Surface enhanced polyetheretherketone materials for orthopaedic implantation

Abstract

Polyetheretherketone (PEEK) has been widely applied as bone substitute in various orthopaedic implantations. However, its bioinertness associates with the unsatisfactory bone-implant integration. Although its bioactivity can be improved by incorporating additional bioactive substance into PEEK matrix, alternation of its original mechanical properties is concerned. Alternatively, surface modification using plasma implantation has been developed in order to incorporate new biofunctional groups onto PEEK surface. This study aims at investigating the feasibility of ammonia and water plasma treatment in enhancing the surface bioactivity of PEEK. The samples measured 5mm in diameter and 3 mm thick were prepared. Water and Ammonia plasma treatments were applied at implantation energy of 10kV, 20kV and 30kV for 2 hours. Surface bioactivity assessments including cell adhesion and proliferation were conducted by using SaOs-2 cells. Alkaline phosphatase (ALP) expression and mineralization assay were applied. The minerals formed on the surfaces were qualified by energy-dispersive X-ray spectroscopy (EDX). The result of cell adhesion testing revealed that more cells attached to all the samples except NH3 10kV as compared with the untreated (p<0.05). The ALP expression of all 30kV samples was higher at Day 7 (p<0.05). However, the ALP expression and mineralization of the 30kV treated samples were not significantly different from the untreated. Apatite-like structure found on the NH3 treated surface was Ca and P rich substances. Our biological testing results suggested that the bioactivity of PEEK could be enhanced by water and ammonia plasma treatments in particular to the initial cell attachment and proliferation.