Silica nanomaterials

The optical properties of a DDSN are mainly determined by the properties of dye molecules. Since silica nanomaterials are effectively transparent they are unlikely to absorb light in the near-infrared, visible or ultraviolet regions, which allows the dye molecules inside the silica matrix to keep their original optical properties [64]. Meanwhile, the presence of the silica matrix provides a new environment for dye molecules and affects dye fluorescence properties. 

The size of the nanomaterial greatly influences its toxicity particularly as the nanomaterial s size decreases, certain of its parameters changed [3, 11, 118, 119]. Many studies have shown that variations in the size of nanomaterials account for the different toxicity levels between nanosized and micrometer-sized materials [97, 99,100,103], It is known that a reduction in size can increase the rate of uptake and translocation of silica nanomaterials in vitro and in vivo, thereby inducing a more severe and transient toxicity [56]. 

Based on well established silica chemistry, the surface of silica nanomaterials can be modified to introduce a variety of functionalizations [3, 11, 118]. The toxicity of surface-modified nanomaterials is largely determined by their surface functional groups. As an example, Kreuter reported that an apolipoprotein coating on silica nanoparticles aided their endocytosis in brain capillaries through the LDL-receptor [122-124]. Overall, silica nanomaterials are low-toxicity materials, although their toxicity can be altered by surface modifications. 

Dose-dependent toxicity has frequently been observed in the study of nanomaterials [110-116], with increasing doses of silica nanomaterials invariably worsening their toxicity. Both, cell proliferation and viability were greatly hampered at higher doses in in vitro studies [111, 113, 116]. 

This section is devoted to the results of ab initio and DFT calculations of PL properties of a variety of point defects in silica nanomaterials, including NBO atoms and their combinations with OVs (Subsection 3.1), silanone and dioxasilyrane defects (Subsection 3.2), and A1 impurity (Subsection 3.3). We demonstrate that the aforementioned defects can give rise to various IR and visible red and green PL bands. 

Giri S Trewyn BG Lin VSY, Mesoporous silica nanomaterial-based biotechnological and biomedical delivery systems, Nanomedicine, 2007, 2, 99 -111. 

The application of MPS in biosensor has received more and more attention in the past few years. It was reported that functionalized mesoporous silica nanomaterials have good biocompatibility to be internalized by animal and plant cells without posing any cytotoxicity issue in vitro [27-29], These findings may generate new types of drug/gene delivery and biosensor, particularly in the development of electrochemical biosensors. We will mainly discuss the advancements in morphology control and surface functionalization of MPS for proteins immobilization and the recent developments of proteins encapsulated MPS biosensors. 

This synthetic method was a simple and reproducible way to produce well-controlled composite metal- or metal-oxide-containing silica nanomaterials displaying interesting catalytic properties for gas-sensing applications. This study demonstrated that a single approach, deposition of a catalyst suspended in a liquid, may allow the sensitivity of gas sensors to be modulated it also showed that the nature of the material employed was critical for obtaining reproducible results. 

The cellular uptake efficiency and kinetics together with the correlation between the particle morphology and aggregation of two kind, spherical and tubeshaped particles, of mesoporous silica nanomaterials (MSNs) were investigated... 

Petushkov A, Ndiege N, Salem AK, Larsen SC (2010) Toxicity of silica nanomaterials zeolites, mesoporous siliea, and ammphous silica nanoparticles. Chapter 7. Elsevier, Amsterdam Pillai O, Dhaniknla AB, Panehagnula R (2001) Curr Opin Chem Biol 5(4) 439-446 Pitt WG (2008) Adv Drag Deliv Rev 60 1095-1096... 

Figure 1.18 Schematic representation of the fusion protein and its use in controlled silica nanomaterial formation.

Helical nanomaterials Asymmetric No Cosurfactants used to modify synthesis of regular mesoporous silica nanomaterials [26]... 

Both spherical fluorescein isothiocyanate-doped mesoporous silica nanomaterials (S-FITC-MSN) and tubular fluorescein isothiocyanate-doped mesoporous silica nanomaterials (T-FITC-MSN) are synthesized to assess the rate of endocy-tosis based on several factors, as described by Trewyn et al. [18]. For general synthetic methods, the mesoporous silica nanomaterials can be prepared by mixing fluorescein isothiocyanate (FTIC) with 3-arninopropyltrunethoxysilane with anhydrous dimethylformamide (DMF) as solvent. N-cetyltrimethylammonium bromide (CTAB) is then dissolved in water and made basic with NaOH, followed by a temperature increase. TEOS is added dropwise to the CTAB solution, after which the other prepared solution is mixed in to produce S-FITC-MSN as an orange powder. 

A third type of measurement is aimed at characterizing the optical properties of the nanomaterials, and for this both conventional optical microscopy and transmission UV-visible spectroscopy are applicable. Another method-circular dichroism-can be used to study the heUcity of silica nanomaterials, while Raman spectroscopy has also been used for their characterization. 

In this chapter we review the current state of research on symmetric and asymmetric silica nanomaterials, or nanosUica, in terms of their synthesis, characterizahon and applications. Both, catalyticaUy and noncatalytically grown nanosilica are discussed, and several types of application for these nanomaterials are described. For asymmetric nanosihca, the focus is on helical nanosilica such as silica nanocoils and other heh-cal nano silica, whereas for symmetric silica nanomaterials the discussion covers more general forms of nanosilica, including nanoparticles, mesoporous nanomaterials and sihca nanotubes. 

As noted above, all of the toxicological studies conducted to date have focused on the effect of Si02 nanowires on cells in various tissue culture systems, and have not explored the consequences of exposure in intact animal models. An extensive search of the available literature revealed that no reports have been made regarding the in vivo toxicity of 1-D silica nanomaterials. Here, we will instead briefly summarize the literature on the in vivo toxicity of related materials, making predictions based not only on these studies but also on those focusing on particles and 1-D silica nanomaterials in cell culture. 

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