Background: Clarifying the physicochemical properties of nanomaterials is crucial for hazard assessment and the safe application of these substances. With this in mind, we analyzed the relationship between particle size and the in vitro effect of amorphous nanosilica (nSP). Specifically, we evaluated the relationship between particle size of nSP and the in vitro biological effects using human keratinocyte cells (HaCaT). Results: Our results indicate that exposure to nSP of 70 nm diameter (nSP70) induced an elevated level of reactive oxygen species (ROS), leading to DNA damage. A markedly reduced response was observed using submicron-sized silica particles of 300 and 1000 nm diameter. In addition, cytochalasin D-treatment reduced nSP70-mediated ROS generation and DNA damage, suggesting that endocytosis is involved in nSP70-mediated cellular effects. Conclusions: Thus, particle size affects amorphous silica-induced ROS generation and DNA damage of HaCaT cells. We believe clarification of the endocytosis pathway of nSP will provide useful information for hazard assessment as well as the design of safer forms of nSPs.

Background: Due to the rising use of nanomaterials (NMs), there is concern that NMs induce undesirable biological effects because of their unique physicochemical properties. Recently, we reported that amorphous silica nanoparticles (nSPs), which are one of the most widely used NMs, can penetrate the skin barrier and induce various biological effects, including an immune-modulating effect. Thus, it should be clarified whether nSPs can be a risk factor for the aggravation of skin immune diseases. Thus, in this study, we investigated the relationship between the size of SPs and adjuvant activity using a model for atopic dermatitis.Results: We investigated the effects of nSPs on the AD induced by intradermaly injected-mite antigenDermatophagoides pteronyssinus(Dp) in NC/Nga mice. Ear thickness measurements and histopathological analysis revealed that a combined injection of amorphous silica particles (SPs) and Dp induced aggravation of AD in an SP size-dependent manner compared to that of Dp alone. In particular, aggravation was observed remarkably in nSP-injected groups. Furthermore, these effects were correlated with the excessive induction of total IgE and a stronger systemic Th2 response. We demonstrated that these results are associated with the induction of IL-18 and thymic stromal lymphopoietin (TSLP) in the skin lesions.Conclusions: A particle size reduction in silica particles enhanced IL-18 and TSLP production, which leads to systemic Th2 response and aggravation of AD-like skin lesions as induced by Dp antigen treatment. We believe that appropriate regulation of nanoparticle physicochemical properties, including sizes, is a critical determinant for the design of safer forms of NMs.

Antibody drugs with a high affinity and specificity are effective and safe for intractable diseases, such as cancers and autoimmune diseases. Furthermore, they have played a central role in drug discovery, currently accounting for eight of the top 20 pharmaceutical products worldwide by sales. Forty years ago, clinical trials on antibody drugs that were thought to be a magic bullet failed, partly due to the immunogenicity of monoclonal antibodies produced in mice. The recent breakthrough in antibody drugs is largely because of the contribution of phage display technology. Here, we reviewed the importance of phage display technology as a powerful platform for antibody drug discovery from various perspectives, such as the development of human monoclonal antibodies, affinity enhancement of monoclonal antibodies, and the identification of therapeutic targets for antibody drugs.

Surface properties are often hypothesized to be important factors in the development of safer forms of nanomaterials (NMs). However, the results obtained from studying the cellular responses to NMs are often contradictory. Hence, the aim of this study was to investigate the relationship between the surface properties of silica nanoparticles and their cytotoxicity against a murine macrophage cell line (RAW264.7). The surface of the silica nanoparticles was either unmodified (nSP70) or modified with amine (nSP70-N) or carboxyl groups (nSP70-C). First, the properties of the silica nanoparticles were characterized. RAW264.7 cells were then exposed to nSP70, nSP70-N, or nSP70-C, and any cytotoxic effects were monitored by analyzing DNA synthesis. The results of this study show that nSP70-N and nSP70-C have a smaller effect on DNA synthesis activity by comparison to unmodified nSP70. Analysis of the intracellular localization of the silica nanoparticles revealed that nSP70 had penetrated into the nucleus, whereas nSP70-N and nSP70-C showed no nuclear localization. These results suggest that intracellular localization is a critical factor underlying the cytotoxicity of these silica nanoparticles. Thus, the surface properties of silica nanoparticles play an important role in determining their safety. Our results suggest that optimization of the surface characteristics of silica nanoparticles will contribute to the development of safer forms of NMs.

Background: Nanomaterials with particle sizes <100 nm have been already applied in various applications such as cosmetics, medicines, and foods. Therefore, ensuring the safety of nanomaterials is becoming increasingly important. Here we examined the localization and biological responses of intranasally administered amorphous nanosilica particles in mice, focusing on the coagulation system. Methods: We used nanosilica particles with diameters of 30, 70, or 100 nm (nSP30, nSP70, or nSP100 respectively), and conventional microscale silica particles with diameters of 300 or 1000 nm (mSP300 or mSP1000, respectively). BALB/c mice were intranasally exposed to nSP30, nSP70, nSP100, mSP300, or mSP1000 at concentrations of 500 μg/mouse for 7 days. After 24 hours of last administration, we performed the in vivo transmission electron microscopy analysis, hematological examination and coagulation tests. Results: In vivo transmission electron microscopy analysis showed that nanosilica particles with a diameter <100 nm were absorbed through the nasal cavity and were distributed into liver and brain. Hematological examination and coagulation tests showed that platelet counts decreased and that the activated partial thromboplastin time was prolonged in nSP30 or nSP70-treated groups of mice, indicating that nanosilica particles might have activated a coagulation cascade. In addition, in in vitro activation tests of human plasma, nanosilica particles had greater potential than did conventional microscale silica particles to activate coagulation factor XII. In nanosilica-particle-treated groups, the levels of soluble CD40 ligand, and von Willebrand factor which are involved in stimulating platelets tended to slightly increase with decreasing particle size. Conclusions: These results suggest that intranasally administered nanosilica particles with diameters of 30 and 70 nm could induce abnormal activation of the coagulation system through the activation of an intrinsic coagulation cascade. This study provides information to advance the development of safe and effective nanosilica particles.

With the increase in use of nanomaterials, there is growing concern regarding their potential health risks. However, few studies have assessed the role of the different physical characteristics of nanomaterials in allergic responses. Here, we examined whether intranasally administered silica particles of various sizes have the capacity to promote allergic immune responses in mice. We used nanosilica particles with diameters of 30 or 70 nm (nSP30 or nSP70, respectively), and conventional micro-sized silica particles with diameters of 300 or 1000 nm (nSP300 or mSP1000, respectively). Mice were intranasally exposed to ovalbumin (OVA) plus each silica particle, and the levels of OVA-specific antibodies (Abs) in the plasma were determined. Intranasal exposure to OVA plus smaller nanosilica particles tended to induce a higher level of OVA-specific immunoglobulin (Ig) E, IgG and IgG1 Abs than did exposure to OVA plus larger silica particles. Splenocytes from mice exposed to OVA plus nSP30 secreted higher levels of Th2-type cytokines than mice exposed to OVA alone. Taken together, these results indicate that nanosilica particles can induce allergen-specific Th2-type allergic immune responses in vivo. This study provides the foundations for the establishment of safe and effective forms of nanosilica particles.