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PubMed1975

Inactivation of hapten-modified bacteriophage by antibody: increased sensitivity of the assay in media containing polyethylene glycol.

Inactivation of dinitrophenylated bacteriophage T4 by porcine and rabbit anti-dinitrophenyl (DNP) antibodies was studied by the complex inactivation methods. The inactivation titers increased 20-30 times when polyethylene glycol, mol. wt. 6000, was added to the incubation media. Consequently, the detection of dinitrophenylated serum albumin with the modified bacteriophage could be carried out with higher sensitivity upon addition of polyethylene glycol.

Antibodies↗
PubMed2003

Surface grafting of glycidyl methacrylate on silica gel and polyethylene beads.

Surface grafting of glycidyl methacrylate (GMA) on silica gel and a polyethylene bead was performed by radical polymerization and radiation-induced polymerization, respectively, in order to improve softness. Subsequently, diethylene triamine (DETA), triethylene tetraamine (TETA), and iminodiacetic acid (IDA) were introduced to the grafted GMA for use as affinity columns. The efficiency of the affinity column was investigated by use of bovine serum albumin (BSA) and hemoglobin (Hb) as model proteins. The affinity degree of BSA was higher than Hb for the DETA and TETA column, whereas the affinity degree of Hb was higher than BSA for the IDA column supported by silica gel. The affinity degree of BSA was higher than Hb for the DETA and TTA column supported by polyethylene (PE) beads.

Amines↗
PubMed1993

Histologic identification of polyethylene wear debris using Oil Red O stain.

Ultra high molecular weight polyethylene (UHMWPE) wear particles are frequently implicated in causing failure of total joint arthroplasties by eliciting a foreign body reaction. The majority of these particles are subcellular and many are submicron in size. Identification of these small particles of UHMWPE by conventional histologic techniques is difficult. We have therefore investigated the utility of Oil Red O (ORO) stain to identify UHMWPE on histologic sections. A wide variety of specimens was studied including an experimental rabbit model with subcutaneous implantation of polyethylene particles as well as specimens from clinical cases with joint arthroplasties. The sensitivity and specificity of ORO stain was compared to conventional polarized light microscopy for the identification of particulate UHMWPE debris. The ORO stain was found to be as sensitive in identifying particulate UHMWPE debris as polarized light microscopy. However, ORO stain was less specific: two specimens did not contain any UHMWPE also stained with ORO. Careful examination of standard hematoxylin and eosin stained sections with polarized light was therefore more specific for the identification of particulate UHMWPE. As a single test, the ORO stain does not appear to offer any clear advantage specifically for the identification of UHMWPE.

Animals↗
PubMed2002

The effect of polyethylene particle phagocytosis on the viability of mature human macrophages.

Macrophages are the major cell type observed in the inflammatory membrane retrieved at implant revision surgery. In this study, mature human monocyte-derived macrophages (MDM) were adapted to a previously established in vitro model to examine the influence of high-density polyethylene (HDPE) particulate (4-10 microm) on MDM viability. HDPE particles were suspended in soluble type I collagen, which subsequently was solidified on glass coverslips. Mature human macrophages, derived from differentiating peripheral blood monocytes on polystyrene for 10 days, were incubated in culture media on collagen controls and collagen-particle substrata for 31 days. Histologic analysis demonstrated that MDMs were in contact with the particles at 2 h. The majority of the particles were associated with the cells within 24 h. Based on electron microscopy, those cells associated with the particles appeared to be morphologically activated rather than necrotic or apoptotic. Assessment of cell viability revealed no differences among the groups at 24 h, but at 31 days significantly more viable cells and higher DNA values were found associated with the particle groups versus the collagen controls. The histologic results validate human mature MDMs as a clinically relevant cell type for study of the role of polyethylene particulate in aseptic loosening. The cell viability results indicate that phagocytosis of HDPE is not toxic to MDMs but in fact prolongs MDM survival. The long-lived MDMs may play a role in perpetuating chronic inflammation surrounding implants.

Cell Separation↗
PubMed2001

Hemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: a review.

In 1984, low-density polyethylene (LDPE) and polymethylsiloxane (PDMS), two primary reference materials (PRM), were made available by the National Heart, Lung, and Blood Institute (NHLBI) as discriminatory tools for the validation of standardized and novel in vitro and in vivo tests in the evaluation of biomaterials. This article reviews the results and conclusions obtained by several studies investigating the hemocompatibility, in vitro biocompatibility, inflammatory response, and in vivo tissue reactions of these two reference materials. Variable results obtained with LDPE and PDMS in ex vivo hemocompatibility studies were attributed to the type of animal model used, the flow velocity of the circulating blood, the time of exposure, and the methodology used to measure blood cell adhesion or activation at the surface of the materials. In contrast, both the LDPE and PDMS appeared to be suitable reference materials when used in in vitro biocompatibility, inflammatory response, and in vivo studies. However, caution must be taken when interpreting the results, because gamma sterilization of these two materials as well as their origin (for example PDMS) are two critically important factors. In conclusion, we see a definite need for standardized hemocompatible parameters and better high-quality hemocompatibility studies on PRM. This review also suggests other materials as potential PRM candidates, namely, Biomer and Intramedic polyethylene.

Animals↗
PubMed1975

Early tissue infiltrate in porous polyethylene implants into bone: a scanning electron microscope study.

The results of the present study demonstrate the utility of the scanning electron microscope for characterizing the ultrastructure of the initial tissue infiltrate in porous polyethylene implants. Shortly after implantation a thin noncellular fibrous-like coating was observed to form on the pore surface. The cells observed in the polyethylene pellets 3 days after implantation were generally consistent with what one would expect to see in a hematoma. As early as 14 days after implantation much of the blood clot was replaced by newly formed bone spicules. Tissue shrinkage accompanying dehydration of the specimen for scanning electron microscope study although a disadvantage occasionally proved useful in that it provided the opportunity to study the internal surface of the fibrous coating when separated from the surface of the implant. Less shrinkage was observed in implants whose pores were filled with bone spicules.

Animals↗
PubMed1980

Detection of aluminum oxide and polyethylene wear particles from joint endoprostheses using cathodoluminescence and x-ray analysis in SEM.

A highly sensitive method to localize aluminum oxide or polyethylene wear particles in biological tissues is presented. Using the scanning electron microscope (SEM) with a special cathodoluminescence detector system, small amounts of these foreign materials can be visualized in simple frozen sections by their bright luminescence, even at low magnifications (200X). At higher magnifications, a differentiation of free as well as phagocytized aluminum oxide and polyethylene particles can be made due to their different behavior in light emission. In addition, aluminum oxide such as other metals can be identified by x-ray microprobe analysis. This combination of SEM with microprobe analysis and with the highly sensitive cathodoluminescence mode enables to detect and identify wear products from all the materials, commonly used in manufacturing artificial joint replacements.

Aluminum↗
PubMed1981

Effect of radiation sterilization and aging on ultrahigh molecular weight polyethylene.

The mechanical properties of polyethylene components used in prosthesis are altered after fabrication by the sterilization procedure and by the environmental and mechanical aging which occurs after implantation. To assess the importance and extent of these alterations, ultrahigh molecular weight polyethylenes from two sources, Hercules 1900 and RCH 1000C, were subjected to gamma-ray irradiation and aging in serum and argon environments. Changes induced by these treatments in the structural and mechanical parameters have been determined by a variety of experimental techniques. The effect of irradiation is to introduce crosslinks and to increase the degree of crystallinity resulting in changes in the tensile properties in the direction of higher stiffness and reduced ductility. Aging for six months produced similar changes with subtle differences. The results suggest that the initially low degree of crystallinity which results from the sluggish mobility of the very long chain molecules offers the opportunity for significant changes in the properties during use in the long run.

Crystallization↗
PubMed1986

In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride.

The cellular biocompatibility of low-density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extra-cellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21-day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In contrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).

Acid Phosphatase↗
PubMed1989

Elastic and ultimate properties of acrylic bone cement reinforced with ultra-high-molecular-weight polyethylene fibers.

A study of the fracture behavior of poly-(methyl methacrylate) (PMMA) bone cement reinforced with short ultra-high-molecular-weight polyethylene (Spectra 900) fibers is presented. Linear elastic and nonlinear elastic fracture mechanics results indicate that a significant reinforcing effect is obtained at fiber contents as low as 1% by weight, but beyond that concentration a plateau value is reached and the fracture toughness becomes insensitive to fiber content. The flexural strength and modulus are apparently not improved by the incorporation of polyethylene fibers in the acrylic cement, probably because of the presence of voids, the poor mixing practice and the weakness of the fiber/matrix interfacial bond. The present polyethylene/PMMA composite presents several advantages as compared to other composite cements, but overall the mechanical performance of this system resembles that of Kevlar 29/PMMA cement, with a few differences. Scanning electron microscopy reveals characteristic micromechanisms of energy absorption in Spectra 900/PMMA bone cement. A scheme for the strength of random fiber-reinforced composites, which is a simple extension of the Kelly and Tyson model for the strength of unidirectional composites, is presented and discussed. Young's modulus and the fracture toughness results are discussed in the framework of existing theories. More fundamental modeling treatments are needed in terms of fracture micromechanisms to understand and optimize the various mechanical properties with respect to structural parameters and cement preparation technique.

Bone Cements↗
PubMed1990

The wear behavior of ion-implanted Ti-6A1-4V against UHMW polyethylene.

Nitrogen-ion-implanted Ti-6A1-4V against UHMW polyethylene was tested on a joint simulator to evaluate the wear behavior under different conditions. It was concluded that the polymer wear rate was not affected by ion implantation. The metallic wear, on the other hand, was substantially reduced by this treatment. It was also found that ion implantation resulted in good protection of the metal surface against third-body wear by PMMA, while the introduction of C.P. titanium particles in the joint initiated tremendous wear. Although ion implantation improved the wear of titanium alloy against UHMW polyethylene, the durability of the implanted layer needs further study.

Alloys↗
PubMed1993

Relationship between arterial thrombosis and neutralization of a polyethylene ionomer.

The influence of three levels of sodium neutralization of an ethylene/methacrylic acid copolymer on in vivo blood compatibility was studied in a canine arterial model. Effects due to sample fabrication methods (thermal pressing versus solution casting) were also monitored. Sodium content, sodium release, hydrogen dissociation, and localization of anionic groups were noted. Polymer surface energy, surface morphology, water uptake, and thermal properties were characterized. Material characterization and in vivo implantation disclose the following: 1) Thermal pressing generated oxidation degradation products that decreased in vivo blood compatibility. Solution-cast samples adhered and activated fewer blood elements. 2) Platelets and leukocytes were sensitive to differences in shear rate in the carotid and femoral arteries, with the femoral site tending toward higher shear, more platelet deposition and fewer leukocytes. 3) The surface properties of the polyethylene control, 0% Na, and 50% Na samples tended to be similar. These properties were different from the 100% Na sample. The 100% Na ionomer was more hydrophilic, had a higher polar component for its surface energy, and was unique in exhibiting discrete ionic clusters 1-10 microns in diameter on its surface. 4) These differences were manifested in vivo by platelet activation and thrombus development on the polyethylene, 0% Na, and 50% Na implants, while the 100% Na implant surfaces were predominantly covered by singly adherent, unactivated platelets. 5) It is proposed that the improvement in biocompatibility for the 100% Na ionomer is due to the cluster development in the neutralized methacrylic component and that either directly, or through appropriate protein adsorption and/or conformational adjustment to the cluster regions, platelets are not activated and do not initiate the coagulation mechanism.

Absorption↗
PubMed1994

Tumorigenicity of poly-L-lactide (PLLA) plates compared with medical-grade polyethylene.

Poly-L-lactide (PLLA) plates, 20 x 10 x 1 mm in size, with flat surfaces, were implanted into 50 young male Wistar rats subcutaneously, and the incidence of tumors for 2 years under specific pathogen-free (SPF) conditions was evaluated. Tumors arose in 22 rats (at the implant sites in 20, and distant from the implantation site in 2). As a control, plates of medical-grade polyethylene of the same shape were implanted into 50 rats. Tumors appeared in 23 of these rats (21 at the sites of the plates, and 2 ectopically). In 30 rats given sham operations, no tumors appeared in the 2 year observation period. Histologically, all the tumors were mesenchymal malignant tumors resembling fibrosarcoma or malignant fibrous histocytoma (MFH) in humans. In 6 of the PLLA tumors and 3 of the PE tumors, bone formation was observed. There was no significant difference between the incidence of tumors caused by PLLA plates and that of tumors caused by medical-grade polyethylene plates. Macroscopically, PLLA plates retained their initial shape for 2 years. Scanning electron microscopy revealed small holes on the surfaces of the plates, and their molecular weight was reduced to 8% of the initial value.

Animals↗
PubMed1995

Low-voltage scanning electron microscopic imaging of ultrahigh-molecular-weight polyethylene.

Submicron ultrahigh-molecular-weight polyethylene (UHMWPE) wear particles from total joint prostheses may contribute to implant failure through particle-mediated aseptic loosening. The purpose of this study was to examine the microstructure of virgin UHMWPE powder to determine its morphology for future comparison with wear debris. A new method of low-voltage scanning electron microscopy (LVSEM) in an oil-free vacuum was applied, which produced high-resolution images of UHMWPE micromorphology, while minimizing specimen damage and obviating the need for image processing. GUR 415 UHMWPE virgin powder particles were examined by using routine high-voltage SEM, LVSEM, and image analyses. LVSEM showed that UHMWPE particles were composed of submicron-size spherical subparticles connected by numerous nanometer-size fibrils. These spherical subparticles had a highly textured surface morphology seen only by LVSEM. Fracture of the nanometer-size fibrils was observed. Routine high-voltage SEM obfuscates the intricate and delicate UHMWPE micromorphology as well as the damage done by the accompanying high-voltage electrons. This study suggests that the micromorphology of wear particles previously studied with routine high-voltage SEM was overlooked or damaged, justifies the need for LVSEM in future studies, and raises the question of what is the true morphology of polyethylene wear debris retrieved from human tissues.

Biocompatible Materials↗
PubMed2003

Ultra-high molecular weight polyethylene oxidation reduces metalloproteinase 2 secretion in human osteoblast-like cells in vitro: a mechanism of modulation of extracellular matrix.

Ultra-high molecular weight polyethylene (UHMWPE) sterilization with gamma rays induced high oxidation levels both on the surface and in the bulk that alter its structure and mechanical properties. The oxidation process of gamma-radiated UHMWPE induces a reduction of molecular weight and, consequently, a less abrasive resistance that has been related, among others, to the failure of UHMWPE in vivo. To explain the role of cells in such events, human osteoblast-like cells were seeded onto UHMWPE and oxidized UHMWPE discs. Cellular viability and morphology were evaluated along with matrix metalloproteinases (MMPs) production and activity. Oxidized UHMWPE did not induce any significant cytotoxic effects as observed by lactate dehydrogenase activity compared to the nonoxidized form; no changes in the cell morphology after 4 and 8 days proliferation were observed. In growth medium metalloproteinase 2 (gelatinase-A, MMP-2) was produced and released by osteoblast-like cells. We observed that cells grown onto oxidized UHMWPE discs decreased the release and activity of MMP-2 after 4 and 8 days culture compared to cells grown on control and non-oxidized UHMWPE discs; metalloproteinase 9 (gelatinase-B, MMP-9) release was not significantly influenced. The absence of cytotoxic and morphological effects in the presence of a down-regulation of MMP-2 release and activity suggest that oxidized polyethylene surfaces may modulate matrix remodeling and, consequently, bone formation.

Biocompatible Materials↗
PubMed2003

Local infusion of FGF-2 enhances bone ingrowth in rabbit chambers in the presence of polyethylene particles.

Osseointegration of porous-coated implants during revision arthroplasty procedures is often impeded due to the presence of residual granuloma, particulate debris, and a sclerotic, dysvascular bone bed. We hypothesized that local infusion of recombinant fibroblast growth factor (FGF-2) would increase bone ingrowth in an in vivo model of tissue differentiation in the rabbit tibia in the presence of phagocytosable polyethylene particles. A drug test chamber (DTC) was implanted in the proximal medial tibial metaphysis of mature rabbits unilaterally. The chamber contained a 1x 1 x 5-mm tunnel for tissue ingrowth, and was connected to an osmotic diffusion pump. FGF-2 was infused at dosages of 0, 0.5, 5, 50, or 500 ng/day for a 3-week period, with subsequent harvesting of the ingrown tissue after each 3-week treatment. The effects of ultrahigh molecular weight polyethylene particles (0.5-microm diameter) on tissue ingrowth were determined by adding particles to the chamber at concentrations of 5.8 x 10(11) (low dose) or 1.7 x 10(12) (high dose) particles/mL, with and without infusion of 50 ng/day of FGF for 3 weeks. The tissue forming in the chamber was harvested after each treatment for histologic processing and morphometric analysis of bone ingrowth. Statistical analysis was performed using parametric tests (ANOVA), nonparametric tests (Kruskal-Wallis test) and post hoc tests. In the absence of particles, infusion of 50 ng FGF-2 per day yielded the greatest amount of bone ingrowth. The high dose of particles suppressed bone ingrowth into the chamber, but the low dose particles did not (p = 0.0002, 95% confidence limits = 9.19-18.80). Infusion of 50 ng FGF-2 per day significantly increased net bone formation in the presence of high-dose UHMWPE particles (p = 0.039, 95% confidence limits = 1.41-6.79). There was a trend for decreased numbers of vitronectin-receptor positive (osteoclast-like) cells with the addition of FGF-2, compared to particles alone (p = 0.08). Local delivery of FGF-2 may prove useful in mitigating the adverse effects of wear debris (e.g., in treating early osteolytic lesions), and facilitating osseointegration of revision total joint replacements in situations where the bone bed is suboptimal and residual particles and granulomatous tissue are present.

Animals↗
PubMed2004

Vacuum ultraviolet treatment of polyethylene to change surface properties and characteristics of protein adsorption.

The effects of vacuum ultraviolet (VUV) treatment on surface chemical composition morphology and albumin adsorption for low-density polyethylene (LDPE) and high-density polyethylene (HDPE) were investigated. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra and contact angle measurements indicated the formation of oxygen-containing polar groups and double bonds under VUV photooxidation in the presence of air or under VUV irradiation in vacuum. Scanning electron microscopy revealed the development of regular structure with the period about 1 microm on the surface of LDPE and HDPE during VUV photooxidation. The correlation between amount of tightly adsorbed albumin and surface concentration of carboxyl groups generated by VUV irradiation was found. The aging effect for protein adsorption during long storage of VUV irradiated samples in air or phosphate-buffered saline (PBS) was studied. The obtained results prove the VUV irradiation provides a high potential to regulate protein adsorption on polymers for biomedical applications.

Adsorption↗
PubMed2005

In vitro evaluation of biocompatibility of beta-tricalcium phosphate-reinforced high-density polyethylene; an orthopedic composite.

Beta-tricalcium phosphate-reinforced high-density polyethylene (beta-TCP/HDPE) is a new biomaterial which was made as a copy of bone composition with the aim of replacement of bony tissues. The composite samples were prepared using medical grade TCP powder and granular polyethylene. The raw materials were first compounded and the resulting composite preforms were compression molded into desired shape. The biocompatibility of composite samples with different volume fractions of TCP (20, 30, and 40 vol %) was assessed by proliferation, alkaline phosphatase (ALP), and cell adhesion assays using G-292 osteoblast cells. Cell-material interaction on the surface of the composites was observed by scanning electron microscopy (SEM). The effect of beta-TCP/HDPE on the behavior of G-292 cells was compared with those of a composite and a negative control samples. Results showed the composite samples had a higher proliferation rate of G-292 cells in the presence of composite samples as compared to the composite control sample after 3, 7, and 14 days of incubation period. ALP production after incubation in the presence of composite samples was seen to peak on the day 7. The number of adhered cells on the composite samples was higher than the numbers adhered on composite and negative control samples after the above incubation periods. Morphology investigation of adhered cells by SEM indicated a normal morphology and also many of the cells were in the process of cell division. The above results indicate that beta-TCP/HDPE samples are biocompatible, nontoxic, and in some cases show an increase in the proliferation rate of the cells, ALP production, and cell adhesion as compared to the control counterparts.

Alkaline Phosphatase↗