Apatite Deposition on NaOH-Treated PEEK and UHMWPE Films for Sclera Materials in Artificial Cornea Implants

Cornea implants consist of a clear optic portion with a surrounding ring known as the skirt, which needs to integrate with the sclera. However, currently used skirt materials lead to poor tissue integration. Improvements in this respect may be achieved by using a bioactive skirt material that adapts to the metabolic activity of the cornea. Polyether etherketone (PEEK) and ultra‐high molecular weight polyethylene (UHMWPE) might provide interesting alternatives, if they can be rendered bioactive. We, therefore, investigated the potential of surface‐modifying PEEK and UHMWPE films through the use of a two‐step treatment. This process involved a suitable chemical surface modification (via immersion in NaOH), with subsequent formation of apatite layers on the polymers' surfaces through exposure to supersaturated simulated body fluid (1.5 SBF). In the present work the effect of 5 and 10 M NaOH on formation of the apatite layer has been investigated with regard to wettability and topography features. In addition, the chemical stability of the apatite layer formed has been analyzed. Our data demonstrate that with an increase in NaOH concentration the wettability of the polymer increased, whilst some changes to the polymer film topography (increase/decrease in roughness) were observed. Most beneficially, the apatite layer that subsequently was grown on pre‐treated PEEK and UHMWPE films through immersion in 1.5 SBF contained phosphate and carbonate ions, in similar ratios to those found in the apatite in dentine, thus, promising good in vivo bioactivity of these polymer films—a necessity if they are to be integrated into artificial cornea. The skirt of cornea implants needs to integrate with the sclera. Currently skirt materials lead to poor tissue integration and this can be improved by using a bioactive skirt material. We developed methodology to improve the bioactivity of PEEK and UHMWPE that are intended to be used as skirts. It was established that two step modification (i) chemical surface modification using NaOH with subsequent (ii) apatite film formation from SBF was an effective method to improve the bioactivity in vivo of the polymer films. We reported on the role of the modification on wettability, topography, and chemical stability of formed bioactive apatite layers.