P 0.05, vs PEEK). Discussion Because of outstanding biocompatibility and mechanical strengths, PEEK has been widely used as biomedical implants for replacing bone tissue, which is also a promising implantable material for dental applications. 27 However, because of bioinert and hydrophobicity, PEEK does not induce adhesion, proliferation, differentiation, mineralization of osteoblasts, or promote bone regeneration both in vitro and in vivo. 28 Bioactive-coated PEEK implants have become a promising bone replacement material, which combines the advantage of both bioactive coating and PEEK. 29 In this study, to endow PEEK surface with bioactivity for tissue regeneration, TP was coated on PEEK (PKTP) by VE. The results showed that the dense TP coating of PKTP (thickness of around 400 nm) was stoichiometric TP, which was tightly bonded with PEEK. Furthermore, the coating of PKTP was non-crystalline TP, showing amorphous phase. PEEK revealed a smooth surface while PKTP exhibited a rough surface duo to the TP coating containing many irregular bulges with sizes of around 10 nm. Therefore, the coating of PKTP was nanostructured TP.