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The influence of structure and morphology on ion permeation in commercial silicone hydrogel contact lenses
Author(s) -
SaezMartinez Virginia,
Mann Aisling,
Lydon Fiona,
Molock Frank,
Layton Siân A.,
Toolan Daniel T. W.,
Howse Jonathan R.,
Topham Paul D.,
Tighe Brian J.
Publication year - 2021
Publication title -
journal of biomedical materials research part b: applied biomaterials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.665
H-Index - 108
eISSN - 1552-4981
pISSN - 1552-4973
DOI - 10.1002/jbm.b.34689
Subject(s) - materials science , self healing hydrogels , oxygen permeability , silicone , polymer , chemical engineering , permeation , differential scanning calorimetry , scanning electron microscope , contact angle , composite material , nanotechnology , oxygen , membrane , polymer chemistry , chemistry , organic chemistry , biochemistry , physics , engineering , thermodynamics
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.