Lysozyme transport in p-HEMA hydrogel contact lenses

Bengani, Lokendrakumar C.; Leclerc, Jenna L; Chauhan, Anuj

doi:10.1016/j.jcis.2012.07.018

Cited by 14 publications

(13 citation statements)

References 23 publications

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“…The enzymatic activity of immobilized enzymes increased with the increase of enzyme concentration in the xanthan solution and the immobilized enzymes presented higher thermal stability . Xanthan hydrogels proved to be efficient carriers for lysozyme (LYZ), an enzyme with isoelectric point (pI) at 10.7 and biocidal properties . At pH 7 the release of LYZ tends to be very low due to attraction between positively charged residues of LYZ and negatively charged xanthan .…”

Section: Xanthan Gum Networkmentioning

confidence: 99%

“…73 Xanthan hydrogels proved to be efficient carriers for lysozyme (LYZ), 45 an enzyme with isoelectric point (pI) at 10.7 75 and biocidal properties. 45,[76][77][78][79] At pH 7 the release of LYZ tends to be very low due to attraction between positively charged residues of LYZ and negatively charged xanthan. 45 The LYZ loaded xanthan hydrogels films presented substantial bactericidal activity because they preserved the native structure, as indicated by CD spectra, making them useful as bactericidal coatings or wound dressings.…”

Section: Xanthan Gum Networkmentioning

confidence: 99%

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Xanthan gum: A versatile biopolymer for biomedical and technological applications

Petri

2015

J of Applied Polymer Sci

334

189

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Xanthan gum is an extracellular polymer produced mainly by the bacterium Xanthomonas campestris. Traditionally it plays an important role in industrial applications as thickener, emulsion stabilizer and it has been added to water-based drilling fluids due to its pseudoplastic behavior and thermal stability. The structural properties of xanthan in solution can be tuned by the temperature and ionic strength; under high ionic strength or low temperature, xanthan chains are arranged in helical conformation, whereas under low ionic strength or high temperature, xanthan chains are coiled. Xanthan high molecular weight favors the building up of physical and chemical networks, which have been used as carriers for drugs and proteins and as scaffolds for cells. In combination with other polymers xanthan has been applied as excipient in tablets or as supporting hydrogels for drug release applications, particularly due to its acid resistance. The large versatility of xanthan gum opens the possibility for the creation of new architectures and additional applications involving this fascinating polymer. AIMSThe purpose of this review is to report on the applications of xanthan gum in biomedical and technological products over the last ten years, but revisiting the background and the highlights of traditional applications as thickener. The in vivo biodegradability and biocompatibility of xanthan gum are fundamental characteristics that allow its use in biomedical applications. The ability to form networks and acid resistance make xanthan gum, as pure excipient or in combination with other polymers, very attractive as drug carriers. The recent combinations with inorganic particles open a range of new applications.

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Section: Xanthan Gum Networkmentioning

confidence: 99%

Section: Xanthan Gum Networkmentioning

confidence: 99%

Xanthan gum: A versatile biopolymer for biomedical and technological applications

Petri

2015

J of Applied Polymer Sci

334

189

View full text Add to dashboard Cite

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“…Similarly, partitioning of tear components in SCLs, such as proteins, salts and lipids, can affect lens behavior during wear [1,[7][8][9][10][11]. Further, solute partitioning is critical for possible use of SCLs as a drug-delivery vehicle [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Fluorescent solute-partitioning characterization of layered soft contact lenses

Dursch

Liu

et al. 2015

Acta Biomaterialia

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a b s t r a c tPartitioning of aqueous packaging, wetting, and care-solution agents into and out of soft contact lenses (SCLs) is important for improving wear comfort and also for characterizing lens physico-chemical properties. We illustrate both features of partitioning by application of fluorescent-solute partitioning into DAILIES TOTAL1 Ò (delefilcon A) water-gradient SCLs, which exhibit a layered structure of a siliconehydrogel (SiHy) core sandwiched between thin surface-gel layers. Two-photon fluorescence confocal laser-scanning microscopy and attenuated total-reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) characterize the lens and assess uptake profiles of six prototypical fluorescent solutes. Comparison of solute uptake in a SiHy-core prototype lens (i.e., O 2 OPTIX TM ) validates the core SiHy structure of DAILIES TOTAL1 Ò . To establish surface-layer charge, partition coefficients and water contents are obtained for aqueous pH values of 4 and 7.4. Solute fluorescence-intensity profiles clearly confirm a layered structure for the DAILIES TOTAL1 Ò lenses. In all cases, aqueous solute partition coefficients are greater in the surface layers than in the SiHy core, signifying higher water in the surface gels. ATR-FTIR confirms surface-layer mass water contents of 82 ± 3%. Water uptake and hydrophilic-solute uptake at pH 4 compared with that at pH 7.4 reveal that the surface-gel layers are anionic at physiologic pH 7.4, whereas both the SiHy core and O 2 OPTIX™ (lotrafilcon B) are nonionic. We successfully confirm the layered structure of DAILIES TOTAL1 Ò , consisting of an 80-lm-thick SiHy core surrounded by 10-lm-thick polyelectrolyte surface-gel layers of significantly greater water content and aqueous solute uptake compared with the core. Accordingly, fluorescent-solute partitioning in SCLs provides information on gel structure and composition, in addition to quantifying uptake and release amounts and rates.

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“…Aqueous-solute diffusivities in hydrogels, D, are diminished relative to those in bulk solution, D o , by nonspecific interaction with the hydrogel-polymer chains including steric obstruction and hydrodynamic resistance [2,7,11,14,[27][28][29][30][31][32][33][34][35][36]. In many cases, aqueous-solute diffusivities are further diminished by specific complexation of solutes to hydrogel-polymer chains that arises when specific solute-hydrogel binding overcomes competing interactions with water [1][2][3][4]7,9,10,12,14,29,[37][38][39]. Aqueous solutes may adsorb reversibly or irreversibly to the interior hydrogel network, hindering solute release rates by orders of magnitude.…”

Section: Introductionmentioning

confidence: 99%

Diffusion of water-soluble sorptive drugs in HEMA/MAA hydrogels

Liu

Dursch

Taylor

et al. 2016

Journal of Controlled Release

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We measure and, for the first time, theoretically predict four prototypical aqueous-drug diffusion coefficients in five soft-contact-lens material hydrogels where solute-specific adsorption is pronounced. Two-photon fluorescence confocal microscopy and UV/Vis-absorption spectrophotometry assess transient solute concentration profiles and concentration histories, respectively. Diffusion coefficients are obtained for acetazolamide, riboflavin, sodium fluorescein, and theophylline in 2-hydroxyethyl methacrylate/methacrylic acid (HEMA/MAA) copolymer hydrogels as functions of composition, equilibrium water content (30-90%), and aqueous pH (2 and 7.4). At pH2, MAA chains are nonionic, whereas at pH7.4, MAA chains are anionic (pKa≈5.2). All studied prototypical drugs specifically interact with HEMA and nonionic MAA (at pH2) moieties. Conversely, none of the prototypical drugs adsorb specifically to anionic MAA (at pH7.4) chains. As expected, diffusivities of adsorbing solutes are significantly diminished by specific interactions with hydrogel strands. Despite similar solute size, relative diffusion coefficients in the hydrogels span several orders of magnitude because of varying degrees of solute interactions with hydrogel-polymer chains. To provide a theoretical framework for the new diffusion data, we apply an effective-medium model extended for solute-specific interactions with hydrogel copolymer strands. Sorptive-diffusion kinetics is successfully described by local equilibrium and Henry's law. All necessary parameters are determined independently. Predicted diffusivities are in good agreement with experiment.

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Lysozyme transport in p-HEMA hydrogel contact lenses

Cited by 14 publications

References 23 publications

Xanthan gum: A versatile biopolymer for biomedical and technological applications

Xanthan gum: A versatile biopolymer for biomedical and technological applications

Fluorescent solute-partitioning characterization of layered soft contact lenses

Diffusion of water-soluble sorptive drugs in HEMA/MAA hydrogels

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