The Challenge of Spectroscopy in the Microanalysis of Biological Surfaces

Abstract

Chemical interactions between solids and their environments are initially characterized by the chemical composition of the surfaces. This is especially true for biochemical processes, such as ionic transport through biological membranes, the maintenance of mineral ion homeostasis which is critically dependent on the activity of the “bone membrane,” the biocompatibility of surgical implants which appears to be only a surface problem, etc. This is because biological surfaces have shown an increased interest for different fields of science. However, biological surfaces are heterogeneous and generally more complex than inorganic ones, and biological subsurfaces (internal surfaces) are not usually identical with the external surfaces. Taking into account that much of the functional significance of biological surfaces is related to the internal surfaces and these are normally hidden, we must expose them for analysis without introducing artifacts during the preparative procedures. As a result, the specimen preparation techniques are to a large extent the first limiting factor. Preparation of fully mineralized tissues such as teeth, bone, and kidney stones consisting of embedding in resin, sectioning, and fine polishing have been successfully accomplished. However, soft biological materials are prepared by cryogenic methods to preserve the original elemental distributions (but altering the tissue morphology) or by chemical fixation and water replacement by embedding media to preserve the morphology (but increasing diffusion and translocation of elements).