The comparative effects of mesoporous silica nanoparticles and colloidal silica on inflammation and apoptosis

HER2-Targeted Multifunctional Silica Nanoparticles Specifically Enhance the Radiosensitivity of HER2-Overexpressing Breast Cancer Cells

We investigated the effects of targeted functionalized silica nanoparticles on the radiosensitivity of cancer cells. Better control of the local concentration of silica nanoparticles may facilitate their use as an adjuvant in conjunction with ionizing radiation to target cancer cells while preventing damage to normal cells. Hyperbranched polyamidoamine (PAMAM) was grafted onto the surface of amorphous silica nanoparticles to functionalize them. The PAMAM-coated silica nanoparticles (PCSNs) were then conjugated with fluorescent dyes. Anti-HER2 antibodies were covalently attached to the labeled PCSNs. The HER2-overexpressing SK-BR3 breast cancer cell line was incubated in medium containing the PCSN probes. After incubation; the cells were exposed to X-ray radiation. Cells were counted in all samples using cell proliferation assays; and apoptotic cells were detected. The cell survival results showed that the combination of the targeted PCSN probes and radiation reduced the survival rate of SK-BR3 cells to a greater extent than when either PCSN probes, PCSNs or radiation were applied individually. The results also showed an increase in apoptosis in the SK-BR3 cells that internalized the PCSN probes and were then irradiated. Based on these data, PCSN probes act as specific radiosensitizing agents for HER2-overexpressing cells.

Fenofibrate Nanocrystals Embedded in Oral Strip-Films for Bioavailability Enhancement

The aim of the present study was to make a fenofibrate (FNB) nanocrystal (NC) by wet media milling, characterizations and formulates into oral strip-films (OSFs). Mechanical properties, redispersion study, and solid-state characterizations results suggested that reduction of drug crystal size at nanoscale and incorporation into OSFs does not affect the solid-state properties of the drug. In vitro dissolution kinetics showed enhanced dissolution rate was easily manipulated by changing the thickness of the OSF. In situ UV-imaging was used to monitor drug dissolution qualitatively and quantitatively in real time. Results confirm that the intrinsic dissolution rates and surface drug concentration measured with this device were in agreement with the USP-IV dissolution profiles. In vivo pharmacokinetics in rabbits showed a significant difference in the pharmacokinetics parameter (1.4 fold increase bioavailability) of FNB NC-loaded OSFs as compared to the marketed formulation “Tricor” and as-received (pristine) drug. This approach of drug nanocrystallization and incorporation into OSFs may have significant applications in cost-effective tools for bioavailability enhancement of FNB.

Global gene expression analysis of macrophage response induced by nonporous and porous silica nanoparticles

Little is known about the global gene expression profile of macrophages in response to changes in size and porosity of silica nanoparticles (SNPs). Spherical nonporous SNPs of two different diameters, and mesoporous spherical SNPs with comparable size were characterized. Reactive oxygen species, mitochondrial membrane potential, lysosome degradation capacity, and lysosome pH were measured to evaluate the influence of nonporous and mesoporous SNPs on mitochondrial and lysosomal function. RNA-sequencing was utilized to generate transcriptional profiles of RAW264.7 macrophages exposed to non-toxic SNP doses. DESeq2, limma, and BinReg2 software were used to analyze the data based on both unsupervised and supervised strategies to identify genes with greatest differences among NP treatments. Utilizing GATHER and DAVID software, possible induced pathways were studied. We found that mesoporous silica nanoparticles are capable of altering gene expression in macrophages at doses that do not elicit acute cytotoxicity, while gene transcription was minimally affected by nonporous SNPs.

Characterization and osteogenic evaluation of mesoporous magnesium–calcium silicate/polycaprolactone/polybutylene succinate composite scaffolds fabricated by rapid prototyping

The properties of scaffolds for bone tissue engineering, including their biocompatibility, highly interconnected porosity, and mechanical integrity, are critical for promoting cell adhesion, proliferation, and osteoinduction. We used various physical and biological assays to obtain in vitro confirmation that the proposed composite scaffolds are potentially suitable for applications to bone tissue engineering. The proposed new composite scaffolds, which we fabricated by a rapid prototyping technique, were composed of mesoporous magnesium–calcium silicate (m_MCS), polycaprolactone (PCL), and polybutylene succinate (PBSu). We systematically evaluated the characteristics of the composite scaffolds, such as the hydrophilicity and bioactivity. We also investigated the proliferation and osteogenic differentiation of human mesenchymal stem cells (MSCs) scaffolded on the m_MCS/PCL/PBSu composite. Our results showed that, compared to the m_MCS/PCL scaffold, the m_MCS/PCL/PBSu scaffold has improved water absorption, in vitro degradability, biocompatibility, and bioactivity in simulated body fluid, while its mechanical strength is reduced. Moreover, the results of the cytotoxicity tests specified in ISO 10993-12 and ISO 10993-5 clearly indicate that the m_MCS/PCL scaffold is not toxic to cells. In addition, we obtained significant increases in initial cell attachment and improvements to the osteogenic MSC differentiation by replacing the m_MCS/PCL scaffold with the m_MCS/PCL/PBSu scaffold. Our results indicate that the m_MCS/PCL/PBSu scaffold achieves enhanced bioactivity, degradability, cytocompatibility, and osteogenesis. As such, this scaffold is a potentially promising candidate for use in stem cell-based bone tissue engineering.

A new composite scaffold consisting of mesoporous magnesium–calcium silicate (m_MCS), polycaprolactone (PCL), and polybutylene succinate (PBSu) was manufactured by a rapid prototyping technique, for stem cell-based bone tissue engineering.

Silica nanoparticles induce NLRP3 inflammasome activation in human primary immune cells

In recent years, the potential use of silica nanoparticles (SiNPs) among different biomedical fields has grown. A deep understanding of the physicochemical properties of nanoparticles (NPs) and their regulation of specific biological responses is crucial for the successful application of NPs. Exposure to NP physicochemical properties (size, shape, porosity, etc.) could result in deleterious effects on cellular functions, including a pro-inflammatory response mediated via activation of the NLRP3 inflammasome. The aim of this study was to evaluate the potential in vitro immunomodulatory effect of 12-nm and 200-nm SiNPs on the expression of pro-inflammatory cytokines and NLRP3 inflammasome components in human primary neutrophils and PBMCs. This study demonstrates that regardless of the size of the nanoparticles, SiNPs induce the production of pro-inflammatory cytokines in a dose-dependent manner. Induced IL-1β production after exposure to SiNPs suggests the involvement of NLRP3 inflammasome components participation in this process. In conclusion, SiNPs induce the production of pro-inflammatory cytokines in a dose-dependent manner. Furthermore, our data suggest that the production and release of IL-1β possibly occurs through the formation of the NLRP3 inflammasome.

Molecular and immunological toxic effects of nanoparticles

Nanoparticles have emerged as a boon for the public health applications such as drug delivery, diagnostic, and imaging. Biodegradable and non-bio degradable nanoparticles have been used at a large scale level to increase the efficiency of the biomedical process at the cellular, animal and human level. Exponential use of nanoparticles reinforces the adverse immunological changes at the human health level. Physical and chemical properties of nanoparticles often lead to a variety of immunotoxic effects such as activation of stress-related genes, membrane disruption, and release of pro-inflammatory cytokines. Delivered nanoparticles in animal or human interact with various components of the immune system such as lymphocytes, macrophages, neutrophils etc. Nanoparticles delivered above the threshold level damages the cellular physiology by the generation of reactive oxygen and nitrogen species. This review article represents the potential of nanoparticles in the field of nanomedicine and provides the critical evidence which leads to develop immunotoxicity in living cells and organisms by altering immunological responses.

Combined Action of Human Commensal Bacteria and Amorphous Silica Nanoparticles on the Viability and Immune Responses of Dendritic Cells

Dendritic cells (DCs) regulate the host-microbe balance in the gut and skin, tissues likely exposed to nanoparticles (NPs) present in drugs, food, and cosmetics. We analyzed the viability and the activation of DCs incubated with extracellular media (EMs) obtained from cultures of commensal bacteria (Escherichia coli, Staphylococcus epidermidis) or pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus) in the presence of amorphous silica nanoparticles (SiO₂ NPs). EMs and NPs synergistically increased the levels of cytotoxicity and cytokine production, with different nanoparticle dose-response characteristics being found, depending on the bacterial species. E. coli and S. epidermidis EMs plus NPs at nontoxic doses stimulated the secretion of interleukin-1β (IL-1β), IL-12, IL-10, and IL-6, while E. coli and S. epidermidis EMs plus NPs at toxic doses stimulated the secretion of gamma interferon (IFN-γ), tumor necrosis factor alpha (TNF-α), IL-4, and IL-5. On the contrary, S. aureus and P. aeruginosa EMs induced cytokines only when they were combined with NPs at toxic concentrations. The induction of maturation markers (CD86, CD80, CD83, intercellular adhesion molecule 1, and major histocompatibility complex class II) by commensal bacteria but not by pathogenic ones was improved in the presence of noncytotoxic SiO₂ NP doses. DCs consistently supported the proliferation and differentiation of CD4⁺ and CD8⁺ T cells secreting IFN-γ and IL-17A. The synergistic induction of CD86 was due to nonprotein molecules present in the EMs from all bacteria tested. At variance with this finding, the synergistic induction of IL-1β was prevalently mediated by proteins in the case of E. coli EMs and by nonproteins in the case of S. epidermidis EMs. A bacterial costimulus did not act on DCs after adsorption on SiO₂ NPs but rather acted as an independent agonist. The inflammatory and immune actions of DCs stimulated by commensal bacterial agonists might be altered by the simultaneous exposure to engineered or environmental NPs.

Nanoparticle impact on innate immune cell pattern-recognition receptors and inflammasomes activation

Nanotechnology-based strategies can dramatically impact the treatment, prevention and diagnosis of a wide range of diseases. Despite the unprecedented success achieved with the use of nanomaterials to address unmet biomedical needs and their particular suitability for the effective application of a personalized medicine, the clinical translation of those nanoparticulate systems has still been impaired by the limited understanding on their interaction with complex biological systems. As a result, unexpected effects due to unpredicted interactions at biomaterial and biological interfaces have been underlying the biosafety concerns raised by the use of nanomaterials. This review explores the current knowledge on how nanoparticle (NP) physicochemical and surface properties determine their interactions with innate immune cells, with particular attention on the activation of pattern-recognition receptors and inflammasome. A critical perspective will additionally address the impact of biological systems on the effect of NP on immune cell activity at the molecular level. We will discuss how the understanding of the NP-innate immune cell interactions can significantly add into the clinical translation by guiding the design of nanomedicines with particular effect on targeted cells, thus improving their clinical efficacy while minimizing undesired but predictable toxicological effects.

Toxicology of silica nanoparticles: an update

Large-scale production and use of amorphous silica nanoparticles (SiNPs) have increased the risk of human exposure to SiNPs, while their health effects remain unclear. In this review, scientific papers from 2010 to 2016 were systematically selected and sorted based on in vitro and in vivo studies: to provide an update on SiNPs toxicity and to address the knowledge gaps indicated in the review of Napierska (Part Fibre Toxicol 7:39, 2010). Toxicity of SiNPs in vitro is size, dose, and cell type dependent. SiNPs synthesized by wet route exhibited noticeably different biological effects compared to thermal route-based SiNPs. Amorphous SiNPs (particularly colloidal and stöber) induced toxicity via mechanisms similar to crystalline silica. In vivo, route of administration and physico-chemical properties of SiNPs influences the toxicokinetics. Adverse effects were mainly observed in acutely exposed animals, while no significant signs of toxicity were noted in chronically dosed animals. The correlation between in vitro and in vivo toxicity remains less well established mainly due to improper-unrealistic-dosing both in vitro and in vivo. In conclusion, notwithstanding the multiple studies published in recent years, unambiguous linking of physico-chemical properties of SiNPs types to toxicity, bioavailability, or human health effects is not yet possible.

An Evaluation of the in vivo Safety of Nonporous Silica Nanoparticles: Ocular Topical Administration versus Oral Administration

Nonporous silica nanoparticles (SiNPs) have potential as promising carriers for ophthalmic drugs. However, the in vivo safety of ocular topical SiNPs remains unclear. This study investigated the in vivo safety of oral and ocular topical applications of 100 nm-sized SiNPs in Sprague-Dawley rats. The rats were divided into the following four groups: low-dose oral administration (total 100 mg/kg of SiNPs mixed with food for one week), high-dose oral administration (total 1000 mg/kg of SiNPs mixed with food for one week), ocular topical administration (10 mg/ml concentration, one drop, applied to the right eyes four times a day for one month), or a negative control (no SiNP treatment). The rats were observed for 12 weeks to investigate any signs of general or ocular toxicity. During the observation period, no differences were observed in the body weights, food and water intakes, behaviors and abnormal symptoms of the four groups. No animal deaths occurred. After 12 weeks, hematologic, blood biochemical parameters and ophthalmic examinations revealed no abnormal findings in any of the animals. The lack of toxicity of the SiNPs was further verified in autopsy findings of brain, liver, lung, spleen, heart, kidneys, intestine, eyeballs, and ovaries or testes.

Impacts of Cross-Linkers on Biological Effects of Mesoporous Silica Nanoparticles

Chemically synthesized cross-linkers play decisive roles in variable cargos attached to nanoparticles (NPs). Previous studies reported that surface properties, such as the size, charge, and surface chemistry, are particularly important determinants influencing the biological fate and actions of NPs and cells. Recent studies also focused on the relationship of serum proteins with the surface properties of NPs (also called the protein corona), which is recognized as a key factor in determining the cytotoxicity and biodistribution. However, there is concern that cross-linkers conjugated onto NPs might induce undesirable biological effects. Cell responses induced by cross-linkers have not yet been precisely elucidated. Herein, using mesoporous silica nanoparticles (MSNs) the surfaces of which were separately conjugated with four popular heterobifunctional cross-linkers, i.e., N-[α-maleimidoacetoxy]succinimide ester (AMAS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and maleimide poly(ethylene glycol) succinimidyl carboxymethyl ester (MAL-PEG-SCM), we investigated cross-linker-conjugated MSNs to determine whether they can cause cytotoxicity, or enhance reactive oxygen species (ROS) generation, nuclear factor (NF)-κB activation, and p-p38 or p21 protein expressions in RAW264.7 macrophage cells. Furthermore, we also separately conjugated two biomolecules containing TAT peptides and bovine serum albumin (BSA) as model systems to study their cell responses in detail. Finally, in vivo mice studies evaluated the biodistribution and blood assays (biochemistry and complete blood count) of PEG-derivative NPs, and results suggested that TAT peptides caused significant white blood cell (WBC)-related cell and platelet abnormalities, as well as liver and kidney dysfunction compared to BSA when conjugated onto MSNs. The results showed that attention to cross-linkers should be considered an issue in the surface modification of NPs. We anticipate that our results could be helpful in developing biosafety nanomaterials.

In Vitro Studies on the Degradability, Bioactivity, and Cell Differentiation of PRP/AZ31B Mg Alloys Composite Scaffold

In recent years, more and more methods have been developed to improve the bioactivity of the biodegradable materials in bone tissue regeneration. In present study, we used rat mesenchymal stem cells (rMSCs) to evaluate the outcomes of Mg alloys (AZ31B, Magnesium, and Aluminum) and Platelet-rich plasma (PRP)/Mg alloys on rMSCs biocompatibility and osteogenic differentiation. Water absorption experiments indicated that both bare AZ31B and PRP/AZ31B were capable of absorbing large amounts of water. But the water absorption ratio for PRP/AZ31B was significantly higher than that for bare AZ31B. The degradability experiments implied that both samples degraded at same speed. rMSCs on the surface of AZ31B distributed more and better than those on the AZ31B scaffold. In ALP activity experiment, the activity of rMSCs on the PRP/AZ31B was markedly higher than that on the AZ31B scaffolds on the 7th day and 14th day. qRT-PCR also showed that OPN and OCN were expressed in both samples. OPN and OCN expression in PRP/AZ31B sample were higher than those in bare AZ31B samples. In summary, the in vitro study implied that AZ31B combined with PRP could remarkably improve cell seeding, attachment, proliferation, and differentiation.

Allergic Responses Induced by the Immunomodulatory Effects of Nanomaterials upon Skin Exposure

Over the past decade, a vast array of nanomaterials has been created through the development of nanotechnology. With the increasing application of these nanomaterials in various fields, such as foods, cosmetics, and medicines, there has been concern about their safety, that is, nanotoxicity. Therefore, there is an urgent need to collect information about the biological effects of nanomaterials so that we can exploit their potential benefits and design safer nanomaterials, while avoiding nanotoxicity as a result of inhalation or skin exposure. In particular, the immunomodulating effect of nanomaterials is one of most interesting aspects of nanotoxicity. However, the immunomodulating effects of nanomaterials through skin exposure have not been adequately discussed compared with the effects of inhalation exposure, because skin penetration by nanomaterials is thought to be extremely low under normal conditions. On the other hand, the immunomodulatory effects of nanomaterials via skin may cause severe problems for people with impaired skin barrier function, because some nanomaterials could penetrate the deep layers of their allergic or damaged skin. In addition, some studies, including ours, have shown that nanomaterials could exhibit significant immunomodulating effects even if they do not penetrate the skin. In this review, we summarize our current knowledge of the allergic responses induced by nanomaterials upon skin exposure. First, we discuss nanomaterial penetration of the intact or impaired skin barrier. Next, we describe the immunomodulating effects of nanomaterials, focusing on the sensitization potential of nanomaterials and the effects of co-exposure of nanomaterials with substances such as chemical sensitizers or allergens, on the onset of allergy, following skin exposure. Finally, we discuss the potential mechanisms underlying the immunomodulating effects of nanomaterials by describing the involvement of the protein corona in the interaction of nanomaterials with biological components and by presenting recent data about the adjuvant effects of well-characterized particle adjuvant, aluminum salt, as an example of immunomodulatory particulate.

Effect of the biodegradation rate controlled by pore structures in magnesium phosphate ceramic scaffolds on bone tissue regeneration in vivo

Similar to calcium phosphates, magnesium phosphate (MgP) ceramics have been shown to be biocompatible and support favorable conditions for bone cells. Micropores below 25μm (MgP25), between 25 and 53μm (MgP53), or no micropores (MgP0) were introduced into MgP scaffolds using different sizes of an NaCl template. The porosities of MgP25 and MgP53 were found to be higher than that of MgP0 because of their micro-sized pores. Both in vitro and in vivo analysis showed that MgP scaffolds with high porosity promoted rapid biodegradation. Implantation of the MgP0, MgP25, and MgP53 scaffolds into rabbit calvarial defects (with 4- and 6-mm diameters) was assessed at two times points (4 and 8weeks), followed by analysis of bone regeneration. The micro-CT and histologic analyses of the 4-mm defect showed that the MgP25 and MgP53 scaffolds were degraded completely at 4weeks with simultaneous bone and marrow-like structure regeneration. For the 6-mm defect, a similar pattern of regeneration was observed. These results indicate that the rate of degradation is associated with bone regeneration. The MgP25 and MgP53 scaffold-implanted bone showed a better lamellar structure and enhanced calcification compared to the MgP0 scaffold because of their porosity and degradation rate. Tartrate-resistant acid phosphatase (TRAP) staining indicated that the newly formed bone was undergoing maturation and remodeling. Overall, these data suggest that the pore architecture of MgP ceramic scaffolds greatly influence bone formation and remodeling activities and thus should be considered in the design of new scaffolds for long-term bone tissue regeneration.

STATEMENT OF SIGNIFICANCE

The pore structural conditions of scaffold, including porosity, pore size, pore morphology, and pore interconnectivity affect cell ingrowth, mechanical properties and biodegradabilities, which are key components of scaffold in bone tissue regeneration. In this study, we designed hierarchical pore structure of the magnesium phosphate (MgP) scaffold by combination of the 3D printing process, self-setting reaction and salt-leaching technique, and first studied the effect of pore structures of bioceramic scaffolds on bone tissue regeneration through both in vitro and in vivo studies (rabbit calvarial model). The MgP scaffolds with higher porosity promoted more rapid biodegradation and enhanced new bone formation and remodeling activities at the same time.

Toxic and adjuvant effects of silica nanoparticles on ovalbumin-induced allergic airway inflammation in mice

Background

Silica nanoparticles (SNPs) can easily enter in respiratory system via inhalation because of their low molecular weight and ease of dispersion. Toxicity and adverse effects of SNPs vary according to the physical characteristics of the particle.

Methods

To evaluate the toxic and adjuvant effects of 3 types of SNPs in the airway system, six-week-old female BALB/c mice were intranasally administered 3 types of SNPs (spherical [S-SNP], mesoporous [M-SNP], and polyethylene glycol-conjugated [P-SNP]) alone or SNPs/ovalbumin (OVA), three times weekly for 2 weeks. Airway hyper-responsiveness (AHR), bronchoalveolar lavage fluid (BALF), cytokine levels, and histology of the lungs were analyzed.

Results

The S-SNPs/OVA group and M-SNPs/OVA group showed significant AHR, compared to the control group. Among all SNP-treated groups, the group administered SNPs/OVA showed greater inflammatory cell infiltration in BALF, extensive pathological changes, and higher cytokine levels (IL-5, IL-13, IL-1β, and IFN-γ) than those administered SNPs alone or saline/OVA.

Conclusion

Exposure to SNPs alone and SNPs/OVA induced toxicity in the respiratory system. SNPs alone showed significant toxic effects on the airway system. Meanwhile, SNPs/OVA exerted adjuvant effects to OVA of inducing allergic airway inflammation. In particular, M-SNPs showed the most severe airway inflammation in both direct toxicity and adjuvant effect assays. P-SNPs induced less inflammation than the other types of SNPs in both models.

Autophagy upregulation promotes macrophages to escape mesoporous silica nanoparticle (MSN)-induced NF-κB-dependent inflammation

BACKGROUND

Our previous studies (Int J Nanomed 10:22, 2015) have indicated that a single large dose of mesoporous silica nanoparticles (MSNs) can induce severe and selective nephrotoxicity, which is closely related to inflammation mediated by the NF-κB pathway. However, the effect of MSNs on other organs and the interactions of nanomaterials with biological systems remain rudimentary.

OBJECTIVE

This study aimed to clarify the biological behaviour and influence of MSNs on macrophages.

METHODS

The mice received a single intraperitoneal injection of a suspension of 150, 300 of 600 mg/kg MSNs, and RAW 264.7 cells were treated with MSNs at various concentrations and times. Cell viability was determined by MTT assay and LDH release assay. The NF-κB pathway and the target proinflammatory cytokines IL-1β and TNF-α were determined by western blotting or ELISA. Autophagy is considered as an emerging mechanism of nanomaterials. So the autophagic ultrastructural analysis, the determination of Beclin-1 and LC3 expression, and the calculation of LC3II dots were employed to verify autophagy activation. In addition, RNA interference, autophagy agonist and inhibitor were used to explore the role of autophagy in inflammation.

RESULTS

The results indicated that MSNs are internalized into macrophages and induce cytotoxicity in a dose- and time-dependent manner. The NF-κB pathway, IL-1β and TNF-α were induced and released by MSNs. The levels of Beclin-1 and LC3II dots were obviously up-regulated by MSNs, which indicated that autophagy was induced in the MSN-treated cells. Moreover, the enhanced autophagy can attenuate the inflammation mediated by the NF-κB pathway, whereas the inhibition of autophagy can contribute to inflammation.

CONCLUSIONS

In summary, our results suggest that autophagy may be a possible protective factor in inflammation induced by MSNs in macrophages.

Immune response to functionalized mesoporous silica nanoparticles for targeted drug delivery

Multifunctional mesoporous silica nanoparticles (MSN) have attracted substantial attention with regard to their high potential for targeted drug delivery. For future clinical applications it is crucial to address safety concerns and understand the potential immunotoxicity of these nanoparticles. In this study, we assess the biocompatibility and functionality of multifunctional MSN in freshly isolated, primary murine immune cells. We show that the functionalized silica nanoparticles are rapidly and efficiently taken up into the endosomal compartment by specialized antigen-presenting cells such as dendritic cells. The silica nanoparticles showed a favorable toxicity profile and did not affect the viability of primary immune cells from the spleen in relevant concentrations. Cargo-free MSN induced only very low immune responses in primary cells as determined by surface expression of activation markers and release of pro-inflammatory cytokines such as Interleukin-6, -12 and -1β. In contrast, when surface-functionalized MSN with a pH-responsive polymer capping were loaded with an immune-activating drug, the synthetic Toll-like receptor 7 agonist R848, a strong immune response was provoked. We thus demonstrate that MSN represent an efficient drug delivery vehicle to primary immune cells that is both non-toxic and non-inflammagenic, which is a prerequisite for the use of these particles in biomedical applications.

Pharmacokinetics, pharmacodynamics and toxicology of theranostic nanoparticles

Nanoparticles (NPs) are considered a promising tool in both diagnosis and therapeutics. Theranostic NPs possess the combined properties of targeted imaging and drug delivery within a single entity. While the categorization of theranostic NPs is based on their structure and composition, the pharmacokinetics of NPs are significantly influenced by the physicochemical properties of theranostic NPs as well as the routes of administration. Consequently, altered pharmacokinetics modify the pharmacodynamic efficacy and toxicity of NPs. Although theranostic NPs hold great promise in nanomedicine and biomedical applications, a lack of understanding persists on the mechanisms of the biodistribution and adverse effects of NPs. To better understand the diagnostic and therapeutic functions of NPs, this review discusses the factors that influence the pharmacokinetics, pharmacodynamics and toxicology of theranostic NPs, along with several strategies for developing novel diagnostic and therapeutic modalities.

Nanoparticle Uptake: The Phagocyte Problem

Phagocytes are key cellular participants determining important aspects of host exposure to nanomaterials, initiating clearance, biodistribution and the tenuous balance between host tolerance and adverse nanotoxicity. Macrophages in particular are believed to be among the first and primary cell types that process nanoparticles, mediating host inflammatory and immunological biological responses. These processes occur ubiquitously throughout tissues where nanomaterials are present, including the host mononuclear phagocytic system (MPS) residents in dedicated host filtration organs (i.e., liver, kidney spleen, and lung). Thus, to understand nanomaterials exposure risks it is critical to understand how nanomaterials are recognized, internalized, trafficked and distributed within diverse types of host macrophages and how possible cell-based reactions resulting from nanomaterial exposures further inflammatory host responses in vivo. This review focuses on describing macrophage-based initiation of downstream hallmark immunological and inflammatory processes resulting from phagocyte exposure to and internalization of nanomaterials.

Mechanistic Investigation of the Biological Effects of SiO₂, TiO₂, and ZnO Nanoparticles on Intestinal Cells

Silicon dioxide (SiO2), titanium dioxide (TiO2), and zinc oxide (ZnO) are currently among the most widely used nanoparticles (NPs) in the food industry. This could potentially lead to unintended exposure of the gastrointestinal tract to these NPs. This study aims to investigate the potential side-effects of these food-borne NPs on intestinal cells and to mechanistically understand the observed biological responses. Among the panel of tested NPs, ZnO NPs are the most toxic. Consistently in all three tested intestinal cell models, ZnO NPs invoke the most inflammatory responses from the cells and induce the highest intracellular production of reactive oxygen species (ROS). The elevated ROS levels induce significant damage to the DNA of the cells, resulting in cell-cycle arrest and subsequently cell death. In contrast, both SiO2 and TiO2 NPs elicit minimum biological responses from the intestinal cells. Overall, the study showcases the varying capability of the food-borne NPs to induce a cellular response in the intestinal cells. In addition to physicochemical differences in the NPs, the genetic landscape of the intestinal cell models governs the toxicology profile of these food-borne NPs.

Nanocarriers in therapy of infectious and inflammatory diseases

Nanotechnology is a growing science that has applications in various areas of medicine. The composition of nanocarriers for drug delivery is critical to guarantee high therapeutic performance when targeting specific host sites. Applications of nanotechnology are prevalent in the diagnosis and treatment of infectious and inflammatory diseases. This review summarizes recent advancements in the application of nanotechnology to the therapy of infectious and inflammatory diseases. The major focus is on the design and fabrication of various nanomaterials, characteristics and physicochemical properties of drug-loaded nanocarriers, and the use of these nanoscale drug delivery systems in treating infectious and inflammatory diseases, such as AIDS, hepatitis, tuberculosis, melanoma, and representative inflammatory diseases. Clinical trials and future perspective of the use of nanocarriers are also discussed in detail. We hope that such a review will be valuable to researchers who are exploring nanoscale drug delivery systems for the treatment of specific infectious and inflammatory diseases.

Nanomaterials and neurodegeneration

The increasing application of nanotechnology in various industrial, environmental, and human settings raises questions surrounding the potential adverse effects induced by nanosized materials to human health, including the possible neurotoxic and neuroinflammatory properties of those substances and their capability to induce neurodegeneration. In this review, a panel of metal oxide nanoparticles (NPs), namely titanium dioxide, silicon dioxide, zinc oxide, copper oxide, iron NPs, and carbon nanotubes have been focused. An overview has been provided of the in vitro and in vivo evidence of adverse effects to the central nervous system. Research indicated that these nanomaterials (NMs) not only reach the brain, but also can cause a certain degree of brain tissue damage, including cytotoxicity, genotoxicity, induction of oxidative stress, and inflammation, all potentially involved in the onset and progression of neurodegeneration. Surface chemistry of the NMs may play an important role in their localization and subsequent effects on the brain of rodents. In addition, NM shape differences may induce varying degrees of neurotoxicity. However, one of the potential biomedical applications of NMs is nanodevices for early diagnostic and novel therapeutic approaches to counteract age related diseases. In this context, engineered NMs were promising vehicles to carry diagnostic and therapeutic compounds across the blood-brain barrier, thereby representing very timely and attractive theranostic tools in neurodegenerative diseases. Therefore, a careful assessment of the risk-benefit ratio must be taken into consideration in using nanosized materials.

Enzyme responsive mesoporous silica nanoparticles for targeted tumor therapy in vitro and in vivo

This study reports a biocompatible controlled drug release system based on mesoporous silica nanoparticles (MSNs) for tumor microenvironment responsive drug delivery. It was fabricated by grafting phenylboronic acid conjugated human serum albumin (PBA-HSA) onto the surfaces of MSNs as a sealing agent, via an intermediate linker of a functional polypeptide, which was composed of two functional units: the polycation cell penetrating peptide (CPP) polyarginine, and matrix metalloproteinase 2 (MMP-2) substrate peptide. A series of characterizations confirmed that the system had been successfully constructed. In vitro tests proved that the anticancer drug loading system could efficiently induce cell apoptosis in vitro. More importantly, the in vivo tumor experiments confirmed that the anticancer loading system could efficiently inhibit tumor growth with minimal side effects.

Internalization and fate of silica nanoparticles in C2C12 skeletal muscle cells: evidence of a beneficial effect on myoblast fusion

The use of silica nanoparticles for their cellular uptake capability opens up new fields in biomedical research. Among the toxicological effects associated with their internalization, silica nanoparticles induce apoptosis that has been recently reported as a biochemical cue required for muscle regeneration. To assess whether silica nanoparticles could affect muscle regeneration, we used the C2C12 muscle cell line to study the uptake of fluorescently labeled NPs and their cellular trafficking over a long period. Using inhibitors of endocytosis, we determined that the NP uptake was an energy-dependent process mainly involving macropinocytosis and clathrin-mediated pathway. NPs were eventually clustered in lysosomal structures. Myoblasts containing NPs were capable of differentiation into myotubes, and after 7 days, electron microscopy revealed that the NPs remained primarily within lysosomes. The presence of NPs stimulated the formation of myotubes in a dose-dependent manner. NP internalization induced an increase of apoptotic myoblasts required for myoblast fusion. At noncytotoxic doses, the NP uptake by skeletal muscle cells did not prevent their differentiation into myotubes but, instead, enhanced the cell fusion.

Salvia plebeia suppresses atopic dermatitis-like skin lesions

Salvia plebeia R. Br. (Lamiaceae) has been used for folk medicines in Asian countries, including Korea and China, to treat skin inflammatory diseases and asthma. In this study, we investigated the effects of S. plebeia extract (SPE) on atopic dermatitis (AD)-like skin lesions and defined underlying mechanisms of action. We established an AD model in BALB/c mice by repeated local exposure of house dust mite extract (Dermatophagoides farinae extract, DFE) and 2,4-dinitrochlorobenzene (DNCB) to the ears. Repeated alternative treatment of DFE/DNCB caused AD-like skin lesions. The oral administration of SPE decreased AD symptoms based on ear thickness and histopathological analysis, in addition to serum IgE and IgG2a levels. SPE suppressed mast cell infiltration into the ear and serum histamine level. SPE inhibited Th1/Th2/Th17 phenotype CD4(+) T lymphocytes expansion in the lymph node and the expression of Th1/Th2/Th17 cytokines in the ear tissue. To define the underlying mechanisms of action, the tumor necrosis factor (TNF)-α and interferon (IFN)-γ activated human keratinocytes (HaCaT) model was used. SPE significantly suppressed the expression of cytokines and chemokines through the down-regulation of mitogen-activated protein kinases, nuclear factor-κB, and STAT1 in HaCaT cells. Taken together, our results suggest that SPE might be a candidate for the treatment of AD.

Renal interstitial fibrosis induced by high-dose mesoporous silica nanoparticles via the NF-κB signaling pathway

Previous studies have indicated that the nephrotoxicity induced by mesoporous silica nanoparticles (MSNs) is closely related to inflammation. Nuclear factor kappa B (NF-κB), a common rapid transcription factor associated with inflammation, plays an important role in the process of many kidney diseases. Acute toxicity assessment with a high-dose exposure is critical for the development of nanoparticle, as a part of standardized procedures for the evaluation of their toxicity. The present study was undertaken to observe the acute toxicity, predict the potential target organs of MSNs injury, and test the hypothesis that the NF-κB pathway plays a role in mediating the acute kidney injury and renal interstitial fibrosis in mice induced by MSNs. Balb/c mice were intraperitoneally injected with MSNs at concentrations of 150, 300, or 600 mg/kg. All of the animals were euthanized 2 and 12 days after exposure, and the blood and kidney tissues were collected for further studies. In vitro, the cytotoxicity, fibrosis markers, and NF-κB pathway were measured in a normal rat kidney cell line (NRK-52E). Acute kidney injury was induced by MSNs in mice after 2 days, some renal tubules regenerated and renal interstitial fibrosis was also observed. The expression of fibrosis markers and the nuclear translocation of NF-κB p65 in the kidney homogenates increased after exposure to MSNs. The in vitro study showed that MSNs cause cytotoxicity in NRK-52E cells and increased the expression of fibrosis markers. In addition, the NF-κB pathway could be induced, and inhibition of the NF-κB pathway could alleviate the fibrosis caused by MSNs. We conclude that inflammation is a major effector of the acute kidney toxicity induced by MSNs and results in renal interstitial fibrosis, which is mediated by the NF-κB signaling pathway.

Evaluation of silica nanoparticle toxicity after topical exposure for 90 days

Silica is a very common material that can be found in both crystalline and amorphous forms. Well-known toxicities of the lung can occur after exposure to the crystalline form of silica. However, the toxicities of the amorphous form of silica have not been thoroughly studied. The majority of in vivo studies of amorphous silica nanoparticles (NPs) were performed using an inhalation exposure method. Since silica NPs can be commonly administered through the skin, a study of dermal silica toxicity was necessary to determine any harmful effects from dermal exposures. The present study focused on the results of systemic toxicity after applying 20 nm colloidal silica NPs on rat skin for 90 days, in accordance with the Organization for Economic Cooperation and Development test guideline 411 with a good laboratory practice system. Unlike the inhalation route or gastrointestinal route, the contact of silica NPs through skin did not result in any toxicity or any change in internal organs up to a dose of 2,000 mg/kg in rats.

In vitro antibacterial capacity and cytocompatibility of SiO2-CaO-P2O5 meso-macroporous glass scaffolds enriched with ZnO

Zn²⁺ ions exhibit osteogenic, angiogenic and antimicrobial properties. For this reason, they are often added in small amounts to bioceramics being investigated for bone tissue engineering. In this paper, the cytocompatibility and antibacterial properties of 80% SiO₂-15% CaO-5% P₂O₅ (mol%) mesoporous bioactive glass (MBG) scaffolds substituted with 4.0% and 7.0% of ZnO were studied and compared with the Zn-free scaffold. Cell proliferation, morphology, differentiation and cytotoxic effects of Zn²⁺ ions released from the samples were examined by culturing human osteoblast-like cells (HOS) osteoblasts both in the presence of sample extracts and on the scaffold surface. The bacterial inhibition capacity of the scaffolds was explored by using Gram-positive Stapylococcus aureus bacteria, responsible for numerous infections in orthopedic surgery, to simulate a severe infection. Our results show that the Zn-MBG scaffolds possess a hierarchical meso-macropore structure suitable for osteoblast growth. Furthermore, the amount of Zn²⁺ released from the scaffold with 4.0% ZnO was found to be more favorable for HOS cell development than that released from the scaffold including 7.0% ZnO. Zn²⁺ released to the medium from both scaffolds exhibited antibacterial properties against S. aureus. Thus, the cytocompatibility and the antibacterial ability exhibited by the MBG scaffold containing 4.0% ZnO make it a suitable candidate for bone regeneration applications.

Subchronic toxicity and immunotoxicity of MeO-PEG-poly(D,L-lactic-co-glycolic acid)-PEG-OMe triblock copolymer nanoparticles delivered intravenously into rats

Although monomethoxy(polyethyleneglycol)-poly (D,L-lactic-co-glycolic acid)-monomethoxy (PELGE) nanoparticles have been widely studied as a drug delivery system, little is known about their toxicity in vivo. Here we examined the subchronic toxicity and immunotoxicity of different doses of PELGE nanoparticles with diameters of 50 and 200 nm (PELGE50 and PELGE200) in rats. Neither size of PELGE nanoparticles showed obvious subchronic toxic effects during 28 d of continuous intravenous administration based on clinical observation, body weight, hematology parameters and histopathology analysis. PELGE200 nanoparticles showed no overt signs of immunotoxicity based on organ coefficients, histopathology analysis, immunoglobulin levels, blood lymphocyte subpopulations and splenocyte cytokines. Conversely, PELGE50 nanoparticles were associated with an increased organ coefficient and histopathological changes in the spleen, increased serum IgM and IgG levels, alterations in blood lymphocyte subpopulations and enhanced expression of spleen interferon-γ. Taken together, these results suggest that PELGE nanoparticles show low subchronic toxicity but substantial immunotoxicity, which depends strongly on particle size. These findings will be useful for safe application of PELGE nanoparticles in drug delivery systems.

Resistance of LPS-activated bone marrow derived macrophages to apoptosis mediated by dexamethasone

Glucocorticoids (GC) display pleiotropic effects on the immune system. Macrophages are a major target for GC action. Here we show that dexamethasone (DEX), a synthetic GC, decreased viability of naïve bone marrow-derived macrophages (BMDM), involving an apoptotic mechanism. Administration of DEX together with lipopolysaccharide (LPS) protected BMDM against DEX-mediated cell death, suggesting that activated BMDM respond to DEX differently than naïve BMDM. An insight to the molecular basis of LPS actions was provided by a 7 fold increase in mRNA levels of glucocorticoid receptor beta (GRβ), a GR dominant-negative splice variant which inhibits GRα's transcriptional activity. LPS did not inhibit all DEX-mediated effects on BMDM; DEX significantly reduced the percentage of BMDM expressing high levels of the cell surface markers F4/80 and CD11b and led to a decrease in macrophage inflammatory protein 1 alpha (MIP1-α) mRNA and protein levels. These two DEX-mediated effects were not prevented by LPS. Our finding that LPS did not reduce the DEX-induced elevation of glucocorticoid-induced leucine zipper (GILZ), a mediator of GCs anti-inflammatory actions, may provide an underlying mechanism. These findings enable a better understanding of clinical states, such as sepsis, in which macrophages are activated by endotoxins and treatment by GCs is considered.

Mechanisms of nanotoxicity: generation of reactive oxygen species

Nanotechnology is a rapidly developing field in the 21^st century, and the commercial use of nanomaterials for novel applications is increasing exponentially. To date, the scientific basis for the cytotoxicity and genotoxicity of most manufactured nanomaterials are not understood. The mechanisms underlying the toxicity of nanomaterials have recently been studied intensively. An important mechanism of nanotoxicity is the generation of reactive oxygen species (ROS). Overproduction of ROS can induce oxidative stress, resulting in cells failing to maintain normal physiological redox-regulated functions. This in turn leads to DNA damage, unregulated cell signaling, change in cell motility, cytotoxicity, apoptosis, and cancer initiation. There are critical determinants that can affect the generation of ROS. These critical determinants, discussed briefly here, include: size, shape, particle surface, surface positive charges, surface-containing groups, particle dissolution, metal ion release from nanometals and nanometal oxides, UV light activation, aggregation, mode of interaction with cells, inflammation, and pH of the medium.

Incorporation of silica particles into decellularized tissue biomaterial and its effect on macrophage activation

Secretion of signaling molecules by macrophages is induced by silica particles deposited onto decellularized tissue derived biomaterials.

Mesoporous silica shell alleviates cytotoxicity and inflammation induced by colloidal silica particles

Core-shell mesoporous silica (MPS) materials have been proven to perform multiple simultaneous functions in biological systems and they demonstrate a vast potential for applications in the medical arena. Exploring such extensive potential requires a meticulous evaluation of their interactions with cells. The aim of this study is to investigate the influence of MPS-shells on the viability and activation of human THP-1 macrophages by comparing core-shell MPS with colloidal silica particles. In the present study we find core-shell MPS particles with a solid colloidal silica core and a thin MPS-shell deliver significantly less cytotoxicity than their nonporous counterparts and induce lower expression and release of the pro-inflammatory cytokines in macrophages. Moreover, core-shell MPS particles show no effect on the activation of mitogen-activated protein kinases (MAPKs), while colloidal silica particles do activate MAPKs under identical conditions. The corona of core-shell MPS particles is composed of a greater amount and variety of proteins as compared with colloidal silica particles. The abundant protein composition of the corona may inhibit the cellular toxicity by masking surface silanol groups at the MPS-cellular interface. In conclusion, the MPS-shell significantly alleviates both cytotoxicity and immune responses induced by colloidal silica particles while greatly improving the biocompatibility of colloidal silica materials.

Ordered nanoporous silica as carriers for improved delivery of water insoluble drugs: a comparative study between three dimensional and two dimensional macroporous silica

The goal of the present study was to compare the drug release properties and stability of the nanoporous silica with different pore architectures as a matrix for improved delivery of poorly soluble drugs. For this purpose, three dimensional ordered macroporous (3DOM) silica with 3D continuous and interconnected macropores of different sizes (200 nm and 500 nm) and classic mesoporous silica (ie, Mobil Composition of Matter [MCM]-41 and Santa Barbara Amorphous [SBA]-15) with well-ordered two dimensional (2D) cylindrical mesopores were successfully fabricated and then loaded with the model drug indomethacin (IMC) via the solvent deposition method. Scanning electron microscopy (SEM), N₂ adsorption, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were applied to systematically characterize all IMC-loaded nanoporous silica formulations, evidencing the successful inclusion of IMC into nanopores, the reduced crystallinity, and finally accelerated dissolution of IMC. It was worth mentioning that, in comparison to 2D mesoporous silica, 3DOM silica displayed a more rapid release profile, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The results obtained from the stability test indicated that the amorphous state of IMC entrapped in the 2D mesoporous silica (SBA-15 and MCM-41) has a better physical stability than in that of 3DOM silica. Moreover, the dissolution rate and stability of IMC loaded in 3DOM silica was closely related to the pore size of macroporous silica. The colorimetric 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Cell Counting Kit (CCK)-8 assays in combination with direct morphology observations demonstrated the good biocompatibility of nanoporous silica, especially for 3DOM silica and SBA-15. The present work encourages further study of the drug release properties and stability of drug entrapped in different pore architecture of silica in order to realize their potential in oral drug delivery.

Understanding engineered nanomaterial skin interactions and the modulatory effects of ultraviolet radiation skin exposure

The study of engineered nanomaterials for the development of technological applications, nanomedicine, and nano-enabled consumer products is an ever-expanding discipline as is the concern over the impact of nanotechnology on human environmental health and safety. In this review, we discuss the current state of understanding of nanomaterial skin interactions with a specific emphasis on the effects of ultraviolet radiation (UVR) skin exposure. Skin is the largest organ of the body and is typically exposed to UVR on a daily basis. This necessitates the need to understand how UVR skin exposure can influence nanomaterial skin penetration, alter nanomaterial systemic trafficking, toxicity, and skin immune function. We explore the unique dichotomy that UVR has on inducing both deleterious and therapeutic effects in skin. The subject matter covered in this review is broadly informative and will raise awareness of potential increased risks from nanomaterial skin exposure associated with specific occupational and life style choices. The UVR-induced immunosuppressive response in skin raises intriguing questions that motivate future research directions in the nanotoxicology and nanomedicine fields.

In vivo biodistribution and synergistic toxicity of silica nanoparticles and cadmium chloride in mice

Silica nanoparticles (SiNPs) are now in daily use due to their low intrinsic toxicity. Cadmium is a ubiquitous environmental pollutant. In spite of real risk of humans' co-exposure to SiNPs and cadmium, their synergistic toxicity is still unclear. Here, we report the synergistic effects of SiNPs and CdCl₂ on their biodistribution and subacute toxicity in mice. The biodistributions, histopathological changes, serum biochemical parameters and oxidative stress responses were determined after intraperitoneal injection of SiNPs and/or CdCl₂ to mice. SiNPs and CdCl₂ have a positive synergistic toxicity in mice. Although SiNPs were low toxic to mice, co-exposure of SiNPs and CdCl₂ significantly enhanced CdCl₂-induced oxidative damage in the liver as indicated by the severe liver dysfunction and histopathological abnormalities. Co-exposure to SiNPs and CdCl₂ markedly increased the cadmium accumulation in the liver, which induced significant hepatic oxidative stress. In vitro binding assays indicated that serum albumin and Cd(2+) mutually enhanced the binding of each other to SiNPs via the interaction of serum albumin and Cd(2+). The uptake of serum albumin- and Cd(2+)-bound SiNPs by the macrophages significantly increased cadmium accumulation in mice. These results demonstrate that serum albumins play an important role in the positive synergistic toxicity of SiNPs and CdCl₂.

Inhibitory effects of Diospyros kaki in a model of allergic inflammation: role of cAMP, calcium and nuclear factor-κB

Diospyros kaki (D. kaki) has been cultivated throughout Eastern Asia for hundreds of years. D. kaki contains various biological active compounds, such as amino acids, carotenoids, flavonoids, tannins, catechins and vitamin A. Previous studies have shown that D. kaki has beneficial effects on homeostasis, constipation, hypertension, atherosclerosis and allergic dermatitis and is a good source of antioxidants, polyphenols and dietary fiber. However, the anti-allergic and anti-inflammatory effects of D. kaki have not yet been elucidated. This study aimed to investigate the protective effects of the aqueous extract of Diospyros kaki (AEDK) on mast cell-mediated allergic inflammation and to determine its possible mechanisms of action by using in vitro and in vivo mast cell-based models. The cAMP and intracellular calcium levels were measured to clarify the mechanisms by which AEDK inhibits the release of histamine from mast cells. AEDK inhibited the release of histamine and β-hexosaminidase from mast cells by modulating cAMP and intracellular calcium levels. We also measured the expression of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β. AEDK decreased gene expression and the secretion of the pro-inflammatory cytokines, TNF-α and IL-1β by inhibiting nuclear factor-κB. In addition, AEDK inhibited systemic and cutaneous allergic reaction. The inhibitory effects of AEDK on allergic reaction and the release of histamine were found to be similar to those of disodium cromoglycate, a known anti-allergic drug. To isolate the active component of AEDK, activity-guided fractionation was performed, based on the inhibitory effects on systemic anaphylaxis. Catechin was identified as an active compound. The present findings provide evidence that AEDK inhibits allergic inflammation and suggest the therapeutic application of AEDK in allergic inflammatory disorders.

Kinetics of silica nanoparticles in the human placenta

The potential medical applications of nanoparticles (NPs) warrant their investigation in terms of biodistribution and safety during pregnancy. The transport of silica NPs across the placenta was investigated using two models of maternal-foetal transfer in human placenta, namely, the BeWo b30 choriocarcinoma cell line and the ex vivo perfused human placenta. Nanotoxicity in BeWo cells was examined by the MTT assay which demonstrated decreased cell viability at concentrations >100 µg/mL. In the placental perfusion experiments, antipyrine crossed the placenta rapidly, with a foetal:maternal ratio of 0.97 ± 0.10 after 2 h. In contrast, the percentage of silica NPs reaching the foetal perfusate after 6 h was limited to 4.2 ± 4.9% and 4.6 ± 2.4% for 25 and 50 nm NPs, respectively. The transport of silica NPs across the BeWo cells was also limited, with an apparent permeability of only 1.54 × 10(-6) ± 1.56 × 10(-6) cm/s. Using confocal microscopy, there was visual confirmation of particle accumulation in both BeWo cells and in perfused placental tissue. Despite the low transfer of silica NPs to the foetal compartment, questions regarding biocompatibility could limit the application of unmodified silica NPs in biomedical imaging or therapy.