Determination of Oxygen Permeability in Soft Contact Lenses Using a Polarographic Method:  Estimation of Relevant Physiological Parameters

González-Meijóme, José Manuel; Compañ-Moreno, V.; Riande, Evaristo

doi:10.1021/ie071403b

Cited by 27 publications

(19 citation statements)

References 45 publications

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“…A close inspection of this figure shows that the apparent permeability coefficient of Hydrogels and Si‐Hy contact lenses is function not only of water content but also of the polymer chemical structure, because the free volume cavity size determines the diffusion coefficient of penetrates, and controls the diffusion selectivity of one penetrant over another. Similar results have been obtained by other researchers . From our experimental results, the value of apparent permeability in pure water from the extrapolation of permeabilities for all the lenses ( P 0 = D 0 k m ) is 5.1 × 10 −6 cm 2 s −1 , and the value of parameter K of Eq.…”

Section: Discussionsupporting

confidence: 91%

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Oxygen, water, and sodium chloride transport in soft contact lenses materials

Gavara

Compañ

2016

J Biomed Mater Res

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Oxygen permeability, diffusion coefficient of the sodium ions and water flux and permeability in different conventional hydrogel (Hy) and silicone-hydrogel (Si-Hy) contact lenses have been measured experimentally. The results showed that oxygen permeability and transmissibility requirements of the lens have been addressed through the use of siloxane containing hydrogels. In general, oxygen and sodium chloride permeability values increased with the water content of the lens but there was a percolation phenomenon from a given value of water uptake mainly in the Si-Hy lenses which appeared to be related with the differences between free water and bound water contents. The increase of ion permeability with water content did not follow a unique trend indicating a possible dependence of the chemical structure of the polymer and character ionic and non-ionic of the lens. Indeed, the salt permeability values for silicone hydrogel contact lenses were one order of magnitude below those of conventional hydrogel contact lenses, which can be explained by a diffusion of sodium ions occurring only through the hydrophilic channels. The increase of the ionic permeability in Si-Hy materials may be due to the confinement of ions in nanoscale water channels involving possible decreased degrees of freedom for diffusion of both water and ions. In general, ionic lenses presented values of ionic permeability and diffusivity higher than most non-ionic lenses. The tortuosity of the ionic lenses is lower than the non-ionic Si-Hy lenses. Frequency 55 and PureVision exhibited the highest water permeability and flux values and, these parameters were greater for ionic Si-Hy lenses than for ionic conventional hydrogel lenses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2218-2231, 2017.

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Section: Discussionsupporting

confidence: 91%

“…Similar results have been obtained by other researchers. 5,56,57 From our experimental results, the value of apparent permeability in pure water from the extrapolation of permeabilities for all the lenses (P 0 5 D 0 k m ) is 5.1 3 10 26 cm 2 s 21 , and the value of parameter K of Eq. (7) is K 5 1.4 6 0.3.…”

Section: Discussionmentioning

confidence: 85%

Oxygen, water, and sodium chloride transport in soft contact lenses materials

Gavara

Compañ

2016

J Biomed Mater Res

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“…It is well known that oxygen permeability through Si Hy is higher than Hy [15,50,52]. However, the transport mechanism and how this is achieved are still a matter of debate within the scientific community.…”

Section: Mds and Experimental Results Of O 2 Permeabilitymentioning

confidence: 99%

Oxygen and ionic transport in hydrogel and silicone-hydrogel contact lens materials: An experimental and theoretical study

Pozuelo

Compañ

González-Meijóme

et al. 2014

Journal of Membrane Science

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The transport of oxygen, water and naked ions of Na þ and Cl across two kind of hydrogels materials, made of a conventional hydrogel (Hy) based on hydroxyethyl methacrylate (pHEMA) and a silicone hydrogel (Si Hy) material containing siloxane moieties, was compared between Molecular Dynamics Simulations (MDS) and experimental measurements. Computer assisted simulations were carried out for wet hydrogels at 310 K and equilibrium water uptake in the range from 10% to 40%. Our results show that in Si Hy materials the aqueous hydrogel and hydrophobic siloxane phases are separated suggesting a co continuous structure, and oxygen moves predominantly through the free volume of the hydrophobic siloxane phase. The values of diffusion coefficient of O 2 , water and Na þ and Cl ions in Si Hy was about one order of magnitude higher than in conventional hydrogels when the water content was above 25 wt% up to a critical value of 35 wt% where a percolation phenomenon is observed. The value of the oxygen diffusion coefficient obtained by simulations are roughly similar to that experimentally found using potentiostatic techniques. Values found experimentally for Na þ diffusion coefficients are between three or five times lower than MDS. For Si Hy materials with 36 wt% of water the Naþ permeability, diffusion coefficient and salt partition coefficient (k m ¼P/D) are 6.770.2 Â 10 7 cm 2 /s, 1.870.5 Â 10 6 cm 2 /s and 0.4270.13, respectively. For Hy materials of 38.6 wt% the values found were 18.471.2 Â 10 7 cm 2 /s, 5.471.0 Â 10 6 cm 2 /s and 0.3470.09, respectively. The coordination number between the fixed groups ( SiO ) and water in HEMA and the particles (O 2 , C l and Na þ ) is slightly larger than unity. The present study might be applied in the modeling of the gas transport in hydrogels as well as in novel polymeric structures for novel polymeric structures for new biomedical and technological applications with the aim of predicting and tuning their physiological behavior.

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“…The values of time lag for oxygen diffusion through the CL displayed in the last column in Table was determined from the coefficient of oxygen diffusion through the CL given in third column and knowing the thickness of the CL (second column of Table )using the formula

τ_{l} = \frac{L_{normall}^{2}}{6 D_{l}}

(see eq. (10) of reference).…”

Section: Methodsmentioning

confidence: 99%

“…The values of the apparent diffusion coefficient and permeability of the lenses given in Table I were obtained following the procedure described previously. [28][29][30][31][32][33] In brief, apparent oxygen diffusion and permeability of these CLs were determined from the measurement of electric current generated at the electrode as a consequence of the reduction process of oxygen that passed through each CL. In the steady-state conditions, apparent permeability of the lens, (P l ), is obtained from eq.…”

Section: Materials and Characterizationmentioning

confidence: 99%

Corneal relaxation time estimation as a function of tear oxygen tension in human cornea during contact lens wear

et al. 2019

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The purpose is to estimate the oxygen diffusion coefficient and the relaxation time of the cornea with respect to the oxygen tension at the cornea–tears interface. Both findings are discussed. From the experimental data provided by Bonanno et al., the oxygen tension measurements in vivo for human cornea–tears–contact lens (CL), the relaxation time of the cornea, and their oxygen diffusion coefficient were obtained by numerical calculation using the Monod‐kinetic model. Our results, considering the relaxation time of the cornea, observe a different behavior. At the time less than 8 s, the oxygen diffusivity process is upper‐diffusive, and for the relaxation time greater than 8 s, the oxygen diffusivity process is lower‐diffusive. Both cases depend on the partial pressure of oxygen at the entrance of the cornea. The oxygen tension distribution in the cornea–tears interface is separated into two different zones: one for conventional hydrogels, which is located between 6 and 75 mmHg, with a relaxation time included between 8 and 19 s, and the other zone for silicone hydrogel CLs, which is located at high oxygen tension, between 95 and 140 mmHg, with a relaxation time in the interval of 1.5–8 s. It is found that in each zone, the diffusion coefficient varies linearly with the oxygen concentration, presenting a discontinuity in the transition of 8 s. This could be interpreted as an aerobic‐to‐anaerobic transition. We attribute this behavior to the coupling formalism between oxygen diffusion and biochemical reactions to produce adenosine triphosphate. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:14–21, 2020.

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Determination of Oxygen Permeability in Soft Contact Lenses Using a Polarographic Method: Estimation of Relevant Physiological Parameters

Cited by 27 publications

References 45 publications

Oxygen, water, and sodium chloride transport in soft contact lenses materials

Oxygen, water, and sodium chloride transport in soft contact lenses materials

Oxygen and ionic transport in hydrogel and silicone-hydrogel contact lens materials: An experimental and theoretical study

Corneal relaxation time estimation as a function of tear oxygen tension in human cornea during contact lens wear

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