tutes is under investigation (5). For centuries it has been
The interaction of solid particles, such as silica and vitreous known that crystalline silica induces silicosis and recently fibers, with different surrounding media which well mimic the has also been suspected to cause lung cancer (6). The extenvarious environments in a biological medium, such as inhaled in sive literature on the medical side does not amount to an vivo or in a cell culture, has been studied by means of the electron adequate insight into the physico-chemical properties, which paramagnetic resonance (EPR) spectra of spin labels attached to give rise to the disease. The mechanisms of action at the the solid surface or spin probes inserted in the surrounding memolecular level are still under debate, but it is generally dium. Among the solid particles, a MCM-41 type mesoporous silica agreed that the surface chemistry of the particle determines was found to be very suitable for investigating the binding between the labels and different molecules, due to the high surface area the pathogenic mechanism (7-9). The complexity of the and the availability of interacting sites in the internal channels of biological responses, found in vivo and in vitro tests ( 6), the structure. The computer-aided analysis of the spectral linesuggests that several particle-cell interactions take place at shape allowed the evaluation of structural and dynamic paramedifferent stages, the overall pathogenicity being the result of ters. A model has been proposed which describes the interactions all these steps (8). In each step a different surface funcof the solid surface with: (a) pure solvents at different polarities; tion-e.g. silanols, siloxanes, dangling bonds in the case of (b) molecules present in biological fluids, which mimic the effect of silica-may be involved. Even when the location of the physiological solutions; (c) the components of the cell membrane particle is analyzed by means of electron microscopy, the (phospholypid or proteins in water solution); and (d) a model chemical processes at the solid-liquid interphase cannot be phospholypid membrane, to mimic the interaction between the evidenced. Information on the particle-cell interactions at solid particles and the cell membrane. The hydration of the surface lets the labels interact preferentially with the water molecules with the chemical level would be of paramount importance for the respect to the surface itself, or the other labels. Apolar molecules evaluation of the early stages of the pathogenic mechanism.
decreased the mobility of the labels attached to the surface. Phos-This aim may be achieved by means of a marker-located pholipid bilayers were formed at the solid surface, whose internal at the particle surface-able to give information on the modstructure was more fluid with respect to noninteracting bilayers, ifications of its chemical environment. The nitroxide spin whereas the external polar groups trapped probe and label molelabels, which can be investigated by electron paramagnetic cules in restricted space at the surface. The labels were partially resonance (EPR), provide a potential interesting marker for extracted from the wet surface of the vitreous fibers by the interacthis kind of research.
tion with a protein (albumin) and distributed in two different environments (at different polarities). แญง 1997 Academic Press
The EPR experiments on particles, which were labeled with nitroxide radicals, have provided an efficient tool for following both the fate and the behavior of the material itself