Surface functionalization of Bioglass Ò -derived porous scaffolds Qi-Zhi Chen a , Kurosch Rezwan a , Virginie Franc ¸on a , David Armitage b , Showan N. Nazhat b , Francis H. Jones b,c , Aldo R. Boccaccini a, * a Department of Materials and Centre for Tissue Engineering and Regenerative Medicine, Imperial College London, Prince Consort Road, London SW7 2BP, UK b Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, University College London, 256 Gray’s Inn Road, London WC1X 8LD, UK c Department of Chemistry, University College London, Christopher Ingold Building, 20 Gordon Street, London WC1H 0AJ, UK Received 16 September 2006; received in revised form 17 December 2006; accepted 25 January 2007 Abstract Like standard tissue culture plates, tissue engineering scaffolds can be chemically treated to couple proteins without losing the con- formation and thus biological function of the proteins; a process called surface functionalization. In this work, the surface of novel 45S5 Bioglass Ò -derived foam-like scaffolds, which exhibit adequate mechanical stability and tailorable bioresorbability, have been modified by applying 3-aminopropyl-triethoxysilane. The efficiency and stability of the surface modification were satisfactorily and quantitatively assessed by X-ray photoemission spectroscopy. It was also found that treatment in buffered (pH 8) water solution at 80 °C for 4 h, applied during the surface functionalization procedure, accelerated the bioreactive kinetics of the scaffolds, i.e. the transition of the rel- atively bioinert but mechanically competent crystalline structure of the struts to a biodegradable but mechanically weak amorphous net- work during immersion in simulated body fluid. Thus the aqueous heat treatment is confirmed to be an important factor that must be considered in the design of these Bioglass Ò -derived glass–ceramic scaffolds. Possible mechanisms responsible for the accelerated biore- activity are proposed. Ó 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Bioactive glass; 3-Aminopropyl-triethoxysilane; Surface functionalization; Bone tissue engineering; Porous scaffold 1. Introduction Most cells are anchorage dependent, i.e. they need to attach and spread out on a substrate before they start their proliferation. Hence, the first and foremost function of a scaffold in tissue engineering is its role as the substratum for cell attachment. Indeed, the ability to support and fos- ter cells is one of the essential criteria for an ideal scaffold [1–3]. In the field of cell culture, great efforts have been invested in understanding cell anchorage on extracellular matrix (ECM) and to utilize the knowledge to promote cell attachment on artificial substrates. Early empirical knowl- edge includes the following: (i) Cells adhere well to glass, particularly to glass with a high silica content (for decades cell biologists grew cells almost exclusively on glass, and prompted the term ‘‘in vitro’’) [4]. (ii) Cells will attach to and spread on glass and plastics that have a slight net sur- face negative charge [5]. (iii) A well-established piece of cell culture lore has it that used glassware supports cell growth better than new ones [5]. It is now known that cells do not attach directly to any substrates (including natural ECMs and artificial substrates), but rather bind to intervening ECM components (i.e. proteins such as fibronectin and col- lagen) that are adsorbed (or derivatized) to the substrate and accepted by specific cell surface receptors (e.g. inte- grins) [6]. Based on the above facts, cell attachment and growth can be improved by pretreating the substrate (a process called surface functionalization) in two steps [6,7]. The first 1742-7061/$ - see front matter Ó 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.actbio.2007.01.008 * Corresponding author. Tel.: +44 207 5946731; fax: +44 207 5946757. E-mail address: a.boccaccini@imperial.ac.uk (A.R. Boccaccini). Acta Biomaterialia 3 (2007) 551–562 www.elsevier.com/locate/actabiomat