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      Physicochemical stability of contact lenses materials for biomedical applications Translated title: Estabilidad fisicoquímica de los materiales de las lentes de contacto, para aplicaciones biomédicas

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          Abstract

          Purpose

          The physicochemical stability, thermal and water plasticizing effect on transport properties of contact lenses (CL) were analyzed to verify its capacity to maintain the original properties after being dehydrated and rehydrated.

          Methods

          Two daily disposable (nesofilcon A and delefilcon A) and two monthly CL (comfilcon A and lotrafilcon B) were used. Measurements of refractive index (RI), water content (WC), chemical structure and thermal properties were taken: new (N), after dehydration (D) and rehydrated (R). RI and WC were accessed using a digital automated refractometer (CLR-12-70). Chemical structure was evaluated by a Fourier Transformed Infrared Spectroscopy (FTIR-ATR) and Differential Scanning Calorimetry (DSC) with a calorimeter (Mettler Toledo DSC-821).

          Results

          The FTIR spectrum of N, D and R was quite similar for all CL, with higher differences observed in the transmission between 3500–3000 cm −1 due to the hydroxyl group (OH). After dehydration and rehydration, there were no significant changes in the chemical structure. RI and WC of the CL rehydrated did not vary significantly from the initial CL (p > 0.05) and thermal properties also confirm that the behavior did not change. It was observed that the glass-transition temperature decrease with increased WC.

          Conclusion

          No significant alterations were observed in the physicochemical structure of the materials after dehydration and rehydration showing a good stability of their components. The strong water plasticizing effect in the silicone hydrogel lens materials improves flexibility and chain mobility and may should be considered for other biomedical applications.

          Resumen

          Objetivo

          Se analizaron la estabilidad fisicoquímica, las propiedades térmicas y el efecto plastificante en las propiedades de transporte de las lentes de contacto (LC), para verificar su capacidad de mantener sus propiedades originales tras la deshidratación y rehidratación.

          Métodos

          Se utilizaron dos lentes de contacto desechables diarias (nesofilcon A y delefilcon A) y dos mensuales (comfilcon A y lotrafilcon B). Se realizaron medidas del índice de refracción (IR), contenido de agua (CA), estructura química y propiedades térmicas: nuevas (N), tras la deshidratación (D) y tras la rehidratación (R). Se accedió a IR y CA utilizando un refractómetro digital automatizado (CLR-12-70). La estructura química se evaluó mediante Espectroscopía de infrarrojos con transformada de Fourier (FTIR-ATR) y Calorimetría diferencial de barrido (DSC) con un calorímetro (Mettler Toledo DSC-821).

          Resultados

          El espectro FTIR de N, D y R fue bastante similar para todas las LC, observándose mayores diferencias en la transmisión entre 3500–3000 cm −1 debido al grupo hidroxilo (OH). Tras la deshidratación y rehidratación no se produjeron cambios significativos en la estructura química. Los valores IR y CA de las LC rehidratadas no variaron significativamente con respecto a la LC inicial (p > 0,05), y las propiedades térmicas confirmaron también que el comportamiento no experimentó cambio alguno. Se observó que la temperatura vidrio-transición disminuía al incrementarse WC.

          Conclusión

          No se observaron alteraciones significativas en la estructura fisicoquímica de los materiales tras la deshidratación y rehidratación, reflejando una buena estabilidad de sus componentes. El fuerte efecto plastificante del agua en los materiales de las lentes de hidrogel de silicona mejora la flexibilidad y la movilidad de la cadena, debiendo considerarse esta circunstancia para otras aplicaciones biomédicas.

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          Most cited references31

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          Hydrogels in pharmaceutical formulations.

          N. Peppas (2000)
          The availability of large molecular weight protein- and peptide-based drugs due to the recent advances in the field of molecular biology has given us new ways to treat a number of diseases. Synthetic hydrogels offer a possibly effective and convenient way to administer these compounds. Hydrogels are hydrophilic, three-dimensional networks, which are able to imbibe large amounts of water or biological fluids, and thus resemble, to a large extent, a biological tissue. They are insoluble due to the presence of chemical (tie-points, junctions) and/or physical crosslinks such as entanglements and crystallites. These materials can be synthesized to respond to a number of physiological stimuli present in the body, such as pH, ionic strength and temperature. The aim of this article is to present a concise review on the applications of hydrogels in the pharmaceutical field, hydrogel characterization and analysis of drug release from such devices.
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            Polymeric hydrogels for novel contact lens-based ophthalmic drug delivery systems: a review.

            Only about 5% of drugs administrated by eye drops are bioavailable, and currently eye drops account for more than 90% of all ophthalmic formulations. The bioavailability of ophthalmic drugs can be improved by a soft contact lens-based ophthalmic drug delivery system. Several polymeric hydrogels have been investigated for soft contact lens-based ophthalmic drug delivery systems: (i) polymeric hydrogels for conventional contact lens to absorb and release ophthalmic drugs; (ii) polymeric hydrogels for piggyback contact lens combining with a drug plate or drug solution; (iii) surface-modified polymeric hydrogels to immobilize drugs on the surface of contact lenses; (iv) polymeric hydrogels for inclusion of drugs in a colloidal structure dispersed in the lens; (v) ion ligand-containing polymeric hydrogels; (vi) molecularly imprinted polymeric hydrogels which provide the contact lens with a high affinity and selectivity for a given drug. Polymeric hydrogels for these contact lens-based ophthalmic drug delivery systems, their advantages and drawbacks are critically analyzed in this review.
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              • Record: found
              • Abstract: not found
              • Article: not found

              Modeling Ophthalmic Drug Delivery by Soaked Contact Lenses

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                Author and article information

                Contributors
                Journal
                J Optom
                J Optom
                Journal of Optometry
                Elsevier
                1888-4296
                1989-1342
                29 November 2019
                Apr-Jun 2020
                29 November 2019
                : 13
                : 2
                : 120-127
                Affiliations
                [a ]Center of Physics, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
                [b ]Center of Chemistry, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
                Author notes
                [* ]Corresponding author at: Center of Physics, School of Sciences, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal. mlira@ 123456fisica.uminho.pt
                Article
                S1888-4296(19)30103-7
                10.1016/j.optom.2019.10.002
                7182778
                31791819
                00ef49fc-c164-464c-8cec-cd62cbb38c5f
                © 2019 Spanish General Council of Optometry. Published by Elsevier España, S.L.U.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 25 July 2019
                : 15 October 2019
                Categories
                Original article

                physicochemical,biomedical,contact lenses,fourier transformed infrared spectrometer,differential scanning calorimetry,fisicoquímico,biomedico,lentes de contacto,espectómetro de infrarrojos con transformada de fourier,calorimetría diferencial de barrido

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