Osteoclast adhesion and activity synthetic hydroxyapatite, carbonated hydroxyapatite, and natural calcium carbonate: Relationship to surface energies

This study investigates the adhesion, cytoskeletal changes, and resorptive activity of disaggregated rat osteoclasts cultured on polished slices of th ree biomaterials: crystalline synthetic hydroxyapatite (HA), carbonated hyd roxyapatite (C-HA), and natural calcium carbonate (C). The surface chemistr y of each substrate was defined by X-ray diffraction and IR spectroscopy, s urface wettability by the dispersive, and the polar components of the surfa ce energies. Osteoclast adhesion was modulated by the polar component of th e surface energy: fewer (p < 0.01) osteoclasts adhered to C-HA (97 +/- 20/s lice, surface energy 9 +/- 5 mJ/m(2)) than to HA (234 +/- 16/slice, surface energy 44 +/- 2 mJ/m(2)) or to C (268 +/- 37/slice, surface energy 58 +/- 0.5 mJ/m(2)). Actin rings, which are the cytoskeletal structure essential f or re-sorption, developed on all three materials. The area of the actin rin g, which is resorbed by local acidification, and the osteoclast area, which reflects osteoclast spreading, were both greater in osteoclasts cultured o n IIA and C-HA than in those cultured on C. C was resorbed, hut HA and C-HA were not. Thus, we surface energy plays an Essential role in osteoclast ad hesion, whereas osteoclast spreading may depend on the surface chemistry, e specially on protein adsorption and/or on newly formed apatite layers. Reso rption may be limited to the solubility of the biomaterial. (C) 1999 John W iley & Sons, Inc.