thus changes in their bioavailability to, and impacts on, daphnids. However, NM safety assessments are also driving innovations in our approaches to toxicity testing, for both chemicals and other emerging contaminants such as microplastics (MPs). These advances include establishing more realistic environmental exposures via medium composition tuning including pre-conditioning by the organisms to provide relevant biomolecules as background, development of microfluidics approaches to mimic environmental flow conditions typical in streams, utilisation of field daphnids cultured in the lab to assess adaption and impacts of pre-exposure to pollution gradients, and of course development of mechanistic insights to connect the first encounter with NMs or MPs to an adverse outcome, via the key events in an adverse outcome pathway. Insights into these developments are presented below to inspire further advances and utilisation of these important organisms as part of an overall environmental risk assessment of NMs and MPs impacts, including in mixture exposure scenarios.

Use of quasi-SMILES to build models based on quantitative results from experiments with nanomaterials

Quasi-SMILES deviate from traditional SMILES (simplified molecular input-line entry system) by the extension of additional symbols that encode for conditions of an experiment. Descriptors calculated with SMILES are useful for the development of quantitative structure-property/activity relationships (QSPRs/QSARs), while descriptors calculated with quasi-SMILES can be useful for the development of quantitative models of experimental results obtained under different conditions. Here, this approach has been applied for the development of generalized models using aquatic nanotoxicity data (i.e., related to fish and daphnia). The statistical quality of the above models (pLC50) is quite good with a determination coefficient for the external validation set ranging from 0.62 to 0.71 and RMSE ranging from 0.58 to 0.60. The principle of the approach includes splitting the experimental data into three random distributions defining training, calibration, and validation sets.

Aquatic organisms modulate the bioreactivity of engineered nanoparticles: focus on biomolecular corona

The increased use of nanoparticle (NP)-enabled materials in everyday-life products have raised concerns about their environmental implications and safety. This motivated the extensive research in nanoecotoxicology showing the possibility that NPs could cause harm to the aquatic organisms if present at high concentrations. By contrast, studies dealing with influence that organisms could exert on the fate and thus effects of NPs are still very rare. Drawing on the existing up-to-date knowledge we critically discuss the formation of biomolecular corona as one of the mechanisms by which organisms exerted control on the NPs fate in the aquatic and biotic environments. We focused the formation of corona by exogeneous and endogenous biomolecules and illustrated the discussion with the specific example of phytoplankton and aquatic invertebrate species. We highlighted the necessity to incorporate the concept of biomolecular corona within more general framework considering the feedback of aquatic organisms and the control they exert in shaping the fate and impact of NPs in the aquatic and biological environment. In our view such broader perspective will contribute to get novel insights into the drivers of environmental transformations of NPs and their mechanisms, which are important in environmental risk assessment.

Genotoxicity of Three Micro/Nanocelluloses with Different Physicochemical Characteristics in MG-63 and V79 Cells

(1) Background: Nanocellulose is an innovative engineered nanomaterial with an enormous potential for use in a wide array of industrial and biomedical applications and with fast growing economic value. The expanding production of nanocellulose is leading to an increased human exposure, raising concerns about their potential health effects. This study was aimed at assessing the potential toxic and genotoxic effects of different nanocelluloses in two mammalian cell lines; (2) Methods: Two micro/nanocelluloses, produced with a TEMPO oxidation pre-treatment (CNFs) and an enzymatic pre-treatment (CMFs), and cellulose nanocrystals (CNCs) were tested in osteoblastic-like human cells (MG-63) and Chinese hamster lung fibroblasts (V79) using the MTT and clonogenic assays to analyse cytotoxicity, and the micronucleus assay to test genotoxicity; (3) Results: cytotoxicity was observed by the clonogenic assay in V79 cells, particularly for CNCs, but not by the MTT assay; CNF induced micronuclei in both cell lines and nucleoplasmic bridges in MG-63 cells; CMF and CNC induced micronuclei and nucleoplasmic bridges in MG-63 cells, but not in V79 cells; (4) Conclusions: All nanocelluloses revealed cytotoxicity and genotoxicity, although at different concentrations, that may be related to their physicochemical differences and availability for cell uptake, and to differences in the DNA damage response of the cell model.

Immunotoxic effects of metal-based nanoparticles in fish and bivalves

There is a global research interest in metal nanoparticles (MNPs) due to their diverse applications, rapidly increasing use, and increased presence in the aquatic environment. Currently, most MNPs in the environment are at levels unlikely to cause overt toxicity. Sub-lethal effects that MNPs may induce, notable immunotoxicity, could however have significant health implications. Thus, deciphering the immunological interactions of MNPs with aquatic organisms constitutes a much-needed area of research. In this article, we critically assess the evidence for immunotoxic effects of MNPs in bivalves and fish, as key wildlife sentinels with widely differing ecological niches that are used as models in ecotoxicology. The first part of this review details the properties, fate, and fundamental physicochemical behavior of MNPs in the aquatic ecosystem. We then consider the toxicokinetics of MNP uptake, accumulation, and deposition in fish and bivalves. The main body of the review then focuses on immune reactions in response to MNPs exposure in bivalves and fish illustrating their immunotoxic potential. Finally, we identify major knowledge gaps in our current understanding of the implications of MNPs exposure for immunological functions and the associated health consequences for bivalves and fish, as well as the general lessons learned on the immunotoxic properties of the emerging class of nanoparticulate contaminants in fish and bivalves.

Immunotoxicity of nanomaterials in health and disease: Current challenges and emerging approaches for identifying immune modifiers in susceptible populations

Nanosafety assessment has experienced an intense era of research during the past decades driven by a vivid interest of regulators, industry, and society. Toxicological assays based on in vitro cellular models have undergone an evolution from experimentation using nanoparticulate systems on singular epithelial cell models to employing advanced complex models more realistically mimicking the respective body barriers for analyzing their capacity to alter the immune state of exposed individuals. During this phase, a number of lessons were learned. We have thus arrived at a state where the next chapters have to be opened, pursuing the following objectives: (1) to elucidate underlying mechanisms, (2) to address effects on vulnerable groups, (3) to test material mixtures, and (4) to use realistic doses on (5) sophisticated models. Moreover, data reproducibility has become a significant demand. In this context, we studied the emerging concept of adverse outcome pathways (AOPs) from the perspective of immune activation and modulation resulting in pro-inflammatory versus tolerogenic responses. When considering the interaction of nanomaterials with biological systems, protein corona formation represents the relevant molecular initiating event (e.g., by potential alterations of nanomaterial-adsorbed proteins). Using this as an example, we illustrate how integrated experimental-computational workflows combining in vitro assays with in silico models aid in data enrichment and upon comprehensive ontology-annotated (meta)data upload to online repositories assure FAIRness (Findability, Accessibility, Interoperability, Reusability). Such digital twinning may, in future, assist in early-stage decision-making during therapeutic development, and hence, promote safe-by-design innovation in nanomedicine. Moreover, it may, in combination with in silico-based exposure-relevant dose-finding, serve for risk monitoring in particularly loaded areas, for example, workplaces, taking into account pre-existing health conditions. This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Materials, surfaces, and interfacial phenomena in nanoplastics toxicology research

In response to the growing worldwide plastic pollution problem, the field of nanoplastics research is attempting to determine the risk of exposure to nanoparticles amidst their ever-increasing presence in the environment. Since little is known about the attributes of environmental nanoplastics (concentration, composition, morphology, and size) due to fundamental limitations in detection and quantification of smaller plastic particles, researchers often improvise by engineering nanoplastic particles with various surface modifications as models for laboratory toxicological testing. Polystyrene and other commercially available or easily synthesized polymer materials functionalized with surfactants or fluorophores are typically used for these studies. How surfactants, additives, fluorophores, the addition of surface functional groups for conjugation, or other changes to surface attributes alter toxicological profiles remains unclear. Additionally, the limited polymers used in laboratory models do not mimic the vast range of polymer types comprising environmental pollutants. Nanomaterials are tricky materials to investigate due to their high surface area, high surface energies, and their propensity to interact with molecules, proteins, and biological probes. These unique properties can often invalidate common laboratory assays. Extreme care must be taken to ensure that results are not artefactual. We have gathered zeta potential values for various polystyrene nanoparticles with different functionalization, in different solvents, from the reported literature. We also discuss the effects of surface engineering and solvent properties on interparticle interactions, agglomeration, particle-protein interactions, corona formation, nano-bio interfaces, and contemplate how these parameters might confound results. Various toxicological exemplars are critically reviewed, and the relevance and shortfalls of the most popular models used in nanoplastics toxicity studies published in the current literature are considered.

Bacteriophages as Solid Tumor Theragnostic Agents

Cancer, especially the solid tumor sub-set, poses considerable challenges to modern medicine owing to the unique physiological characteristics and substantial variations in each tumor's microenvironmental niche fingerprints. Though there are many treatment methods available to treat solid tumors, still a considerable loss of life happens, due to the limitation of treatment options and the outcomes of ineffective treatments. Cancer cells evolve with chemo- or radiation-treatment strategies and later show adaptive behavior, leading to failed treatment. These challenges demand tailored and individually apt personalized treatment methods. Bacteriophages (or phages) and phage-based theragnostic vectors are gaining attention in the field of modern cancer medicine, beyond their bactericidal ability. With the invention of the latest techniques to fine-tune phages, such as in the field of genetic engineering, synthetic assembly methods, phage display, and chemical modifications, noteworthy progress in phage vector research for safe cancer application has been realized, including use in pre-clinical studies. Herein, we discuss the distinct fingerprints of solid tumor physiology and the potential for bacteriophage vectors to exploit specific tumor features for improvised tumor theragnostic applications.

Eco-Interactions of Engineered Nanomaterials in the Marine Environment: Towards an Eco-Design Framework

Marine nano-ecotoxicology has emerged with the purpose to assess the environmental risks associated with engineered nanomaterials (ENMs) among contaminants of emerging concerns entering the marine environment. ENMs’ massive production and integration in everyday life applications, associated with their peculiar physical chemical features, including high biological reactivity, have imposed a pressing need to shed light on risk for humans and the environment. Environmental safety assessment, known as ecosafety, has thus become mandatory with the perspective to develop a more holistic exposure scenario and understand biological effects. Here, we review the current knowledge on behavior and impact of ENMs which end up in the marine environment. A focus on titanium dioxide (n-TiO₂) and silver nanoparticles (AgNPs), among metal-based ENMs massively used in commercial products, and polymeric NPs as polystyrene (PS), largely adopted as proxy for nanoplastics, is made. ENMs eco-interactions with chemical molecules including (bio)natural ones and anthropogenic pollutants, forming eco- and bio-coronas and link with their uptake and toxicity in marine organisms are discussed. An ecologically based design strategy (eco-design) is proposed to support the development of new ENMs, including those for environmental applications (e.g., nanoremediation), by balancing their effectiveness with no associated risk for marine organisms and humans.

Adverse cardiovascular responses of engineered nanomaterials: Current understanding of molecular mechanisms and future challenges

Nanotechnology is spanning multiple fields of study from materials science to computer engineering and drug discovery. Since the early 21st century, nanotechnology and nano-enabled research have received great attention and governmental funding accompanied with interest to ensure human and environmental safety of engineered nanomaterials (ENMs). Optimal functioning of the cardiovascular (CV) system is of utmost importance for the overall health of the body. Following exposure, ENMs essentially end up in the circulation (at least partially) and hence it is key to assess any associated adverse CV consequences. Accumulating research suggests that exposure to ENMs (different compositions and physicochemical properties) has the capacity to directly and indirectly interact with CV components resulting in adverse events and worsening of CV complications. However, the underlying molecular mechanisms driving these events remain to be elucidated. In this article, we review state-of-art literature on ENM-associated adverse CV responses and discuss the potential underlying molecular mechanisms.

Research progress and application opportunities of nanoparticle-protein corona complexes

Nanoparticles (NPs) can be used to design for nanomedicines with different chemical surface properties owing to their size advantages and the capacity of specific delivery to targeted sites in organisms. The discovery of the presence of protein corona (PC) has changed our classical view of NPs, stimulating researchers to investigate the in vivo fate of NPs as they enter biological systems. Both NPs and PC have their specificity but complement each other, so they should be considered as a whole. The formation and characterization of NP-PC complexes provide new insights into the design, functionalization, and application of nanocarriers. Based on progress of recent researches, we reviewed the formation, characterization, and composition of the PC, and introduced those critical factors influencing PC, simultaneously expound the effect of PC on the biological function of NPs. Especially we put forward the opportunities and challenges when NP-PC as a novel nano-drug carrier for targeted applications. Furthermore, we discussed the pros versus cons of the PC, as well as how to make better PC in the future application of NPs.

Scavenger Receptor A1 Mediates the Uptake of Carboxylated and Pristine Multi-Walled Carbon Nanotubes Coated with Bovine Serum Albumin

Previously, we noted that carboxylated multi-walled carbon nanotubes (cMWNTs) coated with Pluronic^® F-108 (PF108) bound to and were accumulated by macrophages, but that pristine multi-walled carbon nanotubes (pMWNTs) coated with PF108 were not (Wang et al., Nanotoxicology2018, 12, 677). Subsequent studies with Chinese hamster ovary (CHO) cells that overexpressed scavenger receptor A1 (SR-A1) and with macrophages derived from mice knocked out for SR-A1 provided evidence that SR-A1 was a receptor of PF108-cMWNTs (Wang et al., Nanomaterials (Basel) 2020, 10, 2417). Herein, we replaced the PF108 coat with bovine serum albumin (BSA) to investigate how a BSA corona affected the interaction of multi-walled carbon nanotubes (MWNTs) with cells. Both BSA-coated cMWNTs and pMWNTs bound to and were accumulated by RAW 264.7 macrophages, although the cells bound two times more BSA-coated cMWNT than pMWNTs. RAW 264.7 cells that were deleted for SR-A1 using CRISPR-Cas9 technology had markedly reduced binding and accumulation of both BSA-coated cMWNTs and pMWNTs, suggesting that SR-A1 was responsible for the uptake of both MWNT types. Moreover, CHO cells that ectopically expressed SR-A1 accumulated both MWNT types, whereas wild-type CHO cells did not. One model to explain these results is that SR-A1 can interact with two structural features of BSA-coated cMWNTs, one inherent to the oxidized nanotubes (such as COOH and other oxidized groups) and the other provided by the BSA corona; whereas SR-A1 only interacts with the BSA corona of BSA-pMWNTs.

Boosting nanotoxicity to combat multidrug-resistant bacteria in pathophysiological environments

Nanomaterials are promising novel antibiotics, but often ineffective. We found that nanomaterial-bacteria complex formation occurred with various nanomaterials. The bactericidal activity of NMs strongly depends on their physical binding to (multidrug-resistant) bacteria. Nanomaterials' binding and antibiotic effect was reduced by various pathophysiological biomolecule coronas strongly inhibiting their antibiotic effects. We show from analytical to in vitro to in vivo that nanomaterial-based killing could be restored by acidic pH treatments. Here, complex formation of negatively-charged, plasma corona-covered, nanomaterials with bacteria was electrostatically enhanced by reducing bacteria's negative surface charge. Employing in vivo skin infection models, acidic pH-induced complex formation was critical to counteract Staphylococcus aureus infections by silver nanomaterials. We explain why nano-antibiotics show reduced activity and provide a clinically practical solution.

Toward Diffusion Measurements of Colloidal Nanoparticles in Biological Environments by Nuclear Magnetic Resonance

Protein corona formation on the surface of nanoparticles (NPs) is observed in situ by measuring diffusion coefficients of the NPs under the presence of proteins with a ¹⁹ F nuclear magnetic resonance (NMR) based methodology. Formation of a protein corona reduces the diffusion coefficient of the NPs, based on an increase in their effective hydrodynamic radii. With this methodology it is demonstrated that the apparent dissociation constant of protein-NP complexes may vary over at least nine orders of magnitude for different types of proteins, in line with the Vroman effect. Using this methodology, the interaction between one type of protein and one type of nanoparticle can be studied quantitatively. Due to the NMR-based detection, this methodology has no interference by absorption/scattering effects, by which optical detection schemes are affected. By using the potential of the NMR chemical shift, the detection of multiple ¹⁹ F signals simultaneously opens the possibility to study the diffusion of several NPs at the same time. The ¹⁹ F labeling of the NPs has negligible effect on their acute toxicity and moderate effect on NPs uptake by cells.

Mechanisms of nanotoxicity - biomolecule coronas protect pathological fungi against nanoparticle-based eradication

Whereas nanotoxicity is intensely studied in mammalian systems, our knowledge of desired or unwanted nano-based effects for microbes is still limited. Fungal infections are global socio-economic health and agricultural problems, and current chemical antifungals may induce adverse side-effects in humans and ecosystems. Thus, nanoparticles are discussed as potential novel and sustainable antifungals via the desired nanotoxicity but often fail in practical applications. In our study, we found that nanoparticles' toxicity strongly depends on their binding to fungal spores, including the clinically relevant pathogen Aspergillus fumigatus as well as common plant pests, such as Botrytis cinerea or Penicillum expansum. Employing a selection of the model and antimicrobial nanoparticles, we found that nanoparticle-spore complex formation is influenced by the NM's physicochemical properties, such as size, identified as a key determinant for our silica model particles. Biomolecule coronas acquired in pathophysiologically and ecologically relevant environments, protected fungi against nanoparticle-induced toxicity as shown by employing antimicrobial ZnO, Ag, or CuO nanoparticles as well as dissolution-resistant quantum dots. Mechanistically, dose-dependent corona-mediated resistance was conferred via reducing the physical adsorption of nanoparticles to fungi. The inhibitory effect of biomolecules on nano-based toxicity of Ag NPs was further verified in vivo, using the invertebrate Galleria mellonella as an alternative non-mammalian infection model. We provide the first evidence that biomolecule coronas are not only relevant in mammalian systems but also for nanomaterial designs as future antifungals for human health, biotechnology, and agriculture.

Interplay between extracellular polymeric substances (EPS) from a marine diatom and model nanoplastic through eco-corona formation

The occurrence of nanoplastics in oceans' surface waters is no more a hypothesis and it could severely affect marine organisms from different trophic levels. Nanoscale particles interaction with dissolved natural organic matter (NOM) significantly influence their behaviour and consequently bioavailability and toxicity to marine species. Extracellular polymeric substances (EPS) are among the main components of the NOM pool in seawater yet have been so far little investigated for their effect in altering the physical-chemical properties of nanosized objects. Here we employed EPS from marine diatom Phaeodactylum tricornutum to study the evolution of an eco-corona formation upon incubation with 60 nm carboxylated polystyrene nanoparticles (PS-COOH NPs), as proxy for nanoplastics in seawater. EPS significantly reduced PS-COOH NPs aggregation rate compared to biomolecule free natural seawater (NSW) and caused the formation of complexes constituted by both carbohydrate and protein components. Size Exclusion Chromatography (SEC) revealed four main distinct groups of peaks, spanning from high (>100 kDa) to low molecular weight (20 kDa) molecules, characterized by a high chemical heterogeneity. The lowering of the chromatographic signals detected after EPS incubation with PS-COOH NPs, mainly in the eluates at high molecular weight, suggests that an important fraction of EPS remained adsorbed on PS-COOH NPs. In agreement, SDS-PAGE analysis of proteins adsorbed on PS-COOH showed the occurrence of an eco-corona formed by proteins in the range of molecular weight 30-100 kDa. No toxicity to diatoms was observed upon PS-COOH exposure (72 h, 1-100 mg L^-1) even by adding a further source of exogenous EPS during exposure. Moreover, the addition of EPS reduced ROS production, even when cells were incubated with PS-COOH NPs at 10 and 50 mg L^-1, suggesting an antioxidant scavenging activity of EPS.

Recent Advances in Understanding the Protein Corona of Nanoparticles and in the Formulation of "Stealthy" Nanomaterials

In the last decades, the staggering progress in nanotechnology brought around a wide and heterogeneous range of nanoparticle-based platforms for the diagnosis and treatment of many diseases. Most of these systems are designed to be administered intravenously. This administration route allows the nanoparticles (NPs) to widely distribute in the body and reach deep organs without invasive techniques. When these nanovectors encounter the biological environment of systemic circulation, a dynamic interplay occurs between the circulating proteins and the NPs, themselves. The set of proteins that bind to the NP surface is referred to as the protein corona (PC). PC has a critical role in making the particles easily recognized by the innate immune system, causing their quick clearance by phagocytic cells located in organs such as the lungs, liver, and spleen. For the same reason, PC defines the immunogenicity of NPs by priming the immune response to them and, ultimately, their immunological toxicity. Furthermore, the protein corona can cause the physical destabilization and agglomeration of particles. These problems induced to consider the PC only as a biological barrier to overcome in order to achieve efficient NP-based targeting. This review will discuss the latest advances in the characterization of PC, development of stealthy NP formulations, as well as the manipulation and employment of PC as an alternative resource for prolonging NP half-life, as well as its use in diagnostic applications.

Nano Meets Micro-Translational Nanotechnology in Medicine: Nano-Based Applications for Early Tumor Detection and Therapy

Nanomaterials have great potential for the prevention and treatment of cancer. Circulating tumor cells (CTCs) are cancer cells of solid tumor origin entering the peripheral blood after detachment from a primary tumor. The occurrence and circulation of CTCs are accepted as a prerequisite for the formation of metastases, which is the major cause of cancer-associated deaths. Due to their clinical significance CTCs are intensively discussed to be used as liquid biopsy for early diagnosis and prognosis of cancer. However, there are substantial challenges for the clinical use of CTCs based on their extreme rarity and heterogeneous biology. Therefore, methods for effective isolation and detection of CTCs are urgently needed. With the rapid development of nanotechnology and its wide applications in the biomedical field, researchers have designed various nano-sized systems with the capability of CTCs detection, isolation, and CTCs-targeted cancer therapy. In the present review, we summarize the underlying mechanisms of CTC-associated tumor metastasis, and give detailed information about the unique properties of CTCs that can be harnessed for their effective analytical detection and enrichment. Furthermore, we want to give an overview of representative nano-systems for CTC isolation, and highlight recent achievements in microfluidics and lab-on-a-chip technologies. We also emphasize the recent advances in nano-based CTCs-targeted cancer therapy. We conclude by critically discussing recent CTC-based nano-systems with high therapeutic and diagnostic potential as well as their biocompatibility as a practical example of applied nanotechnology.

Bovine Serum Albumin Enhances Silver Nanoparticle Dissolution Kinetics in a Size- and Concentration-Dependent Manner

The dissolution of silver nanoparticles (AgNPs) to release Ag(I)(aq) is an important mechanism in potentiating AgNP cytotoxicity and imparting their antibacterial properties. However, AgNPs can undergo other simultaneous biophysicochemical transformations, such as protein adsorption, which can mediate AgNP dissolution behaviors. We report the comprehensive analysis of AgNP dissolution and protein adsorption behaviors with monolayer surface coverage of AgNPs by bovine serum albumin (BSA). AgNP dissolution rate constants, k_dissolution, were quantified over several particle sizes (10, 20, and 40 nm) and BSA concentrations (0-2 nM) using linear sweep stripping voltammetry. Across all particle sizes, the dissolution rate constant increased with increasing BSA concentrations. However, protein-enhanced dissolution behaviors were most pronounced for 10 nm AgNPs, which exhibited 3.6-fold and 7.7-fold relative enhancement when compared to 20 and 40 nm AgNPs, respectively. Changes to AgNP surface properties upon interaction with BSA were monitored using dynamic light scattering and zeta potential measurements, while BSA-AgNP complex formation was evaluated using UV-vis spectroscopy and circular dichroism spectroscopy. A subtle increase in the BSA-AgNP association constant was observed with an increase in the AgNP size. Together, these results suggest that the AgNP size dependence of BSA-enhanced dissolution of AgNPs is possibly mediated through both displacement of Ag(I)(aq)-loaded BSA by excess protein in the bulk solution and minimized accessibility of the AgNP surface because of BSA adsorption.

The hurdles of nanotoxicity in transplant nanomedicine

Nanomedicine has matured significantly in the past 20 years and a number of nanoformulated therapies are cleared by regulatory agencies for use across the globe. Transplant medicine is one area that has significantly benefited from the advancement of nanomedicine in recent times. However, while nanoparticle-based therapies have improved toxicological profiles of some drugs, there are still a number of aspects regarding the biocompatibility and toxicity of nanotherapies that require further research. The goal of this article is to review toxicological profiles of immunosuppressant therapies and their conversion into nanomedicine formulations as well as introduce future challenges associated with current in vitro and in vivo toxicological models.

Is small smarter? Nanomaterial-based detection and elimination of circulating tumor cells: current knowledge and perspectives

Circulating tumor cells (CTCs) are disseminated cancer cells. The occurrence and circulation of CTCs seem key for metastasis, still the major cause of cancer-associated deaths. As such, CTCs are investigated as predictive biomarkers. However, due to their rarity and heterogeneous biology, CTCs’ practical use has not made it into the clinical routine. Clearly, methods for the effective isolation and reliable detection of CTCs are urgently needed. With the development of nanotechnology, various nanosystems for CTC isolation and enrichment and CTC-targeted cancer therapy have been designed. Here, we summarize the relationship between CTCs and tumor metastasis, and describe CTCs’ unique properties hampering their effective enrichment. We comment on nanotechnology-based systems for CTC isolation and recent achievements in microfluidics and lab-on-a-chip technologies. We discuss recent advances in CTC-targeted cancer therapy exploiting the unique properties of nanomaterials. We conclude by introducing developments in CTC-directed nanosystems and other advanced technologies currently in (pre)clinical research.

Metabolomic method to detect a metabolite corona on amino-functionalized polystyrene nanoparticles

Protein coronas on nanoparticles (NPs) affect their physicochemical properties, cellular uptake, and toxicity, and have been described extensively. To date, studies of the occurrence of small molecule (metabolite) coronas are limited. We sought to determine whether a metabolite corona forms on NPs, using high-sensitivity metabolomics combined with a model system for freshwater ecotoxicology (Daphnia magna feeding on Chlorella vulgaris). Using amino-functionalized polystyrene NPs (NH₂-pNPs), we showed the impact of this material on Daphnia feeding to provide a rationale for the detailed molecular investigations. We then employed a targeted LC-MS/MS approach for sodium dodecyl sulfate (SDS) as an analog to signaling molecules known to occur in our freshwater model system and optimized a corona extraction method for this representative metabolite. Next, we performed an untargeted discovery-based metabolomics study - using high-sensitivity nanoelectrospray direct infusion mass spectrometry (DIMS) - to enable an unbiased assessment of the metabolite corona of NH₂-pNPs in the freshwater model system. Our results demonstrate that SDS was successfully recovered from NH₂-pNPs, confirming that the extraction protocol was fit-for-purpose. Untargeted DIMS metabolomics reproducibly detected 100 s of small molecule peaks extracted from NH₂-pNPs exposed to conditioned media from the D. magna-C. vulgaris model system. Attempts to annotate these extracted metabolites, including by using van Krevelen and Kendrick Mass Defect plots, indicate a diverse range of metabolites that were not clustered into any particular class. Overall we demonstrate the existence of an ecologically relevant metabolite corona on the surface of NPs through application of a high-sensitivity, untargeted mass spectrometry metabolomics workflow.

The Human In Vivo Biomolecule Corona onto PEGylated Liposomes: A Proof-of-Concept Clinical Study

The self-assembled layered adsorption of proteins onto nanoparticle (NP) surfaces, once in contact with biological fluids, is termed the "protein corona" and it is gradually seen as a determinant factor for the overall biological behavior of NPs. Here, the previously unreported in vivo protein corona formed in human systemic circulation is described. The human-derived protein corona formed onto PEGylated doxorubicin-encapsulated liposomes (Caelyx) is thoroughly characterized following the recovery of liposomes from the blood circulation of ovarian carcinoma patients. In agreement with previous investigations in mice, the in vivo corona is found to be molecularly richer in comparison to its counterpart ex vivo corona. The intravenously infused liposomes are able to scavenge the blood pool and surface-capture low-molecular-weight, low-abundance plasma proteins that cannot be detected by conventional plasma proteomic analysis. This study describes the previously elusive or postulated formation of protein corona around nanoparticles in vivo in humans and illustrates that it can potentially be used as a novel tool to analyze the blood circulation proteome.

How Entanglement of Different Physicochemical Properties Complicates the Prediction of in Vitro and in Vivo Interactions of Gold Nanoparticles

The physicochemical properties of a set of 21 different gold nanoparticles (spherical and rod-shaped nanoparticles (NPs) of different diameters with three different surface coatings) were studied. Protein corona formation, in vitro uptake, effect on cell viability and proliferation, and in vivo biodistribution of these NPs were determined. The relation of the results of the different NPs was analyzed by hierarchical cluster analysis, which will tell which NPs have the most similar physicochemical properties and biological effects, without having to specify individual physicochemical parameters. The results show that the physicochemical properties of gold nanoparticles (Au NPs) are mainly accounted for by their hydrodynamic diameter and their zeta-potential. The formation of the protein corona is determined by the pH-dependence of their zeta-potential. While several reports found that in vitro uptake and in vivo biodistribution of NPs are correlated to individual physicochemical parameters, e. g., size, shape, or surface chemistry, such direct dependence in the investigated multidimensional set of NPs was not found in our study. This most likely is due to entanglement of the different parameters, which complicates the prediction of the biological effect of NPs in case multiple physicochemical properties are simultaneously varied. The in vitro uptake and in vivo biodistribution of NPs seem to be not directly driven by the protein corona, but the physicochemical properties determine as well the corona as they influence in vitro/ in vivo behaviors, and thus the effect of the protein corona would be rather indirect.

Experimental challenges regarding the in vitro investigation of the nanoparticle-biocorona in disease states

Toxicological evaluation of nanoparticles (NPs) requires the utilization of in vitro techniques due to their number and diverse properties. Cell culture systems are often lacking in their ability to perform comparative toxicity assessment due to dosimetry issues and capacity to simulate in vivo environments. Upon encountering a physiological environment, NPs become coated with biomolecules forming a biocorona (BC), influencing function, biodistribution, and toxicity. Disease-induced alterations in the biological milieu can alter BC formation. This study evaluates the role of low-density lipoprotein (LDL) in altering macrophage responses to iron oxide (Fe₃O₄) NPs. BCs were formed by incubating Fe₃O₄ NPs in serum-free media, or 10% fetal bovine serum with or without LDL present. Following exposures to a normalized dose (25 μg/mL), macrophage association of Fe₃O₄ NPs with a LDL-BC was enhanced. TNF-α mRNA expression and protein levels were differentially induced due to BCs. Cell surface expression of SR-B1 was reduced following all Fe₃O₄ NPs exposures, while only NPs with an LDL-BC enhanced mitochondrial membrane potential. These findings suggest that elevations in LDL may contribute to distinct BC formation thereby influencing NP-cellular interactions and response. Further, our study highlights challenges that may arise during the in vitro evaluation of disease-related variations in the NP-BC.

Probabilistic risk assessment of gold nanoparticles after intravenous administration by integrating in vitro and in vivo toxicity with physiologically based pharmacokinetic modeling

This study aimed to conduct an integrated and probabilistic risk assessment of gold nanoparticles (AuNPs) based on recently published in vitro and in vivo toxicity studies coupled to a physiologically based pharmacokinetic (PBPK) model. Dose-response relationships were characterized based on cell viability assays in various human cell types. A previously well-validated human PBPK model for AuNPs was applied to quantify internal concentrations in liver, kidney, skin, and venous plasma. By applying a Bayesian-based probabilistic risk assessment approach incorporating Monte Carlo simulation, probable human cell death fractions were characterized. Additionally, we implemented in vitro to in vivo and animal-to-human extrapolation approaches to independently estimate external exposure levels of AuNPs that cause minimal toxicity. Our results suggest that under the highest dosing level employed in existing animal studies (worst-case scenario), AuNPs coated with branched polyethylenimine (BPEI) would likely induce ∼90-100% cellular death, implying high cytotoxicity compared to <10% cell death induced by low-to-medium animal dosing levels, which are commonly used in animal studies. The estimated human equivalent doses associated with 5% cell death in liver and kidney were around 1 and 3 mg/kg, respectively. Based on points of departure reported in animal studies, the human equivalent dose estimates associated with gene expression changes and tissue cell apoptosis in liver were 0.005 and 0.5 mg/kg, respectively. Our analyzes provide insights into safety evaluation, risk prediction, and point of departure estimation of AuNP exposure for humans and illustrate an approach that could be applied to other NPs when sufficient data are available.

Undiluted human whole blood uric acid detection using a graphitized mesoporous carbon modified electrode: a potential tool for clinical point-of-care uric acid diagnosis

Direct sensing of uric acid (UA) in an undiluted whole blood sample is reported here taking human whole blood as an analyte and a self-supporting electrolyte. Among various solid electrodes (Pt, Au, GCE, and GCE/Nafion) and carbon nanomaterials (carbon nanofibers, graphene oxide, graphite nanopowder, graphitized mesoporous carbon (GMC), single-walled carbon nanotubes, and multiwalled carbon nanotubes) tested, a GMC-modified glassy carbon electrode, designated as GCE/GMC, showed a remarkable response towards direct electrochemical oxidation of blood uric acid at ∼0.25 V vs. Ag/AgCl, unlike the poor and/or feeble current signals with the other unmodified and modified electrodes. It is plausible that the mesoporous nature of the GMC favours the formation of a blood-GMC bio-corona through internalization and provides straight access to blood-matrixed uric acid. Furthermore, the effects of the scan rate and interference with various biochemicals on the GCE/GMC were analysed. The electrochemical oxidation reaction is found to be diffusion controlled in nature and there is no interference from common biochemicals like ascorbic acid, glucose, tryptophan, H2O2, xanthine, hypoxanthine, cysteine, nitrate, nitrite, and sulfide in blood. Real blood UA sample analysis was demonstrated with comparable UA analysis results from the clinical measurement.

Assessment of interactions of efavirenz solid drug nanoparticles with human immunological and haematological systems

Background

Recent work has developed solid drug nanoparticles (SDNs) of efavirenz that have been demonstrated, preclinically, improved oral bioavailability and the potential to enable up to a 50% dose reduction, and is currently being studied in a healthy volunteer clinical trial. Other SDN formulations are being studied for parenteral administration, either as intramuscular long-acting formulations, or for direct administration intravenously. The interaction of nanoparticles with the immunological and haematological systems can be a major barrier to successful translation but has been understudied for SDN formulations. Here we have conducted a preclinical evaluation of efavirenz SDN to assess their potential interaction with these systems. Platelet aggregation and activation, plasma coagulation, haemolysis, complement activation, T cell functionality and phenotype, monocyte derived macrophage functionality, and NK cell function were assessed in primary healthy volunteer samples treated with either aqueous efavirenz or efavirenz SDN.

Results

Efavirenz SDNs were shown not to interfere with any of the systems studied in terms of immunostimulation nor immunosuppression. Although efavirenz aqueous solution was shown to cause significant haemolysis ex vivo, efavirenz SDNs did not. No other interaction with haematological systems was observed. Efavirenz SDNs have been demonstrated to be immunologically and haematologically inert in the utilised assays.

Conclusions

Taken collectively, along with the recent observation that lopinavir SDN formulations did not impact immunological responses, these data indicate that this type of nanoformulation does not elicit immunological consequences seen with other types of nanomaterial. The methodologies presented here provide a framework for pre-emptive preclinical characterisation of nanoparticle safety.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0349-y) contains supplementary material, which is available to authorized users.

Nanoparticle binding attenuates the pathobiology of gastric cancer-associated Helicobacter pylori

Enteric bacteria may cause severe diseases, including gastric cancer-associated Helicobacter pylori. Their infection paths overlap with the oro-gastrointestinal uptake route for nanoparticles, increasingly occurring during environmental or consumer/medical exposure. By comprehensive independent analytical methods, such as live cell fluorescence, electron as well as atomic force microscopy and elemental analysis, we show that a wide array of nanoparticles (NPs) but not microparticles form complexes with H. pylori and enteric pathogens without the need for specific functionalization. The NP-assembly that occurred rapidly was not influenced by variations in physiological temperature, though affected by the NPs' physico-chemical characteristics. Improved binding was observed for small NPs with a negative surface charge, whereas binding could be reduced by surface 'stealth' modifications. Employing human gastric epithelial cells and 3D-organoid models of the stomach, we show that NP-coating did not inhibit H. pylori's cellular attachment. However, even the assembly of non-bactericidal silica NPs attenuated H. pylori infection by reducing CagA phosphorylation, cytoskeletal rearrangement, and IL-8 secretion. Here we demonstrate that NP binding to enteric bacteria may impact their pathobiology which could be further exploited to rationally modulate the (patho)biology of microbes by nanomaterials.

Nanomaterial–microbe cross-talk: physicochemical principles and (patho)biological consequences

NPs’ characteristics impact their spontaneous binding to microbes, which may affect the (patho)biological identity of both NP and microbes.

Particle Targeting in Complex Biological Media

Over the past few decades, nanoengineered particles have gained increasing interest for applications in the biomedical realm, including diagnosis, imaging, and therapy. When functionalized with targeting ligands, these particles have the potential to interact with specific cells and tissues, and accumulate at desired target sites, reducing side effects and improve overall efficacy in applications such as vaccination and drug delivery. However, when targeted particles enter a complex biological environment, the adsorption of biomolecules and the formation of a surface coating (e.g., a protein corona) changes the properties of the carriers and can render their behavior unpredictable. For this reason, it is of importance to consider the potential challenges imposed by the biological environment at the early stages of particle design. This review describes parameters that affect the targeting ability of particulate drug carriers, with an emphasis on the effect of the protein corona. We highlight strategies for exploiting the protein corona to improve the targeting ability of particles. Finally, we provide suggestions for complementing current in vitro assays used for the evaluation of targeting and carrier efficacy with new and emerging techniques (e.g., 3D models and flow-based technologies) to advance fundamental understanding in bio-nano science and to accelerate the development of targeted particles for biomedical applications.

NanoEHS beyond Toxicity - Focusing on Biocorona

The first phase of environmental health and safety of nanomaterials (nanoEHS) studies has been mainly focused on evidence-based investigations that probe the impact of nanoparticles, nanomaterials and nano-enabled products on biological and ecological systems. The integration of multiple disciplines, including colloidal science, nanomaterial science, chemistry, toxicology/immunology and environmental science, is necessary to understand the implications of nanotechnology for both human health and the environment. While strides have been made in connecting the physicochemical properties of nanomaterials with their hazard potential in tiered models, fundamental understanding of nano-biomolecular interactions and their implications for nanoEHS is largely absent from the literature. Research on nano-biomolecular interactions within the context of natural systems not only provides important clues for deciphering nanotoxicity and nanoparticle-induced pathology, but also presents vast new opportunities for screening beneficial material properties and designing greener products from bottom up. This review highlights new opportunities concerning nano-biomolecular interactions beyond the scope of toxicity.

Biological Fate of Fe₃O₄ Core-Shell Mesoporous Silica Nanoparticles Depending on Particle Surface Chemistry

The biological fate of nanoparticles (NPs) for biomedical applications is highly dependent of their size and charge, their aggregation state and their surface chemistry. The chemical composition of the NPs surface influences their stability in biological fluids, their interaction with proteins, and their attraction to the cell membranes. In this work, core-shell magnetic mesoporous silica nanoparticles (Fe₃O₄@MSN), that are considered as potential theranostic candidates, are coated with polyethylene glycol (PEG) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid bilayer. Their biological fate is studied in comparison to the native NPs. The physicochemical properties of these three types of NPs and their suspension behavior in different media are investigated. The attraction to a membrane model is also evaluated using a supported lipid bilayer. The surface composition of NPs strongly influences their dispersion in biological fluids mimics, protein binding and their interaction with cell membrane. While none of these types of NPs is found to be toxic on mice four days after intravenous injection of a dose of 40 mg kg-1 of NPs, their surface coating nature influences the in vivo biodistribution. Importantly, NP coated with DMPC exhibit a strong accumulation in liver and a very low accumulation in lung in comparison with nude or PEG ones.

Subchronic exposure to palladium nanoparticles affects serum levels of cytokines in female Wistar rats

Recently, palladium nanoparticles (PdNPs) have been increasingly used in many industrial sectors, and this has led to a significant release of nano-sized palladium particles into the environment. However, despite the increase in occupational and general population exposure, information on the potential adverse effects of these PdNPs is still limited and their impact on the immune system constitutes a major health concern. Therefore, the aim of this study was to investigate the potential adverse effects induced by subchronic intravenous administration of PdNPs on the immune system of female Wistar rats by evaluating alterations in Interleukin (IL)-1α, IL-2, IL-4, IL-6, IL-10, IL-12, granulocyte-macrophage colony-stimulating factor (GM-CSF), Interferon (INF)-γ, and Tumor Necrosis Factor (TNF)-α serum levels. Exposed and control animals were randomly divided into five groups (0, 0.012, 0.12, 1.2, and 12 μg PdNPs per kg body weight) which were treated with repeated intravenous injections of vehicle or PdNPs (on day 1, 30, and 60). Subchronic exposure to PdNPs induced a decreasing trend in serum levels in most of the cytokines investigated, with the highest concentration (12 μg/kg) determining significant inhibitory effects. Overall, these results showed that PdNPs are able to alter cytokine serum levels in subchronically treated Wistar rats, suggesting a possible impact of these xenobiotics on the immune system after long-term exposures.

Impact of nanoparticles on DNA repair processes: current knowledge and working hypotheses

The potential health effects of exposure to nanomaterials (NMs) is currently heavily studied. Among the most often reported impact is DNA damage, also termed genotoxicity. While several reviews relate the DNA damage induced by NMs and the techniques that can be used to prove such effects, the question of impact of NMs on DNA repair processes has never been specifically reviewed. The present review article proposes to fill this gap of knowledge by critically describing the DNA repair processes that could be affected by nanoparticle (NP) exposure, then by reporting the current state of the art on effects of NPs on DNA repair, at the level of protein function, gene induction and post-transcriptional modifications, and taking into account the advantages and limitations of the different experimental approaches. Since little is known about this impact, working hypothesis for the future are then proposed.

Quantitative uptake of colloidal particles by cell cultures

The use of nanotechnologies involving nano- and microparticles has increased tremendously in the recent past. There are various beneficial characteristics that make particles attractive for a wide range of technologies. However, colloidal particles on the other hand can potentially be harmful for humans and environment. Today, complete understanding of the interaction of colloidal particles with biological systems still remains a challenge. Indeed, their uptake, effects, and final cell cycle including their life span fate and degradation in biological systems are not fully understood. This is mainly due to the complexity of multiple parameters which need to be taken in consideration to perform the nanosafety research. Therefore, we will provide an overview of the common denominators and ideas to achieve universal metrics to assess their safety. The review discusses aspects including how biological media could change the physicochemical properties of colloids, how colloids are endocytosed by cells, how to distinguish between internalized versus membrane-attached colloids, possible correlation of cellular uptake of colloids with their physicochemical properties, and how the colloidal stability of colloids may vary upon cell internalization. In conclusion three main statements are given. First, in typically exposure scenarios only part of the colloids associated with cells are internalized while a significant part remain outside cells attached to their membrane. For quantitative uptake studies false positive counts in the form of only adherent but not internalized colloids have to be avoided. pH sensitive fluorophores attached to the colloids, which can discriminate between acidic endosomal/lysosomal and neutral extracellular environment around colloids offer a possible solution. Second, the metrics selected for uptake studies is of utmost importance. Counting the internalized colloids by number or by volume may lead to significantly different results. Third, colloids may change their physicochemical properties along their life cycle, and appropriate characterization is required during the different stages.