Feasibility of ceramic – polymer composite cryogels as scaffolds for bone tissue engineering Luis M. Rodriguez-Lorenzo 1,2#∗ , Laura Salda˜ na 2,3# , Lorena Benito-Garz´ on 1,2 , Raul Garc´ ı a-Carrodeguas 4 , Salvador de Aza 4 , Nuria Vilaboa 3,2 and Julio San Rom´ an 1,2 1 ICTP-CSIC, Madrid, Spain 2 CIBER de Bioingenier´ ıa, Biomateriales y Nanomedicina (CIBER-BBN), Madrid, Spain 3 Hospital Universitario La Paz-IdiPAZ, Madrid, Spain 4 ICV-CSIC, Madrid, Spain Abstract The purpose of the current study was to investigate whether the cryopolymerization technique is capable of producing suitable scaffolds for bone tissue engineering. Cryopolymers made of 2- hydroxyethyl methacrylate and acrylic acid with (W1 and W20) and without (W0) wollastonite particles were prepared. The elastic modulus of the specimens rose one order of magnitude from W1 to W20. Total porosity reached 56% for W0, 72% for W1 and 36% for W20, with pore sizes of up to 2 mm, large interconnection sizes of up to 1 mm and small interconnection sizes of 50–80 μm on dry specimens. Cryogels swell up to 224 ± 17% for W0, 315 ± 18% for W1 and 231 ± 27% for W20 specimens, while maintaining the integrity of the bodies. Pore sizes >5 mm can be observed for swollen specimens. The biocompatibility of the samples was tested using human mesenchymal stem cells isolated from bone marrow and adipose tissues. Both types of cells attached and grew on the three tested substrates, colonized their inner regions and organized an extracellular cell matrix. Fibronectin and osteopontin levels decreased in the media from cells cultured on W20 samples, likely due to increased binding on the ECM deposited by cells. The osteoprotegerin-to-receptor activator of nuclear factor-κ B ligand secretion ratios increased with increasing wollastonite content. Altogether, these results indicate that an appropriate balance of surface properties and structure that favours stromal cell colonization in the porous cryogels can be achieved by modulating the amount of wollastonite. Copyright  2011 John Wiley & Sons, Ltd. Received 21 October 2010; Accepted 13 May 2011 Keywords scaffold; bone tissue engineering; cryogels; mesenchymal stem cells; composites; interactions 1. Introduction Scaffold-based tissue engineering aims to repair or regenerate damaged tissues by culturing cells ex vivo on biocompatible scaffolds that must provide a suitable framework for biological interactions. Synthetic scaffolds are designed as highly porous structures, exhibiting an interconnected pore network to guide cell migration and deep cell colonization and to allow the diffusion *Correspondence to: Luis M. Rodriguez-Lorenzo, ICTP-CSIC, Juan de la Cierva 3, 28806 Madrid, Spain. E-mail: luis.rodriguez-lorenzo@ictp.csic.es # These authors contributed equally to this study. of nutrients, oxygen and metabolic waste. Ideally, a scaffold should be manufactured with slowly degrading materials that at the same time sustain sufficient strength to ensure its structural stability until the completion of a functional tissue formation. However, currently applied scaffold designs use fast-degrading polymers which, in combination with a high-porosity (90%) matrix do not provide an appropriate degradation rate and the required structural stability to resist the physiological loads that occur during the processes of integration and healing (Zhou et al., 2007; Dubruel et al., 2007). The purpose of the current study was to investigate whether the cryopolymerization technique is capable of producing suitable scaffolds for bone tissue engineering. Loading polymer matrices with bioactive ceramic particles Copyright  2011 John Wiley & Sons, Ltd. JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE RESEARCH ARTICLE J Tissue Eng Regen Med 2012;6: Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/term.443 421–433. 29 July 2011