Effects of the presence or absence of a protein corona on silica nanoparticle uptake and impact on cells

Differential Protein Adsorption and Cellular Uptake of Silica Nanoparticles Based on Size and Porosity

Slight alterations in nanoparticles' surface properties can significantly influence the corona composition which may alter their interaction with the biological milieu. Size and porosity of silica nanoparticles (SNPs) are known to be predominant factors influencing their dose-dependent toxicity. Little is known however about the extent and type of protein adsorption on SNPs as a function of physicochemical properties and the role this might play on mechanisms of cellular uptake and toxicity. In this work we investigated the influence of size and porosity of SNPs on protein adsorption, cellular uptake, and toxicity in RAW 264.7 macrophages. Toxicity of the SNPs was found to be concentration dependent, and the formation of the protein corona mitigated toxicity for all particles. Detailed analysis of the amount of proteins recovered from each nanoparticle revealed similarities in the protein adsorption profile as a function of size and porosity. The mechanism of uptake was highly dependent on size rather than porosity or the adsorbed proteins.

Magnetite Nanoparticles for Stem Cell Labeling with High Efficiency and Long-Term in Vivo Tracking

Superparamagnetic iron oxide nanoparticles (SPIO-PAA), ultrasmall iron oxide nanoparticles (USPIO-PAA), and glucosamine-modified iron oxide nanoparticles (USPIO-PAA-GlcN) were studied as mesenchymal stem cell (MSCs) labels for cell tracking applications by magnetic resonance imaging (MRI). Pronounced differences were found in the labeling performance of the three samples in terms of cellular dose and labeling efficiency. In combination with polylysine, SPIO-PAA showed nonhomogeneous cell internalization, while for USPIO-PAA no uptake was found. On the contrary, USPIO-PAA-GlcN featured high cellular uptake and biocompatibility, and sensitive detection in both in vitro and in vivo experiments was found by MRI, showing that glucosamine functionalization can be an efficient strategy to increase cell uptake of ultrasmall iron oxide nanoparticles by MSCs.

Fabrication of size-controlled linoleic acid particles and evaluation of their in-vitro lipotoxicity

The biological activities of fatty acids (FAs) can differ with size even for lipids of similar compositions. The aim of this study was to develop size-controlled FA particles and to evaluate their toxicity as a function of size. Well-stabilized nano- and microscale linoleic acid (LA) were fabricated based on specific physical factors. Then, resulting LAs were characterized by size distribution, surface charge, assembly structure, composition, and serum effects. The sizes of the nano- (LA_nano) and microscale (LA_micro) LAs, determined by electron microscopy, were 109 nm and 12 μm, respectively. LA_nano, a multilamellar structure as determined by cryo-electron microscopy, was rapidly internalized into cells via free fatty acid receptor 3. After internalization, LA_nano, but not LA_micro, induced nuclear translocation of fatty acid binding protein 4 (FABP4). Translocation of FABP4 into the nucleus then induced expression of the FA metabolism-related genes InsR and AdipoR1. Their expression was significantly increased in the presence of only LA_nano. Cytotoxicity was also significantly increased in cells treated with LA_nano, but not LA_micro, as indicated by the endoplasmic reticulum stress markers CHOP and GRP78. Therefore, our results demonstrated that FAs with the same composition but varying in size can cause different cellular responses.

Nanoparticle passage through porcine jejunal mucus: Microfluidics and rheology

A micro-slide chamber was used to screen and rank sixteen functionalized fluorescent silica nanoparticles (SiNP) of different sizes (10, 50, 100 and 200 nm) and surface coatings (aminated, carboxylated, methyl-PEG₁₀₀₀ylated, and methyl-PEG₂₀₀₀ylated) according to their capacity to permeate porcine jejunal mucus. Variables investigated were influence of particle size, surface charge and methyl-PEGylation. The anionic SiNP showed higher transport through mucus whereas the cationic SiNP exhibited higher binding with lower transport. A size-dependence in transport was identified - 10 and 50 nm anionic (uncoated or methyl-PEGylated) SiNP showed higher transport compared to the larger 100 and 200 nm SiNP. The cationic SiNP of all sizes interacted with the mucus, making it more viscous and less capable of swelling. In contrast, the anionic SiNP (uncoated or methyl-PEGylated) caused minimal changes in the viscoelasticity of mucus. The data provide insights into mucus-NP interactions and suggest a rationale for designing oral nanomedicines with improved mucopermeability.

Exploiting the protein corona around gold nanorods for low-dose combined photothermal and photodynamic therapy

A nanodevice comprising human serum (HS) protein corona coated gold nanorods (NRs) has been developed to perform both photothermal therapy (PTT) and photodynamic therapy (PDT) simultaneously at a very low dose under irradiation by a single laser. Here, we exploit the protein corona to load a photosensitizer, chlorin e6 (Ce6), to form NR-HS-Ce6, whose excitation wavelength matches with the longitudinal surface plasmon resonance (LSPR) of NRs. When excited by a single laser, the NRs caused photothermal ablation of cancer cells while Ce6 simultaneously produced reactive oxygen species (ROS) to kill cancer cells through oxidative stress in PDT. We found that the protein corona did not affect the photothermal heating of NRs and observed more than 5-fold increase in ROS generation when Ce6 was loaded on NR-HS compared to free HS-Ce6 dissolved in HS. The uptake of Ce6 by Cal 27 oral squamous cell carcinoma (OSCC) cells also increased 57-fold when loaded on NR-HS compared to free HS-Ce6. While both PDT and PTT have established modest success in reducing cancer cell viability on their own, we have shown that the combined therapy can achieve near complete eradication (95.2% cell kill) of cancer cells even at an extremely low dose of 50 pM of NR-HS-Ce6 containing an equivalent of 7.67 μg mL^-1 Au and 4.83 nM Ce6. This near complete cell kill at such a low dose has not been reported previously. The advantages of this nanoscale delivery system showcase the application of protein corona in cancer treatment instead of considering it as an undesirable biological artefact.

Changes in Optical Properties of Plasmonic Nanoparticles in Cellular Environments are Modulated by Nanoparticle PEGylation and Serum Conditions

When plasmonic nanoparticles (NPs) are internalized by cells and agglomerate within intracellular vesicles, their optical spectra can shift and broaden as a result of plasmonic coupling of NPs in close proximity to one another. For such optical changes to be accounted for in the design of plasmonic NPs for light-based biomedical applications, quantitative design relationships between designable factors and spectral shifts need to be established. Here we begin building such a framework by investigating how functionalization of gold NPs (AuNPs) with biocompatible poly(ethylene) glycol (PEG), and the serum conditions in which the NPs are introduced to cells impact the optical changes exhibited by NPs in a cellular context. Utilizing darkfield hyperspectral imaging, we find that PEGylation decreases the spectral shifting and spectral broadening experienced by 100 nm AuNPs following uptake by Sk-Br-3 cells, but up to a 33 ± 12 nm shift in the spectral peak wavelength can still occur. The serum protein-containing biological medium also modulates the spectral changes experienced by cell-exposed NPs through the formation of a protein corona on the surface of NPs that mediates NP interactions with cells: PEGylated AuNPs exposed to cells in serum-free conditions experience greater spectral shifts than in serum-containing environments. Moreover, increased concentrations of serum (10, 25, or 50 %) result in the formation of smaller intracellular NP clusters and correspondingly reduced spectral shifts after 5 and 10 h NP-cell exposure. However, after 24 h, NP cluster size and spectral shifts are comparable and become independent of serum concentration. By elucidating the impact of PEGylation and serum concentration on the spectral changes experienced by plasmonic NPs in cells, this study provides a foundation for the optical engineering of plasmonic NPs for use in biomedical environments.

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.

Mechanisms of cell uptake, inflammatory potential and protein corona effects with gold nanoparticles

Aim: To assess inflammation, cellular uptake and endocytic mechanisms of gold nanoparticles (AuNP) in human epidermal keratinocytes with and without a protein corona. Materials & methods: Human epidermal keratinocytes were exposed to 40 and 80 nm AuNP with lipoic acid, polyethylene glycol (PEG) and branched polyethyleneimine (BPEI) coatings with and without a protein corona up to 48 h. Inhibitors were selected to characterize endocytosis. Results & conclusion: BPEI-AuNP showed the greatest uptake, while PEG-AuNP had the least. Protein coronas decreased uptake and affected their mechanism. AuNP uptake was energy-dependent, except for 40 nm lipoic-AuNP. Most AuNP were internalized by clathrin and lipid raft-mediated endocytosis, except for 40 nm PEG was by raft/noncaveolae mediated endocytosis. Coronas inhibited caveolae-mediated-endocytosis with lipoic acid and BPEI-AuNP and altered 40 nm PEG-AuNP from raft/noncaveolae to clathrin. Inflammatory responses decreased with a plasma corona. Results suggest protein coronas significantly affect cellular uptake and inflammatory responses of AuNP.

Influence of surface passivation of 2-Methoxyestradiol loaded PLGA nanoparticles on cellular interactions, pharmacokinetics and tumour accumulation

In the present work, 2-Methoxyestradiol [2ME2] loaded PLGA nanoparticles [NPs] were stabilized with Casein or poly(ethylene glycol) [PEG] and evaluated for its cellular interactions, pharmacokinetics and tumour accumulation. Surface stabilized PLGA nanoparticles prepared through a modified emulsion route possessed similar size, surface charge, drug loading and release characteristics. Particle-cell interactions as well as the anti-angiogenesis activity were similar for both nanoformulations in vitro. However, in vivo pharmacokinetics and tumour accumulation of the drug were substantially improved for the PEGylated nanoformulation. Reduced protein binding was observed for PEG stabilized PLGA NPs. Thus, it was demonstrated that nanoencapsulation of 2-ME2 within PEGylated PLGA nanocarrier could improve its half-life and plasma concentration and thereby increase the tumour accumulation.

Insights into the Thermodynamics of Polymer Nanodot-Human Serum Albumin Association: A Spectroscopic and Calorimetric Approach

With the advent of newer luminescent nanoparticles for bioimaging applications, their complex interactions with individual biomolecules need to be understood in great detail, before their direct application into cellular environments. Here, we have presented a systematic and detailed study on the interaction between luminescent polymer nanodots (PNDs) and human serum albumin (HSA) in its free and ligand-bound state with the help of spectrophotometric and calorimetric techniques. At physiological pH (pH = 7.4), PNDs quench the intrinsic fluorescence of HSA as a consequence of ground-state complex formation. The binding stoichiometry and various thermodynamic parameters have been evaluated by using isothermal titration calorimetry and the van't Hoff equation. It has been found that the association of PNDs with HSA is spontaneous (ΔG⁰ = -32.48 ± 1.24 kJ mol^-1) and is driven by a favorable negative standard enthalpy change (ΔH⁰ = -52.86 ± 2.12 kJ mol^-1) and an unfavorable negative standard entropy change (ΔS⁰ = -68.38 ± 2.96 J mol^-1 K^-1). These results have been explained by considering hydrogen bonding interactions between amino and hydroxyl groups (-NH₂ and -OH) of PNDs and carboxylate groups (-COO^-) of glutamate (Glu) and aspartate (Asp) residues of HSA. The binding constant of PNDs with HSA is estimated to be 4.90 ± 0.19 × 10⁵ M^-1. Moreover, it has been observed that warfarin-bound HSA (war-HSA) shows a significantly lower binding affinity (K_b = 1.15 ± 0.19 × 10⁵ M^-1) toward PNDs, whereas ibuprofen-bound HSA (ibu-HSA) shows a slightly lower affinity (K_b = 3.47 ± 0.13 × 10⁵ M^-1) compared with the free HSA. In addition, our results revealed that PNDs displace warfarin from site I (subdomain IIA) of HSA because of the partial unfolding of war-HSA. We hope that the present study will be helpful to understand the fundamental interactions of these biocompatible PNDs with various biological macromolecules.

The Intracellular Destiny of the Protein Corona: A Study on its Cellular Internalization and Evolution

It has been well established that the early stages of nanoparticle-cell interactions are governed, at least in part, by the layer of proteins and other biomolecules adsorbed and slowly exchanged with the surrounding biological media (biomolecular corona). Subsequent to membrane interactions, nanoparticles are typically internalized into the cell and trafficked along defined pathways such as, in many cases, the endolysosomal pathway. Indeed, if the original corona is partially retained on the nanoparticle surface, the biomolecules in this layer may play an important role in determining subsequent cellular processing. In this work, using a combination of organelle separation and fluorescence labeling of the initial extracellular corona, we clarify its intracellular evolution as nanoparticles travel within the cell. We show that specific proteins present in the original protein corona are retained on the nanoparticles until they accumulate in lysosomes, and, once there, they are degraded. We also report on how different bare surfaces (amino and carboxyl modified) affect the details of this evolution. One overarching discovery is that the same serum proteins can exhibit different intracellular processing when carried inside cells by nanoparticles, as components of their corona, compared to what is observed when they are transported freely from the extracellular medium.

Silver nanoparticles: Significance of physicochemical properties and assay interference on the interpretation of in vitro cytotoxicity studies

Silver nanoparticles (AgNPs) have generated a great deal of interest in the research, consumer product, and medical product communities due to their antimicrobial and anti-biofouling properties. However, in addition to their antimicrobial action, concerns have been expressed about the potential adverse human health effects of AgNPs. In vitro cytotoxicity studies often are used to characterize the biological response to AgNPs and the results of these studies may be used to identify hazards associated with exposure to AgNPs. Various factors, such as nanomaterial size (diameter), surface area, surface charge, redox potential, surface functionalization, and composition play a role in the development of toxicity in in vitro test systems. In addition, the interference of AgNPs with in vitro cytotoxicity assays may result in false negative or false positive results in some in vitro biological tests. The goal of this review is to: 1) summarize the impact of physical-chemical parameters, including size, shape, surface chemistry and aggregate formation on the in vitro cytotoxic effects of AgNPs; and 2) explore the nature of AgNPs interference in in vitro cytotoxicity assays.

Carbon nanotubes stimulate synovial inflammation by inducing systemic pro-inflammatory cytokines

Carbon nanotubes (CNTs) have promising applications in a wide range of biomedical fields, including imaging, drug/gene delivery and other therapeutics; however, the biosafety concerns of CNTs should be addressed. To date, many reports have documented the toxicological effects on the cells, tissue or organs that are in direct contact with the tubes; however, there is limited evidence to unravel the secondary toxicity upon CNT treatment. Moreover, more effort is needed to gain a definitive understanding of the adverse outcome pathway (AOP) for CNTs, and a pragmatic framework for risk assessment has not been established yet. In the current study, we aimed to decipher the secondary toxicity to joints under CNT exposure. We demonstrated that carboxylated multi-wall CNTs (MWCNTs-COOH) significantly provoked systemic pro-inflammatory responses, leading to synovial inflammation within knee joints, as evidenced by the infiltration of pro-inflammatory cells in the synovium and meniscus. Mechanistic studies showed that MWCNTs-COOH stimulated pro-inflammatory effects by activating macrophages, and the secreted pro-inflammatory cytokines primed the synoviocytes and chondrocytes, resulting in enhanced production of a large array of enzymes involved in articular cartilage degeneration, including matrix metalloproteinase (MMP) members and cyclooxygenase (COX) members, and increased enzymatic activity of MMPs was demonstrated. Blockade of the cytokines by antibodies significantly attenuated the production of these enzymes. Our current study thus suggests that there is a novel secondary toxicity of CNTs, namely a new AOP to understand the indirect effects of carbon nanotubes: synovial inflammation due to the alteration of the priming state of synoviocytes and chondrocytes under CNT-induced systemic inflammatory conditions.

Differential uptake of nanoparticles by human M1 and M2 polarized macrophages: protein corona as a critical determinant

AIM

To investigate the interaction behavior of M1- and M2-type macrophages with nanoparticles of different sizes with/without the presence of serum.

MATERIALS & METHODS

THP-1 human monocytes were differentiated into M1 and M2 macrophages, and the uptake of silica nanoparticle (50-1000 nm) was studied using flow cytometry and different microscopies.

RESULTS

Without serum, higher uptake of all-sized nanoparticles was observed by M1 compared with M2. With serum, uptake of nanoparticles (200-1000 nm) was dramatically increased by M2. Furthermore, serum proteins adsorbed (corona) by nanoparticles were found to be the ligands for receptors expressed by M2, as revealed by SDS-PAGE and gene profiling analyses.

CONCLUSION

The observed differential uptake by M1 and M2 macrophages will help understand the fate of nanoparticles in vivo.

A centrifugation-based physicochemical characterization method for the interaction between proteins and nanoparticles

Nanomedicine requires in-depth knowledge of nanoparticle-protein interactions. These interactions are studied with methods limited to large or fluorescently labelled nanoparticles as they rely on scattering or fluorescence-correlation signals. Here, we have developed a method based on analytical ultracentrifugation (AUC) as an absorbance-based, label-free tool to determine dissociation constants (KD), stoichiometry (Nmax), and Hill coefficient (n), for the association of bovine serum albumin (BSA) with gold nanoparticles. Absorption at 520 nm in AUC renders the measurements insensitive to unbound and aggregated proteins. Measurements remain accurate and do not become more challenging for small (sub-10 nm) nanoparticles. In AUC, frictional ratio analysis allows for the qualitative assessment of the shape of the analyte. Data suggests that small-nanoparticles/protein complexes significantly deviate from a spherical shape even at maximum coverage. We believe that this method could become one of the established approaches for the characterization of the interaction of (small) nanoparticles with proteins.

Zwitterionic surface coating of quantum dots reduces protein adsorption and cellular uptake

We have studied the effect of the zwitterionic surface coating of quantum dots (QDs) on their interaction with a serum supplemented cell medium and their internalization by human cervical carcinoma (HeLa) cells. Zwitterionic QDs showed negligible adsorption of human serum albumin (HSA) selected as a model serum protein, in contrast to similar but negatively charged QDs. The incorporation of zwitterionic QDs by HeLa cells was found to be lower than for negatively charged QDs and for positively charged QDs, for which the uptake yield was largest. Our results suggest that the suppression of protein adsorption, here accomplished by zwitterionic QD surfaces, offers a strategy that allows for reducing the cellular uptake of nanoparticles.

Opsonisation of nanoparticles prepared from poly(β-hydroxybutyrate) and poly(trimethylene carbonate)-b-poly(malic acid) amphiphilic diblock copolymers: Impact on the in vitro cell uptake by primary human macrophages and HepaRG hepatoma cells

The present work reports the investigation of the biocompatibility, opsonisation and cell uptake by human primary macrophages and HepaRG cells of nanoparticles (NPs) formulated from poly(β-malic acid)-b-poly(β-hydroxybutyrate) (PMLA-b-PHB) and poly(β-malic acid)-b-poly(trimethylene carbonate) (PMLA-b-PTMC) diblock copolymers, namely PMLA₈₀₀-b-PHB₇₃₀₀, PMLA₄₅₀₀-b-PHB₄₄₀₀, PMLA₂₅₀₀-b-PTMC₂₈₀₀ and PMLA₄₃₀₀-b-PTMC₁₄₀₀. NPs derived from PMLA-b-PHB and PMLA-b-PTMC do not trigger lactate dehydrogenase release and do not activate the secretion of pro-inflammatory cytokines demonstrating the excellent biocompatibility of these copolymers derived nano-objects. Using a protein adsorption assay, we demonstrate that the binding of plasma proteins is very low for PMLA-b-PHB-based nano-objects, and higher for those prepared from PMLA-b-PTMC copolymers. Moreover, a more efficient uptake by macrophages and HepaRG cells is observed for NPs formulated from PMLA-b-PHB copolymers compared to that of PMLA-b-PTMC-based NPs. Interestingly, the uptake in HepaRG cells of NPs formulated from PMLA₈₀₀-b-PHB₇₃₀₀ is much higher than that of NPs based on PMLA₄₅₀₀-b-PHB₄₄₀₀. In addition, the cell internalization of PMLA₈₀₀-b-PHB₇₃₀₀ based-NPs, probably through endocytosis, is strongly increased by serum pre-coating in HepaRG cells but not in macrophages. Together, these data strongly suggest that the binding of a specific subset of plasmatic proteins onto the PMLA₈₀₀-b-PHB₇₃₀₀-based NPs favors the HepaRG cell uptake while reducing that of macrophages.

Quantitative analysis of the deposited nanoparticle dose on cell cultures by optical absorption spectroscopy

AIM

The delivered nanoparticle dose to cells in vitro may depend on nanoparticle sedimentation rate. Here, the conditions under which optical absorption spectroscopy can be used to quantify the deposited nanoparticle dose in vitro are investigated.

MATERIALS & METHODS

Nanoparticle cytotoxicity in both upright and inverted cell culture orientations is studied in the presence and absence of serum.

RESULTS

Dissolvable nanoparticles, such as ZnO, exhibit no difference in upright and inverted cultures due to dissolved Zn(2+) ions that dominate cytotoxicity. Insoluble nanoparticles, however, exhibit different sedimentation rates and deposited doses that are linked to the observed cytotoxicity.

CONCLUSION

The combined use of upright-inverted cell orientations and optical absorption spectroscopy can provide a simple experimental approach to interpret in vitro nano-biointeractions.

In one harness: the interplay of cellular responses and subsequent cell fate after quantum dot uptake

Rapid growth and expansion of engineered nanomaterials will occur when the technology can be used safely. Quantum dots have excellent prospects in clinical applications, but the issue of toxicity has not yet been resolved. To enable their medical implementation, the effect on, and mechanisms in, live cells should be clearly known and predicted. A massive amount of experimental data dedicated to nanotoxicity has been accumulated to-date, but it lacks a logical structure. The current challenge is to organize existing knowledge into lucid biological and mathematical models. In our review we aim to describe the interplay of various cell death mechanisms triggered by quantum dots as a consequence of particle parameters and experimental conditions.

Preferential binding of positive nanoparticles on cell membranes is due to electrostatic interactions: A too simplistic explanation that does not take into account the nanoparticle protein corona

The internalization of nanoparticles by cells (and more broadly the nanoparticle/cell interaction) is a crucial issue both for biomedical applications (for the design of nanocarriers with enhanced cellular uptake to reach their intracellular therapeutic targets) and in a nanosafety context (as the internalized dose is one of the key factors in cytotoxicity). Many parameters can influence the nanoparticle/cell interaction, among them, the nanoparticle physico-chemical features, and especially the surface charge. It is generally admitted that positive nanoparticles are more uptaken by cells than neutral or negative nanoparticles. It is supposedly due to favorable electrostatic interactions with negatively charged cell membrane. However, this theory seems too simplistic as it does not consider a fundamental element: the nanoparticle protein corona. Indeed, once introduced in a biological medium nanoparticles adsorb proteins at their surface, forming a new interface defining the nanoparticle "biological identity". This adds a new level of complexity in the interactions with biological systems that cannot be any more limited to electrostatic binding. These interactions will then influence cell behavior. Based on a literature review and on an example of our own experience the parameters involved in the nanoparticle protein corona formation as well as in the nanoparticle/cell interactions are discussed.

Knowledge gaps between nanotoxicological research and nanomaterial safety

With the wide research and application of nanomaterials in various fields, the safety of nanomaterials attracts much attention. An increasing number of reports in the literature have shown the adverse effects of nanomaterials, representing the quick development of nanotoxicology. However, many studies in nanotoxicology have not reflected the real nanomaterial safety, and the knowledge gaps between nanotoxicological research and nanomaterial safety remain large. Considering the remarkable influence of biological or environmental matrices (e.g., biological corona) on nanotoxicity, the situation of performing nanotoxicological experiments should be relevant to the environment and humans. Given the possibility of long-term and low-concentration exposure of nanomaterials, the reversibility of and adaptation to nanotoxicity, and the transgenerational effects should not be ignored. Different from common pollutants, the specific analysis methodology for nanotoxicology need development and exploration furthermore. High-throughput assay integrating with omics was highlighted in the present review to globally investigate nanotoxicity. In addition, the biological responses beyond individual levels, special mechanisms and control of nanotoxicity deserve more attention. The progress of nanotoxicology has been reviewed by previous articles. This review focuses on the blind spots in nanotoxicological research and provides insight into what we should do in future work to support the healthy development of nanotechnology and the evaluation of real nanomaterial safety.

Multifunctional organically modified silica nanoparticles for chemotherapy, adjuvant hyperthermia and near infrared imaging

We report a novel system of organically modified silica nanoparticles (Ormosil) capable of near infrared fluorescence and chemotherapy with adjuvant hyperthermia for image guided cancer therapy. Ormosil nanoparticles were loaded with a chemotherapeutic, Doxorubicin (DOX) and cyanine dye, IR820. Ormosil particles had a mean diameter of 51.2±2.4 nanometers and surface charge of -40.5±0.8mV. DOX was loaded onto Ormosil particles via physical adsorption (FDSIR820) or covalent linkage (CDSIR820) to the silanol groups on the Ormosil surface. Both formulations retained DOX and IR820 over a period of 2 days in aqueous buffer, though CDSIR820 retained more DOX (93.2%) compared to FDSIR820 (77.0%) nanoparticles. Exposure to near infrared laser triggered DOX release from CDSIR820. Uptake of nanoparticles was determined by deconvolution microscopy in ovarian carcinoma cells (Skov-3). CDSIR820 localized in the cell lysosomes whereas cells incubated with FDSIR820 showed DOX fluorescence from the nucleus indicating leakage of DOX from the nanoparticle matrix. FDSIR820 nanoparticles showed severe toxicity in Skov-3 cells whereas CDSIR820 particles had the same cytotoxicity profile as bare (No DOX and IR820) Ormosil particles. Furthermore, exposure of CDSIR820 nanoparticles to Near Infrared laser at 808 nanometers resulted in generation of heat (to 43°C from 37°C) and resulted in enhanced cell killing compared to Free DOX treatment. Bio-distribution studies showed that CDSIR820 nanoparticles were primarily present in the organs of Reticuloendothelial (RES) system.

Impact of food components during in vitro digestion of silver nanoparticles on cellular uptake and cytotoxicity in intestinal cells

Because of the rising application of nanoparticles in food and food-related products, we investigated the influence of the digestion process on the toxicity and cellular uptake of silver nanoparticles for intestinal cells. The main food components--carbohydrates, proteins and fatty acids--were implemented in an in vitro digestion process to simulate realistic conditions. Digested and undigested silver nanoparticle suspensions were used for uptake studies in the well-established Caco-2 model. Small-angle X-ray scattering was used to estimate particle core size, size distribution and stability in cell culture medium. Particles proved to be stable and showed radii from 3.6 to 16.0 nm. Undigested particles and particles digested in the presence of food components were comparably taken up by Caco-2 cells, whereas the uptake of particles digested without food components was decreased by 60%. Overall, these findings suggest that in vivo ingested poly (acrylic acid)-coated silver nanoparticles may reach the intestine in a nanoscaled form even if enclosed in a food matrix. While appropriate for studies on the uptake into intestinal cells, the Caco-2 model might be less suited for translocation studies. Moreover, we show that nanoparticle digestion protocols lacking food components may lead to misinterpretation of uptake studies and inconclusive results.

Surface-anchored poly(acryloyl-L(D)-valine) with enhanced chirality-selective effect on cellular uptake of gold nanoparticles

Chirality is one of the ubiquitous phenomena in biological systems. The left handed (L-) amino acids and right handed (D-) sugars are normally found in proteins, and in RNAs and DNAs, respectively. The effect of chiral surfaces at the nanoscale on cellular uptake has, however, not been explored. This study reveals for the first time the molecular chirality on gold nanoparticles (AuNPs) functions as a direct regulator for cellular uptake. Monolayers of 2-mercaptoacetyl-L(D)-valine (L(D)-MAV) and poly(acryloyl-L(D)-valine (L(D)-PAV) chiral molecules were formed on AuNPs surface, respectively. The internalized amount of PAV-AuNPs was several times larger than that of MAV-AuNPs by A549 and HepG2 cells, regardless of the chirality difference. However, the D-PAV-AuNPs were internalized with significantly larger amount than the L-PAV-AuNPs. This chirality-dependent uptake effect is likely attributed to the preferable interaction between the L-phospholipid-based cell membrane and the D-enantiomers.

Characterization of Biological Secretions Binding to Graphene Oxide in Water and the Specific Toxicological Mechanisms

With the widening application of graphene oxide nanosheets (GONS), their safety has attracted much attention. Secretions from aquatic organisms are ubiquitous in natural water, but the effects of secretions on the characteristics and toxicity of GONS remain largely unknown. To help fill this knowledge gap, we characterized the GONS with biological secretions (GOBS) and the associated changes in apparent toxicity. Small organic molecules, proteins, nucleotides and mucopolysaccharides from secretions in zebrafish culture water bound to GONS. Compared with GONS, GOBS showed special nanoplate topography with thicknesses of approximately 10 nm and lateral lengths ranging from 19.5 to 282 nm. GOBS with smaller lateral sizes exhibited more negative surface charges and lower aggregation state than GONS. Furthermore, GOBS triggered higher toxicity than GONS, such as death, malformation, upregulation of β-galactosidase and loss in mitochondrial membrane potential of zebrafish embryos. The well-dispersive GOBS covered embryos, inhibiting oxygen and ion exchange; these phenomena were the specific mechanisms of the adverse effects. In future work, the acquired natural coatings on nanomaterials should be paid much attention in nanotoxicology, especially for the relationships among topography, aggregation state, and toxicity.

Synthetic virus-like particles prepared via protein corona formation enable effective vaccination in an avian model of coronavirus infection

The ongoing battle against current and rising viral infectious threats has prompted increasing effort in the development of vaccine technology. A major thrust in vaccine research focuses on developing formulations with virus-like features towards enhancing antigen presentation and immune processing. Herein, a facile approach to formulate synthetic virus-like particles (sVLPs) is demonstrated by exploiting the phenomenon of protein corona formation induced by the high-energy surfaces of synthetic nanoparticles. Using an avian coronavirus spike protein as a model antigen, sVLPs were prepared by incubating 100 nm gold nanoparticles in a solution containing an optimized concentration of viral proteins. Following removal of free proteins, antigen-laden particles were recovered and showed morphological semblance to natural viral particles under nanoparticle tracking analysis and transmission electron microscopy. As compared to inoculation with free proteins, vaccination with the sVLPs showed enhanced lymphatic antigen delivery, stronger antibody titers, increased splenic T-cell response, and reduced infection-associated symptoms in an avian model of coronavirus infection. Comparison to a commercial whole inactivated virus vaccine also showed evidence of superior antiviral protection by the sVLPs. The study demonstrates a simple yet robust method in bridging viral antigens with synthetic nanoparticles for improved vaccine application; it has practical implications in the management of human viral infections as well as in animal agriculture.

Dual contribution of surface charge and protein-binding affinity to the cytotoxicity of polystyrene nanoparticles in nonphagocytic A549 cells and phagocytic THP-1 cells

Knowledge that links the physicochemical properties of nanoparticles (NP) to their toxicity is key to evaluating and understanding mechanisms underlying toxicity and developing appropriate testing methods for NP; however, this is currently limited since only a small set of NP have been used, with typically poor control of their physical properties. In this study, eight types of polystyrene NP (PLNP) were synthesized with different functional groups, but all based on an identical core. In vitro cell-based assays were performed to determine the influence of changes in physicochemical properties, such as charge, hydrodynamic size, and protein binding potential, in relation to NP-mediated toxicity. The PLNP were incubated with nonphagocytic A549 cells or phagocytic differentiated THP-1 cells for 4 h with/without fetal bovine serum (FBS), followed by incubation for 20 h in FBS-supplemented medium with/without a washing step, to assess cell-type specificity and impact of protein corona formation. The effect of surface charge on cytotoxicity differed between A549 cells and THP-1 cells. In nonphagocytic A549 cells, the zeta potential of PLNP exhibited a negative correlation with cytotoxicity, partly due to the level of coronated protein that might affect cellular uptake. In phagocytic THP-1 cells, the zeta potential of PLNP showed a positive correlation with cytotoxicity but coronated protein levels displayed no marked association with cytotoxicity, owing to the professional uptake efficacy of phagocytic cells. The consistency of our data with THP-1 cells with the surface charge paradigm in nanotoxicology suggests that phagocytic cells are the predominant targets for lung inflammatory reactions induced by PLNP.

Framework to Evaluate Exposure Relevance and Data Needs for Risk Assessment of Nanomaterials using in Vitro Testing Strategies

This article presents a multistage framework for evaluating the strength of evidence of nanomaterial (NM) exposure characterization data to optimize the utility of in vitro testing strategies for human health risk assessment. This framework is intended to aid risk assessors in evaluating the relevance of data from in vitro tests and to optimize the development of new in vitro testing strategies. The initial stage frames the exposure scenarios of interest in advance of testing to incorporate aspects such as release points, route of exposure, biological and environmental transformations, dose metrics, and biological targets in subsequent stages. The second stage considers characterization in the context of a realistic exposure and the third stage involves designing a testing strategy based on expected exposure conditions. For the fourth and final stage, we propose a matrix approach to evaluate the strength of evidence obtained in the first three stages as a basis for determining the best combination of test conditions and analytical methods available to characterize and measure exposure based on the NM type. This approach can also be used to evaluate existing data for their relevance to the expected exposure scenario and to further develop and optimize in vitro testing strategies. Implementation of the proposed strategy will generate meaningful information on NM properties and their interaction with biological systems, based on realistic exposure scenarios, which will be cost effective and can be applied for assessing risk and making intelligent regulatory decisions regarding the use and disposal of NMs.

Protein Corona Modulates Uptake and Toxicity of Nanoceria via Clathrin-Mediated Endocytosis

Particles present in diesel exhaust have been proposed as a significant contributor to the development of acute and chronic lung diseases, including respiratory infection and allergic asthma. Nanoceria (CeO2 nanoparticles) are used to increase fuel efficiency in internal combustion engines, are present in exhaust fumes, and could affect cells of the airway. Components from the environment such as biologically derived proteins, carbohydrates, and lipids can form a dynamic layer, commonly referred to as the "protein corona" which alters cellular nanoparticle interactions and internalization. Using confocal reflectance microscopy, we quantified nanoceria uptake by lung-derived cells in the presence and absence of a serum-derived protein corona. Employing mass spectrometry, we identified components of the protein corona, and demonstrated that the interaction between transferrin in the protein corona and the transferrin receptor is involved in mediating the cellular entry of nanoceria via clathrin-mediated endocytosis. Furthermore, under these conditions nanoceria does not affect cell growth, viability, or metabolism, even at high concentration. Alternatively, despite the antioxidant capacity of nanoceria, in serum-free conditions these nanoparticles induce plasma membrane disruption and cause changes in cellular metabolism. Thus, our results identify a specific receptor-mediated mechanism for nanoceria entry, and provide significant insight into the potential for nanoparticle-dependent toxicity.

Nanomaterial and toxicity: what can proteomics tell us about the nanotoxicology?

1. In the last few years, a substantial scientific work is focused to identify the potential toxicity of nanomaterials by studying the cellular pathways under in vitro and in vivo conditions. Owing to high surface area to volume ratio nanoparticles (NPs) can pass through cell membranes which might be responsible for creating adverse interactions in biological systems. Simultaneously, researchers are also interested to assess the fate of NP inside the living system, which may lead to altered protein expression as well as protein corona formation. 2. According to published reports, NP-mediated toxicity involves altered cellular system including cell morphology, cell differentiation, cell metabolism, cell mobility, cellular immunity, which is derived from the side effects of nanoformulation and leading to apoptosis and necrosis. These results indicate the existence of potential toxic effect of these particles to human health. 3. The advent of proteomics with sophisticated technical improvement coupled with advanced bioinformatics has led to identify altered proteins due to nanomaterial exposure that could provide a new avenue to biomarker discovery. 4. This review aims to provide the current status of safe production and use of nanomaterials.

Study of Gallium Oxide Nanoparticles Conjugated with β-Cyclodextrin: An Application To Combat Cancer

Bioactive nanomaterials, namely, gallium oxyhydroxide GaO(OH), also surface-conjugated GaO(OH) with a giant sugar molecule β-cyclodextrin (CD), have been prepared through a simple wet chemical route such that the same could be suitably used in biomedical diagnostics as well as therapeutic applications. Several physical methods were used for their characterization: powder X-ray diffraction pattern of GaO(OH) NPs for their grain size determination, optical spectroscopic absorption (UV-vis and FT-IR), and fluorescence properties of these NPs to ascertain surface conjugation and also their wide band-gap properties. Besides these, morphological properties of these NPs were studied by transmission electron microscopic (TEM) investigation, justifying the elemental constitution through energy dispersive X-ray analysis (EDX). Further, biological cellular uptake of these nanoparticles have been demonstrated on cancerous HeLa cells and reported with total fetal effect after 72 h, with CD templated GaO(OH) nanoparticles, a fact that has not been reported so far.

Biomolecular Interactions and Biological Responses of Emerging Two-Dimensional Materials and Aromatic Amino Acid Complexes

The present work experimentally investigates the interaction of aromatic amino acids viz., tyrosine, tryptophan, and phenylalnine with novel two-dimensional (2D) materials including graphene, graphene oxide (GO), and boron nitride (BN). Photoluminescence, micro-Raman spectroscopy, and cyclic voltammetry were employed to investigate the nature of interactions and possible charge transfer between 2D materials and amino acids. Graphene and GO were found to interact strongly with aromatic amino acids through π-π stacking, charge transfer, and H-bonding. Particularly, it was observed that both physi and chemisorption are prominent in the interactions of GO/graphene with phenylalanine and tryptophan while tyrosine exhibited strong chemisorption on graphene and GO. In contrast, BN exhibited little or no interactions, which could be attributed to localized π-electron clouds around N atoms in BN lattice. Lastly, the adsorption of amino acids on 2D materials was observed to considerably change their biological response in terms of reactive oxygen species generation. More importantly, these changes in the biological response followed the same trends observed in the physi and chemisorption measurements.

Bioavailability of Fullerene under Environmentally Relevant Conditions: Effects of Humic Acid and Fetal Bovine Serum on Accumulation in Lipid Bilayers and Cellular Uptake

Carbon fullerene (C60) has emerged at the forefront of nanoscale research and application due to its unique properties. As the production of this nanoparticle rapidly increases, it can be released into natural aquatic environments and can accumulate in biological systems. This research examined the effects of humic acid and fetal bovine serum (FBS), which are ubiquitous in aquatic environments and representative of blood plasma in living organisms, respectively, on bioavailability of fullerene. Bioavailability was investigated using in vitro methods for lipid membrane accumulation and cellular uptake studies. Humic acid and FBS significantly changed the characteristics of fullerene including its particle size and surface charge. The effects of humic acid on lipid accumulation of fullerene depended on the lipid head charge. FBS also significantly decreased the lipid accumulation when positively charged and zwitterionic head groups were present on the lipids, possibly due to the higher steric repulsion of the protein coated nanoparticles. In addition, both humic acid and FBS protein effectively lowered the amounts of fullerene taken up by Caco-2 cells, which are derived from a human colorectal adenocarcinoma and have similar functions to the small intestinal epithelium. Results of this study suggest that surface modification of fullerene by environmentally relevant matrices can significantly affect the biological transport, as well as the possible toxicity of this nanomaterial.

Evolution of gold nanoparticle clusters in living cells studied by sectional dark-field optical microscopy and chromatic analysis

The evolution of gold nanoparticle (Au NP) clusters in living cells are studied by using sectional dark-field optical microscopy and chromatic analysis approach. During endocytosis, Au NP clusters undergo fantastic color changes, from green to yellow-orange due to the plasmonic coupling effect. Analysis of brightness/hue values of the dark-field images helps estimate the numbers of Au NPs in the clusters. The Au NP clusters were further categorized into four groups within the endocytosis. As the results, the late endosomes had increased number of large Au NP clusters with time, while clustered numbers in secondary and tertiary groups were first increased and then decreased due to the fusion and fission of the endocytic vesicles. The time constants and cluster numbers for different groups are fitted by using an integrated rate equation, and show a positive correlation with the size of the Au NP cluster. The efficiency of Au NP uptake is only about 50% for normal cells, while 75% for cancer cells. Compared to normal cells, cancer cells show a larger number in uptake, while faster rate in removal. The propose method helps the kinetic study of endocytosed nanoparticles in physiological conditions.

The Age of Cortical Neural Networks Affects Their Interactions with Magnetic Nanoparticles

Despite increasing use of nanotechnology in neuroscience, the characterization of interactions between magnetic nanoparticles (MNPs) and primary cortical neural networks remains underdeveloped. In particular, how the age of primary neural networks affects MNP uptake and endocytosis is critical when considering MNP-based therapies for age-related diseases. Here, primary cortical neural networks are cultured up to 4 weeks and with CCL11/eotaxin, an age-inducing chemokine, to create aged neural networks. As the neural networks are aged, their association with membrane-bound starch-coated ferromagnetic nanoparticles (fMNPs) increases while their endocytic mechanisms are impaired, resulting in reduced internalization of chitosan-coated fMNPs. The age of the neurons also negates the neuroprotective effects of chitosan coatings on fMNPs, attributing to decreased intracellular trafficking and increased colocalization of MNPs with lysosomes. These findings demonstrate the importance of age and developmental stage of primary neural cells when developing in vitro models for fMNP therapeutics targeting age-related diseases.

A comparison of immunotoxic effects of nanomedicinal products with regulatory immunotoxicity testing requirements

Nanomaterials (NMs) are attractive for biomedical and pharmaceutical applications because of their unique physicochemical and biological properties. A major application area of NMs is drug delivery. Many nanomedicinal products (NMPs) currently on the market or in clinical trials are most often based on liposomal products or polymer conjugates. NMPs can be designed to target specific tissues, eg, tumors. In virtually all cases, NMPs will eventually reach the immune system. It has been shown that most NMs end up in organs of the mononuclear phagocytic system, notably liver and spleen. Adverse immune effects, including allergy, hypersensitivity, and immunosuppression, have been reported after NMP administration. Interactions of NMPs with the immune system may therefore constitute important side effects. Currently, no regulatory documents are specifically dedicated to evaluate the immunotoxicity of NMs or NMPs. Their immunotoxicity assessment is performed based on existing guidelines for conventional substances or medicinal products. Due to the unique properties of NMPs when compared with conventional medicinal products, it is uncertain whether the currently prescribed set of tests provides sufficient information for an adequate evaluation of potential immunotoxicity of NMPs. The aim of this study was therefore, to compare the current regulatory immunotoxicity testing requirements with the accumulating knowledge on immunotoxic effects of NMPs in order to identify potential gaps in the safety assessment. This comparison showed that immunotoxic effects, such as complement activation-related pseudoallergy, myelosuppression, inflammasome activation, and hypersensitivity, are not readily detected by using current testing guidelines. Immunotoxicity of NMPs would be more accurately evaluated by an expanded testing strategy that is equipped to stratify applicable testing for the various types of NMPs.

Controlling the Stealth Effect of Nanocarriers through Understanding the Protein Corona

The past decade has seen a significant increase in interest in the use of polymeric nanocarriers in medical applications. In particular, when used as drug vectors in targeted delivery, nanocarriers could overcome many obstacles for drug therapy. Nevertheless, their application is still impeded by the complex composition of the blood proteins covering the particle surface, termed the protein corona. The protein corona complicates any prediction of cell interactions, biodistribution, and toxicity. In particular, the unspecific uptake of nanocarriers is a major obstacle in clinical studies. This Minireview provides an overview of what we currently know about the characteristics of the protein corona of nanocarriers, with a focus on surface functionalization that reduces unspecific uptake (the stealth effect). The ongoing improvement of nanocarriers to allow them to meet all the requirements necessary for successful application, including targeted delivery and stealth, are further discussed.

DLS and zeta potential - What they are and what they are not?

Adequate characterization of NPs (nanoparticles) is of paramount importance to develop well defined nanoformulations of therapeutic relevance. Determination of particle size and surface charge of NPs are indispensable for proper characterization of NPs. DLS (dynamic light scattering) and ZP (zeta potential) measurements have gained popularity as simple, easy and reproducible tools to ascertain particle size and surface charge. Unfortunately, on practical grounds plenty of challenges exist regarding these two techniques including inadequate understanding of the operating principles and dealing with critical issues like sample preparation and interpretation of the data. As both DLS and ZP have emerged from the realms of physical colloid chemistry - it is difficult for researchers engaged in nanomedicine research to master these two techniques. Additionally, there is little literature available in drug delivery research which offers a simple, concise account on these techniques. This review tries to address this issue while providing the fundamental principles of these techniques, summarizing the core mathematical principles and offering practical guidelines on tackling commonly encountered problems while running DLS and ZP measurements. Finally, the review tries to analyze the relevance of these two techniques from translatory perspective.

Dynamic protein coronas revealed as a modulator of silver nanoparticle sulphidation in vitro

Proteins adsorbing at nanoparticles have been proposed as critical toxicity mediators and are included in ongoing efforts to develop predictive tools for safety assessment. Strongly attached proteins can be isolated, identified and correlated to changes in nanoparticle state, cellular association or toxicity. Weakly attached, rapidly exchanging proteins are also present at nanoparticles, but are difficult to isolate and have hardly been examined. Here we study rapidly exchanging proteins and show for the first time that they have a strong modulatory effect on the biotransformation of silver nanoparticles. Released silver ions, known for their role in particle toxicity, are found to be trapped as silver sulphide nanocrystals within the protein corona at silver nanoparticles in serum-containing cell culture media. The strongly attached corona acts as a site for sulphidation, while the weakly attached proteins reduce nanocrystal formation in a serum-concentration-dependent manner. Sulphidation results in decreased toxicity of Ag NPs.

The biomolecule layer adsorbed at the nanoparticle surface and defined as protein corona affects the nanoparticle biophysical properties and functions. Here, the authors suggest that rapidly-exchanging proteins on the outermost layer of the corona modulate sulphidation of silver nanoparticles in vitro.