Sulfur Hexafluoride (SF6) Plasma Treatment of Medical Grade Poly(methyl methacrylate)

Stefano Zanini,Antonio Papagni,Baljit Kaur Thatti,Luca Vaghi,Stephen Barton,Navid Shokri,Neil Williams,Claudia Riccardi

doi:10.3390/coatings10020135

Abstract

Medical-grade poly(methyl methacrylate) (PMMA) is widely employed in the fabrication of intraocular lenses (IOLs), but suffers from opacification, a postoperative complication that leads to the failure of the implanted intraocular lenses. The opacification occurs when inorganic-based deposits accumulate on the surface of the IOL and are prevalent in hydrophilic materials. Here, the surface of medical-grade PMMA has been fluorinated by sulphur hexafluoride (SF6) plasma treatment to increase surface hydrophobicity thus improving the material lifetime in optical applications. Hydrophobic properties of the treated PMMA were investigated by means of contact angle measurements, while chemical modification was assessed by X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR/FTIR) spectroscopy. Surface morphological changes due to possible etching effects were investigated by Atomic Force Microscopy (AFM). The transparency of the treated PMMA was assessed by UV/VIS spectroscopy. Finally, the influence of the plasma treatment on the inorganic salts deposition was investigated by immersion in Simulated Aqueous Humour (SAH), followed by XPS analysis. The modified samples showed less deposition on the surface than the unmodified sample, moreover, a decrease of the transmittance in the UV-violet range (300–430 nm) was detected, open the possibility of interesting applications of this treatment for the creation of a UV filter in ophthalmic optical devices.

Highlights

Crystalline clouding is usually corrected by replacing the opaque crystalline lens with intraocular lenses (IOLs)
Poly(methyl methacrylate) poly(methyl methacrylate) (PMMA) was used for the first IOL implantation by Harold Ridley in 1949 and remains the reference material with which new materials proposed for intraocular lenses are compared [1]
In order to investigate if our treatment has such detrimental effects, we evaluated both the topography and the transparency of the IOLs before and after the plasma treatment

Summary

Introduction

Crystalline clouding (cataract) is usually corrected by replacing the opaque crystalline lens with intraocular lenses (IOLs). Poly(methyl methacrylate) PMMA was used for the first IOL implantation by Harold Ridley in 1949 and remains the reference material with which new materials proposed for intraocular lenses are compared [1]. Even though in some countries, to reduce trauma to the eye during surgery, PMMA implants are being replaced by foldable hydrophilic and silicone IOLs, PMMA IOLs are still widely used, especially in the developing world. Opacification of IOLs occurs when calcium, sodium and potassium-containing deposits build upon their surface. This complication was reported as early as 1999 and results in a failure of the IOL implant following cataract surgery [2,3,4,5,6].

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