Surface and bulk infrared modes of crystalline and amorphous silica particles: a study of the relation of surface structure to cytotoxicity of respirable silica.

Abstract

Surface IR (infrared) modes of crystalline and fumed (amorphous) silica particles, calcined at temperatures up to 1095 degrees C, have been studied by Fourier transform infrared spectroscopy. The ability of these same particles to lyse cells has been measured by a hemolysis protocol. The untreated crystalline and amorphous materials differ by a factor of 40 in specific surface area, and the intensity per unit mass of the sharp surface silanol band near 3745 cm-1 in the amorphous material is an order of magnitude larger than in the crystalline material. A similar difference is observed in the lysing potential of the two materials. The intensity of the silanol band increases after calcination for both materials, reaching peak values near 500 degrees C, followed by a dramatic drop at higher calcination temperatures, and reaching negligible values for materials calcined near 1100 degrees C. The lysing potential data follow essentially the same pattern for both crystalline and fumed silica. These results are consistent with the hypothesis that the surface silanol groups are involved in cell lysis. Further experiments are suggested to evaluate the relationship between the surface structure of silica particles and their potential cytotoxicity.ImagesFIGURE 2. AFIGURE 2. BFIGURE 2. CFIGURE 2. D

Intracellular Localization and Cytotoxicity of Spherical Mesoporous Silica Nano‐ and Microparticles

“…To exclude the effect of surfactant on the cytotoxicity, the surfactant CTAB was removed completely by calcinations, which was supported by the absence of characteristic IR bands between 2800–3000 cm −1 (Figure 7). It is generally thought that the calcination of silica would result in the cytotoxicity reduction due to the absence of surface radicals and the onset of hydrophobicity 46–49. However, it is not known, as far as we know, if the calcination of spherical MS particles has similar effects on the cytotoxicity of common silica particles, and what is the pure relationship between the cytotoxicity and particle size of spherical C‐MS particles.…”

Evidence of an Oxidative Mechanism for the Hemolytic Activity of Silica Particles

“…Although evidence exists that links silica surfaces and hydroxyl radicals to hemolytic activity, it has not yet been shown that free radicals result from the silica-cell membrane contact. Results of our previous research (7) suggest that this issue merits further investigation. The interaction of silica with cell membranes may produce free-radical species and cause the subsequent penetration of these radicals into the cell.…”

“…These authors demonstrated that the hydrogen bonding of polyvinyl-N-oxide (PVPNO) with silanol groups, as well as the bonding of metal cations to the ionized SiOgroups, results in significant decreases in hemolytic activity. Furthermore, it has been found that the complete removal of surface hydroxyl groups from the surface of respirable silica particles nearly eliminates the hemolytic potential of silica (7), suggesting that hydroxyl groups might be involved in other cytotoxic processes associated with silica-induced lung injury.…”

Pulmonary glass particles may persist in the lung suppressing function of immune cells

“…Additionally, SGPs had very difficult shapes for both uptake by phagocytes and circulation in the body. 31,32 Phagocytes are of crucial importance for maintaining healthy tissues because they remove the host's dead (or dying) and damaged cells as well as foreign bodies. 28,[33][34][35] Although both RAW264.7 (peritoneal) and MH-S (alveolar) cells are mouse macrophage cell lines, they express different receptors that can interact with cytotoxic and helper T cells, respectively, and MH-S cells contain very low levels of lysozymes compared to RAW264.7 cells.…”