Crystal preparations cleaned of organic deposits were extracted from cartilage deposits from osteoarthritic (OA) knee joints. These were studied by wide angle X-ray diffraction (WAXD) using a two-dimensional detector in order to ascertain the crystal species composition. Microcrystals in the mixtures were examined by scanning probe microscopy techniques to investigate the form and surfaces of individual particles. This examination resolved surface details on the crystals in the nanometre range. In some hydroxyapatite-rich deposits, small plate-like crystals closely resembling the intrafibrillar hydroxyapatite from calcifying turkey tendon collagen could be seen, suggesting these may have originally formed within collagen fibres. The surface features of triclinic calcium pyrophosphate dihydrate (T-CPPD), which were the predominant species of both synthetic crystals and CPPD from biological deposits, showed areas of relatively regular undulations of the order of 10 nm across and 3 nm deep. Their presence in synthetic crystals confirmed that this roughness, on the scale of a few unit cells, could not have arisen from the biological cleaning process. This suggested a mechanism whereby extra crystal surface could be made available for the location and adhesion of globular proteins, the majority of which tend to be of compatible molecular dimensions. This was tested by incubation of synthetic T-CPPD with human fibronectin, albumin and immunoglobulin G (IgG), followed by washing these free of unbound protein. Re-examination by SPM methods revealed arrays of the proteins located on the crystal surface and this confirmed the binding capacity of such crystals for proteins in vivo.
|Translated title of the contribution||Nanometre-scale surface features of arthropathic microcrystals and their relation to protein adsorption. A study by scanning probe microscopy and wide angle x-ray diffraction|
|Pages (from-to)||511- 516|
|Number of pages||6|
|Journal||Journal of Materials Science: Materials in Medicine|
|Publication status||Published - 1996|