SiO2 Fibers of Two Lengths and Their Effect on Cellular Responses of Macrophage-like Cells.

The immunoreactivity or/and stress response can be induced by nanomaterials' different properties, such as size, shape, etc. These effects are, however, not yet fully understood. This study aimed to clarify the effects of SiO2 nanofibers (SiO2NFs) on the cellular responses of THP-1-derived macrophage-like cells. The effects of SiO2NFs with different lengths on reactive oxygen species (ROS) and pro-inflammatory cytokines TNF-α and IL-1ß in THP-1 cells were evaluated. From the two tested lengths, it was only the L-SiO2NFs with a length ≈ 44 ± 22 µm that could induce ROS. Compared to this, only S-SiO2NFs with a length ≈ 14 ± 17 µm could enhance TNF-α and IL-1ß expression. Our results suggested that L-SiO2NFs disassembled by THP-1 cells produced ROS and that the inflammatory reaction was induced by the uptake of S-SiO2NFs by THP-1 cells. The F-actin staining results indicated that SiO2NFs induced cell motility and phagocytosis. There was no difference in cytotoxicity between L- and S-SiO2NFs. However, our results suggested that the lengths of SiO2NFs induced different cellular responses.

Establishment of a Nanopatterned Renal Disease Model by Mimicking the Physical and Chemical Cues of a Diseased Mesangial Cell Microenvironment.

Modulation of mesangial cell (MC) response by in vitro disease models offers therapeutic strategies for the treatment of several glomerular diseases. However, traditional cell culture models lack the nanostructured extracellular matrix (ECM), which has unique physical and chemical properties, so they poorly reflect the complexities of the native microenvironment. Therefore, a cell disease model with ECM nanostructures is required to better mimic the in vivo diseased nanoenvironment. To establish a renal disease model, we used a titanium dioxide-based disease-mimic nanopattern as the physical cues and transforming growth factor-beta 1 (TGF-ß1) as a chemical cue. The effects of this renal disease model on proliferation and mesangial matrix (MM) component changes in the SV40MES13 (MES13) mouse mesangial cell line were evaluated. Our results showed that both the presence of the disease-mimic nanopattern and TGF-ß1 intensified proliferation and resulted in increased type I collagen and fibronectin and decreased type IV collagen expressions in MES13 cells. These effects could be involved in increased TGF-ß type I receptor expression in MES13 cells. The intracellular reactive oxygen species (ROS) level as a biomarker of this renal disease model indicated that the cells were in a diseased state. A small molecule A83-01 and known drug dexamethasone markedly attenuated the intracellular ROS production in MES13 that was induced by the disease-mimic nanopattern and TGF-ß1. These results highlight the significant effects of physical and chemical cues in facilitating disease-like behavior in MES13 cells, providing an important theoretical basis for developing a drug screening platform for glomerular diseases.

EGF Conjugation Improves Safety and Uptake Efficacy of Titanium Dioxide Nanoparticles.

Titanium dioxide nanoparticles (TiO2 NPs) have a strong potential for cancer therapeutic and bioimaging applications such as photodynamic therapy (PDT) and photodynamic diagnosis (PDD). Our previous results have shown that TiO2 NPs have a low cellular uptake and can induce cell proliferation. This suggests that TiO2 NPs could increase the risk of tumor overgrowth while being used for PDD and PDT. To solve this problem, we constructed epidermal growth factor-ligated polyethylene glycol-coated TiO2 NPs (EGF-TiO2 PEG NPs). In this work, we studied the effect of EGF conjugation on the cellular uptake of TiO2 PEG NPs. Then, we investigated the effect of both non-conjugated and EGF-TiO2 PEG NPs on the A431 epidermal cancer cell line, proliferation and growth via the investigation of EGFR localization and expression. Our results indicated that TiO2 PEG NPs induced EGFRs aggregation on the A431 cells surface and induced cell proliferation. In addition, EGF-TiO2 PEG NPs induced the internalization of EGFRs inside of cells with increased cellular NPs uptake and decreased cellular proliferation compared to TiO2 PEG NPs-treated cells. These findings suggest that EGF conjugation can increase the efficacy of TiO2 PEG NPs for biomedical applications such as PDD and PDT with decreased risk of tumor overgrowth.

The Effects of TiO2 Nanoparticles on Cisplatin Cytotoxicity in Cancer Cell Lines.

There have been many studies on improving the efficacy of cisplatin and on identifying safe compounds that can overcome multi-drug resistance (MDR) acquired by cancer cells. Our previous research showed that polyethylene glycol-modified titanium dioxide nanoparticles (TiO2 PEG NPs) affect cell membrane receptors, resulting in their aggregation, altered localization and downregulation. TiO2 PEG NPs may affect P-glycoprotein (P-gp), a membrane efflux channel involved in MDR. In this study, we investigated the effect of TiO2 PEG NPs on cisplatin cytotoxicity. We used HepG2 cells, which highly express P-gp and A431 cells, which show low expression of P-gp. The results showed that 10 µg/mL 100 nm TiO2 PEG NPs increased intracellular cisplatin levels and cytotoxicity in HepG2 cells but not in A431 cells. TiO2 PEG NPs treatment decreased the expression level of P-gp in HepG2 cells. Our findings indicate that TiO2 PEG NPs enhance cisplatin cytotoxicity by down regulating P-gp and that TiO2 PEG NPs are promising candidates for inhibiting P-gp and reversing drug resistance acquired by cancer cells.

The Influence of a Nanopatterned Scaffold that Mimics Abnormal Renal Mesangial Matrix on Mesangial Cell Behavior.

The alteration of mesangial matrix (MM) components in mesangium, such as type IV collagen (COL4) and type I collagen (COL1), is commonly found in progressive glomerular disease. Mesangial cells (MCs) responding to altered MM, show critical changes in cell function. This suggests that the diseased MM structure could play an important role in MC behavior. To investigate how MC behavior is influenced by the diseased MM 3D nanostructure, we fabricated the titanium dioxide (TiO2)-based nanopatterns that mimic diseased MM nanostructures. Immortalized mouse MCs were used to assess the influence of disease-mimic nanopatterns on cell functions, and were compared with a normal-mimic nanopattern. The results showed that the disease-mimic nanopattern induced disease-like behavior, including increased proliferation, excessive production of abnormal MM components (COL1 and fibronectin) and decreased normal MM components (COL4 and laminin α1). In contrast, the normal-mimic nanopattern actually resulted in cells displaying normal proliferation and the production of normal MM components. In addition, increased expressions of α-smooth muscle actin (α-SMA), transforming growth factor ß1 (TGF-ß1) and integrin α5ß1 were detected in cells grown on the disease-mimic nanopattern. These results indicated that the disease-mimic nanopattern induced disease-like cell behavior. These findings will help further establish a disease model that mimics abnormal MM nanostructures and also to elucidate the molecular mechanisms underlying glomerular disease.

Polystyrene Nanoparticles Induce Apoptosis or Necrosis With or Without Epidermal Growth Factor.

Polystyrene nanoparticles (PS NPs) are biocompatible and low toxic material to biological systems. In this mind, PS NPs are widely used as a model for studying the interaction between nanoparticles and cells. Even PS NPs showed low toxicity, they could affect to some cellular responses. In this study, we investigated the influence of PS NPs on the epidermal growth factor (EGF)-response in the A431 human epithelial carcinoma cell line. The results showed that PS NPs interfered with the normal EGF-response of A431 cells in a dose-dependent manner. In addition, EGF significantly increased the uptake of PS NPs in A431 cells. Localization studies of PS NPs and EGF receptor (EGFR) indicated that changes in the EGF-response of A431 cells are related to the interaction between PS NPs and the EGF-EGFR complexes. The viability of cells exposed to PS NPs or combination of PS NPs and EGF decreased due to PS NPs induced cell death. The results also suggested that without EGF, PS NPs internalized in the cells cause cell death by necrosis, whereas EGF enhances the uptake ratio of PS NPs, and PS NPs in the cytoplasm together with EGF-EGFR complexes may inhibit receptors recycling, leading to apoptosis. This finding could be useful for the safe and effective use of nanoparticles in clinical applications.

Change in Renal Glomerular Collagens and Glomerular Filtration Barrier-Related Proteins in a Dextran Sulfate Sodium-Induced Colitis Mouse Model.

Renal disease is not rare among patients with inflammatory bowel disease (IBD) and is gaining interest as a target of research. However, related changes in glomerular structural have rarely been investigated. This study was aimed at clarifying the changes in collagens and glomerular filtration barrier (GFB)-related proteins of glomeruli in a dextran sulfate sodium (DSS)-induced colitis mouse model. Acute colitis was induced by administering 3.5% DSS in Slc:ICR strain mice for eight days. Histological changes to glomeruli were examined by periodic acid-Schiff (PAS) and Masson's trichrome staining. Expressions of glomerular collagens and GFB-related proteins were analyzed by immunofluorescent staining and Western blot analysis. DSS-colitis mice showed an elevated disease activity index (DAI), colon shortening, massive cellular infiltration and colon damage, confirming that DSS-colitis mice can be used as an IBD animal model. DSS-colitis mice showed increased glycoprotein and collagen deposition in glomeruli. Interestingly, we observed significant changes in glomerular collagens, including a decrease in type IV collagen, and an increment in type I and type V collagens. Moreover, declined GFB-related proteins expressions were detected, including synaptopodin, podocalyxin, nephrin and VE-cadherin. These results suggest that renal disease in DSS-colitis mice might be associated with changes in glomerular collagens and GFB-related proteins. These findings are important for further elucidation of the clinical pathological mechanisms underlying IBD-associated renal disease.

Size-Dependent Effect of Silver Nanoparticles on the Tumor Necrosis Factor α-Induced DNA Damage Response.

Silver nanoparticles (AgNPs) are widely used in many consumer products due to their anti-inflammatory properties. Therefore, the effect of exposure to AgNPs should be investigated in diseased states in addition to healthy ones. Tumor necrosis factor-α (TNFα) is a major cytokine that is highly expressed in many diseased conditions, such as inflammatory diseases, sepsis, and cancer. We investigated the effects of two different sizes of AgNPs on the TNFα-induced DNA damage response. Cells were exposed to 10 and 200 nm AgNPs separately and the results showed that the 200 nm AgNPs had a lower cytotoxic effect with a higher percent of cellular uptake compared to the 10 nm AgNPs. Moreover, analysis of reactive oxygen species (ROS) generation and DNA damage indicated that TNFα-induced ROS-mediated DNA damage was reduced by 200 nm AgNPs, but not by 10 nm AgNPs. Tumor necrosis factor receptor 1 (TNFR1) was localized on the cell surface after TNFα exposure with or without 10 nm AgNPs. In contrast, the expression of TNFR1 on the cell surface was reduced by the 200 nm AgNPs. These results suggested that exposure of cells to 200 nm AgNPs reduces the TNFα-induced DNA damage response via reducing the surface expression of TNFR1, thus reducing the signal transduction of TNFα.

Silver nanoparticles reduce the apoptosis induced by tumor necrosis factor-α.

Silver nanoparticles (AgNPs) are widely known to have anti-inflammatory properties, but the exact mechanism underlying this anti-inflammatory effect is not clearly understood. Tumor necrosis factor-α (TNFα) is a major pro-inflammatory cytokine that is expressed in the early stage of cell inflammation and induces apoptosis by several known pathways. Our study aimed to investigate the effect of AgNPs on the response of lung epithelial cells to TNFα and the molecular mechanism of this response. Lung epithelial cell line NCI-H292 cells were exposed to AgNPs (5 µg/mL) and/or TNFα (20 ng/mL) for 24 h, then cellular uptake was analyzed using flow cytometry. Our results showed that AgNPs were taken up by cells in a dose-dependent manner and that the cellular uptake ratio of AgNPs was significantly increased in the presence of TNFα. Apoptosis assays indicated that exposure to AgNPs significantly decreased the apoptotic effect of TNFα. Confocal microscopy was used to localize the tumor necrosis factor receptor 1 (TNFR1) and revealed that TNFR1 localized on the surface of cells exposed to TNFα. In contrast, TNFR1 localized inside cells exposed to both AgNPs and TNFα, with very few receptors scattered on the cell membrane. The results indicated that AgNPs reduced the cell surface TNFR1 expression level. The results suggested that the reduction of surface TNFR1 reduced cellular response to TNFα, resulting in an anti-apoptotic effect.

PEGylated TiO2 nanoparticles mediated inhibition of cell migration via integrin beta 1.

Nanoparticles (NPs) elicit various physiological responses in cellular environment, and the effect of NPs on cell migration is of high interest. In this work, the effects of NPs on cell migration and their possible mechanisms were studied. Here, we showed that after exposure to pegylated titanium dioxide nanoparticles (TiO2-PEG NPs, where PEG stands for the polyethylene glycol), NCI-H292 cells exhibited slower migration than control cells. Furthermore, larger NPs inhibited cell migration much stronger than smaller NPs. Following NP exposure, the cells showed decreased expression of integrin beta 1 and phosphorylated focal adhesion kinase (pFAK), and disrupted F-actin structures. We demonstrated that a possible mechanism involved NP-mediated promotion of the lysosomal degradation of integrin beta 1, thus leading to reduced expression of pFAK and cytoskeletal disruption and inhibited cell migration. Therefore, our results showed that inhibition of NCI-H292 cell migration by NPs is mediated through integrin beta 1, which provides useful information for the application of NPs in cancer therapy and related fields.

Hierarchically porous, and Cu- and Zn-containing γ-AlOOH mesostrands as adjuvants for cancer immunotherapy.

Alum is the only licensed adjuvant by Food and Drug Administration of USA used in many human vaccines and has excellent safety record in clinical applications. However, alum hardly induces T helper 1 (Th1) immune responses that are required for anti-tumor immunity. In the present study, we fabricated hierarchical copper- and zinc- buds dressing γ-AlOOH mesostrands (Cu- and Zn-AMSs) with randomly wrinkled morphology, mesoscale void- or cave-like pockets, high-exposed surface coverage sites, and positive charge streams in saline. We confirmed that Cu- and Zn-AMSs promoted intracellular uptake of model cancer antigen (ovalbumin, OVA) by THP-1-differentiated macrophage-like cells in vitro. Moreover, Cu- and Zn-AMSs enhanced maturation and cytokine release of bone marrow dendritic cells in vitro. In vivo study demonstrated that Cu- and Zn-AMSs markedly induced anti-tumor-immunity and enhanced CD4+ and CD8+ T cell populations in splenocytes of mice. These findings demonstrated that hierarchical copper- and zinc- buds dressing γ-AlOOH mesostrands, which are oriented in randomly wrinkled matrice, are suitable platforms as novel adjuvants for cancer immunotherapy.

Epidermal Growth Factor Enhances Cellular Uptake of Polystyrene Nanoparticles by Clathrin-Mediated Endocytosis.

The interaction between nanoparticles and cells has been studied extensively, but most research has focused on the effect of various nanoparticle characteristics, such as size, morphology, and surface charge, on the cellular uptake of nanoparticles. In contrast, there have been very few studies to assess the influence of cellular factors, such as growth factor responses, on the cellular uptake efficiency of nanoparticles. The aim of this study was to clarify the effects of epidermal growth factor (EGF) on the uptake efficiency of polystyrene nanoparticles (PS NPs) by A431 cells, a human carcinoma epithelial cell line. The results showed that EGF enhanced the uptake efficiency of A431 cells for PS NPs. In addition, inhibition and localization studies of PS NPs and EGF receptors (EGFRs) indicated that cellular uptake of PS NPs is related to the binding of EGF-EGFR complex and PS NPs. Different pathways are used to enter the cells depending on the presence or absence of EGF. In the presence of EGF, cellular uptake of PS NPs is via clathrin-mediated endocytosis, whereas, in the absence of EGF, uptake of PS NPs does not involve clathrin-mediated endocytosis. Our findings indicate that EGF enhances cellular uptake of PS NPs by clathrin-mediated endocytosis. This result could be important for developing safe nanoparticles and their safe use in medical applications.

Uniform TiO2 nanoparticles induce apoptosis in epithelial cell lines in a size-dependent manner.

The size of titanium dioxide (TiO2) nanoparticles is a vital parameter that determines their cytotoxicity. However, most reported studies have employed irregular shapes and sizes of TiO2 nanoparticles, as it is difficult to produce nanoparticles of suitable sizes for research. We produced good model TiO2 nanoparticles of uniform shape and size for use in studying their cytotoxicity. In this work, spherical, uniform polyethylene glycol-modified TiO2 (TiO2-PEG) nanoparticles of differing sizes (100, 200, and 300 nm) were prepared using the sol-gel method. A size-dependent decrease in cell viability was observed with increasing nanoparticle size. Furthermore, apoptosis was found to be positively associated with nanoparticle size, as evidenced by an increase in caspase-3 activity with increasing nanoparticle size. Larger nanoparticles exhibited higher cellular uptake, suggesting that larger nanoparticles more strongly induce apoptosis. In addition, the cellular uptake of different sizes of nanoparticles was energy dependent, suggesting that there are size-dependent uptake pathways. We found that 100 and 200 nm (but not 300 nm) nanoparticles were taken up via clathrin-mediated endocytosis. These results utilizing uniform nanoparticles suggest that the size-dependent cytotoxicity of nanoparticles involves active cellular uptake, caspase-3 activation, and apoptosis in the epithelial cell line (NCI-H292). These findings will hopefully aid in the future design and safe use of nanoparticles.

Low doses of TiO2-polyethylene glycol nanoparticles stimulate proliferation of hepatocyte cells.

This paper describes the effect of low concentrations of 100 nm polyethylene glycol-modified TiO2 nanoparticles (TiO2-PEG NPs) on HepG2 hepatocellular carcinoma cells. Proliferation of HepG2 cells increased significantly when the cells were exposed to low doses (<100 µg ml-1) of TiO2-PEG NPs. These results were further confirmed by cell counting experiments and cell cycle assays. Cellular uptake assays were performed to determine why HepG2 cells proliferate with low-dose exposure to TiO2-PEG NPs. The results showed that exposure to lower doses of NPs led to less cellular uptake, which in turn decreased cytotoxicity. We therefore hypothesized that TiO2-PEG NPs could affect the activity of hepatocyte growth factor receptors (HGFRs), which bind to hepatocyte growth factor and stimulate cell proliferation. The localization of HGFRs on the surface of the cell membrane was detected via immunofluorescence staining and confocal microscopy. The results showed that HGFRs aggregate after exposure to TiO2-PEG NPs. In conclusion, our results indicate that TiO2-PEG NPs have the potential to promote proliferation of HepG2 cells through HGFR aggregation and suggest that NPs not only exhibit cytotoxicity but also affect cellular responses.

A three-dimensional collagen-sponge-based culture system coated with simplified recombinant fibronectin improves the function of a hepatocyte cell line.

Hepatocytes are widely used in pharmaceutical drug discovery tests, but their hepatic functions decrease rapidly during in vitro culture. Many culture systems have been devised to address this problem. We here report that a three-dimensional (3D) collagen-based scaffold coated with simplified recombinant fibronectin (FN) enhanced the function of a hepatocyte cell line. The developed culture system uses a honeycomb collagen sponge coated with collagen-binding domain (CBD)-cell attachment site (CAS), a chimeric protein comprising the CBD and CAS of FN. The function of HepG2 cells grown on honeycomb collagen sponge coated with CBD-CAS was investigated by determining the messenger RNA (mRNA) expression levels of several genes. The mRNA expression level of albumin increased 3.25 times in cells grown on CBD-CAS-coated honeycomb collagen sponge for 3 days; the expression level of CCAAT/enhancer binding protein (C/EBPα) increased 40-fold after 1 d and up to 150-fold after 3 d. These results suggested that CBD-CAS-coated honeycomb collagen sponge could improve the functions of hepatocytes by inducing C/EBPα expression. The activation of cytochrome P450 (CYP) enzymes in HepG2 cells grown on CBD-CAS-coated honeycomb collagen sponge was measured at the mRNA level and was found to increase between two and six times compared to cells grown without the CBD-CAS coating, showing that this culture system induced CYP gene expression and thus may be useful in drug metabolism assays.

Nanostructures Control the Hepatocellular Responses to a Cytotoxic Agent "Cisplatin".

In drug discovery programs, the alteration between in vivo and in vitro cellular responses to drug represents one of the main challenges. Since the variation in the native extracellular matrix (ECM) between in vivo and 2D in vitro conditions is one of the key reasons for such discrepancies, thus the utilization of substrate that likely mimics ECM characteristics (topography, stiffness, and chemical composition) is needed to overcome such problem. Here, we investigated the role of substrate nanotopography as one of the major determinants of hepatic cellular responses to a chemotherapeutic agent "cisplatin." We studied the substratum induced variations in cisplatin cytotoxicity; a higher cytotoxic response to cisplatin was observed for cells cultured on the nanopattern relative to a flat substrate. Moreover, the nanofeatures with grating shapes that mimic the topography of major ECM protein constituents (collagen) induced alterations in the cellular orientation and chromatin condensation compared to flat surfaces. Accordingly, the developments of biomimetic substrates with a particular topography could have potentials in drug development analyses to reflect more physiological mimicry conditions in vitro.

CXCR4/CXCL12 signaling impacts enamel progenitor cell proliferation and motility in the dental stem cell niche.

Dental stem cells are located at the proximal ends of rodent incisors. These stem cells reside in the dental epithelial stem cell niche, termed the apical bud. We focused on identifying critical features of a chemotactic signal in the niche. Here, we report that CXCR4/CXCL12 signaling impacts enamel progenitor cell proliferation and motility in dental stem cell niche cells. We report cells in the apical bud express CXCR4 mRNA at high levels while expression is restricted in the basal epithelium (BE) and transit-amplifying (TA) cell regions. Furthermore, the CXCL12 ligand is present in mesenchymal cells adjacent to the apical bud. We then performed gain- and loss-of-function analyses to better elucidate the role of CXCR4 and CXCL12. CXCR4-deficient mice contain epithelial cell aggregates, while cell proliferation in mutant incisors was also significantly reduced. We demonstrate in vitro that dental epithelial cells migrate toward sources of CXCL12, whereas knocking down CXCR4 impaired motility and resulted in formation of dense cell colonies. These results suggest that CXCR4 expression may be critical for activation of enamel progenitor cell division and that CXCR4/CXCL12 signaling may control movement of epithelial progenitors from the dental stem cell niche.

IL-12 involvement in myogenic differentiation of C2C12 in vitro.

Recently, the extracellular microenvironment has been shown to be critical for the correct differentiation of stem cells to specific tissues. Many factors, including physical (e.g. biomaterial stiffness and topography) and biological (as growth factors, cytokines and chemokines) components, cooperate to create an ideal microenvironment for muscle stem cells, with many of these factors having been widely investigated. We previously demonstrated that the use of non-proliferating muscle-specific and unrelated cells as feeder layers for skeletal muscle progenitor cell differentiation resulted in significant differences in the ability to form myotubes, suggesting the importance of biological factors in myogenic differentiation. In this study, we investigated the biological factors involved in this process, analyzing the expression profile of 84 genes coding for cytokines and chemokines. We successfully identified a novel role for the cytokine IL-12 in the myogenic differentiation of C2C12 mouse skeletal muscle cells. Experiments involving the overexpression or silencing of the IL-12 gene in C2C12 showed that IL-12 enhanced the myogenic differentiation process. Moreover, when IL-12 was overexpressed in non-biologically related feeder cells, the new co-culture system was able to improve myogenic differentiation of C2C12 seeded on top. Although IL-12 is known to be a cytokine involved in inflammatory responses, it also appears to be involved in the myogenic differentiation process, acting as a positive regulator of this mechanism. This fact is expected to prove to be important for the development of functional biomaterials.

Molecular mechanism of DNA damage induced by titanium dioxide nanoparticles in toll-like receptor 3 or 4 expressing human hepatocarcinoma cell lines.

BACKGROUND: Titanium dioxide nanoparticles (TiO2 NPs) are widely used in the biological sciences. The increasing use of TiO2 NPs increases the risk of humans and the environment being exposed to NPs. We previously showed that toll-like receptors (TLRs) play an important role in the interactions between NPs and cells. Our previous results indicated that TLR4 increased the DNA damage response induced by TiO2 NPs, due to enhanced NP uptake into the cytoplasm, whereas TLR3 expression decreased the DNA damage response induced by TiO2 NPs because of NP retention in the endosome. In this study, we explored the molecular mechanism of the DNA damage response induced by TiO2 NPs using TLR3 or TLR4 transfected cells. We examined the effect of TLR3 or TLR4 over-expression on oxidative stress and the effect of DNA damage induced by TiO2 NPs on gene expression levels. RESULTS: Our results showed evidence for elevated oxidative stress, including the generation of reactive oxygen species (ROS), with increased hydrogen peroxide levels, decreased glutathione peroxidase, and reduced glutathione and activated caspase-3 levels in cells exposed for 48 h to 10 µg/ml TiO2 NPs. These effects were enhanced by TLR4 and reduced by TLR3 over-expression. Seventeen genes related to DNA double-strand breaks and apoptosis were induced, particularly IP6K3 and ATM. CONCLUSION: Our results indicated that TiO2 NPs induced ROS, and the above molecules are implicated in the genotoxicity induced by TiO2 NPs.

The effect of physical and chemical cues on hepatocellular function and morphology.

Physical topographical features and/or chemical stimuli to the extracellular matrix (ECM) provide essential cues that manipulate cell functions. From the physical point of view, contoured nanostructures are very important for cell behavior in general, and for cellular functions. From the chemical point of view, ECM proteins containing an RGD sequence are known to alter cell functions. In this study, the influence of integrated physical and chemical cues on a liver cell line (HepG2) was investigated. To mimic the physical cues provided by the ECM, amorphous TiO2 nanogratings with specific dimensional and geometrical characteristics (nanogratings 90 nm wide and 150 nm apart) were fabricated. To mimic the chemical cues provided by the ECM, the TiO2 inorganic film was modified by immobilization of the RGD motif. The hepatic cell line morphological and functional changes induced by simultaneously combining these diversified cues were investigated, including cellular alignment and the expression of different functional proteins. The combination of nanopatterns and surface modification with RGD induced cellular alignment and expression of functional proteins, indicating that physical and chemical cues are important factors for optimizing hepatocyte function.