NaOH-etched/boron-doped nanohydroxyapatite-coated PEEK implants enhance the proliferation and differentiation of osteogenic cells.

The aim of the present study is to eliminate the bioinertness of polyetheretherketone (PEEK) material and to increase its osteogenic activity by applying a number of surface modifications in order to discover the most effective method. First, the surface of the bare PEEK (B-PEEK) was mechanically modified by sandblasting (S-PEEK). As a second method, physical modification was provided by etching of B-PEEK in 10 M sodium hydroxide (NaOH) solution at 60 °C for 48 h (N-PEEK). Following the sandblasting, S-PEEK samples were also etched with NaOH to obtain SN-PEEK samples. In order to increase osteogenic activity of the mechanically and/or physically modified PEEK samples, they were coated with boron-doped nanohydroxyapatite (B-nHAp) in the presence of microwave energy. Thus, B-PEEK/B-nHAp, S-PEEK/B-nHAp, N-PEEK/B-nHAp and SN-PEEK/B-nHAp samples were obtained. While water contact angles and surface roughness of the B-PEEK samples increased after modification, hydrophilicity increased with B-nHAp coating. Cell culture results demonstrated that high proliferation and differentiation capacities of MC3T3-E1 cells were obtained on the B-nHAP-coated surfaces compared to uncoated specimens. However, channeled texture of both the N-PEEK and N-PEEK/B-nHAp samples enhanced Col1a1 mRNA expression and collagen secretion in addition to increased alkaline phosphatase (ALP) activity when compared to other groups. As a result, it was determined that the bioactivity increased on the modified PEEK surfaces, but the most effective osteogenic activity was provided with B-nHAp coatings. The synergetic effect of NaOH etching and B-nHAp coatings might be used as a promising surface modification method to use PEEK material in orthopedic and dental applications with increased osteogenic activity.