Atomic force microscopy for high resolution imaging of collagen fibrils - A new technique to investigate collagen structure in historic bone tissues

In this study, we present a new technique for the structural analysis of the collagen compound in historic tissues. We therefore used atomic force microscopy (AFM), a new high resolution technique which offers significant information on the fibrillar assembly and ultrastructure of collagen fibrils, which may provide insight into both the physiological and eventually pathogenic patterns of collagen fibrils, but also into possible diagenetic destructive changes of those fibrils. AFM figures three-dimensionally the surface of a sample with high resolution down to a nanometer scale. In our investigation we used the AFM to image paraffin embedded tissue sections from femoral bone tissue of a recent case and an age determined historic sample in ambient conditions. With this technique we were able to identify unambiguously collagen bundles and to determine their diameter. These results led us to differentiate the bundling pattern of collagen type 1 from that of collagen type II. In addition, we identified collagen type I in the historic sample, which provided a fibrillar pattern as that of recent bone. The results were compared to standard immunohistochemical staining techniques of the respective collagen types. In conclusion, our study presents circumstantial evidence that AFM analysis as a novel morphological tehcnique can successfully be applied to historic tissues specimens.