With the recent development of nanotechnology, many nanomaterials with innovative functions have been developed. For example, nanoparticles of titanium dioxide and silica have been used in commercial applications related to medicine, cosmetics and food . In particular, amorphous (noncrystalline) nanosilica particles possess extraordinary advantages, including straightforward synthesis, relatively low cost, and easy surface modification [1, 2]. Nanosilica particles are increasingly being used for many applications, including cosmetics, food technology, medical diagnosis, cancer therapy, and drug delivery [1–4].
As the use of nanomaterials increases, there is rising concern regarding their potential health risks because there is preliminary evidence that the unique electrical and mechanical properties of nanomaterials is associated with undesirable biological interactions [5, 6]. In addition, it has recently become evident that particle characteristics, including particle size and surface properties, are important factors in pathologic alterations and cellular responses [7–10]. For instance, Nishimori et al have previously demonstrated that nanosilica particles with relatively small particle size induce a greater level of toxicity, including liver injury, than do silica particles with larger particle size . To create safe and effective forms of nanomaterials, studies which provide basic information regarding biological responses to nanomaterials are essential.
Numerous studies have shown that several types of nanomaterials increase the incidence of allergic immune diseases [12–14]. Activation of the Th2 response, including production of interleukin (IL)-4, IL-5, and IL-13 from Th2 cells (a subset of CD4+ T cells) and immunoglobulin (Ig) G1 or IgE from B cells, is responsible for many of the pathologic features of allergic immune diseases . Some reports have shown that intranasal or airway exposure to nanomaterials promotes allergic immune responses, indicating the immune-activating potential of nanomaterials [12, 13]. However, the role of the different physical characteristics of nanomaterials in the production of allergic responses has not been elucidated.
Here, we examined whether intranasal exposure to nanosilica particles has the capacity to promote allergic immune responses in mice. In addition, we investigated the relationship between the size of silica particles and allergic immune responses.