Enhancement of bioactivity on medical polymer surface using high power impulse magnetron sputtered titanium dioxide film.

Abstract This study utilizes a novel technique, high power impulse magnetron sputtering (HIPIMS), which provides a higher ionization rate and ion bombardment energy than direct current magnetron sputtering (DCMS), to deposit high osteoblast compatible titanium dioxide (TiO 2 ) coatings with anatase (A-TiO 2 ) and rutile (R-TiO 2 ) phases onto the biomedical polyetheretherketone (PEEK) polymer substrates at low temperature. The adhesions of TiO 2 coatings that were fabricated using HIPIMS and DCMS were compared. The in vitro biocompatibility of these coatings was confirmed. The results reveal that HIPIMS can be used to prepare crystallinic columnar A-TiO 2 and R-TiO 2 coatings on PEEK substrate if the ratio of oxygen to argon is properly controlled. According to a tape adhesion test, the HIPIMS-TiO 2 coatings had an adhesion grade of 5B even after they were immersed in simulated body fluid (SBF) environments for 28 days. Scratch tests proved that HIPIMS-TiO 2 coatings undergo cohesive failure. These results demonstrate that the adhesive force between HIPIMS-TiO 2 coating/PEEK is stronger than that between DCMS-TiO 2 coating/PEEK. After a long period (28 days) of immersion in SBF, a bone-like crystallinic hydroxyapatite layer with a corresponding Ca/P stoichiometry was formed on both HIPIMS-TiO 2 . The osteoblast compatibility of HIPIMS-TiO 2 exceeded that of the bare PEEK substrate. It is also noticeable that the R-TiO 2 performed better in vitro than the A-TiO 2 due to the formation of many negatively charged hydroxyl groups (− OH − ) groups on R-TiO 2 (110) surface. In summary, the HIPIMS-TiO 2 coatings satisfied the requirements for osseointegration, suggesting the possibility of using HIPIMS to modify the PEEK surface with TiO 2 for spinal implants.