SCANNING PROBE MICROSCOPY - A USEFUL TOOL IN LEATHER RESEARCH

Optical microscopy, transmission electron microscopy (TEM) and scannin g electron microscopy (SEM) are widely accepted investigation methods in fundamental and applied leather research. They are under further de velopment, for instance by cryotechnique (cryomicroscopic SEM), rotary shadowing-TEM, use of confocal laser scanner and computer aided micro scopy in general. The further possibilities and the limits of this met hod are physically substantiated and illustrated. Currently, novel met hods of scanning probe microscopy have attracted special attention in physics, chemistry, material science and biology, because they can res olve surface details down to atomic level. Especially, scanning force microscopy (SFM) shows the capability to image isolating surfaces, inc luding biological specimens and coatings, with nanometer resolution. T he main advantages for applications in biology are: the possibility of working in a liquid environment under physiological conditions, to ge t three-dimensional topographic information and the possibility of pro bing local forces, e.g. to obtain information about the mechanical pro perties of the investigated specimen. We have carried out SFM of leath er. The investigations started with collagen monomers and collagen fib rils immobilized as different substrates. So far the best resolution w e could achieve is to image rod-like individual collagen momomers with a diameter of 1.5 nm and a length of 300 nm. In vitro assembled colla gen fibrils showed a diameter of about 100-200 nm and the 67 nm-period icity of native Type I collagen fibrils. Several fibrils are twisted i nto bundles in the form of a right-handed matrix. Changes in fibril mo rphology after calcification have been investigated. The results show that mineralisation occurs with higher density mainly at crossover reg ions of collagen fibrils. It has been found that the formed hydroxyapa tite crystallites are similar in size, typically between 50 and 100 Mn . Investigation on leather samples after various treatments demonstrat e that the applied method is also suited to investigate more complex s amples. The advantage of SFM in comparison to SEM is the possibility o f use to investigate wet samples and to obtain topographic information with high imaging value. In conclusion scanning probe microscopy, esp ecially the scanning force microscopy (SFM), is recommended as an usef ul tool in leather research in addition to the traditional microscopic investigation methods.