Contact Lens Materials Research Articles

Proteoglycan 4 and hyaluronan as boundary lubricants for model contact lens hydrogels.

Clinical data show that in vitro contact lens friction is related to in vivo comfort. Solutions of biological lubricants hyaluronan (HA) and proteoglycan 4 (PRG4, also known as lubricin) reduce friction at a cornea-polydimethylsiloxane (PDMS) interface. The purpose of this study was to (1) determine if PRG4 can sorb to and lubricate model contact lens materials and (2) assess the boundary lubricating ability of PRG4 and HA compared to saline on model contact lens materials. PRG4 was obtained from bovine cartilage culture and suspended in saline at 300µg/mL. N,N-Dimethylacrylamidetris (trimethylsiloxy) silane, (DMAA/TRIS) and methacryloxypropyltris (trimethylsiloxy) silane (pHEMA/TRIS) silicone hydrogels were prepared. A previously described in vitro eyelid-hydrogel and cornea-hydrogel biomechanical friction test was used to determine boundary lubricant effect. PRG4 sorption to the hydrogels was assessed using a soak-rinse protocol and western blotting. PRG4 effectively lubricated both silicone hydrogel materials and HA effectively lubricated pHEMA/TRIS, as indicated by a statistically significant reduction in friction compared to the saline control lubricant. An HA and PRG4 combination showed a synergistic effect for pHEMA/TRIS and effectively lubricated DMAA/TRIS. Biological boundary lubricants HA and PRG4 were shown to effectively lubricate silicone hydrogels when in solution. Additionally, HA and PRG4 showed synergistic lubrication for pHEMA/TRIS. The purpose of this study was not to replicate the friction coefficients of contact lenses, but rather to investigate lubricant-surface interactions for common contact lens constituents. These findings contribute to the potential development of biomolecule based lubricant drops for contact lens wearers. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1329-1338, 2018.

Selectivity and localization of lysozyme uptake in contemporary hydrogel contact lens materials

The purpose of this study was to investigate the early and selective uptake of lysozyme and the location of deposited lysozyme on contemporary hydrogel contact lens (CL) materials after exposure to an artificial tear solution (ATS) for 16 h. Seven different hydrogel CL materials [polymacon, omafilcon A, nelfilcon A, nesofilcon A, ocufilcon B, etafilcon A (Acuvue Moist), and etafilcon A (Acuvue Define)] were incubated in an ATS for various times. Total protein deposition was determined using a modified Bradford technique. Lysozyme, lactoferrin, and albumin deposition on CLs were determined using 125I-radiolabeling method. A confocal laser scanning microscopy (CLSM) technique was utilized to map the location of lysozyme uptake in an asymmetric environment. All lens materials had significant amounts of lysozyme after 1 min of exposure to ATS. After 16 h of incubation, higher levels of total protein deposited on the two etafilcon A-based lenses (Moist and Define), followed by ocufilcon B and both were significantly higher than all other CLs tested (p = 0.0001). The two etafilcon A materials (Moist and Define) also deposited the highest amounts of lysozyme (514.8 ± 28.4 and 527.1 ± 14.7 μg/lens respectively) when compared to other test CLs (p = 0.0001). The CLSM technique revealed that the non-ionic CLs tended to have symmetric distribution of lysozyme throughout the lens materials, while the ionic CLs had an asymmetric distribution, with the highest concentration of lysozyme on and near the exposed surface. The quantity and nature of proteins deposited on CLs varies, depending upon the chemical composition of the material. Among the various lenses tested, etafilcon A deposited the highest amount of total protein, most of it represented by lysozyme, which was largely located near the surface of the lens.

Influence of silicone distribution and mobility on the oxygen permeability of model silicone hydrogels

In order to understand the influence of composition on oxygen permeability, the morphology of model silicone hydrogels in both the dry and hydrated states was characterized using a variety of techniques (AFM, HAADF-STEM, solid-state NMR, and X-ray scattering). The model system studied is heterogeneous on length scales below 20 nm and consists of globular silicone-rich domains that rearrange in response to changes in hydration. In contrast to the well-defined morphologies of block copolymer systems, these radically cured amphiphilic networks are less ordered, showing gradual composition fluctuations. Comprehensive morphology characterization rationalizes the transport behavior of these heterogeneous hydrogels: the non-linear permeability increase with increasing silicone monomer content is not only related to changes in the spatial arrangement of silicone-rich domains but also to their mobility. This understanding is needed for further optimizing soft contact lens materials where oxygen transport and optical clarity are critical features.

Sterilization of silicone-based hydrogels for biomedical application using ozone gas: Comparison with conventional techniques

Sterilization of hydrogels is challenging due to their often reported sensitivity to conventional methods involving heat or radiation. Although aseptic manufacturing is a possibility, terminal sterilization is safer in biological terms, leading to a higher overall efficiency, and thus should be used whenever it is possible.The main goal of this work was to study the applicability of an innovative ozone gas terminal sterilization method for silicone-based hydrogels and compare its efficacy and effects with those of traditional sterilization methods: steam heat and gamma irradiation. Ozone gas sterilization is a method with potential interest since it is reported as a low cost green method, does not leave toxic residues and can be applied to thermosensitive materials.A hydrogel intended for ophthalmological applications, based on tris(trimethylsiloxy)silyl] propyl methacrylate, was prepared and extensively characterized before and after the sterilization procedures. Alterations regarding transparency, swelling, wettability, ionic permeability, friction coefficient, mechanical properties, topography and morphology and chemical composition were monitored. Efficacy of the ozonation was accessed by performing controlled contaminations and sterility tests. In vitro cytotoxicity testes were also performed.The results show that ozonation may be applied to sterilize the studied material. A treatment with 8 pulses allowed sterilizing the material with bioburdens≤103CFU/mL, preserving all the studied properties within the required known values for contact lenses materials. However, a higher exposure (10 pulses) led to some degradation of the material and induced mild cytotoxicity. Steam heat sterilization led to an increase of swelling capacity and a decrease of the water contact angle. Regarding gamma irradiation, the increase of irradiation dose led to an increase of the friction coefficient. The higher dose (25kGy) originated surface degradation and affected the mechanical properties of the hydrogel by inducing a significant increase of the Young's modulus.Overall, the results show that ozonation may be considered as a valid and promising alternative for the sterilization of silicon-based hydrogels for biomedical applications.

Raman imaging of layered soft contact lenses.

Daily disposable contact lenses are gaining in popularity among practitioners and wearers for the improved ocular health and subjective outcomes they offer. Recently a novel daily disposable contact lens material with water gradient technology was introduced. Delefilcon A lenses consist of a 33% water content silicone hydrogel core and an outer hydrogel layer which is totally free of silicone and contains 80% water. The aim of the present study was to confirm the layered structure of delefilcon A contact lenses. Thickness of hydrogel coating on the silicone hydrogel core was assessed using Raman spectroscopy. To investigate the layered structure of the material, depth spectra of the lenses were recorded. The results obtained suggest that at about 6 μm a boundary between the hydrogel layer and silicone hydrogel core exists, which is in good agreement with the manufacturer's data. Data collected in this experiment confirm a water gradient at the delefilcon A lens surface.

A sensitive and disposable indium tin oxide based electrochemical immunosensor for label-free detection of MAGE-1

MAGE-1 (MAGE, for melanoma antigen), was identified by virtue of its processing and cell surface expression as a tumor-specific peptide bound to major histocompatibility complexes which was reactive with autolytic T cells. 3-Glycidoxypropyltrimethoxysilane (3-GOPS) is frequently employed for the preparation of dense heterometal hybrid polymers which are used, e.g., for hard coatings of organic polymers and contact lens materials in the optical industry.In this study, we have improved a new immunological biosensor with indium tin oxide (ITO). Then, Anti-MAGE-1 antibody was covalently immobilized with 3-GOPS which formed a self-assembled monolayers (SAMs) on modified ITO electrodes. Analytical characteristics such as square wave voltammetry, linear determination range, repeatability, reproducibility and regeneration of biosensors are determined. All characterization steps are monitored by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV).The developed biosensor has wide determination range (0.5fg–15fg/mL). To investigate long shelf life of the fabricated biosensor, the immunosensors were stored at 4°C for periods ten weeks. Futhermore, binding kinetics of MAGE1 to antiMAGE-1 is monitored by single frequency technique in real time. Additionally, Kramer's-Kronig transform was used to understand whether the impedance spectra of biosensor system are affected from the variation that occurred because of external factor. Morphological characteristics of constructed biosensor were observed by scanning electron microscopy. Real human serum samples were also analyzed by the proposed biosensor, successfully. A commercial ELISA kit was also used as a reference method to validate the results obtained by the biosensor.Finally, this biosensor was tried in real blood sample and that showed it could be utilized in clinical applications. This biosensor can be preferred due to it has a wide linear range and it can be prepared easily.

The nature and consequence of vitronectin interaction in the non-compromised contact lens wearing eye.

The aim of this work was to investigate the locus and extent of vitronectin (Vn) deposition on ex vivo contact lenses and to determine the influence of wear modality together with surface and bulk characteristics of the lens material. The quantity and location of Vn deposition on the surfaces of contact lens materials was investigated using a novel on-lens cell attachment assay technique. Vn mapping showed that deposition resulted from lens-corneal interaction rather than solely from the tear film. Higher cell counts on the posterior surface of the lenses were determined in comparison to the anterior surface. Overall gross Vn deposition was greater for high water content-low modulus materials (117±4 average cell count per field) than low water content-high modulus materials (88±6 average cell count per field). The role of Vn in plasmin regulation and upregulation is widely recognised. The findings in this paper suggest that the locus of Vn on the contact lens surface, which is affected by material properties such as modulus, is potentially an important factor in the generation of plasmin in the posterior tear film. Consequently, the potential for materials to affect Vn deposition will influence lens-induced inflammatory processes.

Impact of Contact Lens Material, Design, and Fitting on Discomfort.

To review the effect of contact lens (CL) material, design, and fitting characteristics on CL discomfort. A PubMed search identified publications describing subjective comfort and CL material, fitting, and design parameters. The review included clinical signs associated with discomfort that may be a consequence of these parameters. Reduced lens movement or more CL tightness were associated with improved comfort. Increased lens-induced paralimbal conjunctival staining and indentation, considered as quasi-indicators of CL fitting or edge design, were also associated with better comfort. No recent studies have evaluated varying CL design parameters and subjective comfort. Silicone hydrogel CLs are no different in comfort compared with hydrogel CLs. Lower equilibrium water content is associated with improved comfort in hydrogel CL wear. Coefficient of friction shows promise as a material factor potentially associated with comfort. Lid wiper epitheliopathy and lid-parallel conjunctival folds have been linked with comfort in established wearers. Recent studies have confirmed the association between more mobile CLs and more discomfort, whereas closer conformity of the CL to the bulbar conjunctiva improved subjective comfort. There is no evidence to support the perceived comfort difference between silicone hydrogel and hydrogel CL. There has been limited progress in understanding the impact of varying specific CL design parameters. Although specific clinical signs may be predictive of discomfort, their role in the natural history of discomfort remains unclear. A better understanding of the relationship between coefficient of friction and comfort and strategies to improve lubricity may hold promise for limiting CL discomfort.

Modeling soft, permeable matter with the proper generalized decomposition (PGD) approach, and verification by means of nanoindentation.

Understanding sliding and load-bearing mechanisms of biphasic soft matter is crucial for designing synthetic replacements of cartilage, contact-lens materials or coatings for medical instruments. Interstitial fluid pressurization is believed to be the intrinsic load-carrying phenomenon governing the frictional properties. In this study, we have characterized permeability and identified the fluid contribution to the support of load during Atomic Force Microscopy (AFM) nanoindentation of soft polymer brushes in aqueous environments, by means of the Proper Generalized Decomposition (PGD) approach. First, rate-dependent AFM nanoindentation was performed on a poly(acrylamide) (PAAm) brush in an aqueous environment, to probe the purely elastic as well as poro-viscoelastic properties. Second, a biphasic model decoupling the fluid and solid load contributions was proposed, using Darcy's equation for liquid flow in porous media. Using realistic time-dependent simulations requires many direct solutions of the 3D partial differential equation, making modeling very time-consuming. To efficiently alleviate the time-consumption of multi-dimensional modeling, we used PGD to solve a Darcy model defined in a 7D domain, considering all the unknowns and material properties as extra coordinates of the problem. The obtained 7D simulation results were compared to the experimental results by using a direct Newton algorithm, since all sensitivities with respect to the model parameters are readily available. Thus, a simulation-based solution for depth- and rate-dependent permeability can be obtained. From the PGD-based model permeability is calculated, and the velocity- and pressure-fields in the material can be obtained in real-time in 3D by adjusting the parameters to the experimental values. The result is a step forward in understanding the fluid flow, permeability and fluid contributions to the load support of biphasic soft matter.

End-of-day friction of 1-day contact lens materials

End-of-day friction of 1-day contact lens materials

Mechanical properties of contact lenses: The contribution of measurement techniques and clinical feedback to 50 years of materials development.

This review summarises the way in which mechanical property measurements combined with clinical perception have influenced the last half century of materials evolution in contact lens development. Literature concerning the use of in-vitro testing in assessment of the mechanical behaviour of contact lenses, and the mutual deformation of the lens material and ocular tissue was examined. Tensile measurements of historic and available hydrogel lenses have been collected, in addition to manufacturer-generated figures for the moduli of commercial silicone hydrogel lenses. The three conventional modes of mechanical property testing; compression, tension and shear each represent different perspective in understanding the mutual interaction of the cornea and the contact lens. Tensile testing provides a measure of modulus, together with tensile strength and elongation to break, which all relate to handling and durability. Studies under compression also measure modulus and in particular indicate elastic response to eyelid load. Studies under shear conditions enable dynamic mechanical behaviour of the material to be assessed and the elastic and viscous components of modulus to be determined. These different methods of measurement have contributed to the interpretation of lens behaviour in the ocular environment. An amalgamated frequency distribution of tensile moduli for historic and currently available contact lens materials reveals the modal range to be 0.3-0.6MPa. Mechanical property measurements of lens materials have enabled calibration of an important aspect of their ocular interaction. This together with clinical feedback has influenced development of new lens materials and assisted clinical rationalisation of in-eye behaviour of different lenses.

소프트콘택트렌즈 재질과 착색에 따른 눈물성분 침착과 칸디다균 흡착의 상관관계

목적: 본 연구에서는 소프트콘택트렌즈의 재질 특성과 착색 여부가 눈물 성분이 침착된 소프트콘택트렌즈에 칸디다균 흡착에 미치는 영향을 알아보았다. 방법: Etafilcon A, hilafilcon B, nelfilcon A 재질의 투명 소프트콘택트렌즈와 써클 소프트콘택트렌즈를 대상으로 하여 인공눈물에 침착시키기 전과 후의 흡착 균 수를 측정하였다. 또한, 주사전자현미경을 통해 렌즈에 흡착된 균을 관찰하였다. 결과: 칸디다균의 흡착은 콘택트렌즈 재질에 따라 통계적으로 유의하게 차이가 있었다. Etafilcon A 재질에서는 투명 소프트콘택트렌즈와 써클 콘택트렌즈간 균 흡착양 차이가 없었으며, hilafilcon B 및 nelfilcon A 재질에서는 써클 소프트콘택트렌즈에 흡착된 균 수가 다소 많았다. 투명 중심부와 착색부를 비교하였을 때 투명 중심부에 칸디다균 흡착이 더 많았으며, 투명 중심부와 투명 주변부를 비교하였을 때 투명 주변부에서의 균 흡착양이 더 많았다. 눈물 단백질이 침착되었을 경우 흡착된 칸디다균의 수가 감소하였으며 눈물 단백질의 칸디다균에 대한 항균력 유지는 재질에 따라 차이가 있어 etafilcon A 재질 렌즈에서 유지 기간이 가장 길었다. 결론: 본 연구에서는 소프트콘택트렌즈의 재질 특성, 착색여부 및 부위에 따라 흡착되는 칸디다균수가 달라진다는 것을 밝혔으며, 칸디다균의 흡착 특성에 따라 관리 방법을 달리해야 할 것을 제안한다. Purpose: The aim of this study was to figure out how the characteristics of soft contact lens materials and pigmentation affect the adherence of C. albicans on soft contact lenses pre-deposited with tear constituents. Methods: The adherent number of C. albicans on clear soft contact lenses (hereinafter clear lenses) and circle soft contact lenses (hereinafter circle lenses) made of etafilcon A, hilaiflcon B and nelfilcon A, respectively, was measured before and after the deposition of artificial tear. Also, bacteria adherence on lenses were observed by a scanning electron microscope. Results: Adherence of C. albicans was significantly different according to lens materials. The amount of adsorption was not different between clear lenses and circle lenses made of etafilcon A however, the number of bacteria absorption was bigger in hilafilcon B and nelfilcon A lenses. More absorption of C. albicans was found in the non-pigmented central area compared the pigmented area, and non-pigmented peripheral area has more bacterial absorption than non-pigmented central area. The number of C. albicans decreased in the case that tear protein was pre-deposited. The maintenance of antibacterial activity against C. albicans was different according to lens materials thus, etafilcon A has the longest period of its maintenance. Conclusions: It was revealed that the number of C. albicans was different according to the characteristics of lens materials, pigmentation or non-pigmentation, the pigmented area of soft contact lenses. Thus, it is suggested that the management method should be different according to the adsorption characteristics of C. albicans.

A Survey of Presbyopic Contact Lens Wearers in a University Setting.

To determine why presbyopic patients discontinue contact lens wear and describe their opinions of comfort and visual quality with contact lenses. A survey assessing current age, gender, contact lens material/design, and opinions of contact lens comfort and visual quality was mailed to 2400 presbyopic patients (age 40 years and older) that have had eye exams in the Ohio State University College of Optometry's Contact Lens Services over the last 4 years. A total of 496 surveys were analyzed. The mean age of survey respondents was 57 ± 9 years, and 68% of the sample was female. Permanent discontinuation of contact lens wear was reported by 15%. No association was found between contact lens discontinuation and age (p = 0.7), gender (p = 0.2), age of beginning contact lens wear (p = 0.1), or contact lens material (p = 0.1). Poor vision (38%), discomfort (34%), convenience (20%), and cost (6%) were the primary reported reasons for discontinuation. There was no difference between the proportion of subjects reporting "poor vision" as their primary discontinuation reason and those reporting "discomfort" (p = 0.7). Discontinued wearers had a worse overall opinion of their distance (p = 0.03), intermediate (p = 0.01), and near vision (p = 0.002) compared to subjects who were still wearing their contact lenses. Discomfort has been reported as the primary reason for contact lens discontinuation. In this presbyopic population, dissatisfaction with vision and discomfort were reported equally as often as primary reasons for discontinuation. As well, subjects who ceased contact lens wear had worse overall opinions of their vision at all distances than current contact lens wearers. The results of this survey suggest that presbyopes have unique demands and opinions related to contact lens wear.

Impact of Lens Care Solutions on Protein Deposition on Soft Contact Lenses.

To evaluate the effect of four contemporary lens care solutions on total protein, total lysozyme, and active lysozyme extracted from three contact lens materials. Adapted contact lens wearers were recruited at three sites, and all subjects were randomly assigned to daily wear of either etafilcon A, galyfilcon A, or senofilcon A for 2 weeks. Four lens care solutions (Biotrue, OPTI-FREE PureMoist, RevitaLens OcuTec, and ClearCare) were used by each subject in random order with a new pair of lenses after a washout period between solutions of at least 4 days. After 2 weeks of daily wear, contact lenses were collected for analysis. Proteins were extracted from a subset of contact lenses (n = 568) and total protein, total lysozyme, and lysozyme activity were quantified using a modified Bradford assay, an enzyme-linked immunosorbent assay, and a micrococcal assay, respectively. Higher levels of total protein were extracted from etafilcon A when used with Biotrue compared to other solutions (p = 0.0001). There were higher levels of total lysozyme extracted from galyfilcon A lenses when used with PureMoist than with Biotrue or ClearCare (p < 0.006). Higher total lysozyme was extracted from senofilcon A when used with RevitaLens OcuTec compared to Biotrue (p = 0.002). Lower lysozyme activity was recovered from senofilcon A lenses with RevitaLens OcuTec when compared to all other care solutions (all p < 0.004). When Biotrue, PureMoist, or RevitaLens OcuTec were used, higher total lysozyme was extracted from galyfilcon A compared to senofilcon A (p < 0.01). When RevitaLens OcuTec was used, higher levels of active lysozyme were extracted from galyfilcon A compared to senofilcon A (p = 0.02). The ability of lens care solutions to remove protein from lenses varies depending upon the care solution composition and also the polymeric make-up of the contact lens material.

A Systemic Review on Ophthalmic Hydrogel in Contact Lenses

There has been a recent advances in the field of microbiology where hydrogels contact lenses can be extend as the new ophthalmic drug delivery. Rather than the conventional eye drops, these hydrogels can minimize the side effect also prolonged the residence time of drug. Hydrogels are three-dimensional, hydrophilic, and polymeric networks capable of absorbing great volume of water and biological fluid. Hydrogel becomes the leading material for contact lenses because its biocompatibility and transparent characteristic. The purpose of this article is to review on few types of ophthalmic hydrogel in contact lenses and its application.

Chitosan/alginate based multilayers to control drug release from ophthalmic lens

In this study we investigated the possibility of using layer-by-layer deposition, based in natural polymers (chitosan and alginate), to control the release of different ophthalmic drugs from three types of lens materials: a silicone-based hydrogel recently proposed by our group as drug releasing soft contact lens (SCL) material and two commercially available materials: CI26Y for intraocular lens (IOLs) and Definitive 50 for SCLs. The optimised coating, consisting in one double layer of (alginate – CaCl2)/(chitosan+glyoxal) topped with a final alginate-CaCl2 layer to avoid chitosan degradation by tear fluid proteins, proved to have excellent features to control the release of the anti-inflammatory, diclofenac, while keeping or improving the physical properties of the lenses. The coating leads to a controlled release of diclofenac from SCL and IOL materials for, at least, one week. Due to its high hydrophilicity (water contact angle≈0) and biocompatibility, it should avoid the use of further surface treatments to enhance the useŕs comfort. However, the barrier effect of this coating is specific for diclofenac, giving evidence to the need of optimizing the chemical composition of the layers in view of the desired drug.

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

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.

Visualization of a hyaluronan network on the surface of silicone-hydrogel materials.

Biotrue multipurpose solution (MPS) is a bioinspired disinfecting and conditioning solution that includes hyaluronic acid (HA) as a natural wetting agent. Previous studies demonstrated that HA sorbed from Biotrue MPS on both conventional and silicone hydrogel (SiHy) contact lens materials; an in vitro simulated-wear test validated the presence of HA on the lens surfaces for as long as 20 hours. In this study, the morphology and distribution of HA sorbed from both Biotrue and pure HA solution on SiHy contact lens surfaces was examined. Atomic force microscopy imaging was used to illustrate the topography of fresh SiHy contact lens materials before and after incubation with 0.1% (w/v) HA solution. The distribution, as well as fine details of the HA network, were resolved by first staining HA with Gram’s safranin, then imaging with confocal laser-scanning microscopy and differential interference-contrast microscopy. In this approach, SiHy materials take up the dye (safranin) nonspecifically, such that the resultant safranin–HA complex appears dim against the fluorescent lens background. Balafilcon A was chosen as the representative of glassy SiHy lenses that require postpolymerization plasma treatment to increase wettability. Senofilcon A and samfilcon A were chosen as representatives of SiHy materials fabricated with an internal wetting agent. A confluent and dim HA–safranin network was observed adhered to balafilcon A, senofilcon A, and samfilcon A lens surfaces incubated with either 0.1% (w/v) HA solution or Biotrue MPS. Therefore, the conditioning function provided by Biotrue MPS may be in part explained by the presence of the HA humectant layer that readily sorbs on the various types of SiHy contact lens materials.

Drug release from liposome coated hydrogels for soft contact lenses: the blinking and temperature effect.

In this article, liposome-based coatings aiming to control drug release from therapeutic soft contact lenses (SCLs) materials are analyzed. A PHEMA based hydrogel material loaded with levofloxacin is used as model system for this research. The coatings are formed by polyelectrolyte layers containing liposomes of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and DMPC + cholesterol (DMPC + CHOL). The effect of friction and temperature on the drug release is investigated. The aim of the friction tests is to simulate the blinking of the eyelid in order to verify if the SCLs materials coated with liposomes are able to keep their properties, in particular the drug release ability. It was observed that under the study conditions, friction did not affect significantly the drug release from the liposome coated PHEMA material. In contrast, increasing the temperature of release leads to an increase of the drug diffusion rate through the hydrogel. This phenomenon is recorded both in the control and in the coated samples. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1799-1807, 2017.

Remanent magnetization measurements of polymeric materials containing fullerol C60(OH)24 before and after exposure to external magnetic field

ABSTRACTThe problem of low solubility of fullerene is surpassed by its functionalization with –OH groups making a new molecule called fullerol C60(OH)24. Materials used in this study are synthesized by incorporating fullerol into commercial soft contact lens material Definitive74 made by Contamac, UK. Three different mass concentrations of fullerol are used: 0.003%, 0.01% and 0.015%. Hence, three materials are produced and the fourth material, the standard one, was used as a reference sample. The purpose of incorporating fullerol into polymer was to develop new materials for soft contact lenses with improved optical and mechanical characteristics. The magnetic properties of polymers change due to fullerol presence therefore the aim was to show the differences in magnetic properties of the materials before and after the exposure to four different external influences. The measurements of a remanent magnetization of these materials are done by spinner magnetometer, JR-6A.