H. Maachou, K161.E. Bal, Y. Bal, A. Chagnes, G. Cote and D. Alliouche Characterization and In Vitro Bioactivity of Chitosan/Hydroxyapatite Composite Membrane Prepared by Freeze-Gelation Method H. Maachou a, *, K.E. Bal b,c , Y. Bal b,c , A. Chagnes d , G. Cote d and D. Alliouche a a Laboratoire de Physique chimie des polymères fibreux, Université de Boumerdes, 35000 Boumerdes, Algérie; b Laboratoire des Biomatériaux et Phénomènes de Transport (LBPT), Centre Universitaire de Médéa,Quartier Ain D'heb, 26000, Médéa Algérie. c Département de chimie industrielle, Faculté des sciences, Université de Blida, 09000 Blida, Algérie; d Ecole Nationale Supérieure de Chimie de Paris - ENSCP Université Pierre et Marie Curie - Paris6 - Laboratoire d'Electrochimie et de Chimie Analytique - UMR7575 CNRS-ENSCP-Paris6 ENSCP, 11 Rue Pierre et Marie Curie, 75231 Paris Cedex 05, France. * corresponding author e-mail hamidamaachou@yahoo.fr Received 18 September 2007; published online 1 July 2008 This work reports the properties of highly porous (>80%) membrane Chitosan/Hydroxyapatite (Cs/HA) composites obtained by the freeze-gelation processing route. These materials are of great interest for bone regeneration applications due to their ability to nucleate calcium phosphates in presence of simulated body fluid (SBF). The membranes porosity and bioactivity can be easily controlled by adding various amounts of hydroxyapatite to chitosan solution. The structural properties of the composite membrane of Cs/HA at various weight ratio (Cs/HA=70/30, 50/50 and 30/70) have been investigated by scanning electron microscopy (SEM), porosity measurements and FTIR spectroscopy. The surface of the composite membranes after immersion in SBF during more than 14 days shows a regular Ca-P layer as evidenced by FTIR spectroscopy and ICP analysis. These results suggest the potential interest of the Chitosan/hydroxyapatite composite membranes prepared by freeze-gelation process in bone regeneration and especially of the Cs/HA membrane with a ratio of 70/30. © Society for Biomaterials and Artificial Organs (India), 20070918-11. Trends Biomater. Artif. Organs, Vol 22(1), pp 16-27 (2008) http://www.sbaoi.org Introduction Extensive research has been undertaken to develop polymer/hydroxyapatite biomimetic composites as new bone substitute materials due to the presence of hydroxyapatite (HA) which is a bone inorganic component [1, 2, 3]. HA, [Ca 10 (PO 4 ) 6 (OH) 2 ], was used in various biomedical fields such as dental material, bone substitute and hard tissue. HA can accelerate the formation of bone like apatite on the surface of the implant [4]. However, the main limitation of the use of these HA particles lie in the difficulties that surgeons encounter to apply them and keep them in place after implantation [5]. To overcome this problem, one strategy consists to immobilize them in a polymeric matrix such as chitosan. This polymer attracts a particular attention in the development of biomaterial composites because this natural polysaccharide derived from chitin after N-deacetylation is biodegradable and biocompatible. This polymer has been largely used in biomedical applications especially as scaffolds. Ideally, the scaffolds should have a high porosity, a large specific area, a suitable pore size, and a highly interconnected pore structure to provide enough space for the tissue development and to promote neovascularization [6]. This porosity can also control inorganic crystal nucleation, growth, microstructure, and more generally the properties of such mineral-based materials.