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PubMed2006

Preparation of nanosheet polyethylene with heterogeneous metallocene catalyst and formation mechanism of nanosheet polyethylene.

Silica with small and regular pore sizes was synthesized by hydrothermal crystallization and investigated with thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption, and scanning electron microscopy (SEM). The ethylene polymerization was carried out with the silica-supported metallocene catalyst, and the morphology of the resultant polyethylene was investigated with SEM. It was found that the silica could break up into sheet fragments instantaneously during polymerization and the polyethylene could replicate it to obtain nanosheet polyethylene. A possible formation mechanism of the nanosheet polyethylene is proposed.

Catalysis↗

PubMed1988

[Is high-density polyethylene suitable as an implant material in cement-free anchoring of hip endoprostheses? A histomorphologic study of an explanted polyethylene screw-in acetabula].

Firmly attached screw-in polyethylene acetabula which had been implanted for between 16 and 54 months were explanted after autopsies and subjected to macroscopic, radiologic and histologic examination. Metaplasias were seen around the threads and on the floor of the acetabulum. Their tendency to ossify represents an attempt at secondary stabilization. Due to the low stability of the polyethylene this causes increased wear on the floor of the acetabulum. The small defects in the polyethylene found in the threads, resembling damage done by mice, may be a sign of biodegradation. In view of the tissue reactions pointed out, the material stability of the polyethylene needs to be improved or implantation must be restricted to a very limited range of indications.

Acetabulum↗

PubMed2005

The measurement of creep in ultrahigh molecular weight polyethylene: a comparison of conventional versus highly cross-linked polyethylene.

Quantification of creep of highly cross-linked polyethylene would enable separation of creep from wear when evaluating femoral head penetration into polyethylene. We compared creep magnitude of a highly cross-linked versus conventional polyethylene in the laboratory. Twelve acetabular liners of each material were tested, 6 of which had a 32-mm inner diameter (ID) and 6 had 28-mm ID. Creep was measured using coordinate measuring machines during loading at 2 Hz without motion to 4 million cycles. Penetration into 32-mm ID conventional liners reached 97 microm versus 107 microm for highly cross-linked material, not significant. Penetration into 28-mm conventional liners was 132 microm versus 155 microm for highly cross-linked material (P = .017). Ninety percent of the creep had occurred by 2.5 million cycles.

Arthroplasty, Replacement, Hip↗

PubMed2005

Early femoral head penetration of a highly cross-linked polyethylene liner vs a conventional polyethylene liner: a case-controlled study.

Forty highly cross-linked, polyethylene-liner primary total hip arthroplasties were matched by sex, age, and body mass index with 40 conventional polyethylene primary total hip arthroplasties to compare femoral head penetration rates. Both inserts were 10 degrees liners manufactured by the same company and packaged in a nitrogen/vacuum atmosphere. Identical acetabular components and a 28-mm cobalt chrome femoral head were used in all cases. The mean femoral head penetration rate for the highly cross-linked and conventional polyethylene was 0.05 (range, 0.01-0.09) and 0.12 (range, 0.02-0.29) mm/y, respectively, a 58.33% reduction in femoral head penetration (P < .001). In this short-term follow-up study (mean, 47.73 months), both reduced "bedding-in" and reduced wear may contribute to the observed decrease in femoral head penetration.

Aged↗

PubMed2006

Peptide-polyethylene glycol conjugates: synthesis and properties of peptides bearing a C-terminal polyethylene glycol chain.

The introduction of a polyethylene glycol chain has become a popular tool for increasing water solubility and bioavailability. Our interest in the development of catalytically active peptides and the selective recognition of peptides has led us to investigate strategies to increase the solubility of peptides in organic solvents. Specifically, we became interested in the introduction of solubilizing moieties at the C-terminus of two peptides. Here we present different synthetic strategies for the preparation of peptide-polyethylene glycol conjugates and discuss the effect of the polyethylene glycol chain on the solubility and other properties, such as the catalytic activity of these peptides.

Catalysis↗

PubMed2003

Determination of polyethylene glycol in low-density polyethylene by large volume injection temperature gradient packed capillary liquid chromatography.

Polyethylene glycol (PEG) 20000 in low-density polyethylene has been determined using column switching and inverse temperature programming in reversed-phase packed capillary liquid chromatography with evaporative light scattering detection. PEG 20000 was extracted into water from the polyethylene dissolved in toluene and PEG 35000 was added as an internal standard (I.S.). The samples in aliquots of 100 microl were reconcentrated on the enrichment column using a loading mobile phase of acetonitrile-water (3:97, v/v) at a flow-rate of 75 microl/min for 3 min, then back-flushed and separated on the analytical column with acetonitrile-THF-water (40:5:55, v/v) as mobile phase. The column temperature was reduced from 68 to 55 degrees C with a ramp of -1.5 degrees C/min, held constant for 3 min and then reduced further to 45 degrees C with a -1.5 degrees C/min ramp and kept constant for 1 min. The analysis runtime was 20 min. The recovery of PEG 20 000 was determined to 65.1% with 2.8% RSD and the mass limit of detection of PEG 20 000 was 1.25 microg. The within-assay and between day precision of the retention times of both PEG 20000 and PEG 35000 displayed RSD of less than 1.1% (n = 9), while the overall area ratio RSD of 100 microg/ml PEG 20000 over PEG 35000 was 1.3% (n = 9). The method was linear within the investigated concentration range 25-125 microg/ml (R2 = 0.9983). In addition, a mixture of PEG 4000, 8000, 10000, 20000 and 35000 was analysed on the system to demonstrate the possibility of analysing several PEGs in a sample with the use of temperature gradient elution.

Chromatography, Liquid↗

PubMed2002

Revision of polyethylene acetabular liners with a cemented polyethylene cup: a laboratory study.

Various technique parameters for the revision of failed polyethylene acetabular liners using a cemented polyethylene cup were evaluated in this laboratory study. The effects of cement mantle thickness and roughening the inner surface of the shell or outer surface of the cup were determined by measuring cup dissociation strength from the metal shell after cyclic loading of the cup. The use of a cement mantle thickness of 2 to 4 mm provided dissociation strengths 3 to 4 times greater than that of the original, press-fit polyethylene liner. If a failed acetabular liner is revised by a cemented cup within the existing, well-fixed, metal shell, the size of the cup selected should create a cement mantle of <4 mm. Roughening the inside of a smooth shell or one with few screw-holes increases fixation strength approximately 20% but also creates particulate debris.

Arthroplasty, Replacement, Hip↗

PubMed1993

Use of polyethylene glycol-bound superoxide dismutase, polyethylene glycol-bound catalase, and nimodipine to prevent hypoxic ischemic injury to the brain of newborn pigs.

OBJECTIVE: To determine if polyethylene glycol-bound superoxide dismutase and catalase and nimodipine, alone or in combination, will ameliorate hypoxic ischemic injury to the brain. SUBJECTS: A total of 78 newborn (0 to 3 days) pigs were used. DESIGN: Prospective, blinded, randomized, controlled trial. INTERVENTIONS: The piglets were subjected to hypoxic ischemic brain injury. Carotid arteries were ligated at time 0 and BP was reduced one third by hemorrhage. At 15 mins, FIO2 was reduced to 0.6. At 30 mins, carotids were released, blood was reinfused, and FIO2 was increased to 1.0. Pigs were randomly assigned at time 35 mins to receive either: 10,000 U/kg of polyethylene glycol-bound superoxide dismutase and catalase (group 1); 0.5 mg/kg of nimodipine (group 2); both 10,000 U/kg of superoxide dismutase and catalase and 0.5 mg/kg of nimodipine (group 3); or no drugs (controls). MEASUREMENTS: The time after reoxygenation for return of electroencephalogram, respiration, blink and pain were recorded in minutes as well as a neurologic examination at 1, 2, and 3 days and pathologic examination of the brain at 3 days, both by blinded observers. MAIN RESULTS: There were no significant differences in the four groups. CONCLUSIONS: Polyethylene glycol-bound superoxide dismutase and catalase, and nimodipine, either alone or in combination, do not ameliorate hypoxic ischemic injury to the brain in the newborn pig when given 5 mins after reoxygenation.

Animals↗

PubMed1999

Porous polyethylene channel implants: a modified porous polyethylene sheet implant designed for repairs of large and complex orbital wall fractures.

PURPOSE: To evaluate the effectiveness of a modified porous polyethylene implant in orbital fracture repair. A porous polyethylene channel implant (PPCI) has internal channels that accept mini- or microplates from conventional plating systems, facilitating fixation to bone in the reconstruction of large, complex orbital fractures. METHODS: The authors used 29 PPCIs to repair 25 orbits. Seventeen cases involved repair of an acute (less than two weeks after injury) fracture of one or more orbital walls. Eight cases represented delayed reconstruction of orbital walls for late enophthalmos or for residual defects after previous operations. RESULTS: A PPCI provides a stable platform for orbital soft tissue. Excellent results were obtained in all patients with acute orbital fractures, whereas good or excellent corrections of enophthalmos and hypoglobus were achieved in all patients who underwent late repair. There were no instances of orbital infection, implant exposure or migration, worsening diplopia, visual loss, or loss of structural support during 31 months of follow-up. CONCLUSIONS: A PPCI allows controlled placement of a porous polyethylene sheet with secure fixation to stable bone. The implant design allows it to be cantilevered from the orbital rim to serve as a stable platform when fractures are too large to support the implant in the posterior orbit. PPCIs are ideally suited for reconstruction of defects resulting from displacement of orbital walls and for repair of posterior floor fractures, medial wall fractures, and combined floor and medial wall defects.

Adult↗

PubMed1991

Biological responses to polyethylene oxide modified polyethylene terephthalate surfaces.

Polyethylene oxide (PEO) of molecular weights 5,000, 10,000, 18,500, and 100,000 g/mol was covalently grafted to surfaces of otherwise cell adhesive polyethylene terephthalate (PET) films. Analysis of these surfaces by measurement of contact angles and ESCA verified the presence of the grafted PEO. Protein adsorption assays of radiolabeled albumin and fibrinogen showed a marked reduction in adsorbed protein for the 18,500 and 100,000 molecular weight PEO coupled surfaces. Cell growth assays using human foreskin fibroblasts in culture showed that the higher-molecular-weight PEO surfaces supported cell growth to a much lower extent than the two lower-molecular-weight PEOs. Flow of whole blood over these surfaces and visualization of platelet adherence using epifluorescence video-microscopy showed very low platelet adherence only on the two higher-molecular-weight PEO coupled surfaces. Scanning electron microscopy corroborated these results. It was concluded that PEO of molecular weights neighboring 18,500 and higher was effective in reducing protein adsorption and cellular interactions on these surfaces.

Adsorption↗

PubMed2026

Diet-dependent effects of an environmentally relevant dose of polyethylene and polyethylene terephthalate on white adipose tissue and systemic insulin resistance in mice.

As human exposure to micro- and nanoplastics (NPs) is unavoidable, it remains unclear whether dietary composition can modulate their health impacts. To address this, we investigated the metabolic effects of two common yet understudied polymers, polyethylene (PE) and polyethylene terephthalate (PET), in mice with either healthy or energy-dense diet. C57BL/6 J male mice were exposed to an environmentally relevant dose of PE or PET (100 nm, 25 mg/kg BW/day) for 29 weeks under either a normal diet (ND) or a high-fat diet (HFD). The metabolic consequence of NP exposure was highly diet-dependent. In ND-fed mice, PE and PET reduced white adipose tissue (WAT) mass, with PET inducing metabolic changes that toward a lipodystrophy-like state. Conversely, in HFD-fed mice, both polymers impaired systemic insulin sensitivity. Regardless of diet, PE and PET promoted immunoglobin G (IgG) accumulation in epididymal WAT, with PE-exposed lean mice exhibited the most robust IgG elevation, WAT fibrosis and impaired adipogenesis. These findings demonstrate that chronic, environmentally relevant PE or PET exposure disrupts metabolic health in male mice under both dietary contexts. While dietary composition dictates the specific metabolic phenotype, it does not prevent adverse outcomes. This complicates lifestyle-based mitigation strategies and underscores the urgent need for environmental source controls.

Insulin Sensitivity↗

PubMed2006

Oxidation in ultrahigh molecular weight polyethylene and cross-linked polyethylene acetabular cups tested against roughened femoral heads in a hip joint simulator.

This study was aimed at comparing the oxidative degradation of commercial acetabular cups made of cross-linked polyethylene (XLPE) and conventional ultrahigh molecular weight polyethylene (UHMWPE). After testing against deliberately scratched CoCrMo femoral heads in a hip joint simulator, the cups, microtomed parallel to the articulating surface, were analyzed by IR spectroscopy. Due to the potential for artifacts caused by absorbed contaminants, the IR spectra were compared only after hexane extraction; actually, XLPE was found to absorb more serum than UHMWPE. The two sets of unworn acetabular cups showed different oxidation patterns with consequently different distributions of carbonyl species; unworn XLPE was characterized by lower contents of carbonyl species and hydrogen-bonded alcohols and higher contents of trans-vinylene species than unworn UHMWPE. Upon simulator testing, UHMWPE showed more significant changes in oxidation indexes and distribution of carbonyl compounds than XLPE, confirming a better wear behavior for XLPE under the adopted testing conditions.

Biocompatible Materials↗

PubMed2003

Influence of flavour absorption by food-packaging materials (low-density polyethylene, polycarbonate and polyethylene terephthalate) on taste perception of a model solution and orange juice.

The influence of flavour absorption by low-density polyethylene (LDPE), polycarbonate (PC) and polyethylene terephthalate (PET) on taste perception of a model solution containing seven flavour compounds and orange juice in glass bottles was studied with and without pieces of the respective plastic films after dark storage at 20 degrees C. Owing to absorption, the amount of flavour compounds in the model solution exposed to LDPE decreased substantially. From the model flavour solution valencene was almost completely absorbed by LDPE, followed to a lesser extent by decanal, hexyl acetate, octanal and nonanone. Less flavour compounds were absorbed from the model solution by PC and PET. In contrast to LDPE, valencene was absorbed in the lowest amounts and decanal in the highest. Limonene was readily absorbed from orange juice by LDPE, while myrcene, valencene, pinene and decanal were absorbed in smaller quantities. Only three flavour compounds were absorbed from orange juice by PC and PET in very small amounts: limonene, myrcene and decanal. Although the flavour content between controls and polymer-treated samples differed substantially, the loss of flavour compounds due to absorption by LDPE, PC and PET did not influence taste perception of a model solution and orange juice significantly up to 29 days of dark storage at 20 degrees C as determined by triangular taste panel tests.

Absorption↗

PubMed1994

Studies on a novel anterior cruciate ligament polyethylene fiber prosthesis: the histomorphological pattern of organization and bony anchorage of a polyethylene fiber prosthesis in the stifle of the goat.

The anterior cruciate ligament of goats was substituted by a high-tensile polyethylene fiber prosthesis. The animals were sacrificed after 6-12 months. Histologically, the implants were separated from a newly formed bony shell by a thick fibrous interface membrane, which was anchored to the bone by Sharpey-like fibers. Within the joint cavity, the implants were enclosed in thick fibrous sheaths, which were continuous with the intra-osseous interface membranes. While the inner granulomatous layer of the interface membrane extended in between the polyethylene fibrils for a short distance, the bulk of the prosthesis was poorly organized. A thick central fibrous band accompanied the intra-osseous and intra-articular portions of the implants throughout their entire lengths. Oblique fibrous tracks linked the interface membranes with the central fibrous bands. The intra-osseous tunnels were considerably expanded when compared to the initially drilled tunnels.

Animals↗

PubMed2004

Surface analysis of early retrieved acetabular polyethylene liners: a comparison of conventional and highly crosslinked polyethylenes.

In vivo wear behavior of 16 highly cross-linked and 19 conventional polyethylene acetabular explants, at an average in vivo duration of 6 months were studied. Highly cross-linked groups showed machining marks from the original manufacturing process in some areas and extensive scratching and some polishing of the articulating surfaces. The conventional group showed greater loss of machining marks, scratching, and polishing. Representative samples were melted to allow recovery of plastic deformation and to show true removal of material caused by wear. Melt-recovery experiments consistently showed the disappearance of surface scratches and the restoration of the original machining marks in the highly cross-linked explants. In the conventional group, few of the scratches were eliminated and only limited restoration of the machining marks was apparent. These observations support the hypothesis that the early in vivo scratching of highly cross-linked polyethylene acetabular liners is primarily caused by plastic deformation.

Cross-Linking Reagents↗

PubMed2005

Preparation and evaluation of poly(polyethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monolith for protein analysis.

A poly(polyethylene glycol methyl ether acrylate-co-polyethylene glycol diacrylate) monolith was prepared by UV-initiated polymerization. Methanol and ethyl ether were selected as porogens from a variety of organic solvents to achieve the desirable characteristics of the monolith. The preparation of the monolith could be achieved within 10 min. The monolith was macroscopically homogeneous, had low flow resistance, and did not swell or shrink significantly in tetrahydrofuran. Inverse size-exclusion data indicate that the monolith had a total porosity of 75.4% and an internal porosity of 9.1%. The monolith could be used for size-exclusion separation of peptides, although it could not separate proteins with molecular masses between 10 and 100 K due to its unique pore size distribution. It was found to resist adsorption of proteins in capillary liquid chromatography when using 100 mM phosphate buffer (pH 7.0) containing 0.5 M NaCl. Complete recovery of both acidic and basic proteins was achieved. The monolith can be used for applications in which inert materials are required for protein analysis.

Acrylates↗

PubMed1986

Efficacy and safety of hemoglobin-polyethylene glycol conjugate (pyridoxalated polyethylene glycol hemoglobin) as an oxygen-carrying resuscitation fluid.

The safety and efficacy of a conjugate of pyridoxalated hemoglobin and polyethylene glycol (pyridoxalated PEG hemoglobin) were evaluated after administration to rats. The LD50 (lethal dose for 50% survival of group) of pyridoxalated polyethylene glycol (PEG) hemoglobin was greater than 200 ml/kg. Any pro- or anticoagulation activity was not demonstrated in in vitro coagulation tests. One day after 70% exchange-transfusion with pyridoxalated PEG hemoglobin, slight elevations of the serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminase, and blood urea nitrogen values, which were 101.7 +/- 22.6 IU/L, 33.3 +/- 7.2 IU/L, and 23.1 +/- 1.4 mg/dl, respectively, were observed. However, these values were in the normal range after 3 days. With greater than 90% exchange-transfusion, all rats exchange-transfused with pyridoxalated PEG hemoglobin survived for greater than 2 weeks in contrast to the death of all the rats exchange-transfused with stroma-free hemoglobin or albumin.

Animals↗

PubMed1991

In vitro studies of water activity and bacterial growth inhibition of sucrose-polyethylene glycol 400-hydrogen peroxide and xylose-polyethylene glycol 400-hydrogen peroxide pastes used to treat infected wounds.

Water activity and bacterial growth inhibition have been studied in formulations comprising either sucrose or xylose along with polyethylene glycol 400 and hydrogen peroxide. The pastes are chemically stable for 6 months if stored at 2 to 8 degrees C and have been shown to lower water activity to levels below those essential for bacterial growth and to be bactericidal even when diluted up to 50% with serum. Of the organisms tested, Staphylococcus aureus proved the least susceptible to the bactericidal effects of these pastes, and candida and gram-negative organisms proved the most susceptible. Pastes without hydrogen peroxide were less rapidly bactericidal than pastes with hydrogen peroxide, while polyethylene glycol 400 itself was found to have considerable antimicrobial activity. It is suggested that sucrose paste may be of benefit as a treatment for infected and malodorous wounds.

Animals↗