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

DOI: 10.1002/jbm.b.34689 DOI Help

Authors: Virginia Saez‐martinez (Aston University) , Aisling Mann (Aston University) , Fiona Lydon (Aston University) , Frank Molock (Aston University) , Siân A. Layton (Aston University) , Daniel T. W. Toolan (University of Sheffield) , Jonathan R. Howse (University of Sheffield) , Paul D. Topham (Aston University) , Brian J. Tighe (Aston University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biomedical Materials Research Part B: Applied Biomaterials , VOL 18

State: Published (Approved)
Published: July 2020
Diamond Proposal Number(s): 13002

Open Access Open Access

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.

Journal Keywords: contact lens; ESEM; ion permeation; SAXS; silicone hydrogels

Subject Areas: Biology and Bio-materials


Instruments: I22-Small angle scattering & Diffraction

Documents:
jbm.b.34689.pdf

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