Poly HEMA Research Articles

High density star poly HEMA containing bis-indole rich dendrimer inner core for integrated anti-fouling and anti-bacterial coating applications

Multi-arm star polymers with controlled molecular architecture suitable to be used as biomaterials are rapidly developing area of research. Herein, G2 and G3 polyurethane dendrimers containing bio-active bis-indolyl building blocks were converted into corresponding multifunctional ATRP initiators via a single-step reaction and characterized thoroughly. Polymerization of 2-hydroxethyl methacrylate (HEMA) monomer for different time duration using these initiators and CuBr/2,2′-bpy ATRP system yielded star PHEMAs with molecular weight (Mn) in the range of 2.79 × 104 – 4.52 × 105 g mol−1; the poly dispersity indices were in the range of 1.16–1.49. Glass transition temperature of these star PHEMAs was found significantly low compared to the linear PHEMA. Contact angle measurements carried out on the surface of polyethylene terephthalate (PET) film coated with these polymers confirmed that these polymers are more hydrophilic compared to the un-coated PET surface. The integrated anti-fouling and anti-bacterial properties of these polymer coatings were studied with two common pathogens namely E. coli and P. aeruginosa and found that the binding of both of these bacterial cells either in live or dead form was negligibly low in the polymer coated PET surface compared to un-coated films and also found that the percentage of live cells was low compared to dead cells.

Continuous Lactate Monitoring System Based on Percutaneous Microneedle Array.

Lactate measurement is important in the fields of sports and medicine. Lactate accumulation can seriously affect an athlete’s performance. The most common problem caused by lactate accumulation in athletes is muscle soreness due to excessive exercise. Moreover, from a medical viewpoint, lactate is one of the main prognostic factors of sepsis. Currently, blood sampling is the most common approach to lactate measurement for lactate sensing, and continuous measurement is not available. In this study, a low-cost continuous lactate monitoring system (CLMS) is developed based on a percutaneous microneedle array that uses a three-electrode lactate sensor. The working electrode has an area of 10 mm × 6 mm, including a 3 × 3 array of stainless-steel microneedles. The length, width, and thickness of each needle are 1 mm, 0.44 mm, and 0.03 mm, respectively. The working electrode is then plated with gold, polyaniline, lactate enzyme, Nafion, and Poly(2-hydroxyethyl methacrylate) (poly HEMA). The reference electrode is a 2 × 1 array covered with AgCl, and the counter electrode is a 2 × 1 array plated with gold. The sensor is incorporated into the CLMS and connected to a smartphone application and the cloud. The CLMS was tested on 40 human subjects who rode indoor bicycles, starting at 100 W and increasing in steps of 25 W at intervals of 5 min until exhaustion. The data acquired from the app connected to the CLMS were analyzed to determine the subjects’ lactate response to exercise and the feasibility of assessing exercise performance and training exercise intensity by using the proposed system.

Preparation and characterization of a Cu (II)-IDA poly HEMA monolith syringe for proteomic applications.

Herein, we report the preparation of a metal-chelate immobilized hydrophilic poly hydroxyethylmethacrylate-based monolith of 100μL volume in a plastic syringe. The monolith is elastic in nature, contains well interconnected pores with a permeability (k) of 1.3×10-12 m2 . Immobilization of iminodiacetic acid (IDA) is performed via schiff base reaction. Adsortion of IgG on this copper-IDA monolith is of langmuir isotherm with a maximum adsorption capacity of ∼25mg IgG per g monolith. IgG adsorption capacity of this affinity monolith remained unaffected with increase of flow rate. This proposed metal-chelate monolith in syringe format has the potential for application in proteomics.

Adhesion attenuates respiratory burst induced by different modes of triggering in resting or LPS-primed neutrophils

The effects of adherence on neutrophil superoxide anion (O2−) generation triggered by surface, soluble ligand, or adherence were studied. Resting-neutrophils adhered to the uncoated tubes resulting in O2− generation, but not on plasma-, fibrinogen-, vitronectin-, fibronectin-, laminin-, collagen-, or poly HEMA-coated surfaces. Enhanced N-formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated O2− generation by LPS-primed-neutrophils was induced by the incubation on plasma, fibrinogen, vitronectin, fibronectin, or laminin in the absence of Mg2+. In the presence of Mg2+, this response was observed in cells on collagen or poly HEMA. LPS-primed-neutrophils adhered to uncoated, BSA- or IgG-coated tubes and did not respond to fMLP, indicating that the fMLP-response of LPS-primed-neutrophils was suppressed by adherence.Upon incubation on plasma, fibrinogen, vitronectin, fibronectin in the presence of Mg2+, LPS-primed-neutrophils showed O2− generation. Upon incubation on collagen or poly HEMA, the primed-neutrophils neither generated O2− nor adhered. We found that O2− response of LPS-primed-neutrophils was attenuated depending on the time of exposure to plasma-coated surface. This attenuation was evident on plasma or fibrinogen, but not on collagen in the presence of Mg2+, indicating that O2− generation by LPS-primed-neutrophils was attenuated dependent on adherence but not on Mg2+. Thus, adhesion attenuated the O2− generation triggered by both soluble (fMLP) and insoluble (surface) stimuli.

Extended wear therapeutic contact lens fabricated from timolol imprinted carboxymethyl chitosan-g-hydroxy ethyl methacrylate-g-poly acrylamide as a onetime medication for glaucoma

An extended wear therapeutic contact lens (TCL) for the sustained delivery of timolol maleate (TML) was fabricated based on molecular imprinting technique. The designed TCL comprised of a TML imprinted copolymer of carboxymethyl chitosan-g-hydroxy ethyl methacrylate-g-polyacrylamide (CmCS-g-HEMA-g-pAAm) embedded onto a poly HEMA matrix (pHEMA). Successful reloading of TML onto the lens was monitored using a simple and novel UV–Visible spectrophotometric method which showed an excellent reloading capacity of 6.53μgTML/TCL. The in vitro drug release profile in lacrimal fluid after each cycle was fitted onto Higuchi model of drug release suggesting diffusion release mechanism with no polymer degradation. Also, the TML release kinetics indicated a sustained drug delivery which can effectively achieve the therapeutic index of TML leading to a onetime medication for glaucoma. Biological activity of eluted drug after each cycle and cell viability of the TCL were verified using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,3-bis(2-methoxynitro-5-sulfophenyl)-5-(phenylaminocarbonyl)-2H-tetrazolium hydroxide (XTT) assay, respectively.

Hydro gel light-guiding conjunction for absorptive type multi-ions detection

We present a novel miniaturized solid state sensor produced by embedding two optical fibers in a sensing hydro gel conjunction. The conjunction is a poly (2-hydroxyethyl methacrylate) (poly HEMA) hydro gel mixed with two kinds of selective fluorescent probes. Meso-2,6-Dichlorophenyltripyrrinone (TPN-Cl2) is used to react with zinc ion (Zn2+) and the synthesized “Chemosensor 1” is used to detect ferric ion (Fe3+). This hydro gel conjunction can serve as a light-guiding waveguide that allows light signals to transfer between two fibers. By using a multi-wavelength excitation light, a mixed solution that contains Zn2+ and Fe3+ can be detected in real-time. This miniaturized sensor develops an image for real-time monitoring of Zn2+ and Fe3+ ions in vivo.

Solid-state sensing tip for zinc ion with double parallel optical fibers embedded in fluorescent hydrogel

A tip-shaped zinc ion solid-state sensor is made by two parallel optical fibers embedded closely in a sensing hydrogel film. The film is made of poly(2-hydroxyethyl methacrylate) (poly HEMA)hydrogel mixed with the selective fluorescent probe meso-2,6-Dichlorophenyltripyrrinone (TPN-Cl2) with weight ratio of 0.025wt%. A 405nm laser output is sent from one fiber and the 622nm fluorescence of the doped hydrogel is collected by the second fiber. Each fiber diameter is 370μm (core is 300μm), whose sum is roughly the tip diameter. The 0.4cm by 0.5cm tip has real-time response for zinc ion concentration over 10−6M, with marginal signal for 10−7M. The tip is inserted inside an oyster and successfully detects the zinc ions, showing that the sensor works in complex body fluid and tolerates certain mechanical stress. To show the potential application for medicine, the sensing film is applied for primary neuronal cultures. We report for the first time zinc ions release at concentration levels 10−6–10−7M to the medium under stress conditions of ischemia, inflammation, and intoxication. Furthermore, this correlates with the zinc levels detected by biochemical assay. Such sensing tip has great potential for biomedical monitoring ex vivo or in vivo.

Enhanced removal of methyl orange from aqueous solutions by poly HEMA–chitosan-MWCNT nano-composite

A nanocomposite of multi-walled carbon nanotube (MWCNT) functionalized (f) with chitosan (CS) and poly-2-hydroxyethyl methacrylate (pHEMA) was prepared and characterized. The adsorption of methyl orange (MO) on pHEMA–CS-f-MWCNT composites from an aqueous solution was investigated with respect to the contact time, dosage, pH, temperature and initial MO concentration. Pseudo first-order and pseudo second-order kinetics, as well as intra-particle diffusion were adopted to evaluate the experimental data. Our pseudo second-order model, with a correlation coefficient greater than 0.9986, was found to most accurately describe the adsorption kinetics. Additionally, we used Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms to describe equilibrium adsorption in the nanocomposite system. The best agreement was achieved with the Langmuir model with a correlation coefficient of 0.9991. The standard enthalpy change (ΔH0), the standard free energy change (ΔG0) and the standard entropy (ΔS0) were also calculated. The thermodynamic parameters indicate that the adsorption process is spontaneous and endothermic.

Conversion of absorption to fluorescence probe in solid-state sensor for nitric oxide and nitrite

A hydrogel bi-layer structure is used to convert an absorption type to a more convenient fluorescent type probe film for aqueous nitric oxide (NO) and nitrite (NO2-). In the bottom layer the commercial probe molecule 1,2-diaminoanthraquinone (DAQ) is dispersed in poly 2-hydroxyethyl methacrylate (poly HEMA), in the top layer the red inorganic phosphor is dispersed in poly HEMA. Both optical excitation and detection is from the bottom. This bi-layer is integrated with organic light-emitting diode (OLED) and organic photo-detector to form a real-time solid-state sensor. The sensor is responsive to NO bubbling, and remains stable in acid condition.

Electrospun Fibers as a Solid‐State Real‐Time Zinc Ion Sensor with High Sensitivity and Cell Medium Compatibility

Abstractmeso‐2,6‐Dichlorophenyltripyrrinone (TPN‐Cl2), a probe molecule for zinc II ions, is dispersed in a polymer host. The red fluorescence peak at 620 nm appears when the molecule forms a complex with zinc at its center. TPN‐Cl2 has a high selectivity for zinc II and tolerates many common metal ions present in the human body. The probe molecules are blended with a hydrogel polymer, poly(2‐hydroxyethyl methacrylate) (poly HEMA), with 30 wt% dimethylformamide (DMF). The fiber structure with 1 μm diameter is made by electrospinning in DMF solution of the probe and poly HEMA mixture. The fibrous film detects zinc ions with concentrations as low as 10−6 M in real‐time both in water and in the commonly used cell culture liquid media Dulbecco's modified Eagle medium (DMEM) and fetal bovine serum (FBS), which contain many metal ions and proteins. The time‐resolution is 5 min for 10−6 M and 1 min for 10−5 M. This sensitivity and response speed satisfy the requirements for non‐invasive biomedical studies.

A Synergistic Low‐Toxicity Gelcasting System by Using HEMA and PVP

A new low‐toxicity gelcasting system with a 2‐hydroxyethyl methacrylate (HEMA) monomer was applied for casting of alumina ceramics. Polyvinyl pyrrolidone (PVP) was adopted for modifying the homogeneity of the PHEMA (poly‐HEMA) gel. The rheological properties of alumina suspension in the HEMA–PVP premix solution were studied. After preparation of a concentrated alumina suspension, homogenous alumina green body with a relatively high strength of about 19 MPa could be formed through the PVP‐modified HEMA system. Dense complex‐shaped ceramic parts can be successfully produced through the system. Besides, the surface exfoliation phenomenon that seems inherent to the acrylamide gelcasting system could also be eliminated by using the PVP‐modified HEMA system. Analysis of the interaction of HEMA and PVP suggested that the improved microstructure and strength homogeneity, as well as the elimination of surface exfoliation in the new system, should be attributed to the intermolecular hydrogen bonding formed between PHEMA and PVP molecules.

Differentiation of a colon cancer cell line on a reconstituted basement membrane in vitro.

Basement membrane, a thin extracellular matrix, functions as a tissue stabilizer that promotes tissue integrity and differentiated phenotype. We studied a human colon cancer cell line, SNU 61, to evaluate its ability to differentiate on basement membrane. Cells were cultured on plastic, reconstituted basement membrane (Matrigel) or polyhydroxyethyl methacrylate (poly HEMA) for 72 h and evaluated by light and electron microscopy. On Matrigel, the cells showed gland formation with highly polarized cells containing basal nuclei and well developed brush border microvilli on the luminal surface. Apoptosis was noted mainly at the luminal side. On electron microscopic examination, numerous long microvilli, abundant cytoplasmic organelles and intercellular junctions were noted in the Matrigel-cultured cells. Intermediate cytoskeletons were scattered in the cytoplasm and existed on the axes of microvilli. Junctional complexes and desmosomes were frequently formed along intercellular spaces. The cells cultured on poly HEMA, on the other hand, were poorly differentiated and contained a few glandular structures with small lumens. Brush border microvilli, characteristic of enterocytic differentiation, were few in number and were developed on the basal surface. Intermediate filaments and microtubules were fewer than in the Matrigel-cultured cells. Carcinoembryonic antigen was expressed on the luminal surface of the Matrigel-cultured cells and in the cytoplasm of the poly HEMA cultured cells. CD44 stained the basolateral surface in the Matrigel-cultured cells, but the basal side was not stained in the poly HEMA cultured cells. These results are consistent with the different localization of microvilli in the Matrigel and in the poly HEMA cultured cells. Our observations suggest that human colon cancer cells on basement membrane can undergo glandular differentiation and that extracellular matrix is an important factor in morphogenesis.

A Comparison of Visual Function with PMMA and Poly HEMA Intraocular Lenses

OBJECTIVE: To compare visual function in the Alcon Iogel 2000s/sm (poly HEMA) and Alcon MZ30BD all polymethymethacrylate (PMMA) posterior chamber intraocular lenses. STUDY DESIGN: Over a 4-month period all patients with 1 of the above lenses were assessed. Patients with coexistent pathology were excluded. All remaining patients had uncomplicated phacoemulsification performed by a single surgeon. SETTING: Lions Eye Institute, Perth, Western Australia. PATIENTS: Forty-eight eyes of 43 patients were examined, 25 poly HEMA and 23 PMMA lenses. OUTCOME MEASURES: Visual acuity, contrast sensitivity and glare. RESULTS: Poly HEMA lenses were significantly better than PMMA lenses, visual acuity P = 0.0001, contrast sensitivity P = 0.004 and glare P = 0.019. CONCLUSIONS: The poly HEMA lens performed better than the PMMA lens for all tests of visual function. However modulation transfer function and optical design are similar for both lenses. This result may reflect another in vivo property of the poly HEMA lens. However it would require a larger controlled trial to confirm any differences.

Chapter 10 Biodegradation

Chronically implanted devices depending on polymers have contributed significantly to improving the quality of life for many people. Examples of such devices include joint prostheses, cardiac pacemakers, arteriovenous shunts for dialysis, vascular grafts, cerebrospinal fluid (CSF) shunts, urethral catheters, sutures, mammary prostheses, dental prostheses, heart valves, neural stimulators, and implantable defibrillators. Some of the more common examples of polymers generally considered to be implantable and biostable include polyethylene, polypropylene, polyether polyurethanes, (aromatic) polyesters, silicone rubbers, hydrogels (poly HEMA), (solid) acrylics, and fluoro polymers (such as teflon). Many other polymers have physical properties that are very desirable for use in implanted devices, but their biostability is controversial or limits them to use in relatively short-term implants. The polyamides (nylons) and (aliphatic) polyester polyurethanes are examples. Certainly there are implantable devices that are intentionally designed to biodegrade, such as tissue scaffolds. The purpose of this chapter, however, is to review the failure mechanisms that can affect biostable polymers: those polymers that are intended to maintain properties adequate to facilitate the long-term performance of implanted devices. In addition, this chapter will review some of the test methodology needed to qualify a biostable polymer for human use.

Cellular invasion on hydrogel and poly(methyl methacrylate) implants: An in vivo study

Over a two-year postoperative period, cells on hydrogel (poly HEMA) and poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) were observed by specular microscopy. First small, round cells and fibroblast-like cells and later epithelioid-like cells and foreign-body giant cells could be seen on both IOL types. In eyes with prolonged postoperative inflammation a greater number of cells was observed and the cells remained on the IOL surface for a longer period. We found fewer cell reactions on hydrogel IOLs during the postoperative period of our follow-up. Foreign-body giant cells were observed on only 9%. These cells were smaller than those on PMMA IOLs. This finding may suggest that poly HEMA demonstrates greater biocompatibility, with regard to this foreign-body cell reaction, than PMMA. However, we found more pigment dispersion (50%) on the surface of hydrogel IOLs. These pigment deposits induced no cell reactions and there was less phagocytosis of the pigment debris. In 7% of the cases, dust-like, white precipitates of uncertain origin were seen; in 5% amorphous debris was seen. Fine scratches caused by polishing during the manufacturing process were seen in some cases. The postoperative clinical signs for PMMA and hydrogel IOLs were similar.

Drug uptake and release by a hydrogel intraocular lens and the human crystalline lens

Implantation of a hydrogel (IOGEL) intraocular lens in humans has been reported. The polyhydroxyethyl methacrylate (poly HEMA) matrix of this hydrogel is permeable to water soluble drugs and may adsorb agents used intracamerally during cataract extraction or topically during the postoperative period. This study compared the in vitro uptake and release of chloramphenicol, dexamethasone, epinephrine, pilocarpine, and bovine serum albumin by polymethylmethacrylate and hydrogel intraocular lenses with that of the intact crystalline lens of humans and rabbits. An in vivo study compared the uptake and release of chloramphenicol and dexamethasone by hydrogel lenses implanted in the anterior chamber of rabbit eyes with that of the rabbit's crystalline lens. The in vitro uptake and washout of epinephrine and pilocarpine by the hydrogel lens was comparable to the human lens. Uptake of chloramphenicol and dexamethasone by the hydrogel lens exceeded that of the human lens and, following a two-hour washout period, the dexamethasone content of the hydrogel lens remained significantly greater than the human lens. The uptake and washout of bovine serum albumin by the hydrogel lens was half that of the human lens. In vivo, the hydrogel lens efficiently eluted both chloramphenicol and dexamethasone. These studies show that a hydrogel lens will not act as a significant depot for drugs in the eye.

Multicenter trial of an intraocular hydrogel lens implant

Several features suggest that hydrogels may have potential advantages as an intraocular lens material, The IOGEL™ lens is a single piece hydrogel composed of 38% poly HEMA. Clinical experience with the IOGEL lens in Australia has been published, and the safety and efficacy of the lens is currently being investigated in a multicenter trial in Europe, the U.S.A., Canada, Australia, and Japan. This is the first large-scale study of a hydrogel implant. The IOGEL lens clinical study was initiated in May 1986 in Europe, in September 1986 in the U.S.A., and in November 1986 in Canada and Australia. The enrollment progress in May 1987 showed that 501 cases had been implanted in Europe, Canada, and Australia and 100 cases in the U.S.A. The visual acuity outcome is equivalent to that reported in the literature. Patients in the multinational trial achieved 20/40 or better in 86% of cases and in 96% of cases excluding unrelated pathologies. Although hydrogels have only had limited use in the clinical situation, the results of this study suggest that the IOGEL lens is a viable alternative to polymethylmethacrylate lens implants.

Complement activation by hydroxyethylmethacrylate-ethylmethacrylate copolymers.

Certain biomaterials, including nylon oxygenator and cellulosic dialysis membranes, are potent activators of human complement. In this study, the effect of polymers containing 2-hydroxyethyl methacrylate (HEMA) on the human complement system was investigated. Copolymers of HEMA with ethylmethacrylate (EMA) varying from 100 to 40% HEMA in the monomer made by radiation initiation were used to coat glass discs. These were equilibrated with human plasma in vitro and the degree of complement activation was quantitated by C3a radio immunoassay. Significant activation was caused by copolymers made from monomers containing 60% or greater HEMA. A direct relationship between the amount of activation and the percentage of HEMA was found. The degree of activation by poly HEMA, when corrected for surface area, was quite similar to that observed for dialysis and oxygenator membranes. Similar observations were made when solid casts of crosslinked HEMA/N-vinylpyrrolidone (NVP) copolymer gels were tested, but the magnitude of activation was much greater. The results are significant because complement activation may play an important role in the response to foreign surfaces, in both extravascular and intravascular settings. A new concept of molecular biocompatibility is proposed in which surfaces eliciting molecular transformations in any of the biological defense systems are deemed nonbiocompatible. By this criterion, the hydrogel poly-HEMA, which has so frequently been thought of as biocompatible, is considered to be a molecularly non-biocompatible material.

Influence of Drug Loading and Gel Structure on in-Vitro Release Kinetics from Photopolymerized Gels

AbstractPrecious work has shown that stabls and homogenous poly HEMA gels can be prepared using a visible light sensitive initiator system. Gels were prepared from solutions of water and poly-2-hydroxyethyl methacrylate monomer. At concentrations of water greater than 10% v/v, translucent gel resulted. However, polymerization solvents such as glycerol and tertiary butyl alcohol (T.B.T.A) gave transparent, flexible gels over a wider range of concentrations. Subsequent work showed that changes in polymerization solvent and monomer concentration brought about changes in the mechanical and structural properties of the gels.In this work, the effects of drug loading and polymerization solvents on in vitro drug release rate from the photopolymerized polyHEMA gels were studied. Polymerization solvents used included glycerol and tertiary butyl alcohol. Results indicated that the release rate in vitro was a diffusion-controlled process except at high drug concentrations in poly HEMA - T.B.T.A. gels when a departure...

Clinical results of hydrogel lens implantation

Polymethylmethacrylate has proven to be a useful intraocular lens (IOL) implant material and remains the most widely used material for the fabrication of IOLs. Complications, however, from IOL implantation still occur. A hydrogel lens has been designed for posterior chamber placement. A clinical study from August 1983 to June 1985 was undertaken to determine the safety and efficacy of this new lens manufactured from 38% poly HEMA. The noninhammatory postoperative complications were limited to lens decentration and opacification of the lens capsule. Three cases of posterior capsule opacification required YAG laser eapsulotomy. Laser- capsulotomy is feasible and the lens appeared to be more resistant to damage from the YAG laser than polymethylmethacrylate lenses. In general, the material appeared to be well tolerated and there have been no cases of persistent iritis or clinically detectable cystoid macular edema. If the visual acuity outcome by age decade for all patients irrespective of follow-up time is considered, 92% of patients achieved 20/40 or better corrected visual acuity.