The influence of structure and morphology on ion permeation in commercial silicone hydrogel contact lenses

Abstract

The importance of the microstzructure of silicone hydrogels is widely appreciated but is poorly understood and minimally investigated. To ensure comfort and eye health, these materials must simultaneously exhibit both high oxygen and high water permeability. In contrast with most conventional hydrogels, the water content and water structuring within silicone hydrogels cannot be solely used to predict permeability. The materials achieve these opposing requirements based on a composite of nanoscale domains of oxygen‐permeable (silicone) and water‐permeable hydrophilic components. This study correlated characteristic ion permeation coefficients of a selection of commercially available silicone hydrogel contact lenses with their morphological structure and chemical composition. Differential scanning calorimetry measured the water structuring properties through subdivision of the freezing water component into polymer‐associated water (loosely bound to the polymer matrix) and ice‐like water (unimpeded with a melting point close to that of pure water). Small‐angle x‐ray scattering, and environmental scanning electron microscopy techniques were used to investigate the structural morphology of the materials over a range of length scales. Significant, and previously unrecognized, differences in morphology between individual materials at nanometer length scales were determined; this will aid the design and performance of the next generation of ocular biomaterials, capable of maintaining ocular homeostasis.

Publication DOI: https://doi.org/10.1002/jbm.b.34689
Divisions: College of Engineering & Physical Sciences > Aston Institute of Materials Research (AIMR)
College of Engineering & Physical Sciences
College of Engineering & Physical Sciences > School of Infrastructure and Sustainable Engineering > Chemical Engineering & Applied Chemistry
Additional Information: © 2020 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials published by Wiley Periodicals LLC. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Uncontrolled Keywords: ESEM,SAXS,contact lens,ion permeation,silicone hydrogels,Biomaterials,Biomedical Engineering
Full Text Link:
Related URLs: https://onlinel ... bm.b.34689?af=R (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2021-01
Published Online Date: 2020-07-24
Accepted Date: 2020-07-02
Authors: Saez-Martinez, Virginia
Mann, Aisling (ORCID Profile 0000-0002-4075-8831)
Lydon, Fiona
Molock Jr, Frank
Layton, Sian
Toolan, Daniel Thomas William
Howse, Jonathan R.
Topham, Paul (ORCID Profile 0000-0003-4152-6976)
Tighe, Brian (ORCID Profile 0000-0001-9601-8501)

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