The influence of molecular weight on the properties of polyacetal/hydroxyapatite nanocomposites. Part 2. In vitro assessment

A series of polyoxymethylene (POM)/hydroxyapatite (HAp) nanocomposites for long-term bone implants were prepared by melt processing using POM with different molecular weight. Bioactivity was examined by incubating the samples in simulated body fluid. Moreover, in vitro stability, wettability, thermal stability, and formaldehyde release process were investigated. Results of in vitro investigations show that an increase in HAp content in POM nanocomposites facilitates the formation of an apatite layer on the sample surface. There is no significant influence of HAp concentration on the contact angle values as revealed by wettability studies. Thermogravimetric analysis results indicate that with an increase in HAp content the thermal stability of POM matrix decreases significantly depending upon the POM molecular weight. Finally, it was found the amount of formaldehyde leached out of the samples during the incubation period depends on the HAp content: amounts in excess of 3 ppm were emitted for the samples containing only 10% HAp.