Inhibition of hydroxyapatite formation in aqueous solutions by hafnocene dichlorides

The kinetics of crystal growth of hydroxyapatite [Ca5(PO4)3OH, HAP], the thermodynamically most stable calcium phosphate phase at 37 °C, pH 7.40 and ionic strength 0.15 M in the presence of hafnocene dichlorides has been investigated. The kinetic results showed a surface diffusion controlled mechanism. The presence of hafnocene dichlorides used as drugs for therapeutic applications inhibited the crystal growth of HAP, possibly through adsorption onto the active growth sites for crystal growth. The kinetic results favored a Langmuir type isotherm, suggesting a high affinity of hafnocene dichloride for HAP.