Removal thermodynamics and desorption studies of some heavy metal ions such as Co(II), Cu(II) and Pb(II) by polymeric surfaces such as poly 2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) as adsorbent surfaces from aqueous single solution were investigated with respect to the changes in pH of solution, adsorbent composition, contact time and temperature in the individual aqueous solution. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained and the results revealed that the Langmuir isotherm fitted the experiment results better than Freundlich isotherm. Using the Langmuir model equation, the monolayer removal capacity of PHEMA surface was found to be 0.7388, 0.8396 and 3.0367 mg/g for Co(II), Cu(ΙΙ) and Pb(II) ions and removal capacity of P(MMA-HEMA) was found to be 28.8442, 31.1526 and 31.4465 mg/g for Co(II), Cu(ΙΙ) and Pb(II) ions, respectively. Changes in the standard Gibbs free energy (ΔG0), standard enthalpy (ΔH0) and standard entropy (ΔS0) showed that the removals of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293–323 K. The maximum desorption efficiency was 75.26% for Pb(II) using 0.100 M HNO3, 70.10% for Cu(II) using 0.100 M HCl, 59.20% for 0.100 M HCl 63.67% Co(II).
Removal; Polymeric surfaces; Langmuir isotherm; Heavy metal ions; Thermodynamics parameters
There is an urgent need to develop drug-loaded biocompatible nanoscale packages with improved therapeutic efficacy for effective clinical treatment. To address this need, a novel poly (2-hydroxyethyl methacrylate)-poly (lactide)-1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine [PHEMA-g-(PLA-DPPE)] copolymer was designed and synthesized to enable these nanoparticles to be pH responsive under pathological conditions.
The structural properties and thermal stability of the copolymer was measured and confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis. In order to evaluate its feasibility as a drug carrier, paclitaxel-loaded PHEMA-g-(PLA-DPPE) nanoparticles were prepared using the emulsion-solvent evaporation method.
The PHEMA-g-(PLA-DPPE) nanoparticles could be efficiently loaded with paclitaxel and controlled to release the drug gradually and effectively. In vitro release experiments demonstrated that drug release was faster at pH 5.0 than at pH 7.4. The anticancer activity of the PHEMA-g-(PLA-DPPE) nanoparticles was measured in breast cancer MCF-7 cells in vivo and in vitro. In comparison with the free drug, the paclitaxel-loaded PHEMA-g-(PLA-DPPE) nanoparticles could induce more significant tumor regression.
This study indicates that PHEMA-g-(PLA-DPPE) nanoparticles are promising carriers for hydrophobic drugs. This system can passively target cancer tissue and release drugs in a controllable manner, as determined by the pH value of the area in which the drug accumulates.
poly (2-hydroxyethyl methacrylate); controlled release; biocompatibility; antitumor activity; 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine; nanoparticles
Three-dimensional (3D) microperiodic scaffolds of poly(2-hydroxyethyl methacrylate) (pHEMA) have been fabricated by direct-write assembly of a photopolymerizable hydrogel ink. The ink is initially composed of physically entangled pHEMA chains dissolved in a solution of HEMA monomer, comonomer, photoinitiator and water. Upon printing 3D scaffolds of varying architecture, the ink filaments are exposed to UV light, where they are transformed into an interpenetrating hydrogel network of chemically cross-linked and physically entangled pHEMA chains. These 3D microperiodic scaffolds are rendered growth compliant for primary rat hippocampal neurons by absorption of polylysine. Neuronal cells thrive on these scaffolds, forming differentiated, intricately branched networks. Confocal laser scanning microscopy reveals that both cell distribution and extent of neuronal process alignment depend upon scaffold architecture. This work provides an important step forward in the creation of suitable platforms for in vitro study of sensitive cell types.
Tissue Engineering; 3D Cell Culture; Hippocampal Neurons; Direct-Write Assembly
BACKGROUND/AIMS—To investigate a poly(2-hydroxyethyl methacrylate) (PHEMA) orbital implant with a spongy anterior hemisphere and a smooth gel posterior hemisphere, by histology correlated with magnetic resonance images.
METHODS—Following enucleation, eight rabbits received PHEMA implants to which the muscles were directly sutured, and underwent gadolinium enhanced magnetic resonance imaging (MRI) from 3 to 52 weeks. After the rabbits were killed, the implants were removed, cut in a plane corresponding to the scan, and processed for light and electron microscopy.
RESULTS—All eight rabbits retained their implant to the end of the study period without complications. The scans demonstrated muscle attachment to the anterior half of the implant, and enhancement was seen on injection of gadolinium chelate. Histology confirmed muscle attachment, and cellular and vascular ingrowth. Over time, a transformation from reactive inflammatory to relatively non-vascular scar tissue was seen within the implant. Calcium deposits in one implant were detected by imaging and histology.
CONCLUSION—The implants are readily visualised on MRI. Muscle attachment and fibrovascular ingrowth into the anterior hemisphere are seen, while encapsulation of the posterior hemisphere is minimal. Histological findings confirm the progress of the healing response, with initial inflammation and marked vascularisation, developing later into quiescent scar tissue predominantly of fibroblasts.
Matching the mechanical properties of a biomaterial to soft tissue is often overlooked despite the fact that it’s well known that cells respond to and are capable of changing their mechanical environment. In this paper, we used NaCl and alginate beads as porogens to make a series of micro- and macro-porous pHEMA substrates [poly(2-hydroxyethly methacrylate)] and quantified their mechanical behavior under low-magnitude shear loads over physiologically relevant frequencies. Using a stress-controlled rheometer, we performed isothermal (37°C) frequency response experiments between 0.628 and 75.4 rad/s [0.01–12Hz] at 0.1% strain. Both micro- and macro-porous pHEMA substrates were predominately elastic in nature with a narrow range of G′ and G″ values that mimicked the response of human skin. The magnitude of the G′ and G″ values of the macro-porous substrates were designed to closely match human skin. To determine how cell growth might alter their mechanical properties, pHEMA substrates were functionalized and human skin fibroblasts grown on them for fourteen days. As a result of cell growth, the magnitude of G′ and G″ increased at low frequencies while also altering the degree of high frequency dependence, indicating that cellular interactions with the micro-pore infrastructure has a profound effect on the viscoelastic behavior of the substrates. These data could be fit to a mathematical model describing a soft solid. A quantitative understanding of the mechanical behavior of biomaterials in regimes that are physiologically relevant and how these mechanics may change after implantation may aid in the design of new materials.
shear; rheology; viscoelastic; poly (2 hydroxyethyl methacrylate); soft tissue
Biodegradable poly(2-hydroxyethyl methacrylate) hydrogels for engineered tissue constructs were developed using atom transfer radical polymerization (ATRP), a degradable crosslinker and a macroinitiator. Hydrogels are appropriate materials for tissue engineering scaffolds due to their tissue-like mechanical compliance and mass transfer properties. However, many hydrogels that have seen wide application in medicine are not biodegradable or cannot be easily cleared from the body. Poly(2-hydroxyethyl methacrylate) (pHEMA) was selected for the scaffold material due to its reasonable mechanical strength, elasticity, long history of successful use in medicine and because it can be easily fabricated into numerous configurations. pHEMA was studied at various molecular weights between 2 kDa and 50 kDa. The molecular weight range suitable for renal clearance was an important factor in the experimental design. The fabricated hydrogels contain oligomeric blocks of polycaprolactone (PCL), a hydrolytically and enzymatically degradable polymer, as a crosslinking agent. In addition a degradable macroinitiator also containing oligomeric PCL was used to initiate the ATRP. The chain length, crosslink density, and polymerization solvent were found to greatly affect the mechanical properties of the pHEMA hydrogels. Degradation of the pHEMA hydrogels was characterized using 0.007 M NaOH, lipase solutions and phosphate buffered saline. Mass loss, swelling ratio and tensile modulus were evaluated. Degradation products from the sodium hydroxide were measured using gel permeation chromatography (GPC) to verify the polymer lengths and polydispersity. Erosion was only observed in the sodium hydroxide and lipase solutions. However, swelling ratio and tensile modulus indicate bulk degradation in all PCL containing samples. Degradable hydrogels in enzymatic solutions showed 30% mass loss in 16 weeks. Initial cell toxicity studies indicate no adverse cellular response to the hydrogels or their degradation products. These hydrogels have appropriate mechanical properties, a tunable degradation rate, and are composed of materials currently in FDA approved devices. Thus the degradable pHEMA developed in this study has considerable potential as a scaffold for tissue engineering in cardiac and other applications.
PolyHEMA; Polycaprolactone; ATRP; Cardiac Tissue Engineering; Degradation
A 4-amino-naphthalimide derived fluorophore with a triazacryptand moiety ligand was synthesized as a potassium ion (K+) sensor (KS1). This sensor is a monomer possessing a polymerizable vinyl group. By taking advantage of the polymerizable characteristics of the vinyl group, KS1 was polymerized with 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AM) to form K+-sensing films for extracellular sensing. The sensitivity of the films to potassium ions can be further tuned through the adjustment of the HEMA and AM weight ratios as well as introduction of positive or negative charge-containing segments. KS1 and its poly(2-hydroxyethyl methacrylate)-co-poly(acrylamide) (PHEMA-co-PAM) thin films show high selectivity for K+ over competing sodium ions (Na+) at physiological concentrations. Extracellular sensing was demonstrated using a KS1-conjugated PHEMA-co-PAM thin film to measure the K+ efflux of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) stimulated by lysozyme. Meanwhile, KS1 itself permeates human glioblastoma U87MG and human esophagus premalignant CP-A cell lines. KS1 was used to monitor K+ efflux stimulated by adenosine-5'-triphosphate (ATP), amphotericin, and a mixture of nigericin, bumetanide and ouabain, demonstrating application of this material as an intracellular potassium ion sensor.
Potassium ion sensor; Amino-naphthalimide; Intracellular sensing; Extracellular sensing; Fluorescent probe
The use of the enzyme alanine dehydrogenase (AlaDH) for the determination of ammonium ion (NH4+) usually requires the addition of pyruvate substrate and reduced nicotinamide adenine dinucleotide (NADH) simultaneously to effect the reaction. This addition of reagents is inconvenient when an enzyme biosensor based on AlaDH is used. To resolve the problem, a novel reagentless amperometric biosensor using a stacked methacrylic membrane system coated onto a screen-printed carbon paste electrode (SPE) for NH4+ ion determination is described. A mixture of pyruvate and NADH was immobilized in low molecular weight poly(2-hydroxyethyl methacrylate) (pHEMA) membrane, which was then deposited over a photocured pHEMA membrane (photoHEMA) containing alanine dehydrogenase (AlaDH) enzyme. Due to the enzymatic reaction of AlaDH and the pyruvate substrate, NH4+ was consumed in the process and thus the signal from the electrocatalytic oxidation of NADH at an applied potential of +0.55 V was proportional to the NH4+ ion concentration under optimal conditions. The stacked methacrylate membranes responded rapidly and linearly to changes in NH4+ ion concentrations between 10–100 mM, with a detection limit of 0.18 mM NH4+ ion. The reproducibility of the amperometrical NH4+ biosensor yielded low relative standard deviations between 1.4–4.9%. The stacked membrane biosensor has been successfully applied to the determination of NH4+ ion in spiked river water samples without pretreatment. A good correlation was found between the analytical results for NH4+ obtained from the biosensor and the Nessler spectrophotometric method.
biosensor; ammonium ion; reduced nicotinamide adenine dinucleotide; poly(2-hydroxyethyl methacrylate); alanine dehydrogenase
Cardiac and skeletal muscle tissue engineering provides a smart approach to overcome problems associated with organ transplantation and cardiac tissue and also lays a platform for superior alternative approaches in muscle regeneration. The aim of the study was to demonstrate cryogel scaffold potential in the field of skeletal muscle and cardiac tissue engineering. Poly-hydroxyethyl methacrylate (pHEMA)-gelatin cryogel scaffold was synthesized using cryogelation technique and such a designed material is being reported first time. Rheology study of the pHEMA-gelatin (HG) suggested that the cryogel scaffolds were stable at different temperatures and phase angle remained constant in both dry and wet state. HG cryogel was able to bear increased stress without leading to deformation. Monitoring the hydration of HG scaffold showed shift from a stiff to a more pliable material and upon continuing hydration, shear modulus remained constant with no further change observed. However, the change in phase angle <0.24º indicates a gradual increase in stiffness of the material over time. Scaffold synthesised using such polymer combinations gave cells a native environment for proliferation and surface stiffness have shown to help in differentiation of the cells. Myoskeletal cell lines were cultured on these scaffolds to check the biocompatibility and cell proliferation. Alamar blue assay performed over a period of 3 weeks analysed the metabolic activity of cells which showed more than 60% increase in the total cellular activity. DNA content of cells was found to be directly related to number of cells present at a given time point and this was found to have increased by more than 50% in 3 weeks. Since in 3-D scaffold the surface area is more in comparison to 2-D, hence better cell proliferation is observed. Hoechst and DAPI staining showed tubular structure and alignment of the cells during formation of the tubules shows promising cellular response to the cryogel matrix. The mechanical strength, stiffness and elastic measurements of the scaffold indicated potential application of these materials for skeletal and cardiac tissue engineering.
Cryogel; pHEMA-gelatin; C2C12 myocardial cells; Skeletal tissue engineering; Rheology; Myotubes
This preliminary study investigated the use of poly (2-hydroxyethyl methacrylate) (pHEMA) nanoparticles for the delivery of the deoxyribonucleic acid (DNA) vaccine pCAG-HAk, which expresses the full length hemagglutinin (HA) gene of the avian influenza A/Eurasian coot/Western Australian/2727/1979 (H6N2) virus with a Kozak sequence which is in the form of a pCAGGS vector. The loaded and unloaded nanoparticles were characterized using field-emission scanning electron microscopy. Further characterizations of the nanoparticles were made using atomic force microscopy and dynamic light scattering, which was used to investigate particle size distributions. This preliminary study suggests that using 100 μg of pHEMA nanoparticles as a nanocarrier/adjuvant produced a reduction in virus shedding and improved the immune response to the DNA vaccine pCAG-HAk.
nanoparticles; ultrasound; deoxyribonucleic acid; plasmid; bird flu; pandemic
The design of synthetic bone grafts that mimic the structure and composition of bone and possess good surgical handling characteristics remains a major challenge. We report the development of poly(2-hydroxyethyl methacrylate) (pHEMA)-hydroxyapatite (HA) composites termed “FlexBone” that possess osteoconductive mineral content approximating that of human bone yet exhibit elastomeric properties enabling the press-fitting into a defect site. The approach involves crosslinking pHEMA hydrogel in the presence of HA using viscous ethylene glycol as a solvent. The composites exhibit excellent structural integration between the apatite mineral component and the hydroxylated hydrogel matrix. The stiffness of the composite and the ability to withstand compressive stress correlate with the microstructure and content of the mineral component. The incorporation of porous aggregates of HA nanocrystals rather than compact micrometer-sized calcined HA effectively improved the resistance of the composite to crack propagation under compression. Freeze-dried FlexBone containing 50 wt % porous HA nanocrystals could withstand hundreds-of-megapascals compressive stress and >80% compressive strain without exhibiting brittle fractures. Upon equilibration with water, FlexBone retained good structural integration and withstood repetitive moderate (megapascals) compressive stress at body temperature. When subcutaneously implanted in rats, FlexBone supported osteoblastic differentiation of the bone marrow stromal cells pre-seeded on FlexBone. Taken together, the combination of high osteoconductive mineral content, excellent organic-inorganic structural integration, elasticity, and the ability to support osteoblastic differentiation in vivo makes FlexBone a promising candidate for orthopedic applications.
hydrogel; hydroxyapatite; elastomeric composites; osteoblastic differentiation; bone marrow stromal cells
We have developed a new portable taste sensor with a lipid/polymer membrane and conducted experiments to evaluate the sensor's performance. The fabricated sensor consists of a taste sensor chip (40 mm × 26 mm × 2.2 mm) with working and reference electrodes and a portable sensor device (80 mm × 25 mm × 20 mm). The working electrode consists of a taste-sensing site comprising a poly(hydroxyethyl)methacrylate (pHEMA) hydrogel layer with KCl as the electrolyte layer and a lipid/polymer membrane as the taste sensing element. The reference electrode comprises a polyvinyl chloride (PVC) membrane layer with a small hole and a pHEMA layer with KCl. The whole device is the size of a USB memory stick, making it suitable for portable use. The sensor's response to tannic acid as the standard astringency substance showed good accuracy and reproducibility, and was comparable with the performance of a commercially available taste sensing system. Thus, it is possible for this sensor to be used for in-field evaluations and it can make a significant contribution to the food industry, as well as in various fields of research.
taste sensor; lipid/polymer membrane; portable sensor; in-field evaluation
Intraocular lens implantation after opacified natural lens removal is the primary treatment for cataracts in developed countries. Cataract surgery is generally considered safe, but entails significant risks in countries where sophisticated sterile operating theaters are not widely available. Post-operative infection (endophthalmitis) is a potential blinding complication. Infection often results from bacterial colonization of the new lens implant and subsequent antibiotic-tolerant biofilm formation. To combat this risk, we developed a polymeric hydrogel system that can deliver effective levels of antibiotic over an extended period of time within the globe of the eye. Norfloxacin™ antibiotic was loaded into cross-linked poly(2-hydroxyethyl methacrylate) (pHEMA) gels, which were subsequently surface-modified with octadecyl isocyanate to produce a hydrophobic rate-limiting barrier controlling norfloxacin release. Octadecyl surface modification was characterized using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). A 15-min modification leads to a uniform surface coating and near zero order release of norfloxacin from the matrix. Norfloxacin released from coated pHEMA kills Staphylococcus epidermidis in suspension and on a simulated medical implant surface. With these data, we demonstrate a new and effective system for sustained drug release from a hydrogel matrix with specific application for intraocular lens surgery.
Drug delivery; Hydrogel; Intraocular lenses; Endophthalmitis; Infections
In this paper, we describe a graft polymerization/solvent immersion method for generating poly(2-hydroxyethyl methacrylate) (PHEMA) brushes in various patterns. We used a novel fabrication process, involving very-large-scale integration and oxygen plasma treatment, to generate well-defined patterns of polymerized PHEMA on patterned Si(100) surfaces. We observed brush- and mushroom-like regions for the PHEMA brushes, with various pattern resolutions, after immersing wafers presenting lines of these polymers in MeOH and n-hexane, respectively. The interaction between PHEMA and ferritin protein sheaths in MeOH and n-hexane (good and poor solvent for PHEMA, respectively) was used to capture and release ferritins from fluidic system. The “tentacles” behaver for PHEMA brushes was found through various solvents in fluidic system. Using high-resolution scanning electron microscopy, we observed patterned ferritin Fe cores on the Si surface after pyrolysis of the patterned PHEMA brushes and ferritin protein sheaths, which verify the “tentacles” behaver for PHEMA brushes.
PHEMA brush; Nanolithography; Ferritin
HEMA (2-hydroxyethyl methacrylate), a methacrylate commonly used in dentistry, was reported to induce genotoxic effects, but their mechanism is not fully understood. HEMA may be degraded by the oral cavity esterases or through mechanical stress following the chewing process. Methacrylic acid (MAA) is the primary product of HEMA degradation. In the present work we compared cytotoxic and genotoxic effects induced by HEMA and MAA in human gingival fibroblasts (HGFs). A 6-h exposure to HEMA or MAA induced a weak decrease in the viability of HGFs. Neither HEMA nor MAA induced strand breaks in the isolated plasmid DNA, but both compounds evoked DNA damage in HGFs, as evaluated by the alkaline comet assay. Oxidative modifications to the DNA bases were monitored by the DNA repair enzymes Endo III and Fpg. DNA damage induced by HEMA and MAA was not persistent and was removed during a 120 min repair incubation. Results from the neutral comet assay indicated that both compounds induced DNA double strand breaks (DSBs) and they were confirmed by the γ-H2AX assay. Both compounds induced apoptosis and perturbed the cell cycle. Therefore, methacrylic acid, a product of HEMA degradation, may be involved in its cytotoxic and genotoxic action.
Dental restorative materials; 2-hydroxylmethyl methacrylate; HEMA; Degradation; DNA damage; Cell cycle
Many anticancer agents have poor water solubility and therefore the development of novel delivery systems for such molecules has received significant attention. Nanocarriers show great potential in delivering therapeutic agents into the targeted organs or cells and have recently emerged as a promising approach to cancer treatments. The aim of this study was to prepare and use poly-2-hydroxyethyl methacrylate (PHEMA) nanoparticles for the controlled release of the anticancer drug doxorubicin.
PHEMA nanoparticles have been synthesized and characterized using FTIR and scanning electron microscopy (SEM), particle size analysis and surface charge measurements. We also studied the effects of various parameters such as percent loading of drugs, chemical architecture of the nanocarriers, pH, temperature and nature of the release media on the release profiles of the drug. The chemical stability of doxorubicin in PBS was assessed at a range of pH.
Suspension polymerization of 2-hydroxyethyl methacrylate (HEMA) results in the formation of swellable nanoparticles of defined composition. PHEMA nanoparticles can potentially be used for the controlled release of the anticancer drug doxorubicin.
Hydrogels pose unique challenges to nanoindentation including sample preparation, control of experimental parameters, and limitations imposed by mechanical testing instruments and data analysis originally intended for harder materials. The artifacts that occur during nanoindentation of hydrated samples have been described, but the material properties obtained from hydrated nanoindentation have not yet been related to the material properties obtained from macroscale testing. To evaluate the best method for correlating results from microscale and macroscale tests of soft materials, nanoindentation and unconfined compression stress-relaxation tests were performed on poly-2-hydroxyethyl methacrylate (pHEMA) hydrogels with a range of cross-linker concentrations. The nanoindentation data were analyzed with the Oliver–Pharr elastic model and the Maxwell–Wiechert (j = 2) viscoelastic model. The unconfined compression data were analyzed with the Maxwell–Wiechert model. This viscoelastic model provided an excellent fit for the stress-relaxation curves from both tests. The time constants from nanoindentation and unconfined compression were significantly different, and we propose that these differences are due to differences in equilibration time between the microscale and macroscale experiments and in sample geometry. The Maxwell–Wiechert equilibrium modulus provided the best agreement between nanoindentation and unconfined compression. Also, both nanoindentation analyses showed an increase in modulus with each increasing cross-linker concentration, validating that nanoindentation can discriminate between similar, low-modulus, hydrated samples.
There has been generally little attention paid to the utilization of biomaterials as an anti-myopia treatment. The purpose of this study was to investigate whether polymeric hydrogels, either implanted or injected adjacent to the outer scleral surface, slow ocular elongation. White Leghorn (gallus gallus domesticus) chicks were used at 2 weeks of age. Chicks had either (1) strip of poly(2-hydroxyethyl methacrylate) (pHEMA) implanted monocularly against the outer sclera at the posterior pole, or (2) an in situ polymerizing gel [main ingredient: poly(vinyl-pyrrolidone) (PVP)] injected monocularly at the same location. Some of the eyes injected with the polymer were fitted with a diffuser or a −10D lens. In each experiment, ocular lengths were measured at regular intervals by high frequency A-scan ultrasonography, and chicks were sacrificed for histology at staged intervals. No in vivo signs of either orbital or ocular inflammation were observed. The pHEMA implant significantly increased scleral thickness by the third week, and the implant became encapsulated with fibrous tissue. The PVP-injected eyes left otherwise untreated, showed a significant increase in scleral thickness, due to increased chondrocyte proliferation and extracellular matrix deposition. However, there was no effect of the PVP injection on ocular elongation. In eyes wearing optical devices, there was no effect on either scleral thickness or ocular elongation. These results represent “proof of principle” that scleral growth can be manipulated without adverse inflammatory responses. However, since neither approach slowed ocular elongation, additional factors must influence scleral surface area expansion in the avian eye.
poly(2-hydroxyethyl methacrylate); poly(vinyl-pyrrolidone); hydrogel; chick sclera; scleral remodeling; myopia
Econazole-eluting contact lenses with a novel design provided extended antifungal activity against the Candida albicans fungus. This drug-eluting contact lens could be used to treat and prevent fungal ocular infections.
To design a contact lens to treat and prevent fungal ocular infections.
Curved contact lenses were created by encapsulating econazole-impregnated poly(lactic-co-glycolic) acid (PLGA) films in poly(hydroxyethyl methacrylate) (pHEMA) by ultraviolet photopolymerization. Release studies were conducted in phosphate-buffered saline at 37°C with continuous shaking. The contact lenses and their release media were tested in an antifungal assay against Candida albicans. Cross sections of the pre- and postrelease contact lenses were characterized by scanning electron microscopy and by Raman spectroscopy.
Econazole-eluting contact lenses provided extended antifungal activity against Candida albicans fungi. Fungicidal activity varied in duration and effectiveness depending on the mass of the econazole-PLGA film encapsulated in the contact lens.
An econazole-eluting contact lens could be used as a treatment for fungal ocular infections.
Growth of poly(2-hydroxyethyl methacrylate) brushes on magnetic nanoparticles and subsequent brush functionalization with nitrilotriacetate-Ni2+ yield magnetic beads that selectively capture polyhistidine-tagged (His-tagged) protein directly from cell extracts. Transmission electron microscopy, FT-IR spectroscopy, thermogravimetric analysis, and magnetization measurements confirm and quantify the formation of the brushes on magnetic particles, and multilayer protein adsorption to these brushes results in binding capacities (220 mg BSA/g of beads and 245 mg His-tagged Ubiquitin/g of beads) that are an order of magnitude greater than those of commercial magnetic beads. Moreover, the functionalized beads selectively capture His-tagged protein within 5 min. The high binding capacity and protein purity along with efficient protein capture in a short incubation time make brush-modified particles attractive for purification of recombinant proteins.
polymer brush; magnetic beads; His-tagged proteins
A lab-on-a-chip system for pathogen detection is presented that integrates cell preconcentration, purification, PCR, and capillary electrophoretic (CE) analysis. The microdevice is comprised of micropumps and valves, a cell capture structure, a 100 nL PCR reactor, and a 5-cm long CE column for amplicon separation. Sample volumes ranging from 10 to 100 μL are introduced and driven through a fluidized bed of magnetically constrained immunomagnetic beads where the target cells are captured. After cell capture, beads are transferred using the on-chip pumps to the PCR reactor for DNA amplification. The resulting PCR products are electrophoretically injected onto the CE column for separation and detection of E. coli K12 and E. coli O157 targets. A detection limit of 0.2 cfu/μL is achieved using the E. coli O157 target and an input volume of 50 μL. Finally, the sensitive detection of E. coli O157 in the presence of K12 at a ratio of 1:1000 illustrates the capability of our system to identify target cells in a high commensal background. This cell capture-PCR-CE microsystem is a significant advance in the development of rapid, sensitive, and specific lab-on-a-chip devices for pathogen detection.
lab-on-a-chip; pathogen detection; cell capture; PCR; capillary electrophoresis
The objective of this study was to elucidate the effect of chemical structure and composition of the polymer matrix on the degree of vinyl conversion (DC) of copolymers (unfilled resins) and their amorphous calcium phosphate (ACP) composites attained upon photo-polymerization. The DC can also be an indicator of the relative potential of these polymeric materials to leach out into the oral environment un-reacted monomers that could adversely affect their biocompatibility. The following resins were examined: 1) 2,2-bis[p-(2′-hydroxy-3′-methacryloxypropoxy)phenyl]propane (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (1:1 mass ratio; BT resin) combined with hydroxyethyl methacrylate (HEMA; BTH resin) and with HEMA and zirconyl dimethacrylate (BTHZ resin), 2) urethane dimethacrylate (UDMA)/HEMA resins, and 3) pyromellitic glycerol dimethacrylate (PMGDMA)/TEGDMA (PT resin). To make composite specimens, resins were mixed with a mass fraction of 40 % zirconia-hybridized ACP. Copolymers and their composites were evaluated by near infra-red spectroscopy for DC after 1 d and 28 d post-cure at 23 °C. Inclusion of HEMA into the BT and UDMA resins yielded copolymers and composites with the highest DCs. The significantly lower DCs of PT copolymers and their composites are attributed to the rigid aromatic core structure, tetra-vinyl functionality and limited methacrylate side-chain flexibility of the surface-active PMGDMA monomer. There was, however, an increase in the 28 d DC for the PT materials as there was for the BTHZ system. Surprisingly, the usual decrease observed in DC in going from unfilled polymer to composite was reversed for the PT system.
amorphous calcium phosphate; copolymers; composites; degree of vinyl conversion
The objective of this study was to investigate the influence of the chemical structure of methacrylate monomers used in dentin adhesives on degree of conversion (DC), water sorption, and dynamic mechanical properties.
Materials and methods
Experimental adhesives containing 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA), 2-hydroxyethyl methacrylate (HEMA), and co-monomer, 30/45/25 w/w were photo-polymerized. Ethyleneglycol dimethacrylate (EGDM), diethyleneglycol dimethacrylate (DEGDM), triethyleneglycol dimethacrylate (TEGDMA), 1,3-glycerol dimethacrylate (GDM), and glycerol trimethacrylate (GTM) were used as a co-monomer. The adhesives were characterized with regard to DC, water sorption, and dynamic mechanical analysis and compared to control adhesive [HEMA/BisGMA, 45/55 w/w].
DC and water sorption increased with an increase in the number of ethylene glycol units in the monomer. Experimental adhesive containing GDM showed significantly higher storage moduli (p < 0.05) in both dry and wet samples than experimental adhesives containing EGDM or DEGDM. The rubbery moduli of adhesives containing GDM and GTM were found to be significantly greater (p < 0.05) than that of the control. Adhesives containing GTM exhibited the widest tanδ curves, indicating the greatest structural heterogeneity.
The hydrophilicity, functionality and size of monomers in dentin adhesives affected the water sorption, solubility, crosslink density and heterogeneity of the polymer network. The experimental adhesives containing GDM and GTM showed higher rubbery moduli, indicating higher crosslink density accompanied by a decrease in the homogeneity of the polymer network structure.
dentin adhesives; structure/property relationships; dynamic mechanical property; degree of conversion; water sorption
A new methacrylate monomer, trimethylolpropane mono allyl ether dimethacrylate (TMPEDMA), was synthesized and evaluated. This branched methacrylate was designed to increase esterase-resistance when incorporated into conventional HEMA (2-hydroxyethyl methacrylate)/BisGMA (2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane) dental adhesives. The new adhesives, HEMA/BisGMA/TMPEDMA in a 45/30/25 (w/w) ratio were formulated with H2O at 0 (A0T) and 8 wt % water (A8T) and compared with control adhesives (HEMA/BisGMA, 45/55 (w/w), at 0 (A0) and 8 wt % (A8) water). Camphoroquinone (CQ), 2-(dimethylamino) ethyl methacrylate and diphenyliodonium hexafluorophosphate were used as photoinitiators. The new adhesives showed a degree of conversion comparable with the control and improved modulus and glass transition temperature (Tg). Exposure of photopolymerized discs to porcine liver esterase for up to eight days showed that the net cumulative methacrylic acid (MAA) release in adhesives formulated with the new monomer and 8% water (A8T: 182 μg/mL) was dramatically (P < 0.05) decreased in comparison to the control (A8: 361.6 μg/mL). The results demonstrate that adhesives made with the new monomer and cured in water to simulate wet bonding are more resistant to esterase than conventional HEMA/BisGMA adhesive.
dentin adhesive; esterase resistance; methacrylate; biodegradation; properties
The adhesive interactions of block copolymers composed of poly(methyl methacrylate) (PMMA)/poly(acrylic acid) (PAA) and poly(methyl methacrylate)/poly(2-hydroxyethyl methacrylate) (PHEMA) with the proteins fibronectin, bovine serum albumin and collagen were studied by atomic force microscopy. Adhesion experiments were performed both at physiological pH and at a slightly more acidic condition (pH 6.2) to model polymer–protein interactions under inflammatory or infectious conditions. The PMMA/PAA block copolymers were found to be more sensitive to the buffer environment than PMMA/PHEMA owing to electrostatic interactions between the ionized acrylate groups and the proteins. It was found that random, diblock and triblock copolymers exhibit distinct adhesion profiles although their chemical compositions are identical. This implies that biomaterial nanomorphology can be used to control protein–polymer interactions and potentially cell adhesion.
block copolymers; atomic force microscopy; protein adhesion