Coating Polyetheretherketone Implant Surface With Titanium Oxide Nanoparticles and Hyaluronic Acid: An In Vitro Study

Background Recently, polyetheretherketone (PEEK) has emerged as a promising implant material with some limitations. The objective of this investigation was to improve the hydrophilicity and biocompatibility of PEEK implant material through surface coating by nanoporous titanium oxide (TiO₂) and hyaluronic acid (HA), targeting a higher degree of cell viability, proliferation, differentiation, and mineralization around PEEK implants. Methods Prior to titanium film deposition, the PEEK substrates were treated with argon plasma. Using plasma sputtering, the 800 nm thick TiO₂ coatings were applied to the plasma-treated PEEK. The PEEK surface was then coated with a layer of HA. The implant discs were seeded with osteoblast cells. A total of four groups, each containing eight discs, were created. The groups included uncoated PEEK, HA-coated PEEK, HA and nanoporous TiO₂ coated PEEK, and the control group, which contained osteoblast cells only. The 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) test, 4',6-diamidino-2-phenylindole (DAPI) staining method, alkaline phosphatase (ALP) activity, and alizarin red staining were used to assess cell viability, proliferation, differentiation, and mineralization capacity. Results Osteoblast proliferation rates of the HA nanoporous TiO₂ coated group (69.37±6.16), were greater than HA-coated group (60.12±2.41), the uncoated PEEK (53.25±2.37) and the control group (36.37±4.56) after 21 days according to DAPI test. Additionally, the ALP activity on HA nanoporous TiO₂ coated PEEK (0.59±0.15, 2.18±0.23) was higher than HA-coated PEEK disks (0.62±0.17, 1.43±0.16), the uncoated group (0.45±0.11, 0.84±0.24) and the control group (0.17±0.08, 0.32±0.16) after seven and 21 days, respectively. Alizarin red staining in the HA nanoporous TiO₂ coated PEEK (1.41±0.07, 1.72±0.11) was significantly higher than HA-coated PEEK group (1.24±0.11, 1.35±0.07), the uncoated group (1.20±0.10, 1.01±0.08) and the control group (1.00±0.09, 1.00±0.05) at both time intervals, respectively. However, HA-coated PEEK increased cell viability (1.14±0.07, 1.14±0.07) more than the HA nanoporous TiO₂ coated group (1.10±0.40, 1.10±0.40), uncoated PEEK group (0.99±0.07, 0.99±0.07) and the control group (1.00±0.01, 1.00±0.01) after 72 hours and seven days, respectively. Conclusion Double coating of HA and nanoporous TiO₂ on the PEEK implant surface increased its biofunctional properties through the proliferation, differentiation, and mineralization of osteoblasts.