# Comparison between SBMA and MPC coatings on PEEK surface: stability over time and anti-inflammatory effects in vitro

## TL;DR

This study compares two zwitterionic coatings on PEEK implants to reduce inflammation and improve integration in the body.

## Contribution

The study introduces a novel comparison of MPC and SBMA coatings on PEEK surfaces for their anti-inflammatory and stability properties.

## Key findings

- MPC-based coatings on smooth PEEK surfaces significantly reduced pro-inflammatory cytokine release.
- Both MPC and SBMA coatings remained stable on PEEK for up to 8 weeks in simulated physiological conditions.
- Coatings anchored via zwitterionic copolymers and polydopamine adhesive layers showed promising anti-inflammatory effects in vitro.

## Abstract

The foreign body reaction often hinders the success of implantable devices, leading to fibrotic encapsulation. Controlling the post-implantation inflammatory phase is key to mitigating the foreign body reaction and promoting device integration. This paper compares three coating strategies for including anti-inflammatory agents onto polyether-ether-ketone (PEEK) surfaces, applying two different zwitterions, namely the 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA). Two different PEEK surface types were also compared, namely “rough surface” and “smooth surface” (average roughness: 7 μm ± 4 μm and 1.4 μm ± 0.3 μm, respectively). Focused ion beam-scanning electron microscopy (FIB-SEM) confirmed qualitatively the presence of a thin coating layer with an estimated thickness of 100 nm. X-ray photoelectron spectroscopy and water contact angle measurements showed that both MPC and SBMA coatings were highly stable on the PEEK substrates for up to 8 weeks in simulated physiological conditions, when anchored to the PEEK surfaces by exploiting zwitterionic copolymers with N-[3-(dimethylamino)propyl]acrylamide and using a polydopamine adhesive layer. These coatings were also tested in vitro, evaluating their effects on cell adhesion, and the production of inflammatory markers such as interleukin-1β, interleukin-6, tumor necrosis factor-α and nitric oxide from M1 macrophages. The MPC-based coating on smooth PEEK surfaces showed the most remarkable effects, significantly supporting macrophage viability, reducing the release of pro-inflammatory cytokines, and inhibiting nitric oxide release, suggesting a superior capability to modulate inflammation. These findings pave the way for functional coatings to be used in vivo, with the aim of improving PEEK implants’ safety, integration, and longevity.

The online version contains supplementary material available at 10.1038/s41598-025-25082-5.