Three Dimensional Macroporous Calcium Phosphate Scaffolds for Bone Tissue Engineering

Calcium phosphate ceramics are widely used as bone substitutes since they are biocompatible and bioactive. Having a chemical composition close to natural bone, calcium phosphate ceramics are promising bone substitute materials in orthopaedics, maxillofacial surgery and dentistry. Hydroxyapatite (HA) and tricalcium phosphate (TCP) are the most commonly used calcium phosphates, because their calcium/phosphorus (Ca/P) ratios are close to that of natural bone and they are relatively stable in physiological environment. HA is a major constituent of bone materials and is resorbed after a long time of residence in the body. In this work, highly porous hydroxyapatite scaffolds were produced by polymer replication method and their properties evaluated by Scanning Electron Microscopy (SEM) and micro computerized tomography (μ-CT). Introduction Hydroxyapatite is a biocompatible ceramic widely used in dentistry and orthopaedic surgery and can be easily combined with other materials to improve its properties. In bone tissue engineering, the development of ceramics for restoration function and/or substitution has been studied, particularly in the production of three dimensional scaffolds. However, in order to be used in bone regeneration, some criteria must be achieved. In addition to biocompatibility, porosity is also an important parameter to consider when designing a scaffold. The need for cell nutrient transport (oxygen, etc.) and cell attachment sites implies the presence of interconnected macroporosity and microporosity, respectively. [1] SEM is a good technique to visualize the presence of micropores, macropores as well as its distribution along a scaffold (if cross sections are made). Key Engineering Materials Vols. 361-363 (2008) pp. 947-950 online at http://www.scientific.net © (2008) Trans Tech Publications, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 193.137.38.253-18/09/07,10:14:57) Nevertheless, in order to obtain a more accurate quantification of the macro/micro pores present in the structure, in addition to the interconnectivity measurement, it is necessary to compare with other methods. Micro computerized tomography (μ-CT) is an excellent technique, not only to quantify the porosity present but also to visualise the scaffold interior structure. [2] In this work, macroporous hydroxyapatite scaffolds were produced using the polymer replication method [3] and μ-CT and SEM techniques were used to assess and quantify the scaffold porous structure. Materials and Methods Samples preparation: Hydroxyapatite (commercially pure HA from Plasma Biotal, ref. P120) powder was sieved until a particle size less than 75 μm was achieved. The scaffolds were prepared using polyurethane sponges kindly provided by Recticel. These polyurethane sponges were impregnated with ceramic slurry as previously described. [3] Briefly, a ceramic slurry was prepared using several Hydroxyapatite: Water: Surfactant ratios. The polyurethane sponge was then immersed in this slurry and squeezed to remove slurry in excess. Next, the impregnated sponges were submitted to the following sintering cycle: heating at 1oC/min followed by a 1h stage at 600oC; heating at 4oC/min followed by another stage of 1h at 1300oC and then the samples were cooled inside the oven. The samples were partially immersed in resin and gold sputtered for SEM observations. Three-dimension (3D) reconstruction of scaffolds was assessed by μ-CT (μCT 40 Scanco Medical) using a resolution of 10 μm scans and a threshold range of 235 to 1000.