A new hydroxyapatite-based biocomposite for bone replacement Devis Bellucci1,a, Antonella Solaa, Matteo Gazzarrib, Federica Chiellinib and Valeria Cannilloa a Department of Engineering “E. Ferrari”, University of Modena and Reggio Emilia, Via Vignolese 905, 41125 Modena, Italy b Laboratory of Bioactive Polymeric Materials for Biomedical and Environmental Applications (BIOlab) & UdR INSTM, Department of Chemistry & Industrial Chemistry, University of Pisa, Via Vecchia Livornese 1291, 56122 S. Piero a Grado, Pisa, Italy Abstract Since 1970s, various types of ceramic, glass and glass-ceramic materials have been proposed and used to replace damaged bone in many clinical applications. Among them, hydroxyapatite (HA) has been successfully employed thanks to its excellent biocompatibility. On the other hand, the bioactivity of HA and its reactivity with bone can be improved through the addiction of proper amounts of bioactive glasses, thus obtaining HA-based composites. Unfortunately, high temperature treatments (1200°C ÷ 1300°C) are usually required in order to sinter these systems, causing the bioactive glass to crystallize into a glass-ceramic and hence inhibiting the bioactivity of the resulting composite. In the present study novel HA-based composites are realized and discussed. The samples can be sintered at a relatively low 1 Corresponding author: [email protected] (Devis Bellucci) Tel.: +39 059 2056233; fax: +39 059 2056243. 1 temperature (800°C), thanks to the employment of a new glass (BG_Ca) with a reduced tendency to crystallize compared to the widely used 45S5 Bioglass®. The rich glassy phase, which can be preserved during the thermal treatment, has excellent efects in terms of in vitro bioactivity; moreover, compared to composites based on 45S5 Bioglass® having the same HA/glass proportions, the samples based on BG_Ca displayed an earlier response in terms of cell proliferation. KEYWORDS: Composites; Glass-ceramics; Hydroxyapatite; Bioceramics; Bone tissue engineering. 1. Introduction The loss of an organ or tissue due to cancer, disease or trauma is a dramatic problem in human health care. An attractive and promising approach to address such issues is to create biological or hybrid substitutes for implantation into the body, exploiting the self-healing potential of the body itself, as proposed in the framework of the emerging tissue engineering [1-3]. The term “tissue engineering” was oficially coined at the end of ‘80s to mean, as stated by Langer and Vacanti, “an interdisciplinary feld that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function or a whole organ” [4]. Tissue engineering, following the principles of cell transplantation and materials science, seeks to regenerate healthy biological tissues, as opposed to the traditional synthetic implants and organ 2 transplantation. In particular, this latter approach is limited due to (possible) adverse immune responses by the patient and to the large disparity between the need for organs and the real availability for transplantation [1-3]. Among the many tissues in the body, the regeneration of bone with predetermined shapes for orthopaedic surgery applications is of primary interest, since “there are roughly 1 million cases of skeletal defects a year that require bone-graft procedures to achieve union” [5]. Furthermore, bone is a dynamic tissue, in constant resorption and formation, and has the highest potential for regeneration [6]. Unfortunately, bone tissue engineering is currently limited to cancellous (or spongy) bone and there is lack of progress in compact (or cortical) bone engineering for human long bone repair. Biomaterials play a critical role in the success of tissue engineering, since they provide mechanical stability to the self-healing tissues and drive their shape and structure [7]. Moreover, they can control and stimulate the regeneration of the living tissue itself by activating specifc genes through their dissolution or releasing growth factors and drugs. Signalling molecules can be coated onto the biomaterials or directly incorporated into them [8-10]. Among biomaterials for bone tissue engineering, hydroxyapatite (HA) has raised great interest for many applications in both dentistry and orthopaedics, due to its close chemical and crystal resemblance to the mineral phase of bone that results in an excellent biocom

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