| Silicates and other siliceous materials are the dominant components of earth's crust and mantle. Recent explorations by biochemists into the pathogenesis of certain particular and fiber-induced diseases have resulted in a new-found, broader interest in many silicates. The surfaces of silicates and their interfaces with select biocells may play key roles in these pathogenic processes. It is therefore of pertinence to have some means to measure the physical and chemical properties of these silicate surfaces, both separately and when in contact with key biocells. The latter may often be realized using X-ray photoelectron spectroscopy (XPS) or Electron spectroscopy for Chemical Analysis (ESCA). In achieving these XPS measurements, our group and others have shown the value in employing as a binding energy references for nonconductive materials, the C(1s) spectrum of the adventitious carbon that seems to exhibit a near instantaneous presence on the surface of all materials. A detailed discussion of this method is therefore presented herein, including considerations of the types of materials and the electronic energy states involved, e.g., Fermi edges, vacuum levels, etc., and the couplings that must exist for the referencing method to correctly applied. In addition we have initiated several ESCA-based procedures to explain the realized binding energies and correctly identify mixed oxides, particularly those containing aluminum. The present thesis examines the surface chemistry of select silicates (such as, amphiboles and sheet silicates, plus garnets, silica and silicon), both before and after alterations of their physical conditions and also before and after contact with certain in vitro cell cultures (Ehrlich cells (rat tumor) and rat lung (L2) cells). Special attention is provided for fibrous silicates described as asbestoses. We have followed the "in lattice" surface chemistry monitored features such as the simultaneous presence of 4- and 6-coordinate structural aluminum, and the presence of iron in the M4 octahedral position of the amphiboles. Aspects include 'before, during and after' XPS analyses of the silicates, with the implementation of unique methods of cell-silicate separation and also the freeze-drying and surface analysis of the combined systems. Particular attention was paid to the relative amount and chemistry of detected cellular iron and magnesium. The latter studies were supported by extensive atomic absorption spectroscopy (AAS) investigations. Supporting results have also been achieved with optical microscopy, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), electron spin resonance (ESR), X-ray diffraction (XRD), and secondary ion mass spectrometry (SIMS). In this manner we have been able to turn the tables on the conventional biochemical approach and identify cell-induced modifications of the surface chemistry (Si, Mg, Al, Fe, O, Ca) of the silicate components, along with the alterations in the cellular species. We provide several conjectures of the mechanisms for the related environmentally induced diseases. (Abstract shortened by UMI.). |
