JOURNALOF MATERIALS SCIENCE: MATERIALS IN MEDICINE 13 (2002) 1181±1188 Cell adhesion and proliferation on biomimetic calcium-phosphate coatings produced by a sodium silicate gel methodology A. L. OLIVEIRA 1,2* ,C.M.ALVES 1,2 ,R.L.REIS 1,2 1 Department of Polymer Engineering, University of Minho, Campus de Azure Âm, 4800-058 Guimara Äes, Portugal 2 3B's Research Group, Biomaterials, Biodegradables and Biomimetics, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal E-mail: analeite@dep.uminho.pt, rgreis@dep.uminho.pt The present study describes a methodology to produce bioactive coatings on the surface of starch based biodegradable polymers or other polymeric biomaterials. As an alternative to the more typical bioactive glass percursors, a sodium silicate gel is being employed as a nucleating agent, for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat ef®ciently both compact materials and porous3Darchitecturesaimedatbeingusedontissuereplacementapplicationsandasbone tissue engineering scaffolds. This treatment is also very effective in reducing the incubation periods, being possible to observe the formation of an apatite-like layer, only after 6h of immersion in a simulated body ¯uid (SBF). The in¯uence of the SBF concentration on the formation of the apatite coating was also studied. The apatite coatings formed under different conditions were analyzed and compared in terms of morphology, chemical composition and structure. After the ®rst days of SBF immersion, the apatite-like ®lms exhibitthetypicalcauli¯owerlikemorphology.Withincreasingimmersiontimes,these®lms exhibited a partially amorphous nature and the Ca/P ratios became very closer to the value attributedtohydroxyapatite(1.67).Theobtainedresultsareverypromisingforpre-calcifying bone tissue engineering scaffolds. Therefore, in order to study cell behavior and response to these apatite coatings, adhesion, morphology, and proliferation of a human osteoblast cell line (SaOS-2) was also analyzed after being cultured in the coatings formed after 15days of immersioninSBF.Resultsindicateagoodcorrelationbetweencrystallinityoftheapatitelike coatings formed in these conditions and respective cell spreading and morphology. In general, higher cell proliferation was observed for higher crystalline Ca-P coatings. # 2002 Kluwer Academic Publishers 1. Introduction Biodegradable materials are a promising alternative for a range of bone related applications. Starch-based biode- gradable polymers are particularly interesting for bone replacement. Besides being biodegradable, inexpensive (when compared to other biodegradable polymers) and available in large quantities [1, 2], starch-based polymers can be converted into complex geometries that exhibit interesting mechanical properties, by using standard equipment developed for the processing of synthetic polymers [3] or by means of using distinct innovative methodologies [4,5]. Furthermore, in addition to their processing versatility, they exhibit a biocompatible behavior, already demonstrated by in vitro [6±8] and in vivo studies [9]. Therefore, they are under consideration for a wide range of biomedical applications like bone replacement/®xation [10,11], novel hydrogels and partially degradable bone cements [12], drug delivery carriers [4] or temporary scaffolds for tissue engineering applications [4,5]. In case of bone related applications like tissue replacement/®xation, or tissue engineering scaffolds to be applied in load-bearing sites, these systems must exhibit mechanical properties that match those of human bone, associated to degradation kinetics adequate to the healing of the tissues to be replaced or ®xed [10, 11]. Additionally, when coated with a bone-like apatite layer, they can also exhibit a bone-bonding behavior. In the recent years, there has been an increasing interest in the so-called biomimetic preparation of calcium phosphate coatings on implant materials. A biomimetic process for coating an apatite layer on organic polymers or other * Author to whom all correspondence should be addressed. 0957±4530 # 2002 Kluwer Academic Publishers 1181