Preparation of macroporous hydroxyapatite by foaming and gelcasting using ovalbumin and its optimisation by Taguchi method

Abstract

Macroporous hydroxyapatite is a widely researched implant material due to its biocompatibility and bone bonding ability. The process of preparing macroporous HAp foam by foaming and gelcasting using ovalbumin involved four variables, namely ovalbumin amount, pH of ovalbumin solution, method of foaming and hydroxyapatite (HAp) amount, each varied in two levels. The properties for optimisation in this process were density and porosity. Pore size of the foam was considered as an additional criterion. The normal trial and error method of optimising the foam properties do not infer the effect of each factor on the properties. Design of experiment based on Taguchi method reduced the number of trials to eight and also identified the effect of each factor on the properties using the objective function calculated for each trial. The factor effect analysis indicated that HAp amount had the maximum influence and ovalbumin amount had least influence on density, and pH amount had the maximum influence and ovalbumin amount and foaming method had least influence on porosity. It also enabled the calculation of the objective functions for untried combinations which assisted in identifying the combinations that could offer optimum properties. The optimum properties were identified to be produced by one tried combination and two untried combinations. The identified untried combinations were then tried and the properties were calculated experimentally. The optimum combination with higher porosity and higher density with pore size >150 μm was identified using the objective functions and SEM images. This analysis indicated that the macroporous HAp prepared by the addition of 16 vol.-% HAp to 70 wt-% ovalbumin foam prepared at pH 4·7 by agitator had appropriate properties.