Research Article Experimental Study of Diffusion Coefficients of Water through the Collagen: Apatite Porosity in Human Trabecular Bone Tissue Franco Marinozzi, 1 Fabiano Bini, 1 Alessandro Quintino, 2 Massimo Corcione, 2 and Andrea Marinozzi 3 1 Mechanical and Termal Measurements Laboratory, Department of Mechanical and Aerospace Engineering, “Sapienza” University of Rome, Via Eudossiana, 18-00184 Rome, Italy 2 Department of Astronautical, Electrical and Energetic Engineering, “Sapienza” University of Rome, Via Eudossiana, 18-00184 Rome, Italy 3 Orthopaedics and Traumatology Area, University “Campus Bio-Medico”, Via ´ Alvaro del Portillo, 21-00128 Rome, Italy Correspondence should be addressed to Franco Marinozzi; franco.marinozzi@uniroma1.it Received 28 February 2014; Revised 16 April 2014; Accepted 28 April 2014; Published 21 May 2014 Academic Editor: Costantino Del Gaudio Copyright © 2014 Franco Marinozzi et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We frstly measured the swelling of single trabeculae from human femur heads during water imbibition. Since the swelling is caused by water difusing from external surfaces to the core of the sample, by measuring the sample swelling over time, we obtained direct information about the transport of fuids through the intimate constituents of bone, where the mineralization process takes place. We developed an apparatus to measure the free expansion of the tissue during the imbibition. In particular, we measured the swelling along three natural axes (length L, width W, and thickness T) of plate-like trabeculae. For this aim, we developed a 3D analytical model of the water uptake by the sample that was performed according to Fickian transport mechanism. Te results were then utilized to predict the swelling over time along the three sample directions (L, W, T) and the apparent difusion coefcients D T , D W , and D L . 1. Introduction Transport phenomena within living tissues play an essential function for maintaining a proper supply of nutrients and for removing waste products. In bone tissue the transport of fuids and solutes is a concern for the bone formation and remodeling. Tese topics must be kept in mind when designing ECM-like scafolds for tissue engineering to mimic the functions and structure of the biological materials [1]. Perhaps the most studied ECM with particular attention to its permeability and porosity is the bone tissue matrix. Bone is a dynamic and complex composite material with a composition of around 65 wt.% mineral phase, 25 wt.% organic, and 10 wt% water [2–8]. Referring to the volume fractions of the various parts, the bone volume (BV) is constituted by apatite minerals (33–43% BV) and organic constituents (32–44% BV) which are in turn composed of collagen type I (about 90%) and noncollagenous proteins (about 10%). Te remnant is water (15–25% BV) [9] which plays a central role in the biomineralization process and contributes to the overall biomechanical properties of the biocomposite [10–12]. Water in bone may exist in three diferent forms: free water in pores, bound water in the collagen network (includ- ing collagen-mineral interface), and tightly bound water in the mineral phase [13, 14]. Bones with diferent water content display diferences in stifness and strength [15, 16]. Moreover, to describe the mechanical behavior of bone, the contribution of the bound water should be considered carefully by several viewpoints: frst, the bound water in the collagen network will change the viscoelasticity of collagen phase dramatically [17, 18]; second, the bound water on the mineral-collagen interface will change the interfacial bonding properties [19]; third, water may migrate and change its local distribution Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 796519, 8 pages http://dx.doi.org/10.1155/2014/796519