Effect of pH on Macroporosity of Hydroxyapatite Prepared by Foaming and Gelcasting using Ovalbumin

Hydroxyapatite implants with macroporosity helps in better bone bonding and faster bone regeneration. Macroporous hydroxyapatite samples were prepared using sol-gel hydroxyapatite with ovalbumin as a foaming and gelcasting agent. Physical properties were measured for the sample prepared with different concentration and pH of ovalbumin. Ovalbumin solutions at isoelectric pH (4.7) had higher overrun and air phase fraction and at natural pH (6.2) had higher foam density. With increase in concentration of ovalbumin, the hydroxyapatite loading decreased irrespective of the pH of ovalbumin. Hydroxyapatite loaded ovalbumin foams had better stability and nearly identical foam density at isoelectric pH. Macroporous hydroxyapatite samples with higher hydroxyapatite loading had lesser porosity and pore size but higher density at all pH. Samples with isoelectric pH had higher porosity and pore size but lesser density when compared to samples with natural pH at all concentrations. Samples prepared with 16 wt% ovalbumin and 70 vol% hydroxyapatite at pH 4.7 was found to have the required pore size and porosity with acceptable density. The microstructure of the prepared samples were observed using SEM.