Effects of SiO2 nanoparticles on phospholipid membrane integrity and fluidity

Hydrogen bonding-mediated interaction underlies the enhanced membrane toxicity of chemically transformed polystyrene microplastics by cadmium

The global attention on microplastic pollution and its implications for human health has grown in recent years. Additionally, the co-existence of heavy metals may significantly alter microplastics' physicochemical characteristics, potentially amplifying their overall toxicity-a facet that remains less understood. In this study, we focused the membrane toxicity of modified polystyrene microplastics (PS-MPs) following cadmium (Cd) pretreatment. Our findings revealed that Cd-pretreated PS-MPs exacerbated their toxic effects, including diminished membrane integrity and altered phase fluidity in simulated lipid membrane giant unilamellar vesicles (GUVs), as well as heightened membrane permeability, protein damage, and lipid peroxidation in red blood cells and macrophages. Mechanistically, these augmented membrane toxicities can be partially ascribed to modifications in the surface roughness and hydrophilicity of Cd-pretreated PS-MPs, as well as to interactions between PS-MPs and lipid bilayers. Notably, hydrogen bonds emerged as a crucial mechanism underlying the enhanced interaction of PS-MPs with lipid bilayers.

Competitive-like binding between carbon black and CTNNB1 to ΔNp63 interpreting the abnormal respiratory epithelial repair after injury

Airway epithelium is extraordinary vulnerable to damage owning to continuous environment exposure. Subsequent repair is therefore essential to restore the homeostasis of respiratory system. Disruptions in respiratory epithelial repair caused by nanoparticles exposure have been linked to various human diseases, yet implications in repair process remain incompletely elucidated. This study aims to elucidate the key stage in epithelial repair disturbed by carbon black (CB) nanoparticles, highlighting the pivotal role of ΔNp63 in mediating the epithelium repair. A competitive-like binding between CB and beta-catenin 1 (CTNNB1) to ΔNp63 is proposed to elaborate the underlying toxicity mechanism. Specifically, CB exhibits a remarkable inhibitory effect on cell proliferation, leading to aberrant airway epithelial repair, as validated in air-liquid culture. ΔNp63 drives efficient epithelial proliferation during CB exposure, and CTNNB1 was identified as a target of ΔNp63 by bioinformatics analysis. Further molecular dynamics simulation reveals that oxygen-containing functional groups on CB disrupt the native interaction of CTNNB1 with ΔNp63 through competitive-like binding pattern. This process modulates CTNNB1 expression, ultimately restraining proliferation during respiratory epithelial repair. Overall, the current study elucidates that the diminished interaction between CTNNB1 and ΔNp63 impedes respiratory epithelial repair in response to CB exposure, thereby enriching the public health risk assessment on CB-related respiratory diseases.

The effects of iron oxide nanoparticles on antioxidant capacity and response to oxidative stress in Mozambique tilapia (Oreochromis mossambicus, Peters 1852)

Recent research has raised concern about the biocompatibility of iron oxide nanoparticles (IONPs), as they have been reported to induce oxidative stress and inflammatory responses, whilst prolonged exposure to high IONP concentrations may lead to cyto-/genotoxicity. Besides, there is concern about its environmental impact. The aim of our study was to investigate the effects of IONPs on the antioxidant defence system in freshwater fish Mozambique tilapia (Oreochromis mossambicus, Peters 1852). The fish were exposed to IONP concentration of 15 mg/L over 1, 3, 4, 15, 30, and 60 days and the findings compared to a control, unexposed group. In addition, we followed up the fish for 60 days after exposure had stopped to estimate the stability of oxidative stress induced by IONPs. Exposure affected the activity of antioxidant and marker enzymes and increased the levels of hydrogen peroxide and lipid peroxidation in the gill, liver, and brain tissues of the fish. Even after 60 days of depuration, adverse effects remained, indicating long-term nanotoxicity. Moreover, IONPs accumulated in the gill, liver, and brain tissues. Our findings underscore the potential health risks posed to non-target organisms in the environment, and it is imperative to establish appropriate guidelines for safe handling and disposal of IONPs to protect the aquatic environment.

Interactions between CuO NPs and PS: The release of copper ions and oxidative damage

Copper oxide nanoparticles (CuO NPs) can adversely affect lung health possibly by inducing oxidative damage through the release of copper ions. However, the migration and transformation processes of CuO NPs in lung lining fluid is still unclear, and there are still conflicting reports of redox reactions involving copper ions. To address this, we examined the release of copper ions from CuO NPs in simulated lung fluid supplemented with pulmonary surfactant (PS), and further analyzed the mechanisms of PS-CuO NPs interactions and the health hazards. The results showed that the phospholipid of PS was adsorbed on the particle surface, which not only induced aggregation of the particles but also provided a reaction environment for the interaction of PS with CuO NPs. PS was able to promote the release of ions from CuO NPs, of which the protein was a key component. Lipid peroxidation, protein destabilization, and disruption of the interfacial chemistry also occurred in the PS-CuO NPs interactions, during which copper ions were present only as divalent cations. Meanwhile, the contribution of the particle surface cannot be neglected in the oxidative damage to the lung caused by CuO NPs. Through reacting with biomolecules, CuO NPs accomplished ion release and induced oxidative damage associated with PS. This research was the first to reveal the mechanism of CuO NPs releasing copper ions and inducing lipid oxidative damage in the presence of PS, which provides a new idea of transition metal-induced health risk in human body.

Key Role of Choline Head Groups in Large Unilamellar Phospholipid Vesicles for the Interaction with and Rupture by Silica Nanoparticles

For highly abundant silica nanomaterials, detrimental effects on proteins and phospholipids are postulated as critical molecular initiating events that involve hydrogen-bonding, hydrophobic, and/or hydrophilic interactions. Here, large unilamellar vesicles with various well-defined phospholipid compositions are used as biomimetic models to recapitulate membranolysis, a process known to be induced by silica nanoparticles in human cells. Differential analysis of the dominant phospholipids determined in membranes of alveolar lung epithelial cells demonstrates that the quaternary ammonium head groups of phosphatidylcholine and sphingomyelin play a critical and dose-dependent role in vesicle binding and rupture by amorphous colloidal silica nanoparticles. Surface modification by either protein adsorption or by covalent coupling of carboxyl groups suppresses the disintegration of these lipid vesicles, as well as membranolysis in human A549 lung epithelial cells by the silica nanoparticles. Furthermore, molecular modeling suggests a preferential affinity of silanol groups for choline head groups, which is also modulated by the pH value. Biomimetic lipid vesicles can thus be used to better understand specific phospholipid-nanoparticle interactions at the molecular level to support the rational design of safe advanced materials.

Effect of Non-Modified as Well as Surface-Modified SiO2 Nanoparticles on Red Blood Cells, Biological and Model Membranes

Nanoparticles are extremely promising components that are used in diagnostics and medical therapies. Among them, silica nanoparticles are ultrafine materials that, due to their unique physicochemical properties, have already been used in biomedicine, for instance, in cancer therapy. The aim of this study was to investigate the cytotoxicity of three types of nanoparticles (SiO2, SiO2-SH, and SiO2-COOH) in relation to red blood cells, as well as the impact of silicon dioxide nanoparticles on biological membranes and liposome models of membranes. The results obtained prove that hemolytic toxicity depends on the concentration of nanoparticles and the incubation period. Silica nanoparticles have a marginal impact on the changes in the osmotic resistance of erythrocytes, except for SiO2-COOH, which, similarly to SiO2 and SiO2-SH, changes the shape of erythrocytes from discocytes mainly towards echinocytes. What is more, nanosilica has an impact on the change in fluidity of biological and model membranes. The research gives a new view of the practical possibilities for the use of large-grain nanoparticles in biomedicine.

Physico-Chemical Approaches to Investigate Surface Hydroxyls as Determinants of Molecular Initiating Events in Oxide Particle Toxicity

The study of molecular recognition patterns is crucial for understanding the interactions between inorganic (nano)particles and biomolecules. In this review we focus on hydroxyls (OH) exposed at the surface of oxide particles (OxPs) which can play a key role in molecular initiating events leading to OxPs toxicity. We discuss here the main analytical methods available to characterize surface OH from a quantitative and qualitative point of view, covering thermogravimetry, titration, ζ potential measurements, and spectroscopic approaches (NMR, XPS). The importance of modelling techniques (MD, DFT) for an atomistic description of the interactions between membranes/proteins and OxPs surfaces is also discussed. From this background, we distilled a new approach methodology (NAM) based on the combination of IR spectroscopy and bioanalytical assays to investigate the molecular interactions of OxPs with biomolecules and membranes. This NAM has been already successfully applied to SiO₂ particles to identify the OH patterns responsible for the OxPs' toxicity and can be conceivably extended to other surface-hydroxylated oxides.

Silica Nanoparticles Promote the Megakaryocyte Maturation and Differentiation: Potential Implications for Hematological Homeostasis

Silica nanoparticles (SiO₂ NPs) have been widely applied in diverse areas, thus causing the extensive release through multiple routes. Their toxicological effects, especially for the disturbance in hematological homeostasis, have raised public concern. Considering the detrimental role of excessive platelets in many cardiovascular diseases, the regulation of platelet formation offers a unique aspect for studying the blood compatibility of nanomaterials. In this study, the effects of SiO₂ NPs with four sizes (80, 120, 200, and 400 nm) were investigated on the maturation and differentiation of the megakaryocytes into platelets. The results showed that SiO₂ NPs promoted megakaryocyte development as manifested by the occurrence of irregular cell morphology, enlargement of cell size, increases in DNA content and DNA ploidy, and formation of spore-like protrusions. The expression of megakaryocyte-specific antigen (CD41a) was up-regulated, due to SiO₂ NP treatments. The correlation analysis of SiO₂ NP size with the above test bioindicators showed that the smaller the SiO₂ NPs were, the stronger effects they induced. Moreover, exposure to SiO₂ NPs induced the up-regulation of both GATA-1 and FLI-1, while the transcriptional expressions of aNF-E2 and fNF-E2 remained unchanged. The significant positive correlation of GATA-1 and FLI-1 with megakaryocytic maturation and differentiation suggested their crucial roles in the SiO₂ NP-promoted effect. The finding herein provided new insight into the potential health risk of SiO₂ NPs by perturbing the platelet-involved hematological homeostasis.

Quantitative Assessment of Interfacial Interactions Governing Ultrafiltration Membrane Fouling by the Mixture of Silica Nanoparticles (SiO2 NPs) and Natural Organic Matter (NOM): Effects of Solution Chemistry

Mixtures of silica nanoparticles (SiO₂ NPs) and natural organic matter (NOM) are ubiquitous in natural aquatic environments and pose risks to organisms. Ultrafiltration (UF) membranes can effectively remove SiO₂ NP-NOM mixtures. However, the corresponding membrane fouling mechanisms, particularly under different solution conditions, have not yet been studied. In this work, the effect of solution chemistry on polyethersulfone (PES) UF membrane fouling caused by a SiO₂ NP-NOM mixture was investigated at different pH levels, ionic strengths, and calcium concentrations. The corresponding membrane fouling mechanisms, i.e., Lifshitz-van der Waals (LW), electrostatic (EL), and acid-base (AB) interactions, were quantitatively evaluated using the extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory. It was found that the extent of membrane fouling increased with decreasing pH, increasing ionic strength, and increasing calcium concentration. The attractive AB interaction between the clean/fouled membrane and foulant was the major fouling mechanism in both the initial adhesion and later cohesion stages, while the attractive LW and repulsive EL interactions were less important. The change of fouling potential with solution chemistry was negatively correlated with the calculated interaction energy, indicating that the UF membrane fouling behavior under different solution conditions can be effectively explained and predicted using the xDLVO theory.

Human dendritic cell maturation induced by amorphous silica nanoparticles is Syk-dependent and triggered by lipid raft aggregation

BACKGROUND

Synthetic amorphous silica nanoparticles (SAS-NPs) are widely employed in pharmaceutics, cosmetics, food and concretes. Workers and the general population are exposed daily via diverse routes of exposure. SAS-NPs are generally recognized as safe (GRAS) by the Food and Drug Administration, but because of their nanoscale size and extensive uses, a better assessment of their immunotoxicity is required. In the presence of immune "danger signals", dendritic cells (DCs) undergo a maturation process resulting in their migration to regional lymph nodes where they activate naive T-cells. We have previously shown that fumed silica pyrogenic SAS-NPs promote the two first steps of the adaptative immune response by triggering DC maturation and T-lymphocyte response, suggesting that SAS-NPs could behave as immune "danger signals". The present work aims to identify the mechanism and the signalling pathways involved in DC phenotype modifications provoked by pyrogenic SAS-NPs. As a pivotal intracellular signalling molecule whose phosphorylation is associated with DC maturation, we hypothesized that Spleen tyrosine kinase (Syk) may play a central role in SAS-NPs-induced DC response.

RESULTS

In human monocyte-derived dendritic cells (moDCs) exposed to SAS-NPs, Syk inhibition prevented the induction of CD83 and CD86 marker expression. A significant decrease in T-cell proliferation and IFN-γ, IL-17F and IL-9 production was found in an allogeneic moDC:T-cell co-culture model. These results suggested that the activation of Syk was necessary for optimal co-stimulation of T-cells. Moreover, Syk phosphorylation, observed 30 min after SAS-NP exposure, occurred upstream of the c-Jun N-terminal kinase (JNK) Mitogen-activated protein kinases (MAPK) and was elicited by the Src family of protein tyrosine kinases. Our results also showed for the first time that SAS-NPs provoked aggregation of lipid rafts in moDCs and that MβCD-mediated raft destabilisation altered Syk activation.

CONCLUSIONS

We showed that SAS-NPs could act as an immune danger signal in DCs through a Syk-dependent pathway. Our findings revealed an original mechanism whereby the interaction of SAS-NPs with DC membranes promoted aggregation of lipid rafts, leading to a Src kinase-initiated activation loop triggering Syk activation and functional DC maturation.

Damage Effect of Amorphous Carbon Black Nanoparticle Aggregates on Model Phospholipid Membranes: Surface Charge, Exposure Concentration and Time Dependence

Commercial nano-scale carbon blacks (CB) are being harnessed widely and may impose potentially hazardous effects because of their unique properties, especially if they have been modified to grow reactive functional groups on their surface. Cytotoxicity of CB has been well studied but the membrane damage mechanisms and role of surface modification are still open to debate. Negatively and positively charged giant unilamellar vesicles (GUVs) were prepared using three lipids as model cell membranes to examine the mechanistic damage of CB and MCB (modified by acidic potassium permanganate) aggregates. Optical images showed that both anionic CB and MCB disrupted the positively charged but not the negatively charged GUVs. This disruption deteriorated with the rise and extension of exposure concentration and time. Lipids extraction caused by CBNs (CB and MCB together are called CBNs) was found. MCB caused more severe disruption than CB. MCB was enveloped into vesicles through an endocytosis-like process at 120 mg/L. MCB mediated the gelation of GUVs, perhaps through C-O-P bonding bridges. The lower hydrodynamic diameter and more negative charges may have been responsible for the distinction effect of MCB over CB. The adhesion and bonding of CBNs to the membrane were favored by electrostatic interaction and the practical application of CBNs warrants more attention.

A Novel Nanosafety Approach Using Cell Painting, Metabolomics, and Lipidomics Captures the Cellular and Molecular Phenotypes Induced by the Unintentionally Formed Metal-Based (Nano)Particles

Additive manufacturing (AM) or industrial 3D printing uses cutting-edge technologies and materials to produce a variety of complex products. However, the effects of the unintentionally emitted AM (nano)particles (AMPs) on human cells following inhalation, require further investigations. The physicochemical characterization of the AMPs, extracted from the filter of a Laser Powder Bed Fusion (L-PBF) 3D printer of iron-based materials, disclosed their complexity, in terms of size, shape, and chemistry. Cell Painting, a high-content screening (HCS) assay, was used to detect the subtle morphological changes elicited by the AMPs at the single cell resolution. The profiling of the cell morphological phenotypes, disclosed prominent concentration-dependent effects on the cytoskeleton, mitochondria, and the membranous structures of the cell. Furthermore, lipidomics confirmed that the AMPs induced the extensive membrane remodeling in the lung epithelial and macrophage co-culture cell model. To further elucidate the biological mechanisms of action, the targeted metabolomics unveiled several inflammation-related metabolites regulating the cell response to the AMP exposure. Overall, the AMP exposure led to the internalization, oxidative stress, cytoskeleton disruption, mitochondrial activation, membrane remodeling, and metabolic reprogramming of the lung epithelial cells and macrophages. We propose the approach of integrating Cell Painting with metabolomics and lipidomics, as an advanced nanosafety methodology, increasing the ability to capture the cellular and molecular phenotypes and the relevant biological mechanisms to the (nano)particle exposure.

Methods to mechanically perturb and characterize GUV-based minimal cell models

Cells shield organelles and the cytosol via an active boundary predominantly made of phospholipids and membrane proteins, yet allowing communication between the intracellular and extracellular environment. Micron-sized liposome compartments commonly known as giant unilamellar vesicles (GUVs) are used to model the cell membrane and encapsulate biological materials and processes in a cell-like confinement. In the field of bottom-up synthetic biology, many have utilized GUVs as substrates to study various biological processes such as protein-lipid interactions, cytoskeletal assembly, and dynamics of protein synthesis. Like cells, it is ideal that GUVs are also mechanically durable and able to stay intact when the inner and outer environment changes. As a result, studies have demonstrated approaches to tune the mechanical properties of GUVs by modulating membrane composition and lumenal material property. In this context, there have been many different methods developed to test the mechanical properties of GUVs. In this review, we will survey various perturbation techniques employed to mechanically characterize GUVs.

Effect of silica nanoparticles on cell membrane fluidity: The role of temperature and membrane composition

The increasing production and application of silica nanoparticles (SiO₂ NPs) raise public concern regarding their environmental and health risks. The fluidity of the cell membrane is essential for supporting membrane proteins and regulating membrane transport. Changes in membrane fluidity inevitably influence the physiological activities of cells and even cause biological effects. In this study, the effect of SiO₂ NPs on membrane fluidity was studied at 25 °C and 37 °C, and the role of membrane components in SiO₂ NP-membrane interactions was investigated using giant plasma membrane vesicles (GPMVs) isolated from RBL-2H3 cells. SiO₂ NPs cause a more serious membrane fluidity decrease at 37 °C than at 25 °C, which is revealed by the shift of Laurdan fluorescence emission and further quantified via forster resonance energy transfer (FRET) experiments. In addition, after the removal of 75 % cholesterol from the membrane, SiO₂ NPs caused a greater extent of membrane gelation. These results indicate that SiO₂ NPs prefer to interact with membranes that are more dynamic and less densely packed. Moreover, fluorescent experiments confirmed that the existence of phosphatidyl ethanolamine (PE) and phosphoinositide (PI) can mitigate NP-induced membrane gelation. Molecular dynamics simulation further demonstrated that SiO₂ NPs form hydrogen bonds with the terminal of PE or PI but with the -PO₄^-- group in the middle of phosphatidylcholine (PC). The bonding that occurs in the terminal gives less restriction of phospholipid movement and a weaker effect on membrane fluidity. This research provides both evidence and mechanisms of SiO₂ NP-induced membrane fluidity changes, which are helpful for understanding cell membrane damage and the biological effects of NPs.

Lubricant-entrenched Slippery Surface-based Nanocarriers to Avoid Macrophage Uptake and Improve Drug Utilization

INTRODUCTION

Reducing the protein adsorption of nanoparticles (NPs) as drug carriers to slow their rapid clearance by macrophages uptake is a critical challenge for NPs clinical translational applications. Despite extensive research efforts to inhibit cellular uptake, including covering biological agents or surface chemical coatings to impart "stealth" properties to NPs, their stability remains insufficient.

OBJECTIVES

Developed a novel surface modification technology based on a physical infusion engineering approach to achieve persistent inhibition of protein adhesion and cellular uptake by nanocarriers.

METHODS

The nanoparticles were prepared based on conventional drug carrier mesoporous silica NPs through a two-step process. A functional nanoscale slippery surface was formed by grafting "liquid-like" brushes on the particles surface, and then a lubricant-entrenched slippery surfaces (LESS) was formed by infusing silicone oil lubricant into the entire surface. Co-incubation with macrophages (in vitro and in vivo) was used to examine the anti-uptake properties of modified NPs. The anti-adhesion properties of LESS coating surfaces to various liquids, proteins and cells were used to analyze the anti-uptake mechanism. Loaded with drugs, combined with tumor models, to evaluate the drug utilization of modified NPs.

RESULTS

Relying on the stable and slippery LESS coating, the modified surface could prevent the adhesion of various liquids and effectively shield against the adhesion of proteins and cells, as well as remarkably reduce macrophage cellular uptake in vitro and in vivo. In addition, the LESS coating does not affect cell activity and allows NPs to be loaded with drugs, significantly improving the utilization of drugs in vitro and in vivo. This allows the NPs to reach to the target tumor site for drug delivery without active clearance by macrophages.

CONCLUSION

Our research introduces a new nanocarrier technology to improve anti-biofouling performance and stealth efficiency that will facilitate the development of nanomedicines for clinical transformation applications.

Impacts of engineered nanoparticles and antibiotics on denitrification: Element cycling functional genes and antibiotic resistance genes

The wide presence of antibiotics and minerals warrants their combined effects on the denitrification in natural aquatic environment. Herein, we investigated the effects of two antibiotics, sulfamethazine (SMZ) and chlortetracycline (CTC), on the reduction of NO₃^--N and accumulation of NO₂^--N in the absence and presence of engineered nanoparticles (NPs) (Al₂O₃, SiO₂, and geothite) using 16 S rRNA sequencing and high-throughput quantitative PCR. The results showed that the addition of antibiotics inhibited the reduction of NO₃^--N by changing the bacterial community structure and reducing the abundance of denitrification genes, while engineered NPs promoted the denitrification by increasing the abundance of denitrification genes. In the binary systems, engineered NPs alleviated the inhibitory effect of antibiotics through enriching the denitrification genes and adsorbing antibiotics. Antibiotics and its combination with engineered NPs changed the composition of functional genes related to C, N, P, S metabolisms (p < 0.01). The addition of antibiotics and/or engineered NPs altered the bacterial community structure, which is dominated by the genera of Enterobacter (40.7-90.5%), Bacillus (4.9-58.5%), and Pseudomonas (0.21-12.7%). The significant relationship between denitrification, carbon metabolism genes, and antibiotic resistance genes revealed that the heterotrophic denitrifying bacteria may host the antibiotic resistance genes and denitrification genes simultaneously. The findings underscore the significance of engineered NPs in the toxicity assessment of pollutants, and provide a more realistic insight into the toxicity of antibiotics in the natural aquatic environment.

Chronic effects of two rutile TiO2 nanomaterials in human intestinal and hepatic cell lines

Background

TiO₂ nanomaterials (NMs) are present in a variety of food and personal hygiene products, and consumers are exposed daily to these NMs through oral exposition. While the bulk of ingested TiO₂ NMs are eliminated rapidly in stool, a fraction is able to cross the intestinal epithelial barrier and enter systemic circulation from where NMs can be distributed to tissues, primarily liver and spleen. Daily exposure to TiO₂ NMs, in combination with a slow rate of elimination from tissues, results in their accumulation within different tissues. Considerable evidence suggests that following oral exposure to TiO₂ NMs, the presence of NMs in tissues is associated with a number of adverse effects, both in intestine and liver. Although numerous studies have been performed in vitro investigating the acute effects of TiO₂ NMs in intestinal and hepatic cell models, considerably less is known about the effect of repeated exposure on these models. In this study, we investigated the cytotoxic effects of repeated exposure of relevant models of intestine and liver to two TiO₂ NMs differing in hydrophobicity for 24 h, 1 week and 2 weeks at concentrations ranging from 0.3 to 80 µg/cm². To study the persistence of these two NMs in cells, we included a 1-week recovery period following 24 h and 1-week treatments. Cellular uptake by TEM and ToF–SIMS analyses, as well as the viability and pro-inflammatory response were evaluated. Changes in the membrane composition in Caco-2 and HepaRG cells treated with TiO₂ NMs for up to 2 weeks were also studied.

Results

Despite the uptake of NM-103 and NM-104 in cells, no significant cytotoxic effects were observed in either Caco-2 or HepaRG cells treated for up to 2 weeks at NM concentrations up to 80 µg/cm²_. In addition, no significant effects on IL-8 secretion were observed. However, significant changes in membrane composition were observed in both cell lines. Interestingly, while most of these phospholipid modifications were reversed following a 1-week recovery, others were not affected by the recovery period.

Conclusion

These findings indicate that although no clear effects on cytotoxicity were observed following repeated exposure of differentiated Caco-2 and HepaRG cells to TiO₂ NMs, subtle effects on membrane composition could induce potential adverse effects in the long-term.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00470-1.

Mechanistic study of the adsorption and penetration of modified SiO2 nanoparticles on cellular membrane

SiO₂ nanoparticles (NPs) are ubiquitous in the atmosphere and have been proved to be harmful to human by bioaccumulation. The bioaccumulation of SiO₂ NPs begins with their partitioning into membrane phospholipids. However, the uptake of SiO₂ particle onto lipid bilayers has been not completely understood. In this study, the uptake process of different modified SiO₂ particles (with adsorbed trace gas molecules, including formic acid (FA), methyl vinyl ketone (MVK), and methacrolein (MAC)) into DPPC bilayers were investigated by molecular dynamics (MD) simulations. Results suggest that after the SiO₂ particle absorbed on the surface of bilayers, it spun by itself to form the most stable adsorption configurations. MAC and MVK molecule tend to be absorbed into DPPC bilayer while FA molecule was more likely located at the surface region of bilayer from the viewpoint of thermodynamics. Besides, it was also found apart from the commonly accepted "Trojan-horse" effect, SiO₂ NPs may increase biohazard via modulating the concentration of pollutants. This work is beneficial for understanding the toxicity and bioaccumulation of FA, MVK, MAC, and SiO₂ NPs at molecular level.

Biomimetic Curvature and Tension-Driven Membrane Fusion Induced by Silica Nanoparticles

Fusion events in living cells are intricate phenomena that require the coordinate action of multicomponent protein complexes. However, simpler synthetic tools to control membrane fusion in artificial cells are highly desirable. Native membrane fusion machinery mediates fusion, driving a delicate balance of membrane curvature and tension between two closely apposed membranes. Here, we show that silica nanoparticles (SiO₂ NPs) at a size close to the cross-over between tension-driven and curvature-driven interaction regimes initiate efficient fusion of biomimetic model membranes. Fusion efficiency and mechanisms are studied by Förster resonance energy transfer and confocal fluorescence microscopy. SiO₂ NPs induce a slight increase in lipid packing likely to increase the lateral tension of the membrane. We observe a connection between membrane tension and fusion efficiency. Finally, real-time confocal fluorescence microscopy reveals three distinct mechanistic pathways for membrane fusion. SiO₂ NPs show significant potential for inclusion in the synthetic biology toolkit for membrane remodeling and fusion in artificial cells.

Molecular insights into the uptake of SiO2 nanoparticles on phospholipid membrane: Effect of surface properties and particle size

Silica (SiO₂) nanoparticles (NPs) have attracted much attention due to the potential for a wide range of applications and they have been confirmed to be hazardous to humans. Partitioning to phospholipid bilayers is an important way for their bioaccumulation. However, the detailed mechanism of SiO₂ NPs uptake by membrane phospholipids remains uncertain. In this work, molecular dynamics (MD) simulations were employed to study the uptake process of SiO₂ NPs into DPPC bilayers. Results show that these SiO₂ NPs uptake onto DPPC bilayer surface is favorable from the viewpoint of thermodynamics. During the uptake process, the SiO₂ NP needed to adjust the angle of interaction with the DPPC surface until the most stable adsorption configuration was reached. After incorporating into DPPC bilayers, the interaction between PO₄^- group and SiO₂ particle is stronger than -N⁺(CH₃)₃ group and SiO₂. Small SiO₂ NP was found to adsorb to the surface of DPPC bilayer without disturbing the morphology or membrane. In contract, bioaccumulation of large SiO₂ NP to DPPC induced a strong local membrane deformation. In addition, the effect of SiO₂ NP surface functionalization on its interaction with DPPC was also investigated. This molecular-level study reports a complete description of the interaction between SiO₂ NPs and DPPC bilayer, aiming to provide some insights for the further work on the bioaccumulation and hemolytic activity of SiO₂ NPs.

Localized surface plasmon resonance for enhanced electrocatalysis

Electrocatalysis plays a vital role in energy conversion and storage in modern society. Localized surface plasmon resonance (LSPR) is a highly attractive approach to enhance the electrocatalytic activity and selectivity with solar energy. LSPR excitation can induce the transfer of hot electrons and holes, electromagnetic field enhancement, lattice heating, resonant energy transfer and scattering, in turn boosting a variety of electrocatalytic reactions. Although the LSPR-mediated electrocatalysis has been investigated, the underlying mechanism has not been well explained. Moreover, the efficiency is strongly dependent on the structure and composition of plasmonic metals. In this review, the currently proposed mechanisms for plasmon-mediated electrocatalysis are introduced and the preparation methods to design supported plasmonic nanostructures and related electrodes are summarized. In addition, we focus on the characterization strategies used for verifying and differentiating LSPR mechanisms involved at the electrochemical interface. Following that are highlights of representative examples of direct plasmonic metal-driven and indirect plasmon-enhanced electrocatalytic reactions. Finally, this review concludes with a discussion on the remaining challenges and future opportunities for coupling LSPR with electrocatalysis.

Silica Nanoparticles Inhibit Responses to ATP in Human Airway Epithelial 16HBE Cells

Because of their low cost and easy production, silica nanoparticles (SiNPs) are widely used in multiple manufacturing applications as anti-caking, densifying and hydrophobic agents. However, this has increased the exposure levels of the general population and has raised concerns about the toxicity of this nanomaterial. SiNPs affect the function of the airway epithelium, but the biochemical pathways targeted by these particles remain largely unknown. Here we investigated the effects of SiNPs on the responses of 16HBE14o- cultured human bronchial epithelial (16HBE) cells to the damage-associated molecular pattern ATP, using fluorometric measurements of intracellular Ca2+ concentration. Upon stimulation with extracellular ATP, these cells displayed a concentration-dependent increase in intracellular Ca2+, which was mediated by release from intracellular stores. SiNPs inhibited the Ca2+ responses to ATP within minutes of application and at low micromolar concentrations, which are significantly faster and more potent than those previously reported for the induction of cellular toxicity and pro-inflammatory responses. SiNPs-induced inhibition is independent from the increase in intracellular Ca2+ they produce, is largely irreversible and occurs via a non-competitive mechanism. These findings suggest that SiNPs reduce the ability of airway epithelial cells to mount ATP-dependent protective responses.

Preparation of New Sargassum fusiforme Polysaccharide Long-Chain Alkyl Group Nanomicelles and Their Antiviral Properties against ALV-J

Avian leukosis virus subgroup J (ALV-J) is an immunosuppressive virus which has caused heavy losses to the poultry breeding industry. Currently, there is no effective medicine to treat this virus. In our previous experiments, the low-molecular-weight Sargassum fusiforme polysaccharide (SFP) was proven to possess antiviral activity against ALV-J, but its function was limited to the virus adsorption stage. In order to improve the antiviral activity of the SFP, in this study, three new SFP long-chain alkyl group nanomicelles (SFP-C12M, SFP-C14M and SFP-C16M) were prepared. The nanomicelles were characterized according to their physical and chemical properties. The nanomicelles were characterized by particle size, zeta potential, polydispersity index, critical micelle concentration and morphology. The results showed the particle sizes of the three nanomicelles were all approximately 200 nm and SFP-C14M and SFP-C16M were more stable than SFP-C12M. The newly prepared nanomicelles exhibited a better anti-ALV-J activity than the SFP, with SFP-C16M exhibiting the best antiviral effects in both the virus adsorption stage and the replication stage. The results of the giant unilamellar vesicle exposure experiment demonstrated that the new virucidal effect of the nanomicelles might be caused by damage to the phospholipid membrane of ALV-J. This study provides a potential idea for ALV-J prevention and development of other antiviral drugs.

C-coordinated O-carboxymethyl chitosan Cu(II) complex exerts antifungal activity by disrupting the cell membrane integrity of Phytophthora capsici Leonian

Damage to the cell membrane is an effective method to prevent drug resistance in plant fungal diseases. Here, we proposed a negative remodeling model of the cell membrane structure induced by the C-coordinated O-carboxymethyl chitosan Cu (II) complex (O-CSLn-Cu). FITC-labeled O-CSLn-Cu (FITC-O-CSLn-Cu) was first synthesized via a nucleophilic substitution reaction and confirmed by FT-IR. FITC-labeled O-CSLn-Cu could pass through the fungal cell membrane, as detected by confocal laser scanning microscopy (CLSM) coupled with fluorescein isothiocyanate (FITC)-fluorescence. O-CSLn-Cu treatment led to apparent morphological changes in the membranes of P. capsici Leonian and giant unilamellar vesicles (GUVs) by transmission electron microscopy (TEM). Then, we performed component analysis of the cell membrane from the P. capsici Leonian affected by O-CSLn-Cu with a particular interest in membrane physicochemical properties. Many unsaturated fatty acids (UFAs) and key enzymes promoting UFA synthesis of the cell membrane were downregulated. Similarly, a large number of membrane proteins responsible for substance transport and biochemical reactions were downregulated. Furthermore, O-CSLn-Cu treatments increased plasma membrane permeability with significant leakage of intercellular electrolytes, soluble proteins and sugars, and lipid peroxidation with decreasing membrane fluidity. Finally, aquaporin 10 was proven to be a potential molecular target sensitive to antimicrobial agents according to composition analysis of membrane structure and immunohistochemistry.

Graphene nanosheets damage the lysosomal and mitochondrial membranes and induce the apoptosis of RBL-2H3 cells

The induced membrane damage is a key mechanism for the cytotoxicity of graphene nanosheets (GNSs). In this research, the physical interaction of GNSs on model membranes was investigated using artificial membranes and plasma membrane vesicles. The effects of the GNSs on plasma membrane, lysosomal and mitochondrial membranes were investigated using rat basophilic leukemia (RBL2H3) cells via lactate dehydrogenase (LDH) assay, acridine orange staining and JC-1 probe, respectively. The physical interaction with model membranes was dominated by electrostatic forces, and the adhered GNSs disrupted the membrane. The degree of physical membrane disruption was quantified by the quartz crystal microbalance with dissipation (QCM-D), confirming the serious membrane disruption. The internalized GNSs were mainly distributed in the lysosomes. They caused plasma membrane leakage, increased the lysosomal membrane permeability (LMP), and depolarized the mitochondrial membrane potential (MMP). The increased cellular levels of reactive oxygen species (ROS) were also detected after GNS exposure. The combination of physical interaction and the excess ROS production damaged the plasma and organelle membranes in living RBL-2H3 cells. The lysosomal and mitochondrial dysfunction, and the oxidative stress further induced cell apoptosis. Specially, the exposure to 25 mg/L GNSs caused severest cell mortality, plasma membrane damage, ROS generation, MMP depolarization and apoptosis. The research findings provide more comprehensive information on the graphene-induced plasma and organelle membrane damage, which is important to understand and predict the cytotoxicity of carbon-based nanomaterials.

Crystalline phase and surface coating of Al2O3 nanoparticles and their influence on the integrity and fluidity of model cell membranes

Aluminium oxide nanoparticles (Al₂O₃ NPs) potentially cause health hazards after their release into the environment. The crystalline phase of Al₂O₃ NPs determines their surface structure and the number of functional groups. The adsorption of natural organic matter (NOM) or biomolecules on the surface Al₂O₃ NPs also alters their surface properties and subsequent interactions with organisms. In this study, the roles of the Al₂O₃ crystalline phase and the surface coating of the nanoparticles on the membrane integrity and fluidity were investigated. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes to detect membrane disruption after exposure to Al₂O₃ NPs. Due to amorphous structure and high surface activity of γ-Al₂O₃ NPs, they had a stronger affinity with the membrane and caused more serious membrane rupture than that of α-Al₂O₃ NPs. The deposition of Al₂O₃ NPs on the membrane and the induced membrane disruption were monitored by a quartz crystal microbalance with dissipation (QCM-D) method. HA-coated Al₂O₃ NPs disrupted the SUV layer on the QCM-D sensor, while BSA-coated Al₂O₃ NPs only adhered to the membrane and induced unremarkable vesicle disruption. In addition, untreated γ-Al₂O₃ NPs induced remarkable gelation of a negatively charged membrane, but other types of Al₂O₃ NPs caused negligible membrane phase changes. The outcomes of this study demonstrate that the crystalline phase of the Al₂O₃ NPs affects the integrity and fluidity of cell membranes. The protein coatings on the NPs weaken the NP-membrane interaction, while HA coatings increase the damage of the NP-induced interaction.

A closer look into the physical interactions between lipid membranes and layered double hydroxide nanoparticles

Layered double hydroxide nanoparticles (LDH-NPs) constitute promising nanocarriers for drug and gene delivery. Although their cell internalization has been studied, the interaction between LDH-NPs and biological membrane models, such as giant unilamellar vesicles (GUVs), remains unexplored. These vesicles are widely-used membrane models that allow minimizing the complexity and uncertainty associated with biological systems to study the physical interactions in the absence of cell metabolism effects. With such an approach the physicochemical properties of the membrane can be differentiated from the biological functionalities involved in cell internalization and the membrane-mediated internalization can be directly understood. In this work, we describe for the first time the interaction of LDH-NPs with freestanding negatively charged POPC:POPS GUVs by fluorescence microscopy. The experiments were performed with fluorescein labeled LDH-NPs of about 100 nm together with different fluorophores in order to evaluate the NPs interactions with the vesicles as well as their impact on the membrane morphology and permeability. Positively charged LDH-NPs are electrostatically accumulated at the GUVs membrane, altering its lateral phospholipid distribution and increasing the stiffness and permeability of the membrane. The adsorption of albumin (LDH@ALB) or polyacrylic acid (LDH@PA) passivates the surface of LDH-NPs eliminating long-range electrostatic attraction. The absence of membrane-mediated internalization of either LDH@ALB or LDH@PA, represents an advantage in the use of LDH-NPs as drug or nucleic acids nanocarriers, because suitable functionalization will allow an optimal cell targeting.

Immunomodulatory Potential of Differently-Terminated Ultra-Small Silicon Carbide Nanoparticles

Ultra-small nanoparticles with sizes comparable to those of pores in the cellular membrane possess significant potential for application in the field of biomedicine. Silicon carbide ultra-small nanoparticles with varying surface termination were tested for the biological system represented by different human cells (using a human osteoblastic cell line as the reference system and a monocyte/macrophage cell line as immune cells). The three tested nanoparticle surface terminations resulted in the observation of different effects on cell metabolic activity. These effects were mostly noticeable in cases of monocytic cells, where each type of particle caused a completely different response ('as-prepared' particles, i.e., were highly cytotoxic, -OH terminated particles slightly increased the metabolic activity, while -NH2 terminated particles caused an almost doubled metabolic activity) after 24 h of incubation. Subsequently, the release of cytokines from such treated monocytes and their differentiation into activated cells was determined. The results revealed the potential modulation of immune cell behavior following stimulation with particular ultra-small nanoparticles, thus opening up new fields for novel silicon carbide nanoparticle biomedical applications.

Interactions between PAMAM dendrimers and DOPC lipid multilayers: Membrane thinning and structural disorder

BACKGROUND

Understanding the structure of hybrid nanoparticle-lipid multilayers is of fundamental importance to their bioanalytical applications and nanotoxicity, where nanoparticle-membrane interactions play an important role. Poly(amidoamine) (PAMAM) dendrimers are branched polymeric nanoparticles with potential biomedical applications due to precise tunability of their physicochemical properties. Here, the effect of PAMAM dendrimers (2.9-4.5 nm) with either a hydrophilic amine (NH₂) or a hydrophobic C₁₂ chain surface termination on the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) multilayers has been studied for the first time.

METHODS

DOPC multilayers were created by the liposome-rupture method via drop-casting dendrimer-liposome dispersions with the dendrimers added at different concentrations and at three different stages. The multilayer structure was evaluated via the analysis of the synchrotron X-ray reflectivity (XRR) curves, obtaining the bilayer d-spacing, the coherence length from the Scherrer (L_s) analysis of the Bragg peaks, and the paracrystalline disorder parameter (g).

RESULTS

Dendrimer addition led to lipid bilayer thinning and more disordered multilayer structures. Larger hydrophobic dendrimers caused greater structural disruption to the multilayers compared to the smaller dendrimers. The smallest, positively charged dendrimers at their highest concentration caused the most pronounced bilayer thinning. The dendrimer-liposome mixing method also affected the multilayer structure due to different dendrimer aggregation involved.

CONCLUSIONS

These results show the complexity of the effect of dendrimer physicochemical properties and the addition method of dendrimers on the structure of mixed dendrimer-DOPC multilayers.

GENERAL SIGNIFICANCE

These insights are useful for fundamental understanding of nanotoxicity and future biomedical application of nanocomposite multilayer materials in which nanoparticles are added for enhanced properties and functionality.

Effect of silver nanoparticles on gill membranes of common carp: Modification of fatty acid profile, lipid peroxidation and membrane fluidity

Although the toxicity of silver nanoparticles (AgNPs) in aquatic organisms has been extensively investigated, the mechanism by which AgNPs damage membranes remains unclear. This study investigated the toxic effects of a series of sub-lethal concentrations of AgNPs on the membranes of freshwater carp (Cyprinus carpio) gills, based on changes in membrane fatty acid (FA) profile, membrane fluidity, membrane lipid peroxidation, and histopathology. Most of the FAs in fish gill membrane was not significantly affected by exposure to multiple AgNPs concentrations, only few significant changes occurred in some specific FAs species at a high concentration of AgNPs exposure. In particular, high concentrations of AgNPs significantly decreased the proportions of two important long-chain n-3 series polyunsaturated FAs (C20: 5n3, and C22: 6n3), resulting in a decreased ratio of n-3 polyunsaturated FAs to n-6 polyunsaturated FAs (Σn-3UFA/Σn-6UFA). The AgNPs also caused a dose-dependent decrease in fish gill membrane fluidity, increased the level of lipid peroxidation, and inhibited Na⁺/K⁺-ATPase enzyme activity. Further histopathological examination revealed that exposure to AgNPs can cause toxic responses in the lamellae, including the thinning of the basement membrane, malformation, and inflammation. Together, the results suggest that the mechanism of AgNPs membrane toxicity involves the oxidization of long-chain omega-3 unsaturated FAs to saturated FAs via lipid peroxidation, resulting in, decreased membrane fluidity and ultimately the destruction of the normal physiological function of the fish gill membrane. The findings contribute significantly to our understanding of nanoparticle-induced membrane toxicity and potential risks in aquatic environments.

Novel core-shell nanocomposites based on TiO2 -covered magnetic Co3 O4 for biomedical applications

Magnetic Co₃ O₄ nanoparticles (NPs) have great potential for applications in biomedicine, as contrast enhancement agents for magnetic resonance imaging, or for drug delivery. Although these NPs are so attractive, their potential toxicity raises serious questions about decreasing cellular viability. In this context, Co₃ O₄ NPs were prepared via sol-gel method and encapsulated with a layer of TiO₂ , a biocompatible oxide, and subjected to structural, magnetic and toxicity characterization. X-ray diffractograms of the samples demonstrate the successful synthesis of the spinel and Raman spectroscopy confirms the coating of the Co₃ O₄ spinel with TiO₂ . The Co₃ O₄ cores showed a very intense superparamagnetic character; however, this behavior is strongly suppressed when the material is covered with TiO₂ . According to the neutral red uptake assay, the coating of the cores with TiO₂ significantly decreases the cytotoxic character of the Co₃ O₄ particles and, as it can be observed with the zeta (ξ) potential measurements, they form a stable colloidal dispersion at cytoplasmic pH. The effect of the thermal treatment enhances the biocompatibility even further, with no statistically significant effect on cell viability even at the highest analyzed concentration. The proposed pathway presents a successful sol-gel method for the preparation of Co₃ O₄ @TiO₂ core-shell nanoparticles. This work opens up possibilities for future application of these materials not only for magnetic resonance imaging but also in catalysis and hyperthermia.

The role of positively charged sites in the interaction between model cell membranes and γ-Fe2O3 NPs

The various applications of iron oxide nanoparticles (NPs) in clinical care and wastewater treatment are rapidly developing, thus their biological safety is worth attention. The electrostatic interaction between cell membranes and NPs is the key mechanism behind membrane damage and membrane penetration. Cell membranes are generally negatively charged with a few positively charged domains. The role of the positively charged sites in the NP-membrane interaction needs further investigation. In this study, the ratio of the positively charged sites was adjusted in two model cell membranes: giant and small unilamellar vesicles (GUVs and SUVs). After exposure to negatively charged γ-Fe₂O₃ NPs, the adhesion of NPs on the membranes and the induced membrane disruption were studied by microscopic observation and quartz crystal microbalance (QCM) monitoring. γ-Fe₂O₃ NPs adhered to and disrupted the membranes containing even few positively charged sites, although the whole membrane exhibited a negative zeta potential and hence electrostatically repels the NPs. The number of adhered γ-Fe₂O₃ NPs increased remarkably on membranes with overall positive zeta potential, but more serious disruption happened to membranes with higher ratios of positively charged sites. Therefore, the membrane rupture was more correlated to the number of positively charged sites than to the zeta potential of the whole membrane. In addition, exposure to γ-Fe₂O₃ NPs decreased the order of the lipid molecules and hence increased the fluidity of the membrane phase, and the most significant phase change occurred in the negatively charged membrane with the highest ratio of positively charged sites. Infrared spectra indicated that γ-Fe₂O₃ NPs probably interact with the membranes via the phosphodiester and trimethylamine groups in the lipid head groups. Our research furthers our knowledge of the electrostatic interaction between NPs and cell membranes, which should help to predict the biological effects of γ-Fe₂O₃ NPs.

Coarse-grained molecular dynamics simulation for uptake of nanoparticles into a charged lipid vesicle dominated by electrostatic interactions

We use a coarse-grained molecular dynamics simulation to investigate the interaction between neutral or charged nanoparticles (NPs) and a vesicle consisting of neutral and negatively charged lipids. We focus on the interaction strengths of hydrophilic and hydrophobic attraction and electrostatic interactions between a lipid molecule and an NP. A neutral NP passes through the lipid membrane when the hydrophobic interaction is sufficiently strong. As the valence of the positively charged NP increases, the membrane permeation speed of the NP is increased compared with the neutral NP and charged lipids are accumulated around the charged NP. A charged NP with a high valence passes through the lipid membrane via a transient channel formed by charged lipids or transportlike endocytosis. These permeation processes can be classified based on analyses of the density correlation function. When the nonelectrostatic interaction parameters are large enough, a negatively charged NP can be adsorbed on the membrane and a neutral lipid-rich region is formed directly below the NP. The NP is spontaneously incorporated into the vesicle under various conditions and the incorporation is mediated by the membrane curvature. We reveal how the NP's behavior depends on the NP valence, size, and the nonelectrostatic interaction parameters.

Evaluation of immunoresponses and cytotoxicity from skin exposure to metallic nanoparticles

Nanotechnology is an interdisciplinary science that has developed rapidly in recent years. Metallic nanoparticles (NPs) are increasingly utilized in dermatology and cosmetology, because of their unique properties. However, skin exposure to NPs raises concerns regarding their transdermal toxicity. The tight junctions of epithelial cells form the skin barrier, which protects the host against external substances. Recent studies have found that NPs can pass through the skin barrier into deeper layers, indicating that skin exposure is a means for NPs to enter the body. The distribution and interaction of NPs with skin cells may cause toxic side effects. In this review, possible penetration pathways and related toxicity mechanisms are discussed. The limitations of current experimental methods on the penetration and toxic effects of metallic NPs are also described. This review contributes to a better understanding of the risks of topically applied metallic NPs and provides a foundation for future studies.

Quantification of C60-induced membrane disruption using a quartz crystal microbalance

Direct contact between fullerene C₆₀ nanoparticles (NPs) and cell membranes is one of mechanisms for its cytotoxicity. In this study, the influence of C₆₀ NPs on lipid membranes was investigated. Giant unilamellar vesicles (GUVs) were used as model cell membranes to observe the membrane disruption after C₆₀ exposure. C₆₀ NPs disrupted the positively charged GUVs but not the negatively charged vesicles, confirming the role of electrostatic forces. To quantify the C₆₀ adhesion on membrane and the induced membrane disruption, a supported lipid bilayer (SLB) and a layer of small unilamellar vesicles (SUVs) were used to cover the sensor of a quartz crystal microbalance (QCM). The mass change on the SLB (Δm_SLB) was caused by the C₆₀ adhesion on the membrane, while the mass change on the SUV layer (Δm_SUV) was the combined result of C₆₀ adhesion (mass increase) and SUV disruption (mass loss). The surface area of SLB (A_SLB) was much smaller than the surface area of SUV (A_SUV), but Δm_SLB was larger than Δm_SUV after C₆₀ deposition, indicating that C₆₀ NPs caused remarkable membrane disruption. Therefore a new method was built to quantify the degree of NP-induced membrane disruption using the values of Δm_SUV/Δm_SLB and A_SUV/A_SLB. In this way, C₆₀ can be compared with other types of NPs to know which one causes more serious membrane disruption. In addition, C₆₀ NPs caused negligible change in the membrane phase, indicating that membrane gelation was not the mechanism of cytotoxicity for C₆₀ NPs. This study provides important information to predict the environmental hazard presented by fullerene NPs and to evaluate the degree of membrane damage caused by different NPs.

Fullerene C₆₀ NPs adhere on lipid membrane due to electrostatic force and cause membrane disruption.

Carbon Black Nanoparticles Inhibit Aromatase Expression and Estradiol Secretion in Human Granulosa Cells Through the ERK1/2 Pathway

Secretion of 17-β-estradiol (E2) by human granulosa cells can be disrupted by various environmental toxicants. In the current study, we investigated whether carbon black nanoparticles (CB NPs) affect the steroidogenic activity of cultured human granulosa cells. The human granulosa cell line KGN and granulosa cells from patients undergoing in vitro fertilization were treated with increasing concentrations of CB NPs (1 to 100 µg/mL) together or not with follicle-stimulating hormone (FSH). We observed that CB NPs are internalized in KGN cells without affecting cell viability. CB NPs could be localized in the cytoplasm, within mitochondria and in association with the outer face of the endoplasmic reticulum membrane. In both cell types, CB NPs reduced in a dose-dependent manner the activity of aromatase enzyme, as reflected by a decrease in E2 secretion. A significant decrease was observed in response to CB NPs concentrations from 25 and 50 µg/mL in KGN cell line and primary cultures, respectively. Furthermore, CB NPs decreased aromatase protein levels in both cells and reduced aromatase transcript levels in KGN cells. CB NPs rapidly activated extracellular signal-regulated kinase 1 and 2 in KGN cells and pharmacological inhibition of this signaling pathway using PD 98059 significantly attenuated the inhibitory effects of CB NPs on CYP19A1 gene expression and aromatase activity. CB NPs also inhibited the stimulatory effect of FSH on aromatase expression and activity. Altogether, our study on cultured ovarian granulosa cells reveals that CB NPs decrease estrogens production and highlights possible detrimental effect of these common NPs on female reproductive health.

Adhesion of CdTe quantum dots on model membranes and internalization into RBL-2H3 cells

Quantum dots (QDs) have attracted broad attention due to their special optical properties and promising prospect in medical and biological applications. However, the process of QDs on cell membrane is worth further investigations because such process may lead to harmful effects on organisms and also important for QD application. In this study, adhesion of amino- and carboxyl-coated CdTe QDs (A-QDs and C-QDs) on cell membrane and the subsequent internalization are studied using a series of endocytosis-free model membranes, including giant and small unilamellar vesicles, supported lipid bilayers and giant plasma membrane vesicles (GPMVs). The adhered QD amounts on model membranes are quantified by a quartz crystal microbalance. The CdTe QD adhesion on model membranes is governed by electrostatic forces. Positively charged A-QDs adhere on GPMV surface and passively penetrate the plasma membrane via endocytosis-free mechanism, but negatively charged C-QDs cannot. Rat basophilic leukemia (RBL-2H3) cells are exposed to CdTe QDs to monitor the QD internalization process. Both A- and C-QDs are internalized by RBL-2H3 cells mainly via endocytosis. CdTe QDs do not accumulate on the plasma membrane of living cells due to the fast endocytosis and the weakened electrostatic attraction in biological medium, resulting in low chance of passive penetration. The suspended cells after trypsin digestion take more QDs than the adherent cells. A-QDs cause lower cell viability than C-QDs, probably because the approach of positively charged QDs to cells is favored and the smaller aggregates of A-QDs.

Effects of charge and surface defects of multi-walled carbon nanotubes on the disruption of model cell membranes

The direct contact between multi-walled carbon nanotubes (MWCNTs) and cell membranes causes membrane disruption, potentially leading to cytotoxicity. However, the role of electrostatic forces and MWCNT properties is still open to debate. In this study, the influences of charge and MWCNT surface defects on membrane disruption were investigated by microscopy and a quartz crystal microbalance with dissipation monitoring (QCM-D). Positively/negatively charged giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs) were made as model cell membranes. Negatively charged MWCNTs disrupted the GUVs containing positively charged lipids, which confirmed the electrostatically mediated interaction. However, the mass loss was detected from the negatively charged SLBs after MWCNT exposure, which suggests the extraction of phospholipids. The defect degree of MWCNTs correlated with their adhesion amount on the membranes. Both the oxygenated functional groups and unoxidized dangling carbon bonds were active sites for MWCNT-membrane interactions. The MWCNTs were observed to be engulfed inside the GUVs. The results clearly demonstrate that phospholipid extraction by MWCNTs could occur in electrostatically repulsive conditions, and MWCNT defects were active binding sites whether or not they were oxygenated. Our findings should be helpful in the design and safe applications of carbon nanomaterials.

Effects of rhamnolipids on the cell surface characteristics of Sphingomonas sp. GY2B and the biodegradation of phenanthrene

The mechanism of the interaction of rhamnolipids on strain GY2B.

Role of bovine serum albumin and humic acid in the interaction between SiO2 nanoparticles and model cell membranes

Silica nanoparticles (SiO₂ NPs) can cause health hazard after their release into the environment. Adsorption of natural organic matter and biomolecules on SiO₂ NPs alters their surface properties and cytotoxicity. In this study, SiO₂ NPs were treated by bovine serum albumin (BSA) and humic acid (HA) to study their effects on the integrity and fluidity of model cell membranes. Giant and small unilamellar vesicles (GUVs and SUVs) were prepared as model cell membranes in order to avoid the interference of cellular activities. The microscopic observation revealed that the BSA/HA treated (BSA-/HA-) SiO₂ NPs took more time to disrupt membrane than untreated-SiO₂ NPs, because BSA/HA adsorption covered the surface SiOH/SiO^- groups and weakened the interaction between NPs and phospholipids. The deposition of SiO₂ NPs on membrane was monitored by a quartz crystal microbalance with dissipation (QCM-D). Untreated- and HA-SiO₂ NPs quickly disrupted the SUV layer on QCM-D sensor; BSA-SiO₂ NPs attached on the membranes but only caused slow vesicle disruption. Untreated-, BSA- and HA-SiO₂ NPs all caused the gelation of the positively-charged membrane, which was evaluated by the generalized polarity values. HA-SiO₂ NPs caused most serious gelation, and BSA-SiO₂ NPs caused the least. Our results demonstrate that the protein adsorption on SiO₂ NPs decreases the NP-induced membrane damage.

Determining the relationship between nanoparticle characteristics and immunotoxicity: key challenges and approaches

The growing wealth of information regarding the influence that physicochemical characteristics play on nanoparticle biocompatibility and safety is allowing improved design and rationale for their development and preclinical assessment. Accurate and appropriate measurement of these characteristics accompanied by informed toxicological assessment is a necessity for the development of safe and effective nanomedicines. While particle type, formulation and mode of administration dictate the individual causes for concern through development, the benefits of nanoformulation for treatment of the diseased state are great. Here we have proposed certain considerations and suggestions, which could lead to better-informed preclinical assessment of nanomaterials for nanomedicine, as well as how this information can and should be extrapolated to the physiological state of the end user.

The relevance of membrane models to understand nanoparticles-cell membrane interactions

Over the past two decades, numerous types of nanoparticles (NPs) have been developed for medical applications; however only a few nanomedicines are actually available on the market. One reason is the lack of understanding and data concerning the NP fate and their behavior upon contact with biological media and cell membranes. Biomimetic membrane models are interesting tools to approach and understand NPs-cell membrane interactions. The use of these models permits one to control physical and chemical parameters and to rapidly compare membrane types and the influence of different media conditions. The interactions between NPs and cell membranes can be qualified and quantified using analytical and modeling methods. In this review, the major studies concerning NPs-cell membrane models and associated methods are described. The advantages and drawbacks for each method are compared for the different models. The key mechanisms of interactions between NPs and cell membranes are revealed using cell membrane models and are interrogated in comparison with the NP behavior in cellulo or in vivo. Investigating the interactions between NPs and cell membrane models is now proposed as an intermediate step between physicochemical characterization of NPs and biological assays.

Effects of nano bamboo charcoal on PAHs-degrading strain Sphingomonas sp. GY2B

Nano bamboo charcoal (NBC) has been commonly used in the production of textiles, plastics, paint, etc. However, little is known regarding their effects towards the microorganisms. The effects of NBC on phenanthrene degrading strain Sphingomonas sp. GY2B were investigated in the present study. Results showed that the addition of NBC could improve the phenanthrene removal by Sphingomonas sp. GY2B, with removal efficiencies increased by 10.29-18.56% in comparison to the control at 24h, and phenanthrene was almost completely removed at 48h. With the presence of low dose of NBC (20 and 50mgL(-1)), strain GY2B displayed a better growth at 6h, suggesting that NBC was beneficial to the growth of GY2B and thus resulting in the quick removal of phenanthrene from water. However, the growth of strain GY2B in high dose of NBC (200mgL(-1)) was inhibited at 6h, and the inhibition could be attenuated and eliminated after 12h. NBC-effected phenanthrene solubility experiment suggested that NBC makes a negligible contribution to the solubilization of phenanthrene in water. Results of electronic microscopy analysis (SEM and TEM) indicated NBC may interact with the cell membrane, causing the enhanced membrane permeability and then NBC adsorbed on the membrane would enter into the cells. The findings of this work would provide important information for the future usage and long-term environmental risk assessment of NBC.

Dispersion of atmospheric fine particulate matters in simulated lung fluid and their effects on model cell membranes

Atmospheric fine particulate matter (PM2.5) was collected to investigate its dispersion in simulated lung fluid (SLF) and its interaction with model cell membranes. Organic acids, NH4(+), SO4(2-) and NO3(-) were detected in PM2.5 soluble fraction, and heavy metals were detected from the total mass. The insoluble fraction contained kaolinite, CaCO3, aliphatic carbons, aromatic rings, carboxyl and hydroxyl groups reflected by the infrared spectra. Proteins dispersed PM2.5 in SLF, resulted in smaller hydrodynamic diameter (dH) and slower sedimentation rate. Conversely, phospholipids increased dH value and accelerated sedimentation rate. Giant unilamellar vesicles (GUVs) and supported lipid bilayers (SLBs) were used as model cell membranes. PM2.5 adhered on and disrupted the membrane containing positively-charged lipids but not the membrane containing neutrally- and negatively-charged lipids, which was monitored by microscopy and a quartz crystal microbalance with dissipation (QCM-D). The cationic sites on membrane were necessary for PM2.5 adhesion, but membrane should be disrupted by the combined action of electrostatic forces and hydrogen bonds between PM2.5 oxygen containing groups and the lipid phosphate groups. Our results specified the roles of proteins and phospholipids in PM2.5 dispersion and transport, highly suggested that the health hazard of PM2.5 was related to the biomolecules in the lung fluid and the particle surface groups.

Interaction of silver nanoparticles with tethered bilayer lipid membranes

Silver nanoparticles are well-known for their antibacterial properties. However, the detailed mechanism describing the interaction between the nanoparticles and a cell membrane is not fully understood, which can impede the use of the particles in biomedical applications. Here, a tethered bilayer lipid membrane has been used as a model system to mimic a natural membrane and to study the effect of exposure to small silver nanoparticles with diameters of about 2 nm. The solid supported membrane architecture allowed for the application of surface analytical techniques such as electrochemical impedance spectroscopy and atomic force microscopy. Exposure of the membrane to solutions of the silver nanoparticles led to a small but completely reversible perturbation of the lipid bilayer.