The influence of processes for the purification of human bone allografts on the matrix surface and cytocompatibility

Different industrial processes exist to purify allogenic bone, providing safe and cleaned blocks for bone allografting. However, they often make use of chemical reagents that can be aggressive for the bone matrix. Bone samples were processed with several soaking techniques used in industry: NaHCO3, H2O2, NaOH and H2O2+NaOH combined; the consequences on the bone matrix and cytocompoatibility were evaluated on femoral heads from osteoarthritic patients. Alterations of matrix were searched by histochemistry, atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cytocompatibility was evaluated by coculturing human osteoblast-like cells (SaOS-2) on bone slices. Collagen fibers were dramatically altered at the surface of bone treated with H2O2, NaOH (and their association), but not with NaHCO3. A marked reduction in the number of hydroxyapatite crystals was observed on the trabecular surfaces by TEM and morphological changes were evidenced in SEM and AFM. Argyrophilic proteins of the bone matrix were removed by H2O2 and NaOH (and their association), but not by NaHCO3. As a consequence, attachment, spreading, proliferation and alkaline phosphatase activity of SaOS-2 were reduced by H2O2 and NaOH treatments. Strong oxidizing reagents altered matrix integrity by modifying collagenous and non-collagenous proteins. Whether these changes have clinical consequences on the bone bonding and osseointegration in human necessitate further investigations.