Effect of porosity and pore size on microstructures and mechanical proper-ties of poly-ε-caprolactone-hydroxyapatite composites

The influence of variant pore-size and porosity on the microstructure and the mechanical properties of poly-epsilon-caprolactone (PCL) and hydroxyapatite (HA) composite were examined for an optimal scaffold in bone tissue engineering. Three various amounts of sodium chloride (NaCl, as porogens) with two distinct particle size ranges (212-355 pin and 355-600 pin) were blended into PCL and HA mixture, followed by a leaching technique to generate PCL-HA scaffolds with various pores and porosity. The porosities of the scaffolds were correlated with the porogen size and concentration. The morphological properties of the resulting scaffolds were assessed by micro-computerized tomography (mu CT), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). Extensive PCL-HA pore interconnections with thinner pore walls were present in scaffolds with higher concentration (4:1 w/w) and larger particulate of porogen used in the fabrication process. Embedding of HA particles in the scaffold resulted in rough surfaces on the composites. Instron actuator testing indicated that the tensile strengths and Young's moduli of scaffolds were influenced by both the porosities and pore sizes of the scaffold. It was apparent that increasing the concentration of porogen compromised the mechanical properties; and a larger porogen particle size led to increased tensile strength but a reduction in Young's modulus. Overall, the data indicated that modification of the concentration and particle size of porogen altered the porous features and mechanical strength of HA-PCL scaffolds. This provided means to manipulate the properties of biocompatible cell-supporting scaffolds for use as bone graft substitutes. (C) 2008 Wiley Periodicals, Inc.