In Vitro Evaluation of Optimized PEEK Surfaces for Enhanced Osseointegration

The materials traditionally used for implant applications, such as titanium alloys, cobalt chromium, and zirconium, often require surface modifications to achieve the desired osseointegration. These materials still have the problematic stress-shielding effect. To limit stress shielding, PEEK is the superior alternative to fulfill implant needs. However, the traditional methods of modifying and functionalizing the surface of PEEK are often expensive, time consuming, and are not easily translated into commercialization. Sulfonation is a process, which is dependent on controllable factors. Thus far, no research has been performed to optimize the sulfonation process. Our data suggest that the process factors can be controlled and optimized. Cellular activity was examined on the optimized PEEK surfaces through testing with pre-osteoblast MC3T3-E1 cells through cell viability (MTT assay), cell proliferation (DNA assay), cell differentiation (ALP assay), and cell mineralization (Alizarin red assay). Overall, sulfonated and heat-treated PEEK exhibited a statistically significant increase in DNA content over the course of 21 days, indicating more cell proliferation and viability for that surface. In vitro testing results showed that the optimized sulfonated and heat-treated PEEK exhibited superior cell proliferation and mineralization performance over smooth PEEK and sulfonated-only PEEK.