Polyethyleneimine incorporated hydroxyapatite for improved colloidal stability

We report on the preparation of a polyethyleneimine-incorporated hydroxyapatite (PEI-HAP) and its enhanced colloidal stability. Three PEI-HAPs having different amine contents are synthesized by hydrothermal treatment (200 °C) of the HAP prepared at room temperature (rt-HAP). The crystallinity of PEI-HAP is improved compared to rt-HAP due to the heat treatment. In addition, the size of PEI-HAP (50.4 nm) increased compared to rt-HAP (32.1 nm) after heat treatment. However, the presence (or concentration) of PEI has little effect on the crystallinity and size of the samples. Ninhydrin test indicates the presence of amine group in PEI-HAPs. XPS experiments verified that maximum amine content amounts to 2.81%. As the amount of amine increases, the zeta potential is changed from −22.6 to +31.7 mV due to the adsorption of PEI on HAP surface. Consequently, the sample having high positive valuable zeta potential of +31.7 mV exhibits colloidal stability of more than 6 h.