Effects of surface undulations of biphasic calcium phosphate tablets on human osteoblast behavior Euler A. dos Santos, 1 Adriana B. R. Linhares, 2 Alexandre M. Rossi, 3 Marcos Farina, 2 Gloria A. Soares 1 1 Dep. de Eng. Metal. e de Materiais, UFRJ, P.O.Box 68505, Rio de Janeiro, 21941-972, RJ, Brasil 2 Laboratorio de Biomineralizac ¸a ˜o, ICB, UFRJ, Rio de Janeiro, 21941-590, RJ, Brasil 3 Centro Brasileiro de Pesquisas Fı ´sicas (CBPF), Rua Dr. Xavier Sigaud, 150, Rio de Janeiro, 22290-180, RJ, Brasil Received 5 January 2004; received 16 September 2004; accepted 19 October 2004 Published online 11 July 2005 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.a.30234 Abstract: In this work, the in vitro behavior of human osteoblast cells on the undulated surfaces of biphasic cal- cium phosphate tablets was investigated. The tablets were produced by uniaxial pressing with convex cylindrical un- dulations occupying only half of the surface area; the other half was flat. Chemical and physical characterization was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Fou- rier transform infrared spectroscopy (FTIR). XRD and FTIR analyses revealed the presence of hydroxyapatite (HA) and -tricalcium phosphate (-TCP) in a well-defined ratio. Moreover, microtopography, evaluated by SEM and AFM, was similar on the flat region and on that with undulations. However, surface undulations induced different cellular ar- rangements, confirming the influence of the macrotopogra- phy on the cells orientation. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 74A: 315–324, 2005 Key words: human osteoblast cells; biphasic calcium phos- phate tablets; macrotopography INTRODUCTION It is known that cellular behavior largely depends on the physical and chemical characteristics of ma- terials surface, such as chemical composition, 1–4 crystallinity, 5,6 particle size, 7 and topography. 8 –11 Several in vitro studies have shown that certain surface topographies strongly affect the initial events of cell adhesion and, consequently, its pro- liferation capability, differentiation, and extracellu- lar matrix production. 12–15 Topographical variations can yield true surface channels for nutrients trans- port, making possible the escape of several sub- stances produced by the cells. The phenomenon of cell orientation has been studied basically in grooved surfaces, 8,16,17 and these studies mostly focus on the creation of orga- nized tissues. Cell orientation occurs when cells start to have a polarized growth, that is, a preferen- tial spreading direction. Both fibroblasts and osteo- blasts may exhibit such behavior. 17,18 The orienta- tion phenomenon can be employed to cultivate fibroblasts on oriented scaffolds for repairing a rup- tured tendon, or to induce osteoblasts organization on implant surface. The surface topography of bioinert materials like titanium and other metallic alloys used to fabricate implants is usually designed (in macro-, micro-, and nanoscale) so as to increase the rate of tissue/implant integration. It has been shown that osteoblast-like cells attach more rapidly and synthesize more extracellular matrix when in contact with rough surfaces, 12,13 al- though there is a lack of consensus about the optimal roughness range. Hydroxyapatite (HA) and tricalcium phosphate (TCP) in its two allotropic forms (-TCP or -TCP) have been widely used as bone-substitute ceramics. HA is more stable than TCP under physiological conditions, as it has a lower solubility and slower resorption kinetics. 19 –21 Thus, when fast bone re- modeling is desired, a biphasic HA/TCP ceramic can be used. Nevertheless, little has been reported in terms of cells orientation on ceramic surfaces. Thus, in this work, we have investigated the behavior of human osteoblast cells on biphasic ceramics (HA/ TCP), presenting two kinds of topography: convex cylindrical undulations and flat regions. This knowl- edge may help the design of synthetic scaffolds for bone engineering. Correspondence to: G. de Almeida Soares; e-mail gloria@ ufrj.br Contract grant sponsor: CAPES Contract grant sponsor: CNPq © 2005 Wiley Periodicals, Inc.