Analysis of the biological and chemical reactivity of zeolite-based aluminosilicate fibers and particulates.

Abstract

Environmental and/or occupational exposure to minerals, metals, and fibers can cause lung diseases that may develop years after exposure to the agents. The presence of toxic fibers such as asbestos in the environment plus the continuing development of new mineral or vitreous fibers requires a better understanding of the specific physical and chemical features of fibers/particles responsible for bioactivity. Toward that goal, we have tested aluminosilicate zeolites to establish biological and chemical structure-function correlations. Zeolites have known crystal structure, are subject to experimental manipulation, and can be synthesized and controlled to produce particles of selected size and shape. Naturally occurring zeolites include forms whose biological activity is reported to range from highly pathogenic (erionite) to essentially benign (mordenite). Thus, we used naturally occurring erionite and mordenite as well as an extensively studied synthetic zeolite based on faujasite (zeolite Y). Bioactivity was evaluated using lung macrophages of rat origin (cell line NR8383). Our objective was to quantitatively determine the biological response upon interaction of the test particulates/fibers with lung macrophages and to evaluate the efficacy of surface iron on the zeolites to promote the Fenton reaction. The biological assessment included measurement of the reactive oxygen species by flow cytometry and chemiluminescence techniques upon phagocytosis of the minerals. The chemical assessment included measuring the hydroxyl radicals generated from hydrogen peroxide by iron bound to the zeolite particles and fibers (Fenton reaction). Chromatography as well as absorption spectroscopy were used to quantitate the hydroxyl radicals. We found that upon exposure to the same mass of a specific type of particulate, the oxidative burst increased with decreasing particle size, but remained relatively independent of zeolite composition. On the other hand, the Fenton reaction depended on the type of zeolite, suggesting that the surface structure of the zeolite plays an important role.

Azo-dye orange II degradation by the heterogeneous Fenton-like process using a zeolite Y-Fe catalyst—Kinetics with a model based on the Fermi's equation

“…The XRD pro-files show that the crystalline structure of the zeolite changed after ion exchange, i.e. a loss of crystallinity is observed after the ion exchange process, some authors relating this loss of crystallinity to the effect of the charge on the ion-exchanging cation in the zeolite structure [35,36]. The XRD pattern of the non-exchanged zeolite allows to calculate a unit cell size of 24.50 Å using an idealized cell cubic Fd 3 m (Faujasite).…”

The effect of iron on the biological activities of erionite and mordenite

“…Our previous study demonstrated that in cell free systems, erionite, a known carcinogen, induces the generation of hydroxyl radicals to a greater degree than mordenite, a zeolite fiber that is not carcinogenic (Fach et al, 2002). To further examine the role of reactive oxygen species induction as it relates to the cytotoxic and genotoxic properties of these fibers, we utilized the AS52 cell line as a model system to determine the role iron may have in modulating the biological activity of these fibers.…”

“…While erionite and mordenite share several physiochemical properties, they elicit very different biological responses (Wagner et al, 1985;Guthrie, 1992;Both et al, 1994;Eborn and Aust, 1995). Our studies have demonstrated that erionite is more efficient than mordenite at generating hydroxyl radicals in cell free systems (Fach et al, 2002). To further examine the relationship between zeolite-induced ROS production and the biological response to zeolite exposure, we used the AS52 cells as a model to quantitate the cytotoxicity and mutagenic potential of these zeolites.…”

“…Mordenite and erionite were fractionated as we have described (Fach et al, 2002). Briefly, the zeolite was suspended in water and allowed to settle.…”

“…It has been suggested that the biological activity of erionite is due to the presence of iron on its surface (Eborn and Aust, 1995;. We have been using these natural zeolites as a model system to determine what physicochemical properties of these zeolites are responsible for their biological response(s) and to evaluate the parameters that influence these responses (Hogg et al, 1996;Long et al, 1997, Fach et al, 2002. The purpose of the present study was to determine the mutagenic potential of erionite and mordenite and to determine whether this mutagenic potential was modulated by iron.…”