Smadfa

Biomaterials 29 (2008) 4392–4402

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Biomaterials
journal homepage: www.elsevier.com/locate/biomaterials

The responses of osteoblasts, osteoclasts and endothelial cells to zirconium modified calcium-silicate-based ceramic
Yogambha Ramaswamy a, Chengtie Wu a, Annika Van Hummel a, Valery Combes b, Georges Grau b, Hala Zreiqat a, *
a b

TissueEngineering and Biomaterials Research Unit, Biomedical Engineering, School of AMME, NSW 2006, Sydney, Australia Vascular Immunology Unit, Faculty of Medicine, NSW 2006, Sydney, Australia

a r t i c l e i n f o
Article history: Received 12 May 2008 Accepted 5 August 2008 Available online 30 August 2008 Keywords: Calcium silicate Zirconium Osteoblasts Osteoclasts Endothelial cells Gene expression

ab s t r a c t
In this study we have developed Ca3ZrSi2O9 (Baghdadite) ceramics by incorporating Zirconium in Ca–Si system and determined their biological properties. Ca3ZrSi2O9 ceramics possess apatite-formation ability in simulated body fluid, indicating their potential bioactivity. The response of human osteoblast like cells (HOB), osteoclast and endothelial cells when cultured on Ca3ZrSi2O9ceramics was investigated. Scanning electron microscopy and immunofluorescence studies demonstrated that this material supports HOB cell attachment with organized cytoskeleton structure. Compared to CaSiO3, Ca3ZrSi2O9 ceramics induced increased HOB proliferation and differentiation as shown by increased methyltetrazidium salt (MTS), alkaline phosphatase activity, and mRNA expression levels ofbone-related genes (Collagen type I, alkaline phosphatase, Bone Sialoprotein, receptor activator of NF-kB ligand and osteoprotegerin). Ca3ZrSi2O9 ceramics supported the fusion of monocytes to form functional osteoclasts with their characteristic features of f-actin ring structures and the expression of avb3 integrin consistent with functional activity. Osteoclasts cultured on Ca3ZrSi2O9 expressedincreased levels of osteoclast-related genes; Cathepsin K, Carbonic Anhydrase II, Matrix metalloproteinase-9, receptor activator of NF-kB and Calcitonin Receptor, consistent with the formation of functional osteoclasts. In addition to HOB and osteoclasts, Ca3ZrSi2O9 supported the attachment of endothelial cells, which expressed the endothelial cell markers; ZO-1 and VE-Cadherin. Results presented hereindicate that Ca3ZrSi2O9 ceramics have the potential for applications in bone tissue regeneration. Ó 2008 Elsevier Ltd. All rights reserved.

1. Introduction Bone defects are a great challenge to reconstructive surgery. With population ageing and prolonged life expectancy, there is increasing demand for synthetic materials that can regenerate lost or diseased bone [1]. Despite the increasingnumber of these procedures, there is no ideal bone graft substitute. Over the past two decades, calcium silicate (Ca–Si) based ceramics have been introduced as potential bioactive materials for skeletal tissue applications due to their excellent bioactivity [2]. Pseudowollastonite (CaSiO3) is a classic example of the calcium-silicate-based ceramics that exhibits excellent bioactivity and degradability[3]. However, major drawbacks of the CaSiO3 ceramics are their high dissolution rate and induction of high pH values in their surrounding environment retarding cell growth and thereby affecting their osseointegration ability [4,5]. Zirconium (Zr) is widely used to build prosthetic devices due to its good mechanical strength and biocompatibility. In vivo studies indicated that Zr
* Correspondingauthor. Tel.: þ61 2 93512392; fax: þ61 2 93517060. E-mail address: hzreiqat@usyd.edu.au (H. Zreiqat). 0142-9612/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2008.08.006

implants exhibit excellent osseointegration and zirconium-related materials, such as zirconia ceramics and coatings, have previously been used as bone implant materials [6,7]....