Real-Time Nanoparticle-Cell Interactions in Physiological Media by Atomic Force Microscopy

Polymeric nanocarrier-based adjuvants to enhance a locally produced mucosal coryza vaccine in chicken

Infectious coryza (IC) is an acute upper respiratory disease of chicken caused by Avibacterium (A.) paragallinarum. This disease results in an increased culling rate in meat chicken and a marked decrease in egg production (10% to more than 40%) in laying and breeding hens. Vaccines were first used against IC and effectively controlled the disease. Nanotechnology provides an excellent way to develop a new generation of vaccines. NPs have been widely used in vaccine design as adjuvants and antigen delivery vehicles and as antibacterial agents; thus, they can be used as inactivators for bacterial culture. In this research, the antibacterial effects of several nanoparticles (NPs), such as silicon dioxide with chitosan (SiO2-CS), oleoyl-chitosan (O.CS), silicon dioxide (SiO2), and iron oxide (Fe3O4), on A. paragallinarum were studied. Additionally, different A. paragallinarum vaccines were made using the same nanomaterials at a concentration of 400 µg/ml to help control infectious coryza disease in chicken. A concentration of 400 µg/ml of all the NPs tested was the best concentration for the inactivation of A. paragallinarum. Additionally, this study showed that the infectious coryza vaccine adjuvanted with SiO2 NPs had the highest immune response, followed by the infectious coryza vaccine adjuvanted with Fe3O4 NPs, the infectious coryza vaccine adjuvanted with SiO2-CS NPs, and the infectious coryza vaccine adjuvanted with O.CS NPs in comparison with the infectious coryza vaccine adjuvanted with liquid paraffin (a commercial vaccine).

Exploring Curcumin-Loaded Lipid-Based Nanomedicine as Efficient Targeted Therapy for Alzheimer's Diseases

Alzheimer's disease (AD) is a neurological condition currently with 47 million people suffering from it globally. AD might have many reasons such as genetic issues, environmental factors, and Aβ accumulation, which is the biomarker of the disease. Since the primary reason is unknown, there is no targeted treatment at the moment, but ongoing research aims to slow its progression by managing amyloid-beta peptide production rather than symptomatic improvement. Since phytochemicals have been demonstrated to possess antioxidant, anti-inflammatory, and neuroprotective properties, they may target multiple pathological factors and can reduce the risk of the disease. Curcumin, as a phytochemical found in turmeric known for its antioxidant, free radical scavenging properties, and as an antiamyloid in treating AD, has come under investigation. Although its low bioavailability limits its efficacy, a prominent drug delivery system (DDS) is desired to overcome it. Hence, the potency of lipid-based nanoparticles encapsulating curcumin (LNPs-CUR) is considered in this study as a promising DDS. In vivo studies in animal models indicate LNPs-CUR effectively slow amyloid plaque formation, leading to cognitive enhancement and reduced toxicity compared to free CUR. However, a deeper understanding of CUR's pharmacokinetics and safety profile is crucial before LNPs-CUR can be considered as a medicine. Future investigations may explore the combination of NPs with other therapeutic agents to increase their efficacy in AD cases. This review provides the current position of CUR in the AD therapy paradigm, the DDS suggestions for CUR, and the previous research from the point of analytical view focused on the advantages and challenges.

Biocompatibility Evaluation of TiO2, Fe3O4, and TiO2/Fe3O4 Nanomaterials: Insights into Potential Toxic Effects in Erythrocytes and HepG2 Cells

Nanomaterials such as titanium dioxide and magnetite are increasingly used in several fields, such as water remediation and agriculture. However, this has raised environmental concerns due to potential exposure to organisms like humans. Nanomaterials can cause adverse interactions depending on physicochemical characteristics, like size, morphology, and composition, when interacting with living beings. To ensure safe use and prevent the risk of exposure to nanomaterials, their biocompatibility must be assessed. In vitro cell cultures are beneficial for assessing nanomaterial-cell interactions due to their easy handling. The present study evaluated the biocompatibility of TiO2, Fe3O4, and TiO2/Fe3O4 nanomaterials thermally treated at 350 °C and 450 °C in erythrocytes and HepG2 cells. According to the hemolysis experiments, non-thermally treated NMs are toxic (>5% hemolysis), but their thermally treated counterparts do not present toxicity (<2%). This behavior indicates that the toxicity derives from some precursor (solvent or surfactant) used in the synthesis of the nanomaterials. All the thermally treated nanomaterials did not show hemolytic activity under different conditions, such as low-light exposure or the absence of blood plasma proteins. In contrast, non-thermally treated nanomaterials showed a high hemolytic behavior, which was reduced after the purification (washing and thermal treatment) of nanomaterials, indicating the presence of surfactant residue used during synthesis. An MTS cell viability assay shows that calcined nanomaterials do not reduce cell viability (>11%) during 24 h of exposure. On the other hand, a lactate dehydrogenase leakage assay resulted in a higher variability, indicating that several nanomaterials did not cause an increase in cell death as compared to the control. However, a holotomographic microscopy analysis reveals a high accumulation of nanomaterials in the cell structure at a low concentration (10 µg mL-1), altering cell morphology, which could lead to cell membrane damage and cell viability reduction.

Rational nanoparticle design: Optimization using insights from experiments and mathematical models

Polymeric nanoparticles are highly tunable drug delivery systems that show promise in targeting therapeutics to specific sites within the body. Rational nanoparticle design can make use of mathematical models to organize and extend experimental data, allowing for optimization of nanoparticles for particular drug delivery applications. While rational nanoparticle design is attractive from the standpoint of improving therapy and reducing unnecessary experiments, it has yet to be fully realized. The difficulty lies in the complexity of nanoparticle structure and behavior, which is added to the complexity of the physiological mechanisms involved in nanoparticle distribution throughout the body. In this review, we discuss the most important aspects of rational design of polymeric nanoparticles. Ultimately, we conclude that many experimental datasets are required to fully model polymeric nanoparticle behavior at multiple scales. Further, we suggest ways to consider the limitations and uncertainty of experimental data in creating nanoparticle design optimization schema, which we call quantitative nanoparticle design frameworks.

Method for nanoparticles uptake evaluation based on double labeled fluorescent cells scanned in enhanced darkfield microscopy

We present a method that integrates the standard imaging tools for locating and detecting unlabeled nanoparticles (NPs) with computational tools for partitioning cell volumes and NPs counting within specified regions to evaluate their internal traffic. The method uses enhanced dark field CytoViva optical system and combines 3D reconstructions of double fluorescently labeled cells with hyperspectral images. The method allows the partitioning of each cell image into four regions: nucleus, cytoplasm, and two neighboring shells, as well as investigations across thin layers adjacent to the plasma membrane. MATLAB scripts were developed to process the images and to localize NPs in each region. Specific parameters were computed to assess the uptake efficiency: regional densities of NPs, flow densities, relative accumulation indices, and uptake ratios. The results of the method are in line with biochemical analyses. It was shown that a sort of saturation limit for intracellular NPs density is reached at high extracellular NPs concentrations. Higher NPs densities were found in the proximity of the plasma membranes. A decrease of the cell viability with increasing extracellular NPs concentration was observed and explained the negative correlation of the cell eccentricity with NPs number.

Drying of bio-colloidal sessile droplets: Advances, applications, and perspectives

Drying of biologically-relevant sessile droplets, including passive systems such as DNA, proteins, plasma, and blood, as well as active microbial systems comprising bacterial and algal dispersions, has garnered considerable attention over the last decades. Distinct morphological patterns emerge when bio-colloids undergo evaporative drying, with significant potential in a wide range of biomedical applications, spanning bio-sensing, medical diagnostics, drug delivery, and antimicrobial resistance. Consequently, the prospects of novel and thrifty bio-medical toolkits based on drying bio-colloids have driven tremendous progress in the science of morphological patterns and advanced quantitative image-based analysis. This review presents a comprehensive overview of bio-colloidal droplets drying on solid substrates, focusing on the experimental progress during the last ten years. We provide a summary of the physical and material properties of relevant bio-colloids and link their native composition (constituent particles, solvent, and concentrations) to the patterns emerging due to drying. We specifically examined the drying patterns generated by passive bio-colloids (e.g., DNA, globular, fibrous, composite proteins, plasma, serum, blood, urine, tears, and saliva). This article highlights how the emerging morphological patterns are influenced by the nature of the biological entities and the solvent, micro- and global environmental conditions (temperature and relative humidity), and substrate attributes like wettability. Crucially, correlations between emergent patterns and the initial droplet compositions enable the detection of potential clinical abnormalities when compared with the patterns of drying droplets of healthy control samples, offering a blueprint for the diagnosis of the type and stage of a specific disease (or disorder). Recent experimental investigations of pattern formation in the bio-mimetic and salivary drying droplets in the context of COVID-19 are also presented. We further summarized the role of biologically active agents in the drying process, including bacteria, algae, spermatozoa, and nematodes, and discussed the coupling between self-propulsion and hydrodynamics during the drying process. We wrap up the review by highlighting the role of cross-scale in situ experimental techniques for quantifying sub-micron to micro-scale features and the critical role of cross-disciplinary approaches (e.g., experimental and image processing techniques with machine learning algorithms) to quantify and predict the drying-induced features. We conclude the review with a perspective on the next generation of research and applications based on drying droplets, ultimately enabling innovative solutions and quantitative tools to investigate this exciting interface of physics, biology, data sciences, and machine learning.

Physiological relevance of in-vitro cell-nanoparticle interaction studies as a predictive tool in cancer nanomedicine research

Cell uptake study is a routine experiment used as a surrogate to predict in vivo response in cancer nanomedicine research. Cell culture conditions should be designed in such a way that it emulates 'real' physiological conditions and avoid artefacts. It is critical to dissect the steps involved in cellular uptake to understand the physical, chemical, and biological factors responsible for particle internalization. The two-dimensional model (2D) of cell culture is overly simplistic to mimic the complexity of cancer tissues that exist in vivo. It cannot simulate the critical tissue-specific properties like cell-cell interaction and cell-extracellular matrix (ECM) interaction and its influences on the temporal and spatial distribution of nanoparticles (NPs). The three dimensional model organization of heterogenous cancer and normal cells with the ECM acts as a formidable barrier to NP penetration and cellular uptake. The three dimensional cell culture (3D) technology is a breakthrough in this direction that can mimic the barrier properties of the tumor microenvironment (TME). Herein, we discuss the physiological factors that should be considered to bridge the translational gap between in and vitro cell culture studies and in-vivo studies in cancer nanomedicine.

Biogenic Selenium Nanoparticles in Biomedical Sciences: Properties, Current Trends, Novel Opportunities and Emerging Challenges in Theranostic Nanomedicine

Selenium is an important dietary supplement and an essential trace element incorporated into selenoproteins with growth-modulating properties and cytotoxic mechanisms of action. However, different compounds of selenium usually possess a narrow nutritional or therapeutic window with a low degree of absorption and delicate safety margins, depending on the dose and the chemical form in which they are provided to the organism. Hence, selenium nanoparticles (SeNPs) are emerging as a novel therapeutic and diagnostic platform with decreased toxicity and the capacity to enhance the biological properties of Se-based compounds. Consistent with the exciting possibilities offered by nanotechnology in the diagnosis, treatment, and prevention of diseases, SeNPs are useful tools in current biomedical research with exceptional benefits as potential therapeutics, with enhanced bioavailability, improved targeting, and effectiveness against oxidative stress and inflammation-mediated disorders. In view of the need for developing eco-friendly, inexpensive, simple, and high-throughput biomedical agents that can also ally with theranostic purposes and exhibit negligible side effects, biogenic SeNPs are receiving special attention. The present manuscript aims to be a reference in its kind by providing the readership with a thorough and comprehensive review that emphasizes the current, yet expanding, possibilities offered by biogenic SeNPs in the biomedical field and the promise they hold among selenium-derived products to, eventually, elicit future developments. First, the present review recalls the physiological importance of selenium as an oligo-element and introduces the unique biological, physicochemical, optoelectronic, and catalytic properties of Se nanomaterials. Then, it addresses the significance of nanosizing on pharmacological activity (pharmacokinetics and pharmacodynamics) and cellular interactions of SeNPs. Importantly, it discusses in detail the role of biosynthesized SeNPs as innovative theranostic agents for personalized nanomedicine-based therapies. Finally, this review explores the role of biogenic SeNPs in the ongoing context of the SARS-CoV-2 pandemic and presents key prospects in translational nanomedicine.

Disturbed Flow-Facilitated Margination and Targeting of Nanodisks Protect against Atherosclerosis

Disturbed blood flow induces endothelial pro-inflammatory responses that promote atherogenesis. Nanoparticle-based therapeutics aimed at treating endothelial inflammation in vasculature where disturbed flow occurs may provide a promising avenue to prevent atherosclerosis. By using a vertical-step flow apparatus and a microfluidic chip of vascular stenosis, herein, it is found that the disk-shaped versus the spherical nanoparticles exhibit preferential margination (localization and adhesion) to the regions with the pro-atherogenic disturbed flow. By employing a mouse model of carotid partial ligation, superior targeting and higher accumulation of the disk-shaped particles are also demonstrated within disturbed flow areas than that of the spherical particles. In hyperlipidemia mice, administration of disk-shaped particles loaded with hypomethylating agent decitabine (DAC) displays greater anti-inflammatory and anti-atherosclerotic effects compared with that of the spherical counterparts and exhibits reduced toxicity than "naked" DAC. The findings suggest that shaping nanoparticles to disk is an effective strategy for promoting their delivery to atheroprone endothelia.

In Situ Assay of Interfacial Interaction between ZnO Nanoparticles and Live Cell Disturbed by Surfactants

The interfacial interaction between pollutants and organisms is a critical process in controlling the environmental fates of pollutants; however, in situ assay of the interaction is still a great challenge. Here, in situ determination of dissociation constants (K_d) for ZnO nanoparticles (ZnO NPs) from live algal cells disturbed by different-charged surfactants was established using microscale thermophoresis (MST). Moreover, in situ measurement of the adhesion force between the ZnO NPs probe and live single cell was performed using an atomic force microscope (AFM). Results showed that the cationic cetyltrimethylammonium chloride (CTAC) and anionic sodium dodecylbenzenesulfonate (SDBS) increased but nonionic Triton X-100 (TX-100) decreased the adhesion of ZnO NPs on cells. However, the force signature exhibited a smooth single retracted peak at short distances in the SDBS- and TX-100-treated groups, distinguished from the "see-saw" pattern peak in the CTAC-treated groups. The extended Derjaguin-Landau-Verway-Overbeek (XDLVO) calculation further confirmed that SDBS and TX-100 mainly disturbed the short-range hydration on the NP-cell interface, while CTAC reduced the long-range electrostatic repulsion. Furthermore, an excellent linear correlation between Zn bioaccumulation and two parameters (K_d and adhesion force) indicated that NP-cell interfacial interactions affected Zn bioaccumulation. Thus, in situ assay provides a quantitative basis for the pollutant-organism interfacial interaction to evaluate the environmental fate and ecological risk of pollutants.

Tools shaping drug discovery and development

Spectroscopic, scattering, and imaging methods play an important role in advancing the study of pharmaceutical and biopharmaceutical therapies. The tools more familiar to scientists within industry and beyond, such as nuclear magnetic resonance and fluorescence spectroscopy, serve two functions: as simple high-throughput techniques for identification and purity analysis, and as potential tools for measuring dynamics and structures of complex biological systems, from proteins and nucleic acids to membranes and nanoparticle delivery systems. With the expansion of commercial small-angle x-ray scattering instruments into the laboratory setting and the accessibility of industrial researchers to small-angle neutron scattering facilities, scattering methods are now used more frequently in the industrial research setting, and probe-less time-resolved small-angle scattering experiments are now able to be conducted to truly probe the mechanism of reactions and the location of individual components in complex model or biological systems. The availability of atomic force microscopes in the past several decades enables measurements that are, in some ways, complementary to the spectroscopic techniques, and wholly orthogonal in others, such as those related to nanomechanics. As therapies have advanced from small molecules to protein biologics and now messenger RNA vaccines, the depth of biophysical knowledge must continue to serve in drug discovery and development to ensure quality of the drug, and the characterization toolbox must be opened up to adapt traditional spectroscopic methods and adopt new techniques for unraveling the complexities of the new modalities. The overview of the biophysical methods in this review is meant to showcase the uses of multiple techniques for different modalities and present recent applications for tackling particularly challenging situations in drug development that can be solved with the aid of fluorescence spectroscopy, nuclear magnetic resonance spectroscopy, atomic force microscopy, and small-angle scattering.

1,4-Benzenedithiol-Bridged Nanogap-Based Individual Particle Surface-Enhanced Raman Spectroscopy Mechanical Probe for Revealing the Endocytic Force

1,4-Benzenedithiol (BDT)-bridged core-satellite assemblies, as surface-enhanced Raman spectroscopy (SERS) mechanical probes, can be employed for real-time monitoring of the dynamics of endocytic forces and the accompanying trajectory of nanoparticles during the endocytosis process. These mechanical probes exhibit good responses in terms of SERS intensity ratios while undergoing mechanical pressure. Force tracing and the accompanying trajectory of nanoparticles are resolved accurately to render the endocytosis process in live cells. Density functional theory simulation results further proved the sensing scheme due to the electrons transforming between BDT and gold nanoparticles. Furthermore, this SERS mechanical probe is a valid method to visualize endocytic forces at multiple locations and establish a direct criterion to discriminate between cancer cells and normal cells.

Atomic force microscopy applied to interrogate nanoscale cellular chemistry and supramolecular bond dynamics for biomedical applications

Understanding biological interactions at a molecular level grants valuable information relevant to improving medical treatments and outcomes. Among the suite of technologies available, Atomic Force Microscopy (AFM) is unique in its ability to quantitatively probe forces and receptor-ligand interactions in real-time. The ability to assess the formation of supramolecular bonds and intermediates in real-time on surfaces and living cells generates important information relevant to understanding biological phenomena. Combining AFM with fluorescence-based techniques allows for an unprecedented level of insight not only concerning the formation and rupture of bonds, but understanding medically relevant interactions at a molecular level. As the ability of AFM to probe cells and more complex models improves, being able to assess binding kinetics, chemical topographies, and garner spectroscopic information will likely become key to developing further improvements in fields such as cancer, nanomaterials, and virology. The rapid response to the COVID-19 crisis, producing information regarding not just receptor affinities, but also strain-dependent efficacy of neutralizing nanobodies, demonstrates just how viable and integral to the pre-clinical development of information AFM techniques are in this era of medicine.

Structural changes in selected human proteins induced by exposure to quantum dots, their biological relevance and possible biomedical applications

Quantum dots (QDs) are semi-conductor luminescent nanocrystals usually of 2-10 nm diameter, attracting the significant attention in biomedical studies since emerged. Due to their unique optical and electronic properties, i.e. wide absorption spectra, narrow tunable emission bands or stable, bright photoluminescence, QDs seem to be ideally suited for multi-colour, simultaneous bioimaging and cellular labeling at the molecular level as new-generation probes. A highly reactive surface of QDs allows for conjugating them to biomolecules, what enables their direct binding to areas of interest inside or outside the cell for biosensing or targeted delivery. Particularly protein-QDs conjugates are current subjects of research, as features of QDs can be combined with protein specific functionalities and therefore used as a complex in variety of biomedical applications. It is known that QDs are able to interact with cells, organelles and macromolecules of the human body after administration. QDs are reported to cause changes at proteins level, including unfolding and three-dimensional structure alterations which might hamper proteins from performing their physiological functions and thereby limit the use of QD-protein conjugates in vivo. Moreover, these changes may trigger unwanted cellular outcomes as the effect of different signaling pathways activation. In this review, characteristics of QDs interactions with certain human proteins are presented and discussed. Besides that, the following manuscript provides an overview on structural changes of specific proteins exposed to QDs and their biological and biomedical relevance.

Modulus characterization of cells with submicron colloidal probes by atomic force microscope

Colloidal probes have been increasingly demanded for the characterization of cellular modulus in atomic force microscope because of their well-defined geometry and large contact area with cell. In this work, submicron colloidal probes are prepared by scanning electron microscope/focused ion beam and compared with sharp tip and micron colloidal probe, in conjunction with loading velocity and indentation depth on the apparent elastic modulus. NIM and cartilage cells are used as specimens. The results show that modulus value measured by sharp tip changes significantly with loading velocity while remains almost stable by colloidal probes. Also, submicron colloidal probe is superior in characterizing the modulus with increasing indentation depth, which could help reveal the mechanical details of cellular membrane and the modulus of the whole cell. To test the submicron colloidal probe further, the modulus distribution map of cell is scanned with submicron colloidal probe of 50 nm radius during small and large indentation depths with high spatial resolution. The outcome of this work will provide the effective submicron colloidal probe according to the effect of loading velocity and indentation depth, characterizing the mechanical properties of the cells.

Co-exposure to boscalid and TiO2 (E171) or SiO2 (E551) downregulates cell junction gene expression in small intestinal epithelium cellular model and increases pesticide translocation

A recent published study showed that TiO₂ (E171) and SiO₂ (E551), two widely used nano-enabled food additives, increased the translocation of the commonly used pesticide boscalid by 20% and 30% respectively. Such increased absorption of pesticides due to the presence of engineered nanomaterials (ENMs) in food raises health concerns for these food additives. In this companion study, mRNA expression of genes related to cell junctions in a small intestinal epithelial cellular model after exposure to simulated digestas of fasting food model (phosphate buffer) containing boscalid (150 ppm) with or without either TiO₂ or SiO₂ (1% w/w) were analyzed. Specific changes in cell barrier function underlying or contributing to the increased translocation of boscalid observed in the previous study were assessed. Results showed that exposure to boscalid alone has no significant effect on cell junction genes, however, co-exposure to boscalid and TiO₂ significantly regulated expression of cell-matrix junction focal adhesion-related genes, e.g., downregulating Cav1 (- 1.39-fold, p<0.05), upregulating Cav3 (+ 3.30-fold, p<0.01) and Itga4 (+ 3.30-fold, p<0.05). Similarly, co-exposure to boscalid and SiO₂ significantly downregulated multiple cell-cell junction genes, including tight junction genes (Cldn1, Cldn11, Cldn16, Cldn18, and Jam3), adherens junction genes (Notch1, Notch3, Pvrl1) and gap junction genes (Gja3 and Gjb2), as well as cell-matrix junction focal adhesion genes (Itga4, Itga6, Itga7). Together, these findings suggest that co-ingestion of boscalid with TiO₂ (E171) or SiO₂ (E551) could cause weakening of cell junctions and intercellular adhesion, which could result in dysregulation of paracellular transport, and presumably contributed to the previously observed increased translocation of boscalid at the presence of these ENMs. This novel finding raises health safety concerns for such popular food additives.

Adhesion force spectroscopy with nanostructured colloidal probes reveals nanotopography-dependent early mechanotransductive interactions at the cell membrane level

Mechanosensing, the ability of cells to perceive and interpret the microenvironmental biophysical cues (such as the nanotopography), impacts strongly cellular behaviour through mechanotransductive processes and signalling. These events are predominantly mediated by integrins, the principal cellular adhesion receptors located at the cell/extracellular matrix (ECM) interface. Because of the typical piconewton force range and nanometre length scale of mechanotransductive interactions, achieving a detailed understanding of the spatiotemporal dynamics occurring at the cell/microenvironment interface is challenging; sophisticated interdisciplinary methodologies are required. Moreover, an accurate control over the nanotopographical features of the microenvironment is essential, in order to systematically investigate and precisely assess the influence of the different nanotopographical motifs on the mechanotransductive process. In this framework, we were able to study and quantify the impact of microenvironmental nanotopography on early cellular adhesion events by means of adhesion force spectroscopy based on innovative colloidal probes mimicking the nanotopography of natural ECMs. These probes provided the opportunity to detect nanotopography-specific modulations of the molecular clutch force loading dynamics and integrin clustering at the level of single binding events, in the critical time window of nascent adhesion formation. Following this approach, we found that the nanotopographical features are responsible for an excessive force loading in single adhesion sites after 20-60 s of interaction, causing a drop in the number of adhesion sites. However, by manganese treatment we demonstrated that the availability of activated integrins is a critical regulatory factor for these nanotopography-dependent dynamics.

Characterization of drug delivery vehicles using atomic force microscopy: current status

INTRODUCTION

The field of nanomedicine, utilizing nano-sized vehicles (nanoparticles and nanofibers) for targeted local drug delivery, has a promising future. This is dependent on the ability to analyze the chemical and physical properties of these drug carriers at the nanoscale and hence atomic force microscopy (AFM), a high-resolution imaging and local force-measurement technique, is ideally suited.

AREAS COVERED

Following a brief introduction to the technique, the review describes how AFM has been used in selected publications from 2015 to 2018 to characterize nanoparticles and nanofibers as drug delivery vehicles. These sections are ordered into areas of increasing AFM complexity: imaging/particle sizing, surface roughness/quantitative analysis of images, and analysis of force curves (to extract nanoindentation and adhesion data).

EXPERT OPINION

AFM imaging/sizing is used extensively for the characterization of nanoparticle and nanofiber drug delivery vehicles, with surface roughness and nanomechanical/adhesion data acquisition being less common. The field is progressing into combining AFM with other techniques, notably SEM, ToF-SIMS, Raman, Confocal, and UV. Current limitations include a 50 nm resolution limit of nanoparticles imaged within live cells and AFM tip-induced activation of cytoskeleton proteins. Following drug release real-time with AFM-spectroscopic techniques and studying drug interactions on cell receptors appear to be on the horizon.

Nano-TiO2 Drives Epithelial-Mesenchymal Transition in Intestinal Epithelial Cancer Cells

The majority of cancer mortality is associated with cancer metastasis. Epithelial-to-mesenchymal transition (EMT) is a process by which cells attain migratory and invasive properties, eventually leading to cancer metastasis. Here, it is shown that titanium dioxide nanoparticles (nano-TiO₂ ), a common food additive, can induce the EMT process in colorectal cancer cells. Nano-TiO₂ exposure is observed to activate transforming growth factor-β (TGF-β)/mitogen-activated protein kinase (MAPK) and wingless (Wnt) pathways, and drive the EMT process. Similarly, silica nanoparticles (nano-SiO₂ ) and hydroxyapatite nanoparticles (nano-HA), as food-based additives, can be ingested and accumulated in the stomach, and are found to be able to induce the EMT progression. The implication of this work can be profound for colorectal cancer patients where these food additives may unknowingly and unnecessarily hasten the progression of their cancers.

Nanoparticle Wettability Influences Nanoparticle-Phospholipid Interactions

We explored the influence of nanoparticle (NP) surface charge and hydrophobicity on NP-biomolecule interactions by measuring the composition of adsorbed phospholipids on four NPs, namely, positively charged CeO₂ and ZnO and negatively charged BaSO₄ and silica-coated CeO_2, after exposure to bronchoalveolar lavage fluid (BALf) obtained from rats, and to a mixture of neutral dipalmitoyl phosphatidylcholine (DPPC) and negatively charged dipalmitoyl phosphatidic acid (DPPA). The resulting NP-lipid interactions were examined by cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM). Our data show that the amount of adsorbed lipids on NPs after incubation in BALf and the DPPC/DPPA mixture was higher in CeO₂ than in the other NPs, qualitatively consistent with their relative hydrophobicity. The relative concentrations of specific adsorbed phospholipids on NP surfaces were different from their relative concentrations in the BALf. Sphingomyelin was not detected in the extracted lipids from the NPs despite its >20% concentration in the BALf. AFM showed that the more hydrophobic CeO₂ NPs tended to be located inside lipid vesicles, whereas less hydrophobic BaSO₄ NPs appeared to be outside. In addition, cryo-TEM analysis showed that CeO₂ NPs were associated with the formation of multilamellar lipid bilayers, whereas BaSO₄ NPs with unilamellar lipid bilayers. These data suggest that the NP surface hydrophobicity predominantly controls the amounts and types of lipids adsorbed, as well as the nature of their interaction with phospholipids.

Detrimental impact of silica nanoparticles on the nanomechanical properties of Escherichia coli, studied by AFM

Despite great innovative and technological promises, nanoparticles (NPs) can ultimately exert an antibacterial activity by affecting the cell envelope integrity. This envelope, by conferring the cell its rigidity and protection, is intimately related to the mechanical behavior of the bacterial surface. Depending on their size, surface chemistry, shape, NPs can induce damages to the cell morphology and structure among others, and are therefore expected to alter the overall mechanical properties of bacteria. Although Atomic Force Microscopy (AFM) stands as a powerful tool to study biological systems, with high resolution and in near physiological environment, it has rarely been applied to investigate at the same time both morphological and mechanical degradations of bacteria upon NPs treatment. Consequently, this study aims at quantifying the impact of the silica NPs (SiO₂-NPs) on the mechanical properties of E. coli cells after their exposure, and relating it to their toxic activity under a critical diameter. Cell elasticity was calculated by fitting the force curves with the Hertz model, and was correlated with the morphological study. SiO₂-NPs of 100 nm diameter did not trigger any significant change in the Young modulus of E. coli, in agreement with the bacterial intact morphology and membrane structure. On the opposite, the 4 nm diameter SiO₂-NPs did induce a significant decrease in E. coli Young modulus, mainly associated with the disorganization of lipopolysaccharides in the outer membrane and the permeation of the underlying peptidoglycan layer. The subsequent toxic behavior of these NPs is finally confirmed by the presence of membrane residues, due to cell lysis, exhibiting typical adhesion features.

Investigation of adhesive interactions in the specific targeting of Triptorelin-conjugated PEG-coated magnetite nanoparticles to breast cancer cells

The understanding of adhesive interaction at the nanoscale between functionalized nanoparticles and biological cells is of great importance to develop effective theranostic nanocarriers for targeted cancer therapy. Here, we report a combination of experimental and computational approaches to evaluate the adhesion between Triptorelin (a Luteinizing Hormone-Releasing Hormone (LHRH) agonist)-conjugated poly-(ethylene glycol) (PEG)-coated magnetite nanoparticles (Triptorelin-MNPs) and breast cells. The adhesion forces between Triptorelin-MNPs and normal/cancerous breast cells are obtained using atomic force microscopy. The corresponding work of adhesion is then estimated using Johnson-Kendall-Roberts model. Our results demonstrate that Triptorelin-MNPs have a fourteen-fold greater work of adhesion to breast cancer cells than to normal breast cells. In addition, the work of adhesion between Triptorelin-MNPs and breast cancer cells is found to be three times more than that between unmodified MNPs and breast cancer cells. Hence, the experimental observation indicates that Triptorelin ligands facilitate the specific targeting of breast cancer cells. Furthermore, molecular dynamics simulations are performed to investigate the molecular origins of the adhesive interactions. The simulations reveal that the interactions between molecules (e.g. Triptorelin and PEG) and LHRH receptors are dominated by van der Waals energies, while the interactions of these molecules with cell membrane are dominated by electrostatic interactions. Moreover, both experimental and computational results reveal that PEG serves as an effective coating that enhances adhesive interactions to breast cancer cells that over-express LHRH receptors, while reduces the adhesion to normal breast cells. Our results highlight the potential to develop Triptorelin-MNPs into tumor-specific MRI contrast agents and drug carriers.

STATEMENT OF SIGNIFICANCE

Systematic investigation of adhesive interactions between functionalized nanoparticles and cancer cells is of great importance in developing effective theranostic nanocarriers for targeted cancer therapy. Herein, we use a combination of atomic force microscopy technique and molecular dynamics simulations approach to explore the adhesive interactions at the nanoscale between Triptorelin-conjugated polyethylene glycol (PEG)-coated magnetite nanoparticles and normal/cancerous breast cells. This study characterizes and quantifies the work of adhesion, as well as adhesion forces, at the nanocarrier/cell interfaces, unravels the molecular origins of adhesive interactions and highlights the effectiveness of PEG coatings and Triptorelin ligands in the specific targeting of breast cancer cells. Our findings expand the fundamental understanding of nanoparticle/cell adhesion and provide guidelines for the design of more rational nanocarriers.

Development of reference metal and metal oxide engineered nanomaterials for nanotoxicology research using high throughput and precision flame spray synthesis approaches

There is a growing need to develop and characterize reference metal and metal oxide engineered nanomaterials (ENMs) of high purity and tunable intrinsic properties suitable for nanotoxicology research. Here a high throughput (volume) and precision flame spray pyrolysis (FSP) approach coupled with state-of-the-art characterization techniques are utilized to generate such reference ENMs. The lab-based and industrially relevant FSP system, termed as Versatile Engineered Nanomaterials Generation System (VENGES), synthesizes the metals and metal oxides, at high throughput manner with controlled properties, such as primary particle size, aggregate diameter, shape, crystallinity, stoichiometry and surface chemistry. A nanopanel of nine reference ENMs (silica, silver, silver supported on silica, alumina, ceria and iron oxide) was synthesized and characterized using combined electron microscopy, advanced spectroscopic techniques and physical analyses (e.g., BET, XRD, TEM, pycnometry, XPS, ICP-MS and FTIR). ENMs show a high degree of chemical purity and stoichiometry, and low content of carbon residuals, and are sterile and free of bacteria and endotoxins. Further, their colloidal properties and their implication in in-vitro dosimetry have been also investigated in both environmental and test biological media. The suitability of reference ENMs and protocols developed in this study brings forth new arenas to generate reliable and reproducible toxicological data in an effort to reduce conflicting and contradicting inter-laboratory data on relative toxic effects of ENMs.

Effective delivery of sonication energy to fast settling and agglomerating nanomaterial suspensions for cellular studies: Implications for stability, particle kinetics, dosimetry and toxicity

Typical in vitro assays used for high throughput toxicological screening and measuring nano-bio interactions are conducted by pipetting suspensions of engineered nanomaterials (ENMs) dispersed in nutrient-rich culture media directly onto cells. In order to achieve fairly monodisperse and stable suspensions of small agglomerates, ultrasonic energy is usually applied to break apart large agglomerates that can form upon suspension in liquid. Lack of standardized protocols and methods for delivering sonication energy can introduce variability in the ENM suspension properties (e.g. agglomerate size, polydispersity, suspension stability over time), and holds significant implications for in vitro dosimetry, toxicity, and other nano-bio interactions. Careful assessment of particle transformations during dispersion preparation and sonication is therefore critical for accurate interpretation of in vitro toxicity studies. In this short communication, the difficulties of preparing stable suspensions of rapidly settling ENMs are presented. Furthermore, methods to optimize the delivery of the critical sonication energy required to break large agglomerates and prepare stable, fairly monodispersed suspensions of fast settling ENMs are presented. A methodology for the efficient delivery of sonication energy in a discrete manner is presented and validated using various rapidly agglomerating and settling ENMs. The implications of continuous vs. discrete sonication on average hydrodynamic diameter, and polydispersity was also assessed for both fast and slow settling ENMs. For the rapidly agglomerating and settling ENMs (Ag15%/SiO2, Ag and CeO2), the proposed discrete sonication achieved a significant reduction in the agglomerate diameter and polydispersity. In contrast, the relatively slow agglomerating and settling Fe2O3 suspension did not exhibit statistically significant differences in average hydrodynamic diameter or polydispersity between the continuous and discrete sonication approaches. Our results highlight the importance of using the proposed material-specific discrete sonication method to effectively deliver the critical sonication energy necessary to reproducibly achieve stable and fairly monodispersed suspensions that are suitable for in vitro toxicity testing.

Interaction of poly-l-lysine coating and heparan sulfate proteoglycan on magnetic nanoparticle uptake by tumor cells

Background

Poly-l-lysine (PLL) enhances nanoparticle (NP) uptake, but the molecular mechanism remains unresolved. We asked whether PLL may interact with negatively charged glycoconjugates on the cell surface and facilitate uptake of magnetic NPs (MNPs) by tumor cells.

Methods

PLL-coated MNPs (PLL-MNPs) with positive and negative ζ-potential were prepared and characterized. Confocal and transmission electron microscopy was used to analyze cellular internalization of MNPs. A colorimetric iron assay was used to quantitate cell-associated MNPs (MNP_cell).

Results

Coadministration of PLL and dextran-coated MNPs in culture enhanced cellular internalization of MNPs, with increased vesicle size and numbers/cell. MNP_cell was increased by eight- to 12-fold in response to PLL in a concentration-dependent manner in human glioma and HeLa cells. However, the application of a magnetic field attenuated PLL-induced increase in MNP_cell. PLL-coating increased MNP_cell regardless of ζ-potential of PLL-MNPs, whereas magnetic force did not enhance MNP_cell. In contrast, epigallocatechin gallate and magnetic force synergistically enhanced PLL-MNP uptake. In addition, heparin, but not sialic acid, greatly reduced the enhancement effects of PLL; however, removal of heparan sulfate from heparan sulfate proteoglycans of the cell surface by heparinase III significantly reduced MNP_cell.

Conclusion

Our results suggest that PLL-heparan sulfate proteoglycan interaction may be the first step mediating PLL-MNP internalization by tumor cells. Given these results, PLL may facilitate NP interaction with tumor cells via a molecular mechanism shared by infection machinery of certain viruses.

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.

Mechanical determination of particle–cell interactions and the associated biomedical applications

Mechanical determination of particle–cell interactions and the associated biomedical applications.

Protein corona: implications for nanoparticle interactions with pulmonary cells

Background

We previously showed that cerium oxide (CeO₂), barium sulfate (BaSO₄) and zinc oxide (ZnO) nanoparticles (NPs) exhibited different lung toxicity and pulmonary clearance in rats. We hypothesize that these NPs acquire coronas with different protein compositions that may influence their clearance from the lungs.

Methods

CeO₂, silica-coated CeO₂, BaSO₄, and ZnO NPs were incubated in rat lung lining fluid in vitro. Then, gel electrophoresis followed by quantitative mass spectrometry was used to characterize the adsorbed proteins stripped from these NPs. We also measured uptake of instilled NPs by alveolar macrophages (AMs) in rat lungs using electron microscopy. Finally, we tested whether coating of gold NPs with albumin would alter their lung clearance in rats.

Results

We found that the amounts of nine proteins in the coronas formed on the four NPs varied significantly. The amounts of albumin, transferrin and α-1 antitrypsin were greater in the coronas of BaSO₄ and ZnO than that of the two CeO₂ NPs. The uptake of BaSO₄ in AMs was less than CeO₂ and silica-coated CeO₂ NPs. No identifiable ZnO NPs were observed in AMs. Gold NPs coated with albumin or citrate instilled into the lungs of rats acquired the similar protein coronas and were cleared from the lungs to the same extent.

Conclusions

We show that different NPs variably adsorb proteins from the lung lining fluid. The amount of albumin in the NP corona varies as does NP uptake by AMs. However, albumin coating does not affect the translocation of gold NPs across the air-blood barrier. A more extensive database of corona composition of a diverse NP library will develop a platform to help predict the effects and biokinetics of inhaled NPs.

An integrated methodology for assessing the impact of food matrix and gastrointestinal effects on the biokinetics and cellular toxicity of ingested engineered nanomaterials

BACKGROUND

Engineered nanomaterials (ENMs) are increasingly added to foods to improve their quality, sensory appeal, safety and shelf-life. Human exposure to these ingested ENMs (iENMS) is inevitable, yet little is known of their hazards. To assess potential hazards, efficient in vitro methodologies are needed to evaluate particle biokinetics and toxicity. These methodologies must account for interactions and transformations of iENMs in foods (food matrix effect) and in the gastrointestinal tract (GIT) that are likely to determine nano-biointeractions. Here we report the development and application of an integrated methodology consisting of three interconnected stages: 1) assessment of iENM-food interactions (food matrix effect) using model foods; 2) assessment of gastrointestinal transformations of the nano-enabled model foods using a three-stage GIT simulator; 3) assessment of iENMs biokinetics and cellular toxicity after exposure to simulated GIT conditions using a triculture cell model. As a case study, a model food (corn oil-in-water emulsion) was infused with Fe2O3 (Iron(III) oxide or ferric oxide) ENMs and processed using this three-stage integrated platform to study the impact of food matrix and GIT effects on nanoparticle biokinetics and cytotoxicity .

METHODS

A corn oil in phosphate buffer emulsion was prepared using a high speed blender and high pressure homogenizer. Iron oxide ENM was dispersed in water by sonication and combined with the food model. The resulting nano-enabled food was passed through a three stage (mouth, stomach and small intestine) GIT simulator. Size distributions of nano-enabled food model and digestae at each stage were analyzed by DLS and laser diffraction. TEM and confocal imaging were used to assess morphology of digestae at each phase. Dissolution of Fe2O3 ENM along the GIT was assessed by ICP-MS analysis of supernatants and pellets following centrifugation of digestae. An in vitro transwell triculture epithelial model was used to assess biokinetics and toxicity of ingested Fe2O3 ENM. Translocation of Fe2O3 ENM was determined by ICP-MS analysis of cell lysates and basolateral compartment fluid over time.

RESULTS

It was demonstrated that the interactions of iENMs with food and GIT components influenced nanoparticle fate and transport, biokinetics and toxicological profile. Large differences in particle size, charge, and morphology were observed in the model food with and without Fe2O3 and among digestae from different stages of the simulated GIT (mouth, stomach, and small intestine). Immunoflorescence and TEM imaging of the cell culture model revealed markers and morphology of small intestinal epithelium including enterocytes, goblet cells and M cells. Fe2O3 was not toxic at concentrations tested in the digesta. In biokinetics studies, translocation of Fe2O3 after 4 h was <1% and ~2% for digesta with and without serum, respectively, suggesting that use of serum proteins alters iENMs biokinetics and raises concerns about commonly-used approaches that neglect iENM - food-GIT interactions or dilute digestae in serum-containing media.

CONCLUSIONS

We present a simple integrated methodology for studying the biokinetics and toxicology of iENMs, which takes into consideration nanoparticle-food-GIT interactions. The importance of food matrix and GIT effects on biointeractions was demonstrated, as well as the incorporation of these critical factors into a cellular toxicity screening model. Standardized food models still need to be developed and used to assess the effect of the food matrix effects on the fate and bioactivity of iENMs since commercial foods vary considerably in their compositions and structures.

Physicochemical and colloidal aspects of food matrix effects on gastrointestinal fate of ingested inorganic nanoparticles

Inorganic nanoparticles, such as titanium dioxide, silicon dioxide, iron oxide, zinc oxide, or silver nanoparticles, are added to some food products and food packaging materials to obtain specific functional attributes, such as lightening, powder flow, nutrition, or antimicrobial properties. These engineered nanomaterials (ENMs) all have dimensions below 100nm, but may still vary considerably in composition, morphology, charge, surface properties and aggregation state, which effects their gastrointestinal fate and potential toxicity. In addition to their intrinsic physicochemical and morphological properties, the extrinsic properties of the media they are suspended in also affects their biotransformation, gastrointestinal fate and bioactivity. For instance, inorganic nanoparticles are usually consumed as part of a food or meal that contains numerous other components, such as lipids, proteins, carbohydrates, surfactants, minerals, and water, which may alter their gastrointestinal fate. This review article provides an overview of the potential effects of food components on the behavior of ENMs in the gastrointestinal tract (GIT), and highlights some important physicochemical and colloidal mechanisms by which the food matrix may alter the properties of inorganic nanoparticles. This information is essential for developing appropriate test methods to establish the potential toxicity and biokinetics of inorganic nanoparticles in foods.

Mesoporous Silica Nanoparticles as an Antitumoral-Angiogenesis Strategy

Tumors depend heavily on angiogenesis for nutrient derivation and their subsequent metastasis. Targeting tumor induced angiogenesis per se can address both tumor growth and progression simultaneously. Here, we show that we could elegantly restrict the endothelial cells angiogenic behavior through digital size control of mesoporous silica nanoparticle (MSN). This antiangiogenesis effect was derived from the particle size dependent uptake and production of intracellular reactive oxygen species (ROS) that directly interfered with p53 tumor suppressor pathway. The resulting signaling cascade wrestled back the tumoral control of endothelial cells' migration, invasion, and proliferation. Overall, a mere control over the size of a highly oxidative reactive surfaced nanoparticle could provide an alternative strategy to curb the tumor induced angiogenesis process in a conventional drug-free manner.

Preparation, characterization, and in vitro dosimetry of dispersed, engineered nanomaterials

Evidence continues to grow of the importance of in vitro and in vivo dosimetry in the hazard assessment and ranking of engineered nanomaterials (ENMs). Accurate dose metrics are particularly important for in vitro cellular screening to assess the potential health risks or bioactivity of ENMs. To ensure meaningful and reproducible quantification of in vitro dose, with consistent measurement and reporting between laboratories, it is necessary to adopt standardized and integrated methodologies for (i) generation of stable ENM suspensions in cell culture media; (ii) colloidal characterization of suspended ENMs, particularly of properties that determine particle kinetics in an in vitro system (size distribution and formed agglomerate effective density); and (iii) robust numerical fate and transport modeling for accurate determination of the ENM dose delivered to cells over the course of the in vitro exposure. Here we present an integrated comprehensive protocol based on such a methodology for in vitro dosimetry, including detailed standardized procedures for each of these three critical aims. The entire protocol requires ∼6-12 h to complete.

Fluorescent polymeric nanovehicles for neural stem cell modulation

Nanomaterials are emerging as strong candidates for applications in drug delivery and offer an alternative platform to modulate the differentiation and activity of neural stem cells. Herein we report the synthesis and characterization of two different classes of polymeric nanoparticles: N-isopropylacrylamide-based thermoresponsive nanogels RM1 and P(TEGA)-b-P(_d,lLA)₂ nano-micelles RM2. We covalently linked the nanoparticles with fluorescent tags and demonstrate their ability to be internalized and tracked in neural stem cells from the postnatal subventricular zone, without affecting their proliferation, multipotency and differentiation characteristics up to 150 μg ml^-1. The difference in chemical structure of RM1 and RM2 does not appear to impact toxicity however it influences the loading capacity. Nanogels RM1 loaded with retinoic acid improve solubility of the drug which is released at 37 °C, resulting in an increase in the number of neurons, comparable to what can be obtained with a solution of the free drug solubilised with a small percentage of DMSO.

The Role of the Food Matrix and Gastrointestinal Tract in the assessment of biological properties of ingested engineered nanomaterials (iENMs): State of the science and knowledge gaps

Many foods contain appreciable levels of engineered nanomaterials (ENMs) (diameter < 100 nm) that may be either intentionally or unintentionally added. These ENMs vary considerably in their compositions, dimensions, morphologies, physicochemical properties, and biological responses. From a toxicological point of view, it is often convenient to classify ingested ENMs (iENMs) as being either inorganic (such as TiO₂, SiO₂, Fe₂O₃, or Ag) or organic (such as lipid, protein, or carbohydrate), since the former tend to be indigestible and the latter are generally digestible. At present there is a relatively poor understanding of how different types of iENMs behave within the human gastrointestinal tract (GIT), and how the food matrix and biopolymers transform their physico-chemical properties and influence their gastrointestinal fate. This lack of knowledge confounds an understanding of their potential harmful effects on human health. The purpose of this article is to review our current understanding of the GIT fate of iENMs, and to highlight gaps where further research is urgently needed in assessing potential risks and toxicological implications of iENMs. In particular, a strong emphasis is given to the development of standardized screening methods that can be used to rapidly and accurately assess the toxicological properties of iENMs.

Buoyant Nanoparticles: Implications for Nano-Biointeractions in Cellular Studies

In the safety and efficacy assessment of novel nanomaterials, the role of nanoparticle (NP) kinetics in in vitro studies is often ignored although it has significant implications in dosimetry, hazard ranking, and nanomedicine efficacy. It is demonstrated here that certain nanoparticles are buoyant due to low effective densities of their formed agglomerates in culture media, which alters particle transport and deposition, dose-response relationships, and underestimates toxicity and bioactivity. To investigate this phenomenon, this study determines the size distribution, effective density, and assesses fate and transport for a test buoyant NP (polypropylene). To enable accurate dose-response assessment, an inverted 96-well cell culture platform is developed in which adherent cells are incubated above the buoyant particle suspension. The effect of buoyancy is assessed by comparing dose-toxicity responses in human macrophages after 24 h incubation in conventional and inverted culture systems. In the conventional culture system, no adverse effects are observed at any NP concentration tested (up to 250 μg mL(-1) ), whereas dose-dependent decreases in viability and increases in reactive oxygen species are observed in the inverted system. This work sheds light on an unknown issue that plays a significant role in vitro hazard screening and proposes a standardized methodology for buoyant NP assessments.

Effects of engineered nanomaterial exposure on macrophage innate immune function

Increasing use of engineered nanomaterials (ENMs) means increased human exposures. Potential adverse effects include those on the immune system, ranging from direct toxicity to impairment of defenses against environmental pathogens and toxins. Effects on lung macrophages may be especially prominent, because they serve to clear foreign materials like ENMs and bacterial pathogens. We investigated the effects of 4 hour exposures over a range of concentrations, of a panel of industry-relevant ENMs, including SiO₂, Fe₂O₃, ZnO, CeO₂, TiO₂, and an Ag/SiO2 composite, on human THP-1 macrophages. Effects on phagocytosis of latex beads, and phagocytosis and killing of Francisella tularensis (FT), as well as viability, oxidative stress and mitochondrial integrity, were measured by automated scanning confocal microscopy and image analysis. Results revealed some notable patterns: 1) Phagocytosis of unopsonized beads was increased, whereas that of opsonized beads was decreased, by all ENMs, with the exception of ZnO, which reduced both opsonized and unopsonized uptake; 2) Uptake of opsonized and unopsonized FT was either impaired or unaffected by all ENMs, with the exception of CeO₂, which increased phagocytosis of unopsonized FT; 3) Macrophage killing of FT tended to improve with all ENMs; and 4) Viability was unaffected immediately following exposures with all ENMs tested, but was significantly decreased 24 hours after exposures to Ag/SiO₂ and ZnO ENMs. The results reveal a complex landscape of ENM effects on macrophage host defenses, including both enhanced and reduced capacities, and underscore the importance of robust hazard assessment, including immunotoxicity assessment, of ENMs.

The role of natural processes and surface energy of inhaled engineered nanoparticles on aggregation and corona formation

The surface chemistry of engineered nanoparticles (ENPs) becomes more important as their size decreases and enters the nanometer-range. This review explains the fundamental properties of the surface chemistry of nanoparticles, and argues that their agglomeration and the formation of corona around them are natural processes that reduce surface energy. ENP agglomeration and surface corona formation are further discussed in the context of inhaled ENPs, as the lung is a major port of ENP entry to the body. The pulmonary surfactant layer, which the inhaled ENPs first encounter as they land on the lung surface, represents a unique environment with a variety of well-defined biomolecules. Many factors, such as hydrophobicity, surface charge of ENPs, protein/phospholipid concentrations of the alveolar lining fluid, etc. influence the complex processes of ENP agglomeration and corona formation in the alveolar lining fluid, and these events occur even before the ENPs reach the cells. We suggest that molecular dynamic simulations can represent a promising future direction for research of the behavior of inhaled ENPs, complementing the experimental approaches. Moreover, we want to remind biologists working on ENPs of the importance relationship between ENP surface energy and size.

Advanced computational modeling for in vitro nanomaterial dosimetry

Background

Accurate and meaningful dose metrics are a basic requirement for in vitro screening to assess potential health risks of engineered nanomaterials (ENMs). Correctly and consistently quantifying what cells “see,” during an in vitro exposure requires standardized preparation of stable ENM suspensions, accurate characterizatoin of agglomerate sizes and effective densities, and predictive modeling of mass transport. Earlier transport models provided a marked improvement over administered concentration or total mass, but included assumptions that could produce sizable inaccuracies, most notably that all particles at the bottom of the well are adsorbed or taken up by cells, which would drive transport downward, resulting in overestimation of deposition.

Methods

Here we present development, validation and results of two robust computational transport models. Both three-dimensional computational fluid dynamics (CFD) and a newly-developed one-dimensional Distorted Grid (DG) model were used to estimate delivered dose metrics for industry-relevant metal oxide ENMs suspended in culture media. Both models allow simultaneous modeling of full size distributions for polydisperse ENM suspensions, and provide deposition metrics as well as concentration metrics over the extent of the well. The DG model also emulates the biokinetics at the particle-cell interface using a Langmuir isotherm, governed by a user-defined dissociation constant, K_D, and allows modeling of ENM dissolution over time.

Results

Dose metrics predicted by the two models were in remarkably close agreement. The DG model was also validated by quantitative analysis of flash-frozen, cryosectioned columns of ENM suspensions. Results of simulations based on agglomerate size distributions differed substantially from those obtained using mean sizes. The effect of cellular adsorption on delivered dose was negligible for K_D values consistent with non-specific binding (> 1 nM), whereas smaller values (≤ 1 nM) typical of specific high-affinity binding resulted in faster and eventual complete deposition of material.

Conclusions

The advanced models presented provide practical and robust tools for obtaining accurate dose metrics and concentration profiles across the well, for high-throughput screening of ENMs. The DG model allows rapid modeling that accommodates polydispersity, dissolution, and adsorption. Result of adsorption studies suggest that a reflective lower boundary condition is appropriate for modeling most in vitro ENM exposures.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-015-0109-1) contains supplementary material, which is available to authorized users.

Silica coating influences the corona and biokinetics of cerium oxide nanoparticles

BACKGROUND

The physicochemical properties of nanoparticles (NPs) influence their biological outcomes.

METHODS

We assessed the effects of an amorphous silica coating on the pharmacokinetics and pulmonary effects of CeO2 NPs following intratracheal (IT) instillation, gavage and intravenous injection in rats. Uncoated and silica-coated CeO2 NPs were generated by flame spray pyrolysis and later neutron-activated. These radioactive NPs were IT-instilled, gavaged, or intravenously (IV) injected in rats. Animals were analyzed over 28 days post-IT, 7 days post-gavage and 2 days post-injection.

RESULTS

Our data indicate that silica coating caused more but transient lung inflammation compared to uncoated CeO2. The transient inflammation of silica-coated CeO2 was accompanied by its enhanced clearance. Then, from 7 to 28 days, clearance was similar although significantly more (141)Ce from silica-coated (35%) was cleared than from uncoated (19%) (141)CeO2 in 28 days. The protein coronas of the two NPs were significantly different when they were incubated with alveolar lining fluid. Despite more rapid clearance from the lungs, the extrapulmonary (141)Ce from silica-coated (141)CeO2 was still minimal (<1%) although lower than from uncoated (141)CeO2 NPs. Post-gavage, nearly 100% of both NPs were excreted in the feces consistent with very low gut absorption. Both IV-injected (141)CeO2 NP types were primarily retained in the liver and spleen. The silica coating significantly altered the plasma protein corona composition and enhanced retention of (141)Ce in other organs except the liver.

CONCLUSION

We conclude that silica coating of nanoceria alters the biodistribution of cerium likely due to modifications in protein corona formation after IT and IV administration.

A critical review of in vitro dosimetry for engineered nanomaterials

A major obstacle in the development of accurate cellular models for investigating nanobio interactions in vitro is determination of physiologically relevant measures of dose. Comparison of biological responses to nanoparticle exposure typically relies on administered dose metrics such as mass concentration of suspended particles, rather than the effective dose of particles that actually comes in contact with the cells over the time of exposure. Adoption of recently developed dosimetric methodologies will facilitate determination of effective dose delivered to cells in vitro, thereby improving the accuracy and reliability of in vitro screening data, validation of in vitro with in vivo data, and comparison across multiple datasets for the large variety of nanomaterials currently in the market.

Understanding and exploiting nanoparticles' intimacy with the blood vessel and blood

While the blood vessel is seldom the target tissue, almost all nanomedicine will interact with blood vessels and blood at some point of time along its life cycle in the human body regardless of their intended destination. Despite its importance, many bionanotechnologists do not feature endothelial cells (ECs), the blood vessel cells, or consider blood effects in their studies. Including blood vessel cells in the study can greatly increase our understanding of the behavior of any given nanomedicine at the tissue of interest or to understand side effects that may occur in vivo. In this review, we will first describe the diversity of EC types found in the human body and their unique behaviors and possibly how these important differences can implicate nanomedicine behavior. Subsequently, we will discuss about the protein corona derived from blood with foci on the physiochemical aspects of nanoparticles (NPs) that dictate the protein corona characteristics. We would also discuss about how NPs characteristics can affect uptake by the endothelium. Subsequently, mechanisms of how NPs could cross the endothelium to access the tissue of interest. Throughout the paper, we will share some novel nanomedicine related ideas and insights that were derived from the understanding of the NPs' interaction with the ECs. This review will inspire more exciting nanotechnologies that had accounted for the complexities of the real human body.

Concentrating nanoparticles in environmental monitoring

There are significant challenges in assessing the toxicity of nanoparticles in the environment in which effective methods for detection are crucial. An inexpensive method that uses superhydrophobic well with an evaporating droplet followed by a simple squeeze flow is described here and found to provide practical high nanoparticle collection from samples for detection. The process could be hastened by placing a radiant heater close to the droplet if temperature rises in the sample can be tolerated.

Characterizing nanoparticles in complex biological media and physiological fluids with depolarized dynamic light scattering

Light scattering is one of the few techniques available to adequately characterize suspended nanoparticles (NPs) in real time and in situ. However, when it comes to NPs in multicomponent and optically complex aqueous matrices - such as biological media and physiological fluids - light scattering suffers from lack of selectivity, as distinguishing the relevant optical signals from the irrelevant ones is very challenging. We meet this challenge by building on depolarized scattering: Unwanted signals from the matrix are completely suppressed. This approach yields information with an unprecedented signal-to-noise ratio in favour of the NPs and NP-biomolecule corona complexes, which in turn opens the frontier to scattering-based studies addressing the behaviour of NPs in complex physiological/biological fluids.