Rapid surface modification of PEEK by ambient temperature sulfonation for high shelf-life biomedical applications

The aim of this study is to develop a rapid, simple, and economical surface treatment process for Poly (etherether-ketone) (PEEK) using concentrated sulfuric acid. PEEK is a biocompatible material, with a bonelike elastic modulus and is mechanically superior to other implant materials like titanium, stainless steel etc. This property brings PEEK to limelight as a promising alternative for bone implants. However, a strong challenge is observed of osseointegration mainly due to its inert surface behavior and poor hydrophilicity. Chemical surface modification is considered as one of the best ways to bioactivate the PEEK surface. In this work, two different sulfonation treatment methodologies have been designed and the effect of reaction time is systematically studied over its changing surface properties and favorable cellular growth. In one treatment, only rapid sulfonation is implemented while in other treatment processes, scaffolds are treated with NaOH solution to terminate the sulfonation process. The modified PEEK surface is next evaluated using Fourier transform infra-red spectroscopy (FTIR), contact angle, optical profilometer and scanning electron microscopy to ascertain its behavior. The modified surface is observed to possess higher hydrophilicity, higher surface roughness and high porosity. No significant difference in hydrophilicity is observed for over a month once treated, showing permanency in modification. A 90 second treatment is observed to have the highest hydrophilicity and thus selected for cellular integration studies. No sign of cell toxicity was observed in the modified surfaces, which also showed improved protein adsorption, cell viability, cell adhesion, and proliferation compared to untreated PEEK. The proposed chemical modifications are promising techniques for a rapid, easy, and economical bioactivation of PEEK polymer for improved cellular activity.