Gentle sample preparation methods for specimen contained in complex matrix.

The target of this work is to present different sample preparation methods that permits to characterize, by different TEM techniques, the inorganic fibers or particulate matters contained in an organic or artificial complex matrix. We will present two type of methods: the first kind includes the complete removal of the matrix component, in order to concentrate the analyses only on the target fibers or particles; the second kind, is planned in order to conserve and allows to characterize also the matrix component. The used method has to avoid any damage to the inorganic material extracted from the matrix. Moreover, it should not generate artefacts through chemicals or mechanical stress. In this study, different techniques of preparation have been evaluated and tested, giving priority to the most rapid and simple ones. For organic matrix, we preferred chemical digestion for the first kind methods and embedding techniques combined with microtomy for the second kind. The digestion of the biological component of the sample was performed by sodium hypochlorite (NaClO 14%) in an oven at 60 °C for 6-24 hours. The embedding was made in paraffin and epoxy resin. For the artificial matrix (in this case cement), we choose to use different amount of mechanical stress to partially or totally separate the matrix from the fibers/particles. The mechanical stress in this case is represented by grinding and sonication. The cement pieces was suspended in acetone to avoid dispersion and the possible chemical interaction between the sample and the suspension medium. Substantially, a simple preparation allows an appreciable flexibility of applications. With the possibility to modify and adapt the steps at the different biological (e.g. urine, intestine tissues etc) or artificial samples (concrete, wallpaper, ropes etc). This technique allows to make TEM detailed investigation to fully characterize exogenous inorganic materials that enter the organism or lies in manufacts and the transformations that occur during mineral-matrix interactions. The extrapolated data can be used in an interdisciplinary study (by mineralogists, chemists, biologists, pathologists) to better understand the pathological effects caused by the inorganic materials penetrated into human body.