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°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 ofthe sharp surface silanol band near 3745 cm-' 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°C, followed by a dramatic drop at higher calcination temperatures, and reaching negligible values for materials calcined near 1100C. 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.

Surface reactivity in the pathogenic response to particulates.

“…The various crystalline silica polymorphs exhibit remarkable differences in their pathogenic potential related to differences in crystal structure (1,3,8,(19)(20)(21). Even specimens of the same silica polymorph, e.g., cristobalite dusts of different origin (22,23) (22,33). Correspondingly, the membranolysis potential decreases (33,34).…”

“…Even specimens of the same silica polymorph, e.g., cristobalite dusts of different origin (22,23) (22,33). Correspondingly, the membranolysis potential decreases (33,34). The reversible adsorption of water, reported in Figure 1 for cristobalite heated at different temperatures, measures the extent of silanols patches, i.e., the extent of hydrophilic sites (18).…”

Crystalline Silica Particles Mediated Lung Injury

“…Similarly, another critical analysis that considered all physicochemical characteristics like particle size, specific surface areas, experimental uncertainties 32) indicated a slight difference between the cytotoxicity of the three most common crystalline forms of silica (quartz, cristobalite and tridymite) when compared on the basis of equal number of particle number and surface area. The toxicity of crystalline silica can be markedly reduced by surface-modifications using a coating on the particle surface 7) .…”

Characterization by Scanning Transmission Electron Microscopy of Silica Particles from Alveolar Macrophages of Coal Miners

“…We collected data with a VG HB5 field emission scanning transmission electron microscope (STEM), operated at 100 keV, with a probe size of 20 A. We conducted X-ray analysis using an energy dis-AM dCI am -, .. 9 & a M persive X-ray analyzer through the characteristic excitation of X-rays caused by energy losses from the inelastic collisions of electrons with atoms. Elements of atomic number 5 (boron) and greater can be detected by this approach.…”

“…Furthermore, in vitro studies of the membranolytic activity and cytotoxicity of mineral dust particles have shown no unique relationship with the bulk concentration of quartz in such dusts (3)(4)(5). On the other hand, many in vitro and in vivo studies of the effect on cytotoxicity of the surface characteristics of mineral particles have shown positive correlations with different related variables (6)(7)(8)(9). Also, Rehn et al (10) have shown that the presence of admixed minerals affects the rate of elimination of inhaled dusts from the lung.…”