Biomimetic hydroxyapatite grown on biomedical polymer coated with titanium dioxide interlayer to assist osteocompatible performance

• Crystallinity and film thickness of HAp layer was effectively enhanced by adopting TiO2 interlayer in SBF environment.
• R-TiO2/PEEK specimen exhibit superior ability to induce HAp formation, due to negatively charged –OH− groups on its surface.
• Osteocompatibility performance correlated positively with the extent of HAp layer formation.

A widely utilized spinal implant material, polyetheretherketone (PEEK), with its bio-inert and hydrophobic surface was persistently paid attention for bioactive surface modification. Hydroxyapatite (HAp), exhibiting excellent osteoconductive property, has also been regarded as a promising candidate for biomedical applications. The present study employed an arc ion plating (AIP) technique to respectively deposit rutile-rich titanium dioxide (R-TiO2) and anatase-rich titanium dioxide (A-TiO2) as an interlayer onto PEEK substrates for inducing HAp layer growth in simulated body fluid (SBF) at low temperature. Consequently, this materials are expected to promote osteoblast compatibility for PEEK to be used as spinal implants. For comparison, microstructure characterization of the as-grown HAp are examined and growth mechanism is proposed. Finally, osteocompatibility test are carried out to evaluate the effect of HAp grown on the TiO2-coated PEEK specimens.Experimental results showed that HAp growth can effectively be enhanced by adopting TiO2 interlayer in SBF environment, with the crystallinity and film thickness of the grown HAp layer proportional to immersion time. It was also worth to note that the R-TiO2/PEEK specimen exhibit superior ability to induce HAp formation, due most likely to the pre-absorbed negatively charged –OH− groups on R-TiO2 coating surface at early growth stage. This also accounts for the ultimate osteocompatibility provided by the R-TiO2 as the interlayer for growing the fastest and the highest crystallinic HAp.