HEMA Hydrogel Research Articles

PH-Responsive removal of dyes from wastewater using MXene composited L-Cysteine-grafted HEMA hydrogel: Dynamics, selectivity, regeneration and mechanism

In this work, a MXene composited cysteine-grafted hydroxyethyl methacrylate hydrogel (PHGC/MXene) was successfully synthesized, exhibiting excellent cycle stability and high selectivity toward ionic dyes at different pH. In mixed dyes system, PHGC/MXene exhibited remarkable adsorption selectivity and excellent property of pH-responsivenes for methyl blue (AB93) at pH=2.0 and for methylene blue (MB) at pH=11.0, with maximum adsorption capacity of 207.47 mg/g and 555.56 mg/g, respectively. Even after 12 desorption-regeneration cycles, the removal rates for AB93 and MB remained above 90 %. The study further analyzed the dynamic fixed-bed adsorption behavior of PHGC/MXene for MB, revealing optimal conditions at an inlet concentration of 75 mg/L MB dye and a bed depth of 9 cm. The adsorption mechanism was proposed combined with molecular dynamics simulations. PHGC/MXene emerges as an easily synthesized, highly selective adsorbent with significant potential for the purification of dyes from wastewater in both strongly acidic and strongly alkaline environments.

Hydrogels for Textile Applications - Review

Hydrogels are widely used in biomedical area of research. Hydrogels are usually used in fabrication of contact lenses, hygiene products, biosensors, wound dressings, and tissue engineering applications. The polymer 2-hydroxyethyl methacrylate (HEMA) based hydrogel synthesis and their use in textiles industry was also reviewed. Poly-Hema is a soft, flexible, water absorbing plastic used in making soft contact lenses. HEMA is a clear liquid compound obtained by reacting methacrylic acid with ethylene oxide or propylene oxide. HEMA and polymer hydrogel filler are used for soft tissue reconstruction by facile polymerization. The synthesis of random copolymer including HEMA through free radical polymerization is also reviewed. Polymeric fillers are widely used as an alternative for breast reconstruction materials. This review focuses on recent advancements in several types of biomedical hydrogels including conductive hydrogels, injectable, responsive, nanocomposite hydrogels, etc. Thermo responsive hydrogels use temperature as external stimulus to show sol-gel transition and they can form hydrogel around the body temperature. Textile based transdermal therapy is currently being applied using drug loaded thermoresponsive hydrogel. Hydrogels made by natural and synthetic polymers for textile based transdermal treatments are mentioned.

The effect of heterobifunctional crosslinkers on HEMA hydrogel modulus and toughness.

The use of hydrogels in load bearing applications is often limited by insufficient toughness. 2-Hydroxyethyl methacrylate (HEMA) based hydrogels are appealing for translational work, as they are affordable and the use of HEMA is FDA approved. Furthermore, HEMA is photopolymerizable, providing spatiotemporal control over mechanical properties. We evaluated the ability of vinyl methacrylate (VM), allyl methacrylate (AM), and 3-(Acryloyloxy)-2-hydroxypropyl methacrylate (AHPM) to tune hydrogel toughness and Young’s modulus. The crosslinkers were selected due to their heterobifunctionality (vinyl and methacrylate) and similar size and structure to EGDMA, which was shown previously to increase toughness as compared to longer crosslinkers. Vinyl methacrylate incorporation into HEMA hydrogels gave rise to hydrogels with Young’s moduli spanning ranges for ligament to cartilage, with a peak toughness of 519 ± 70 kJ/m3 under physiological conditions. We report toughness (work of extension) as a function of modulus and equilibrium water content for all formulations. The hydrogels exhibited 80%-100% cell viability, which suggests they could be used in tissue engineering applications.

Development of poly(2-hydroxyethyl methacrylate)/clay composites as drug delivery systems of paracetamol

In this work the synthesis of hydrogel/clay nanocomposites based on poly(2-hydroxyethyl methacrylate) (HEMA) has been performed through in situ free radical polymerization in order to examine their potential use in biomedical applications as drug carriers. 2-hydroxyethyl methacrylate monomer has been intercalated into the interlayer spaces of a clay mineral using sodium montmorillonite (MMT) nanoparticles and then polymerized. The influence of different amounts of MMT on the structural properties of the resulting novel materials HEMA/MMT was investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). X ray diffraction analysis has been used to evaluate the state of dispersion of the clay particles in the hydrogel matrix. TGA, DSC and swelling results have revealed that the clay sheets acted as effective multifunctional cross-linkers. Paracetamol incorporation efficiency in the HEMA/MMT hydrogels was determined by UV–vis spectroscopy. The DSC study revealed an amorphization of paracetamol in the drug loaded hydrogel. The effect of varying the concentration of MMT within the hydrogel was investigated to obtain optimum conditions to control the drug release. The burst effect was significantly reduced and the releasing equilibrium time was extended in the nanocomposites HEMA/MMT in comparison to the HEMA hydrogel.

Corneal health and contact lens wear: Ion chromatography as an electrolyte probe

Purpose: Tear osmolarity and the concentrations of ocular electrolytes in the eye are known to influence corneal health. Similarly, corneal cells are known to be sensitive to changes in electrolyte balance. Ion transport through contact lenses can influence electrolyte equilibration between preand post-lens tear film. Until now no suitable technique has been identified to quantify these effects. This study utilised ion chromatography to examine multiple ion transport through lenses and the measurement of ex-vivo tear samples. Methods:AmodifiedDionex ion chromatographenabled simultaneous measurement of Na+/K+/Ca2+ and Mg2+ concentrations in both single (5 l) tear samples and lens/membrane permeation studies. In addition to commercial contact lenses, conventional HEMA membranes (40% water) and acrylamide-based corneal model hydrogel membranes (ca 90% water) were mounted in purpose-designed permeability cells and the transport of mixed electrolytes (e.g. 0.25M NaCl, KCl and CaCl2) measured. Results: In baseline studies, the relative ratio of the main tear cations measured in healthy tear film samples was found to be Na+:K+:Ca2+:Mg2+ =140:11:1.2:1. This accord with the observation that the range of K+ concentrations in tears (ca 15–30mM) is high and Ca2+ and Mg2+ concentrations (ca 0.4–0.8 and 0.5–1.1mM) is low, relative to serum. The relative permeability coefficients of lenses and membranes were consistent (i.e. NaCl <KCl » CaCl2) ranging between 141.2×10−7: 148.2×10−7: 98.2×10−7 cm2/s (±5% for 90% acrylamide based hydrogel) and 2.8×10−7:3.2×10−7:0.7×10−7 cm2/s (±5% for 40% HEMA hydrogel). Conclusions: Ion chromatography enables tear electrolytes to be accurately monitored in 5 l samples. This, coupled with tear envelope sampling, provides a means of correlating clinical signs and symptoms with post-lens electrolyte concentrations and the ion permeability coefficients of individual lenses. Anisa Mahomed completed an MEng in Chemical Engineering and then obtained her PhD from the Biomaterials Research Group at Aston University. Her thesis discussed the aspects of the fabrication of novel hydrogels for dermal and ocular applications. She is currently a postdoctoral researcher and her interests include investigating factors that affect the uptake, release and transport of various species from hydrogels and developing analytical techniques to enable the understanding of clinical adverse events related to the use multipurpose solutions.

Plasma protein influx in contact lens wear

Purpose: Tear osmolarity and the concentrations of ocular electrolytes in the eye are known to influence corneal health. Similarly, corneal cells are known to be sensitive to changes in electrolyte balance. Ion transport through contact lenses can influence electrolyte equilibration between preand post-lens tear film. Until now no suitable technique has been identified to quantify these effects. This study utilised ion chromatography to examine multiple ion transport through lenses and the measurement of ex-vivo tear samples. Methods:AmodifiedDionex ion chromatographenabled simultaneous measurement of Na+/K+/Ca2+ and Mg2+ concentrations in both single (5 l) tear samples and lens/membrane permeation studies. In addition to commercial contact lenses, conventional HEMA membranes (40% water) and acrylamide-based corneal model hydrogel membranes (ca 90% water) were mounted in purpose-designed permeability cells and the transport of mixed electrolytes (e.g. 0.25M NaCl, KCl and CaCl2) measured. Results: In baseline studies, the relative ratio of the main tear cations measured in healthy tear film samples was found to be Na+:K+:Ca2+:Mg2+ =140:11:1.2:1. This accord with the observation that the range of K+ concentrations in tears (ca 15–30mM) is high and Ca2+ and Mg2+ concentrations (ca 0.4–0.8 and 0.5–1.1mM) is low, relative to serum. The relative permeability coefficients of lenses and membranes were consistent (i.e. NaCl <KCl » CaCl2) ranging between 141.2×10−7: 148.2×10−7: 98.2×10−7 cm2/s (±5% for 90% acrylamide based hydrogel) and 2.8×10−7:3.2×10−7:0.7×10−7 cm2/s (±5% for 40% HEMA hydrogel). Conclusions: Ion chromatography enables tear electrolytes to be accurately monitored in 5 l samples. This, coupled with tear envelope sampling, provides a means of correlating clinical signs and symptoms with post-lens electrolyte concentrations and the ion permeability coefficients of individual lenses. Anisa Mahomed completed an MEng in Chemical Engineering and then obtained her PhD from the Biomaterials Research Group at Aston University. Her thesis discussed the aspects of the fabrication of novel hydrogels for dermal and ocular applications. She is currently a postdoctoral researcher and her interests include investigating factors that affect the uptake, release and transport of various species from hydrogels and developing analytical techniques to enable the understanding of clinical adverse events related to the use multipurpose solutions.

Hemocompatibility and cytocompatibility of styrenesulfonate-grafted PDMS–polyurethane–HEMA hydrogel

Copolymerization of polydimethylsiloxane, polyurethane, and hydroxyethyl methacrylate (PDMS–PU–HEMA) hydrogel was performed. After treating with oxygen plasma, the sodium salt of 4-styrenesulfonic acid (NASS) was grafted onto the hydrogel in a one-step process. The surface density of peroxide active groups was determined by the iodide method. The hydrophilicity of the hydrogels surface was evaluated by measuring the water contact angle and water retention. The result demonstrated that oxygen plasma treatment and NASS grafting can improve the hydrophilicity. In addition, in order to evaluate cell compatibility, L929 fibroblasts cells were cultured on the surface of these hydrogels and the cell number was determined by the MTT testing. The results show that plasma treatment and NASS grafting can cause higher cell adhesion and cell growth rates than untreated PDMS–PU–HEMA. Furthermore, NASS grafting can also reduce the platelet adhesion and protein adsorption, hence effectively extending the blood coagulation times. Consequently hydrophilicity, cytocompatibility and hemocompatibility were greatly enhanced by the NASS grafting of PDMS–PU–HEMA.

Behaviour of human mesenchymal stem cells on a polyelectrolyte-modified HEMA hydrogel for silk-based ligament tissue engineering

The aim of this study was to design a functional bio-engineered material to be used as scaffold for autologous mesenchymal stem cells in ligament tissue engineering. Polyelectrolyte modified HEMA hydrogel (HEMA-co-METAC), applied as coating on silk fibroin fibres, has been formulated in order to take advantage of the biocompatibility of the polyelectrolyte by increasing its mechanical properties with silk fibres. Human bone marrow mesenchymal stem cells behaviour on such reinforced polyelectrolyte has been studied by evaluating cell morphology, cell number, attachment, spreading and proliferation together with collagen matrix production and its mRNA expression. Silk fibroin fibres matrices with HEMA-co-METAC coating exhibited acceptable mechanical behaviour compared to the natural ligament, good human mesenchymal stem cell adhesion and with mRNA expression studies higher levels of collagen types I and III expression when compared to control cells on polystyrene. These data indicate high expression of mRNA for proteins responsible for the functional characteristics of the ligaments and suggest a potential for use of this biomaterial in ligament tissue-engineering applications.

Formulation optimization of photocrosslinked polyacrylic acid modified with 2-hydroxyethyl methacrylate hydrogel as an adhesive for a dermatological patch

A photopolymerization technique was applied in the preparation of a hydrogel composed of polyacrylic acid (PAA) in which 2-hydroxyethyl methacrylate (HEMA) was modified. The formulation of photocrosslinked PAA modified with HEMA hydrogel as an adhesive for a dermatological patch was optimized based on the simultaneous optimization technique. Photocrosslinked PAA modified with HEMA hydrogels that retained a large amount of water, above 85%, were successfully prepared. Based on the analysis of ANOVA, the gel strength and adhesiveness increased with an increase in the degree of modification with HEMA and the concentration of PAA modified with HEMA in the aqueous solution. For the optimization study, the modification with HEMA and the concentration of initiator were selected as causal factors. Gel yield, probe tack, degree of swelling and turbidity were selected as response variables. A set of causal factors and response variables was used as a tutorial date for the prediction of optimal formulation with a quadratic regression model, an artificial neural network (ANN) and a multivariate spline interpolation (MSI). Response surfaces generated with MSI well represented the nonlinear relationship between the factors and the responses, and all the observed values of the response variables coincided with the predictions. A high functional photocrosslinked PAA modified with HEMA hydrogel as an adhesive for a dermatological patch was successfully created using the simultaneous optimization technique incorporating MSI.

Transcorneal and transscleral iontophoresis of dexamethasone phosphate using drug loaded hydrogel

Purpose To evaluate dexamethasone penetration to the eye after a short transcorneal and transscleral iontophoresis using a drug loaded hydrogel assembled on a portable iontophoretic device. Methods Iontophoresis of dexamethasone phosphate was studied in healthy rabbits using drug loaded disposable HEMA hydrogel sponges and portable iontophoretic device. Corneal iontophoretic administration was performed with a current intensity of 1 mA for 1 and 4 min. Transconjunctival and transscleral iontophoresis were performed twice for 2 min at two near places in the pars-plana area, on the conjunctival membrane or directly on the sclera. Dexamethasone concentrations were assayed using HPLC. Results Dexamethasone levels in the rabbit cornea after a single transcorneal iontophoresis for 1 min were up to 30 fold higher compared to those obtained after frequent eye drop instillation. Also, high drug concentrations were obtained in the retina and sclera 4 h after transscleral iontophoresis. Conclusions A short low current non-invasive iontophoretic treatment using dexamethasone-loaded hydrogels has potential clinical value in increasing drug penetration to the anterior and posterior segments of the eye.

Meshless steady-state analysis of chemo-electro-mechanical coupling behavior of pH-sensitive hydrogel in buffered solution

The objective of the present study is to simulate the phenomenological behavior of the pH-sensitive hydrogels when the pH of their buffered aqueous environment is changed. A chemo-electro-mechanical formulation, referred to as the multi-effect-coupling pH-stimulus (MECpH) model, is also presented. This mathematical model, consisting of coupled nonlinear partial differential equations, takes account of the diffusion of ionic species, electric potential coupling and mechanical equilibrium deformation. On top of that, the correlation between diffusive hydrogen ion and charge groups fixed to the hydrogel polymeric chains is quantitatively incorporated into the MECpH model. As a novel meshless technique, the Hermite–Cloud method is employed to solve one-dimensional steady-state problems. For examination of the MECpH model, the computed results are compared numerically with experimental data available from literature, in which transitional volume changes in the HEMA hydrogel are studied when the environmental solution is in the range of pH 4.5–7.5. The comparisons validate the accuracy and robustness of the MECpH model. Additionally, several numerical studies are carried out to simulate the swelling hydrogel immersed in buffered solution. It is observed that the fixed-charge groups and the mechanical properties of the pH-stimulus-responsive hydrogel have significant influences on the volume variations of the hydrogels.

Dispersion of microemulsion drops in HEMA hydrogel: a potential ophthalmic drug delivery vehicle

Approximately 90% of all ophthalmic drug formulations are now applied as eye-drops. While eye-drops are convenient and well accepted by patients, about 95% of the drug contained in the drops is lost due to absorption through the conjunctiva or through the tear drainage. A major fraction of the drug eventually enters the blood stream and may cause side effects. The drug loss and the side effects can be minimized by using disposable soft contact lenses for ophthalmic drug delivery. The essential idea is to encapsulate the ophthalmic drug formulations in nanoparticles, and disperse these drug-laden particles in the lens material. Upon insertion into the eye, the lens will slowly release the drug into the pre lens (the film between the air and the lens) and the post-lens (the film between the cornea and the lens) tear films, and thus provide drug delivery for extended periods of time. This paper focuses on dispersing stabilized microemulsion drops in poly-2-hydroxyethyl methacrylate (p-HEMA) hydrogels. The results of this study show that the p-HEMA gels loaded with a microemulsion that is stabilized with a silica shell are transparent and that these gels release drugs for a period of over 8 days. Contact lenses made of microemulsion-laden gels are expected to deliver drugs at therapeutic levels for a few days. The delivery rates can be tailored by controlling the particle and the drug loading. It may be possible to use this system for both therapeutic drug delivery to eyes and the provision of lubricants to alleviate eye problems prevalent in extended lens wear.

The Effect of Water Hydraulic Permeability on the Settling of a Soft Contact Lens on the Eye

Purpose: Silicone-elastomer soft contact lenses (SCLs) adhere to the cornea during wear, whereas silicone-hydrogel soft contact lenses exhibit adequate on-eye movement. One explanation for the observed immunity to binding of silicone-hydrogel lenses is that some interstitial water is expelled during blinking, therefore maintaining a more stable post-lens tear film (PoLTF). We examine quantitatively whether or not water can be squeezed by hydrodynamic flow through a silicone-hydrogel membrane driven by the applied lid force during a blink. Methods: A rigid, porous-disk model of a contact lens was devised to calculate the relative settling rates of a permeable versus a completely impermeable SCL. The settling rate depended strongly on the value of the hydraulic permeability for pressure-driven water flow through the lens. Because the hydraulic permeability of water through silicone-hydrogel materials is not well-known, we measured this value. At steady state, water was forced through flat membranes of representative lens materials under known pressure drops. The resulting volumetric flows were measured by following the transient rise height of water in a vertical, precision-bore glass capillary. Darcy's law permitted calculation of the hydrodynamic permeability. Results: The settling-rate model indicated that tear can be squeezed through a SCL only when the Darcy-law hydrodynamic permeability is greater than about 10 μ m2 (i.e., greater than 10 Darcy). Our measurements for silicone and HEMA hydrogel membranes reveal hydrodynamic permeabilities of the order 10−8 μ m2, almost 9 orders of magnitude smaller than that necessary to initiate hydrodynamic flow through a SCL. Conclusions: We conclude that the squeeze-through mechanism cannot quantitatively account for the observed on-eye movement of silicone-hydrogel lenses. Also, we find that the lid-applied pressure cannot squeeze enough water out of a SCL during a blink to stabilize the PoLTF. Neither a squeeze-through nor a squeeze-out mechanism can maintain a stable PoLTF and prevent adherence.

Measurement of Friction Associated with Lotrafilcon and Hema Hydrogel Contact Lenses

Measurement of Friction Associated with Lotrafilcon and Hema Hydrogel Contact Lenses

Radiation crosslinking and sorption properties of hydrogels based on 1‐vinyl‐2‐pyrrolidone, hydroxyethyl methacrylate, and their copolymers

AbstractThis work has been concerned with the synthesis of the hydrogels of poly (vinyl pyrrolidone) (NVP), poly (hydroxy ethylmethacrylate) (HEMA), and their copolymer under the effect of gamma radiation in the presence of N,N‐methylenebisacryl‐amide (MBAm) as a crosslinking agent. The effect of the different factors that may affect the gelation and yield product, such as solvent composition and irradiation dose, was investigated. The formed hydrogels were characterized in terms of swelling in water and different organic solvents, X‐ray diffraction (XRD), and IR spectroscopic analysis. The sorption capability of these hydrogels towards some commercial basic and acid dyesstuffs was also studied. The results showed that a solvent mixture composed of equal contents of water and methanol is the most suitable to afford the minimum sol fraction and the highest yield product at a minimal irradiation dose of 10 kGy. It was observed that NVP hydrogel displayed the highest swelling in water, alcohols, and dimethyformamide of ∼1300% and a lower tendency to swell in nonpolar solvents. The results showed that HEMA hydrogel has a high affinity to absorb basic dyes while NVP has a tendency for acid dyes. Also, the sorption of either the basic or acid dyes by the different hydrogels was found to greatly depend on the concentration of dye in solution and the mass of the used hydrogel. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3274–3280, 2004

Permeability and diffusivity for water transport through hydrogel membranes

Water transport through soft contact lenses is important to their behavior on the human eye. For the first time, we report gradient-driven diffusion rates of water through HEMA hydrogel membranes prototypical of commercial soft contact lenses. Water is evaporated from one surface of the membrane into known relative humidity air, and the weight loss of a water reservoir at the other membrane surface is followed in time. Typical water permeabilities are around 1–5 cm/s, increasing with the saturated water content of the membrane. Binary Fickian diffusion coefficients are near 10 −7 cm 2/s. We also garner binary Stefan–Maxwell diffusion coefficients based on Flory–Rehner theory for polymer solutions. Stefan–Maxwell diffusion coefficients are useful because, in general, they depend less strongly on concentration, and they can be readily incorporated into multicomponent transport though membranes. Both the binary Fickian and Stefan–Maxwell diffusion coefficients increase somewhat with the initial water content of the individual lens materials.

Water transport in crosslinked 2-hydroxyethyl methacrylate

Water transport in crosslinked 2-hydroxyethyl methacrylate (HEMA) was investigated. Crosslinked HEMA was irradiated by gamma ray in vacuum for this study. The sorption data of de-ionized water transport in crosslinked HEMA subjected to various gamma ray dosages are in excellent agreement with Harmon's model which accounts for Case I, Case II, as well as the anomalous transport processes. The diffusion coefficient for Case I transport and velocity for Case II transport satisfy the Arrhenius equation for all dosages. The transport process was exothermic and the equilibrium-swelling ratio satisfied the van't Hoff plot. The pH value of de-ionized water after the sorption/de-sorption treatment of the irradiated crosslinked HEMA specimen was analyzed. The transmittance of irradiated crosslinked HEMA treated by de-ionized water was also studied. The effect of irradiation on the polymer chains was revealed by the measurement of glass transition temperature and the quantitative determination of water structures in crosslinked HEMA hydrogel. The UV cut-off wavelength of crosslinked HEMA shifted to longer wavelength side with increasing irradiation dosage, but the trend of transmittance after water treatment was opposite. The effect of specimen thickness on water transport was also studied.

Immobilization of lipase on poly(N‐vinyl‐2‐pyrrolidone‐co‐2‐hydroxyethyl methacrylate) hydrogel for the synthesis of butyl oleate

AbstractLipase from Candida rugosa was immobilized by entrapment on poly(N‐vinyl‐2‐pyrrolidone‐co‐2‐hydroxyethyl methacrylate) [poly(VP‐co‐HEMA)] hydrogel, cross‐linked with ethylene glycol dimethacrylate (EDMA). The immobilized enzyme was used in the esterification of oleic acid with butanol in hexane. The activities of the immobilized enzyme preparations and the leaching of the enzyme from the hydrogel supports with respect to composition were investigated. The thermal, solvent, and storage stability of the immobilized preparations also were determined. Increasing the percentage VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized onto VP(%):HEMA(%), 90:10 hydrogel had the highest activity. Increasing the hydrophobicity of the hydrogel (increasing the percentage HEMA) seemed to decrease leaching of the enzyme from the support. Immobilized lipase on 100% HEMA hydrogel indicated highest entrapment and lowest leaching by hexane washing. The lipase immobilized on VP(%):HEMA(%), 50:50 hydrogel showed highest thermal, solvent, and storage stability compared to lipase immobilized on other hydrogel compositions as well as the native lipase.

Ampicillin release from swellable controlled system

Ampicillin was incorporated to HEMA Hydrogel produced by radio-induced polymerization. Gamma radiation from 60Co was used at low temperature with doses ranging up to 25 kGy. The following studies were performed: (a) In vitro ampicillin release kinetics, through dilution test and by biological activity measurements in Micrococcus luteus. (b) in vivo release kinetics and comparison with a traditional commercial preparation. Results show that released ampicillin represented as the accumulated amount by unit area is proportional to the square root of time and that it inhibited Micrococcus luteus growth in agar for 24 h. Drug release from the new formulation, as measured by instantaneous concentration in dog blood and compared with the drug release from a commercial tablet showed improved bioavailability, resulting in an average blood availability about twice the traditional one.

Comparison of the contamination resistance ofHEMA, modified HEMA and non-HEMA hydrogel lenses

Comparison of the contamination resistance ofHEMA, modified HEMA and non-HEMA hydrogel lenses