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PubMed2004

Bisphenol A from dental polycarbonate crown upregulates the expression of hTERT.

Bisphenol A (BPA) is one of the endocrine-disrupting chemicals (EDCs) that possess estrogen-like biologic activity. Many dental materials have been reported to release BPA. However, there are few reports available on the release of BPA from dental polycarbonates. The purpose of this study was to investigate the release of BPA from dental polycarbonate crowns and to evaluate the estrogenic activity of BPA. Polycarbonate crowns were immersed in five solvents (water, ethanol, n-hepthane, acetic acid, and acetonitrile) at 37 or 65 degrees C for 24 h. The elution from the material was analyzed by high-performance liquid-chromatography (HPLC) and mass-spectrometry (MS) analysis. BPA release was detected corresponding to the degradation of dental polycarbonates under the some storage conditions (ethanol, acetic acid, and acetonitrile). A previous report proved that estrogen increased human telomerase catalytic subunit (hTERT) mRNA, whereas the effect of EDCs on the hTERT promoter has never been reported. The estrogenic activity of BPA was analyzed by luciferase assay with the use of the hTERT promoter. This assay revealed that BPA was a positive regulator of hTERT transcription. In addition, quantitative real-time PCR analysis showed that BPA increased the expression level of hTERT mRNA in MCF7 cells. Herein, it is demonstrated that hTERT is a new target of BPA.

Benzhydryl Compounds↗

PubMed1986

Universal polycarbonate fracture splint and its direct bonding potential.

A polycarbonate splint has been presented which offers the advantage of the ability of being bonded and/or wired into place. This new type of splint offers several advantages over traditional steel splints. The splint can be bonded and/or wired to the dental arch; the bonding method can be a time-saver. The polycarbonate material is readily malleable and does not possess an intrinsic tension or spring usually found in plastics when they are bent or shaped. The splint is highly esthetic when compared to steel splints. Polycarbonate splints are more economical than steel splints. Molded plastic surfaces are smoother and are more compatible with the oral mucosal than the stamped steel surfaces. Finally, and most importantly, the patient acceptance of polycarbonate splints appears to be very good in comparison with steel splints. The above advantages seem to indicate that the future acceptance of this type of splint for maxillofacial injuries will be good, although, it should be understood that plastic splints are not as strong as steel splints and may occasionally break after several weeks of use. Breakage, however, may not cause the splint to become unusable and usually does not occur until after the 4th week of use, if at all.

Acid Etching, Dental↗

PubMed2000

Bonding of light-cured glass ionomer cement to polycarbonate resin treated with experimental primers.

The effect of experimental primers on the shear bond strength of polycarbonate composite resin with light-cured glass ionomer cements was investigated. Mixtures of methylmethacrylate (MMA) with the comonomers 2-hydroxyethyl methacrylate (HEMA), triethyleneglycol methacrylate (TEGDMA), and bisphenol-A-glycidymethacrylate (bisGMA) were used as primers. Polycarbonate composite resin rods of circular cross section and plates were bonded, with and without precured and nonprecured primers, using 2 light-cured glass ionomer cements (commercially available [LC] and experimental [EX]). In addition, commercial polycarbonate composite resin brackets with precured 50% TEGDMA/MMA primer were bonded to etched human enamel with both cements. Shear bond strengths were measured. Results were compared by ANOVA and Scheffe's tests at P = .05. The 30% HEMA/MMA, 50% TEGDMA/ MMA, 10% bisGMA/MMA, and 30% bisGMA/MMA primers produced the higher shear bond strengths (9.5 to 20.8 MPa) with LC and EX to polycarbonate composite resin. The 50% TEGDMA/MMA primer was most effective in improving the shear bond strengths of both LC and EX. Precured 50% TEGDMA/ MMA primer on a commercial resin bracket was effective in providing good shear bond strength to enamel.

Acrylic Resins↗

PubMed1998

Potential exposure to bisphenol A from food-contact use of polycarbonate resins.

The potential exposure to bisphenol A (BPA) from the use of consumer products or packages made from bisphenol A-derived polycarbonate resins was calculated. The calculation was made on the basis of migration data from moulded discs prepared from a composite of polycarbonate resins. The data were obtained using the customary experimental procedures developed by the United States Food and Drug Administration (FDA). The potential migration of BPA to food from its contact with articles made from polycarbonate resins was determined using food-simulating solvents and time and temperature conditions recommended by FDA. The study demonstrates that no detectable BPA was found in the extracts obtained under FDA's most severe default testing condition using a method sensitive to 5 parts per billion (ppb) in the food simulants. Using these data, along with FDA's conventional procedure for estimating potential dietary exposure using food simulating migration data, the potential dietary exposure to bisphenol A from use of polycarbonate resins was determined to be less than 0.25 ppb.

Benzhydryl Compounds↗

PubMed1986

Biocompatibility and hemodynamic studies during polycarbonate versus cuprophane membrane dialysis.

A new noncellulosic membrane (polycarbonate) has been tested in terms of biocompatibility and hemodynamic tolerance. The following results were obtained: The polycarbonate membrane manufactured by Gambro Hechingen induces activation of the complement system (slight decrease of CH50 and C3, no increase of C5a) to lower extent and causes a less severe leukopenia than the cuprophane membrane. During dialysis with the polycarbonate membrane hypoxemia does not occur and the pulmonary vascular resistances and pulmonary arterial pressure remain stable. The good biocompatibility of the polycarbonate membrane allows a better outcome of hemodialysis treatments.

Acetates↗

PubMedDate not supplied

An improved technique for the retention of polycarbonate crowns.

The following conclusions may be drawn from this study: Composite resins do not bond to polycarbonate crowns. A technique for priming the internal surfaces of polycarbonate crowns is indicated, in order to create such a bond. Priming the polycarbonate crown with methyl methacrylate monomer alone produces a bond with composite resins. Priming the polycarbonate crown with a syrup of methyl methacrylate monomer and (poly) methyl methacrylate powder appears to produce a stronger bond with composite resins than the monomer alone.

Carbonates↗

PubMed2000

13C-14N REAPDOR and 13C-2D theta-REDOR NMR on a blend of tri-p-tolylamine and bisphenol-A-polycarbonate.

Solid-state NMR experiments are performed on amorphous blends of tri-p-tolylamine (TTA) and polycarbonate. Amines that are similar to TTA are blended with polycarbonates and used as photoconducting components in xerography. Because of its simple molecular structure, TTA is a charge-transporting molecule that is used as a model to understand charge transport in photoconducting materials. Charge transfer between amine molecules must depend on the separation and relative orientation between amine molecules. However, little information is known about the structural relationship between the amine molecules and the polymer host, presumably because of the difficulties associated with characterizing amorphous materials. We report the results of 13C-14N rotational-echo, adiabatic-passage, double-resonance (REAPDOR) and 13C-2D theta-rotational-echo, double-resonance (theta-REDOR) magic-angle spinning NMR experiments on a TTA/polycarbonate blend. The experiments provide information about the organization of TTA relative to polycarbonate.

Aniline Compounds↗

PubMed1999

Totally implantable artificial hearts and left ventricular assist devices: selecting impermeable polycarbonate urethane to manufacture ventricles.

In the development of a new generation of totally implantable artificial hearts and left ventricular assist devices (VADs) for long-term use, the selection of an acceptable material for the fabrication of the ventricles probably represents one of the greatest challenges. Segmented polyether urethanes used to be the material of choice due to their superior flexural performance, acceptable blood compatibility, and ease of processing. However, because they are known to degrade and to be readily permeable to water, they cannot meet the rigorous requirements needed for a new generation of implantable artificial hearts and VADs. Therefore, the objective of the present study was to identify alternative polymeric materials that would be satisfactory for fabricating the ventricles, and in particular, to determine the water permeability through membranes made from four commercial polycarbonate urethanes (Carbothane PC3570A, Chronoflex AR, Corethane 80A, and Corethane 55D) in comparison to those made from two traditional polyether urethanes (Tecoflex EG80A and Tecothane TT-1074A). In addition to determining the rate of water transmission through the six membranes by exposing them to deionized water, saline, and albumin-Krebs solution under pressure and measuring the displacement of liquid by means of a recently developed capillary method, the inherent surface and chemical properties of the six membranes were characterized by SEM, contact angle measurements, FTIR, DSC, and GPC techniques. The results of the study demonstrated that the rate of water transmission through the four polycarbonate urethane membranes was significantly lower than through the two polyether urethanes. In fact the lowest values were recorded with the two Corethane membranes, and the harder type 55D polymer had a lower value (2.7 x 10(-7) g/s cm2) than the softer 80A version (3.3 x 10(-7) g/s cm2). This level of water vapor permeability, which appears to be controlled primarily by a Fickian diffusion mechanism, is between 2 and 4 times lower than that obtained with traditional polyether urethane membranes of equivalent thickness. The superior performance of the polycarbonate urethanes is likely due to the inherently lower chain mobility of the carbonate structure in the soft segment phase. In addition, the study shows that additional impermeability to water vapor can be achieved by selecting a polyurethane polymer with a high hard segment content, an aromatic rather than aliphatic diisocyanate comonomer, and a more hydrophobic surface. The use of a higher molecular weight polyurethane is not necessarily efficacious if the above requirements are not met. As expected by Raoult's Law, the study found that the use of physiological media instead of deionized water further decreases the rate of water vapor transmission. Because none of today's commercial polyurethanes are totally impervious to water vapor transmission, additional work is needed to develop permeable polymers or to apply additional treatments to existing candidates to achieve an acceptable impermeable ventricle material.

Biocompatible Materials↗

PubMed2007

Chemical micropatterning of polycarbonate for site-specific peptide immobilization and biomolecular interactions.

Polycarbonate (PC) is a useful substrate for the preparation of microfluidic devices. Recently, its utility in bioanalysis has attracted much attention owing to the possibility of using compact discs as platforms for the high-throughput analysis of biomolecular interactions. In this article we report a novel method for the chemical micropatterning of polycarbonate based on the printing of functionalized silica nanoparticles. The semicarbazide groups present on the surface of the nanoparticles were used for the site-specific semicarbazone ligation of unprotected peptides derivatized by an alpha-oxoaldehyde group. The peptide micropatterns permitted the specific capture of antibodies. We report also the characterization of micropatterns on PC by using a wide-field optical imaging technique called Sarfus; this allows the detection of nm-thick films by using nonreflecting PC substrates and an optical microscope working with reflected differential interference contrast. The method described here is an easy way to modify polycarbonate surfaces for biomolecular interaction studies and should stimulate the use of PC for developing plastic biosensors.

Enzymes, Immobilized↗

PubMed2002

Stability of polycarbonate and polystyrene surfaces after hydrophilization with high intensity oxygen RF plasma.

A general drawback observed with plasma treatment is the limited stability of the hydrophilic-treated surfaces toward washing, storage, or heating. It has recently been found that oxygen, air, or argon radiofrequency plasmas with higher intensities than normally used can give hydrophilic surfaces having good wash stability. High intensity oxygen plasma treatment of polystyrene and polycarbonate surfaces was therefore carried out using two different capacitively coupled RF reactors with internal shelf electrodes. The obtained surface characteristics and stability were evaluated using contact angle measurements, XPS, AFM, and nanoindentation. For both materials, low water contact angles were found to correlate with high surface oxygen content. Only the surfaces exposed to relatively intense treatments, with self-bias voltages above 140 V (polystyrene) or 240 V (polycarbonate), could withstand washing in ethanol and remain highly hydrophilic. Substantial amounts of nonsoluble material were observed on the plastic substrates after treatment. Furthermore, for polycarbonate Young's modulus of the surface was found to increase with increasing intensity of the plasma. These observations were taken as an indication that extensive cross-linking of the surface layer took place. After more than 6 months of storage, the samples treated with the most intense plasmas (self-bias voltages in the range of 480-600 V) still had water contact angles around 20 degrees .

Oxygen↗

PubMed1987

A novel polycarbonate (Nuclepore) membrane demonstrates chemotaxis, unaffected by chemokinesis, of polymorphonuclear leukocytes in the Boyden chamber.

A novel polycarbonate (Nuclepore) membrane having capillary pores of 3 microns diameter and occupying 0.1% of surface area (average minimum spacing of 48 +/- 18.5 microns), a standard polycarbonate filtration membrane (pores 3 microns in diameter occupying 5% of surface area and having average minimum spacing of 3.9 +/- 2.8 microns) as well as a 3 microns pore cellulose acetate filtration membrane, were compared for their abilities to demonstrate chemotactic movement uninfluenced by chemokinetic movement of polymorphonuclear leukocytes in a Boyden-type chemotactic chamber. The chemoattractant used was dilute Escherichia coli culture filtrate employed in a gradient across the membranes to measure chemotaxis and in non-gradient conditions to measure chemokinesis. The new polycarbonate (Nuclepore) membrane provided the clearest demonstration of chemotaxis unaffected by chemokinesis of the polymorphonuclear leukocytes.

Cell Movement↗

PubMed1989

Polycarbonate membranes: a novel surface for solid-phase determinations with utility in field format serological assays.

A dipstick suitable for immunoassay procedures has been developed, and its utility demonstrated by the development of tests for the determination of immunoglobulin levels in newborn bovine blood, and for the detection of bovine antibodies against Brucella abortus. The dipstick is of simple design, consisting of three components: a polycarbonate membrane, an adhesive, and a support material. The polycarbonate membrane is a porous filter material upon which the immunoassay is undertaken. Biomolecules bind to the membrane with sufficient affinity to permit the development of useful immunoassay procedures; however, this membrane exhibits low non-specific binding of reagents. Collectively, these properties make polycarbonate a useful material for solid-phase immunoassay procedures.

Animals↗

PubMed2000

Hydrolytic degradation of tyrosine-derived polycarbonates, a class of new biomaterials. Part II: 3-yr study of polymeric devices.

The kinetics and mechanisms of in vitro degradation of tyrosine-derived polycarbonates, a new class of polymeric biomaterials, were studied extensively at 37 degrees C. These polymers carry an alkyl ester pendent chain that allows the fine-tuning of the polymer's material properties, its biological interactions with cells and tissue, and its degradation behavior. The polymer carrying an ethyl ester pendent chain, poly(DTE carbonate), has been established as a promising orthopedic implant material, exhibiting bone apposition when in contact with hard tissue. Tyrosine-derived polycarbonates are relatively stable and degrade only very slowly in vitro. Therefore, accelerated studies were conducted at 50 and 65 degrees C to observe the behavior of polymers during the later stages of degradation. Varying the pendent chain length affected the rate of water uptake, initial degradation rate, and physical stability of the polymeric devices. During the 3-yr study, the polymer degraded by random chain cleavage of the carbonate bonds, accompanied by a relatively small amount of pendent chain de-esterification. No mass loss was observed during this period at 37 degrees C, but mass loss was readily evident during the accelerated studies at 50 and 65 degrees C. Thus, it is reasonable to assume that mass loss will occur also at 37 degrees C, albeit only after extensive backbone carbonate cleavage and pendent chain ester hydrolysis. The dimension and surface area of the devices influenced the initial degradation rate, but did not significantly affect the overall rate of degradation. No evidence of "acid dumping" or the release of acidic residues found during the degradation of poly(D,L-lactic acid) were observed for this family of tyrosine-derived polycarbonates.

Biocompatible Materials↗

PubMed2003

Enzyme induced biodegradation of polycarbonate-polyurethanes: dose dependence effect of cholesterol esterase.

The current study has investigated the influence of esterase activity (80-400units/ml) on the biodegradation of polycarbonate-urethanes (PCNUs) by cholesterol esterase (CE), with a particular interest in studying the influence of different hard segment structures and their contribution to sensitizing the polymer towards enzyme catalyzed hydrolysis. Polycarbonate based polyurethanes were synthesized with varying hard segment content as well as hard segment chemistry based on three different diisocyanates, 1,6-hexane diisocyanate (HDI), 4,4'-methylene bisphenyl diisocyanate (MDI) and 4,4-methylene biscyclohexyl diisocyanate (HMDI). The effect of different chemistry on surface contact angle was measured in order to define the relative chemical nature of the surfaces. The enzyme dose response was found to be lower when hard segment content in the polymer was high. There was a very strong dependence on enzyme concentration for polyurethanes with different hard segment chemistry, despite the fact that the nature of the hydrolysable polycarbonate segment remained the same. The PCNU which showed the most dramatic dependence on enzyme concentration was synthesized with HMDI. At low enzyme concentration (80units/ml) this material was the most stable of the polymers while at elevated CE concentration (400units/ml) the polymer underwent a catastrophic breakdown. The findings suggested that protein binding on the surfaces was saturated even though enzyme degradation did not achieve saturation on any of the surfaces. The role of protein binding in modulating the hydrolytic action of the enzymes at different activity levels highlights a need for further study in this area.

Cyanates↗

PubMed2003

The copolymerization of carbon dioxide and [2-(3,4-epoxycyclohexyl)ethyl]trimethoxysilane catalyzed by (salen)CrCl. Formation of a CO2 soluble polycarbonate.

The copolymerization of 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane and carbon dioxide catalyzed by (salen)Cr(III)Cl (H(2)salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-ethylenediimine) with 2.5 equiv of N-MeIm as cocatalyst affords a polycarbonate devoid of polyether linkages, along with only a trace quantity of cyclic carbonate. The presence of the trimethoxysilane functionality in the epoxide not only provided the reactant monomer and product copolymer high solubility in liquid carbon dioxide but also provided the ability to cross-link the copolymer and thereby greatly alter the physical properties of the thus formed polycarbonate. In addition, the enhanced solubility of the copolymer in liquid CO(2) furnishes a ready means of removing the highly colored metal catalyst from the polycarbonate product.

Journal Article↗

PubMed1989

The application of bovine brain microvessel endothelial-cell monolayers grown onto polycarbonate membranes in vitro to estimate the potential permeability of solutes through the blood-brain barrier.

Previously our laboratory (Rim et al., Int. J. Pharm. 32:79-84. 1986) described an in vitro blood-brain barrier (BBB) model consisting of cultured bovine brain microvessel endothelial cells (BMECs) grown onto regenerated cellulose acetate membranes. However, the utility of this in vitro BBB model system was limited because the regenerated cellulose acetate membrane and not the monolayer of bovine BMECs was rate limiting for the permeability of very lipophilic compounds. Therefore, in this study we have evaluated polycarbonate membranes as supports for growing bovine BMECs and for conducting in vitro drug permeability studies. Bovine BMECs were cultured on collagen-coated polycarbonate membranes (13-mm diameter, 12-microns pore size) which were then mounted into side-by-side diffusion cells for transport studies. The permeabilities of a series of solutes of varying lipophilicity (progesterone, estrone, testosterone, haloperidol, propranolol, antipyrine, caffeine, urea, acyclovir, ganciclovir, ribavirin, and glycerol) were determined and an excellent correlation (r = 0.97) was established between the permeability coefficients of the solutes and their log partition coefficients (PC)/(MW)1/2. These results suggest that bovine BMECs cultured onto polycarbonate membranes can be used as an in vitro model system for estimating the potential permeability of a solute through the BBB in vivo.

Animals↗

PubMed2003

Increased migration levels of bisphenol A from polycarbonate baby bottles after dishwashing, boiling and brushing.

Baby bottles are often made of polycarbonate plastic. Impurities remaining in the bottle from the monomer bisphenol A can migrate from the plastic bottles into baby food, thereby causing a health concern. Previous migration testing of new baby bottles showed only trace migration levels of the substance. In the present work, polycarbonate baby bottles were subjected to simulated use by dishwashing, boiling and brushing. Migration testing performed with both new and used bottles revealed a significant increase in migration of bisphenol A due to use. This finding might be explained by polymer degradation. Bisphenol A was determined in 200-ml samples of water food simulant by a method based on solid-phase extraction followed by gas chromatography coupled with mass spectrometry. The detection limit was 0.1 microg l(-1). Twelve different polycarbonate baby bottles were tested by filling them with hot water (100 degrees C) for 1 h. The mean bisphenol A level from new bottles was 0.23 + -0.12 microg l(-1), while the mean levels from bottles subjected to simulated use were 8.4 + -4 microg l(-1) (dishwashed 51 times) and 6.7 + -4 microg l(-1) (dishwashed 169 times), respectively. None of the bottles released bisphenol A at levels that exceed the recently established provisional tolerable daily intake (0.01 mg kg(-1) body weight/day) in the European Union.

Benzhydryl Compounds↗

PubMed1996

Shear bond strength of a new polycarbonate bracket--an in vitro study with 14 adhesives.

Shear bond strength and failure location were used to evaluate the effectiveness of plastic bracket primers for bonding diacrylate adhesives on a new fibre-reinforced polycarbonate bracket. Maxillary incisor polycarbonate and mesh-based brackets as control were bonded to human incisors with 14 different adhesives (four filled diacrylate two-paste, six diacrylate one-step and four power-liquid acrylic adhesives), and after thermo-cycling for 2000 cycles between 5 degrees and 55 degrees C, tested in shear. A non-parametric test (Mann-Whitney U test) was used to compare the shear bond strength of the polycarbonate brackets with the mesh based brackets and a One-way test (according to Scheffe) to compare the shear bond strength of different adhesives. The following conclusions can be made: 1. Seven of the 14 adhesives used in this study with both types of brackets demonstrated adequate shear bond strength values for the clinical application. The exceptions were: Achieve Mix, No-Mix:30 Silkon, Lee Insta-Bond, Ortho-Loc and Bond-Eze, all with too low a shear bond strength for one or both types of brackets, and finally Quasar, which used with the plastic brackets sometimes caused enamel fractures, due to high bond strength. 2. The adhesives with their own plastic primer demonstrated higher blood strength values than those without plastic primer, and two-paste adhesives used with plastic primer displayed a higher bond strength than the other adhesives. 3. Generally, the shear bond strength values of the one-step adhesives were lower compared with the two-paste adhesives. 4. The liquid-powder adhesives demonstrated very different values for bond strength.

Composite Resins↗