RESUMEN
The enzyme PETase fromIdeonella sakaiensis (IsPETase) strain 201-F6 can catalyze the hydrolysis of polyethylene terephthalate (PET), mainly converting it into mono(2-hydroxyethyl) terephthalic acid (MHET). In this study, we used quantum mechanics/molecular mechanics (QM/MM) simulations to explore the molecular details of the catalytic reaction mechanism of IsPETase in the formation of MHET. The QM region was described with AM1d/PhoT and M06-2X/6-31+G(d,p) potential. QM/MM simulations unveil the complete enzymatic PET hydrolysis mechanism and identify two possible reaction pathways for acylation and deacylation steps. The barrier obtained at M06-2X/6-31+G(d,p)/MM potential for the deacylation step corresponds to 20.4 kcal/mol, aligning with the experimental value of 18 kcal/mol. Our findings indicate that deacylation is the rate-limiting step of the process. Furthermore, per-residue interaction energy contributions revealed unfavorable contributions to the transition state of amino acids located at positions 200-230, suggesting potential sites for targeted mutations. These results can contribute to the development of more active and selective enzymes for PET depolymerization.
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Tereftalatos Polietilenos , Teoría Cuántica , Tereftalatos Polietilenos/química , Tereftalatos Polietilenos/metabolismo , Simulación de Dinámica Molecular , Burkholderiales/enzimología , Burkholderiales/metabolismo , Hidrólisis , Biodegradación Ambiental , Biocatálisis , AcilaciónRESUMEN
The overwhelming use of PET plastic in various day-to-day activities led to the voluminous increase in PET waste and growing environmental hazards. A plethora of methods have been used that are associated with secondary pollutants. Therefore, microbial degradation of PET provides a sustainable approach due to its versatile metabolic diversity and capacity. The present work highlights the cutinase enzyme's role in PET degradation. This study focuses on the bacterial cutinases homologs screened from 43 reported phylum of bacteria. The reported bacterial cutinases for plastic degradation have been chosen as reference sequences, and 917 sequences have shown homology across the bacterial phyla. The dienelactone hydrolase (DLH) domain was identified for attaining specificity towards PET binding in 196 of 917 sequences. Various computational tools have been used for the physicochemical characterization of 196 sequences. The analysis revealed that most selected sequences are hydrophilic, extracellular, and thermally stable. Based on this analysis, 17 sequences have been further pursued for three-dimensional structure prediction and validation. The molecular docking studies of 17 selected sequences revealed efficient PET binding with the three sequences derived from the phylum Bacteroidota, the lowest binding energy of -5.9 kcal/mol, Armatimonadota, and Nitrososphaerota with -5.8 kcal/mol. The two enzyme sequences retrieved from the phylum Bacteroidota and Armatimonadota are metagenomically derived. Therefore, the present studies concluded that there is a high probability of finding cutinase homologs in various environmental resources that can be further explored for PET degradation.
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Bacterias , Proteínas Bacterianas , Hidrolasas de Éster Carboxílico , Simulación del Acoplamiento Molecular , Hidrolasas de Éster Carboxílico/metabolismo , Hidrolasas de Éster Carboxílico/genética , Hidrolasas de Éster Carboxílico/química , Bacterias/enzimología , Bacterias/genética , Bacterias/clasificación , Bacterias/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Proteínas Bacterianas/química , Especificidad por Sustrato , Tereftalatos Polietilenos/metabolismo , Tereftalatos Polietilenos/química , Biodegradación Ambiental , Simulación por Computador , FilogeniaRESUMEN
Several hydrolases have been described to degrade polyethylene terephthalate (PET) at moderate temperatures ranging from 25°C to 40°C. These mesophilic PET hydrolases (PETases) are less efficient in degrading this plastic polymer than their thermophilic homologs and have, therefore, been the subject of many protein engineering campaigns. However, enhancing their enzymatic activity through rational design or directed evolution poses a formidable challenge due to the need for exploring a large number of mutations. Additionally, evaluating the improvements in both activity and stability requires screening numerous variants, either individually or using high-throughput screening methods. Here, we utilize instead the design of chimeras as a protein engineering strategy to increase the activity and stability of Mors1, an Antarctic PETase active at 25°C. First, we obtained the crystal structure of Mors1 at 1.6 Å resolution, which we used as a scaffold for structure- and sequence-based chimeric design. Then, we designed a Mors1 chimera via loop exchange of a highly divergent active site loop from the thermophilic leaf-branch compost cutinase (LCC) into the equivalent region in Mors1. After restitution of an active site disulfide bond into this chimera, the enzyme exhibited a shift in optimal temperature for activity to 45°C and an increase in fivefold in PET hydrolysis when compared with wild-type Mors1 at 25°C. Our results serve as a proof of concept of the utility of chimeric design to further improve the activity and stability of PETases active at moderate temperatures.
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Hidrolasas , Tereftalatos Polietilenos , Tereftalatos Polietilenos/química , Tereftalatos Polietilenos/metabolismo , Regiones Antárticas , Hidrolasas/química , Hidrólisis , Ingeniería de Proteínas , PlásticosRESUMEN
Antimony is present in different types of plastics as a catalyzer residue and/or as a synergistic fire retardant; relatively high concentrations of this element reported in polyethylene terephthalate (PET) bottles and wrappers as well as its migration to the edible products or to different environment compartments are of concern. In this work, Sb determination is such products had been undertaken using hydride generation - microwave plasma - atomic emission spectrometry. To avoid harsh conditions typically reported for the digestion of PET, alkaline methanolysis was introduced whereas water samples were analyzed directly. Another original approach was to perform quantification by partial least squares regression (PLS1), taking spectral data from 2-nm range that comprised two emission lines (217.581 nm and less intense 217.919 nm). For PET, the calibration solutions contained Sb-free digest and covered the Sb concentration range 80-230 µg L-1. For the analysis of water, the calibration range was 0.5-10 µg L-1 and aqueous standard solutions were used. PLS1 provided reliable prediction, eliminating spectral interferences detected in the presence of PET digests and compensating for the spectral changes observed at low Sb concentrations. After standard addition to the real-world samples, the percentage recoveries were in the range 93.8-99.3% and 68-102% for PET and for bottled water, respectively. The method quantification limit for PET was 10 mg kg-1 and for water it corresponded to 0.20 µg L-1. The concentrations of Sb found in the analyzed samples were: 154-279 mg kg-1 for PET bottles and <0.5-5.30 µg L-1 for water.
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Agua Potable , Tereftalatos Polietilenos , Tereftalatos Polietilenos/química , Antimonio/química , Microondas , Análisis de los Mínimos Cuadrados , Agua Potable/química , Análisis EspectralRESUMEN
Poly(ethylene terephthalate) (PET) is one of the main synthetic plastics produced worldwide. The extensive use of this polymer causes several problems due to its low degradability. In this scenario, biocatalysts dawn as an alternative to enhance PET recycling. The enzymatic hydrolysis of PET results in a mixture of terephthalic acid (TPA), ethylene glycol (EG), mono-(2-hydroxyethyl) terephthalate (MHET) and bis-(2-hydroxyethyl) terephthalate (BHET) as main products. This work developed a new methodology to quantify the hydrolytic activity of biocatalysts, using BHET as a model substrate. The protocol can be used in screening enzymes for PET depolymerization reactions, amongst other applications. The very good fitting (R2 = 0.993) between experimental data and the mathematical model confirmed the feasibility of the Michaelis-Menten equation to analyze the effect of BHET concentration (8-200 mmol L-1) on initial hydrolysis rate catalyzed by Humicola insolens cutinase (HiC). In addition to evaluating the effects of enzyme and substrate concentration on the enzymatic hydrolysis of BHET, a novel and straightforward method for MHET synthesis was developed using an enzyme load of 0.025 gprotein gBHET-1 and BHET concentration of 60 mmol L-1 at 40 °C. MHET was synthesized with high selectivity (97 %) and yield (82 %). The synthesized MHET properties were studied using differential scanning calorimetry (DSC), thermogravimetry (TGA), and proton nuclear magnetic resonance (1H NMR), observing the high purity of the final product (86.7 %). As MHET is not available commercially, this synthesis using substrate and enzyme from open suppliers adds new perspectives to monitoring PET hydrolysis reactions.
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Tereftalatos Polietilenos , Protones , Glicol de Etileno/química , Etilenos , Hidrólisis , Ácidos Ftálicos , Plásticos/química , Tereftalatos Polietilenos/química , PolímerosRESUMEN
Surface functionalization of polymers aims to introduce novel properties that favor bioactive responses. We have investigated the possibility of surface functionalization of polyethylene terephthalate (PET) sheets by the combination of laser ablation with hot embossing and the application of such techniques in the field of stem cell research. We investigated the response of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to topography in the low micrometer range. HiPSC-CMs are expected to offer new therapeutic tools for myocardial replacement or regeneration after an infarct or other causes of cardiac tissue loss. However, hiPSC-CMs are phenotypically immature compared to myocytes in the adult myocardium, hampering their clinical application. We aimed to develop and test a high-throughput technique for surface structuring that would improve hiPSC-CMs structural maturation. We used laser ablation with a ps-laser source in combination with nanoimprint lithography to fabricate large areas of homogeneous micron- to submicron line-like pattern with a spatial period of 3 µm on the PET surface. We evaluated cell morphology, alignment, sarcomeric myofibrils assembly, and calcium transients to evaluate phenotypic changes associated with culturing hiPSC-CMs on functionalized PET. Surface functionalization through hot embossing was able to generate, at low cost, low micrometer features on the PET surface that influenced the hiPSC-CMs phenotype, suggesting improved structural and functional maturation. This technique may be relevant for high-throughput technologies that require conditioning of hiPSC-CMs and may be useful for the production of these cells for drug screening and disease modeling applications with lower costs.
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Técnicas de Cultivo de Célula/métodos , Células Madre Pluripotentes Inducidas/citología , Miocitos Cardíacos/citología , Nanotecnología/métodos , Células Cultivadas , Ensayos Analíticos de Alto Rendimiento , Humanos , Tereftalatos Polietilenos/química , Propiedades de SuperficieRESUMEN
Accumulation of plastic wastes and their effects on the ecosystem have triggered an alarm regarding environmental damage, which explains the massive investigations over the past few years, aiming technological alternatives for their proper destination and valorization. In this context, biological degradation emerges as a green route for plastic processing and recycling in a circular economy approach. Some of the main polymers produced worldwide are poly(ethylene terephthalate) (PET), polyethylene (PE) and polypropylene (PP), which are among the most recalcitrant materials in the environment. In comparison to other polymers, PET biodegradation has advanced dramatically in recent years concerning microbial and enzymatic mechanisms, being positioned in a higher technology readiness level (TRL). Even more challenging, polyolefins (PE and PP) biodegradation is hindered by their high recalcitrance, which is mainly related to stable carbon-carbon bonds. Potential microbial biocatalysts for this process have been evaluated, but the related mechanisms are still not fully elucidated. This review aims to discuss the latest developments on key microbial biocatalysts for degradation of these polymers, addressing biodegradation monitoring, intellectual property, and TRL analysis of the bioprocessing strategies using biodegradation performance, process time and scale as parameters for the evaluation.
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Plásticos/química , Reciclaje/métodos , Biocatálisis , Biodegradación Ambiental , Ecosistema , Polienos/química , Tereftalatos Polietilenos/químicaRESUMEN
Massive plastics production has raised concerns about low recycling rates and disposal of these materials in nature, causing environmental and economic impacts. Poly(ethylene terephthalate) (PET) is one of main polymers used for manufacture of plastic packaging (e.g. bottles, trays). Enzymatic recycling of PET has been a route of increasing study aiming at to recover its monomers (terephthalic acid and ethylene glycol), resulting in a circular production chain. In this study, investigation of pH control and fractionation of enzyme feeding were explored in post-consumed PET (PC-PET) hydrolysis reactions catalyzed by Humicola insolens cutinase (HiC) in stirred reactors. It was found that the unbuffered reaction provided of pH control by 0.5 M NaOH addition showed 2.39-fold improvement in the released monomers (to a total of 26.3 mM), comparatively to the Tris-HCl-buffered reaction. In addition, it was observed a possibility of reducing the enzyme loading used in the process by half, leading to an increase of 2.41-fold in the specific terephthalic acid concentration released per protein amount, whilst maintaining a high products concentration (97 mM). A simplified cost analysis of reaction consumables was performed, and the data reported here demonstrates that these alternative process strategies contribute to costs reduction on the enzymatic depolymerization reactions of PET.
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Biocatálisis , Hidrolasas de Éster Carboxílico/química , Hongos del Género Humicola/enzimología , Proteínas Fúngicas/química , Tereftalatos Polietilenos/químicaRESUMEN
Cellulose nanocrystals (CNCs), castor oil (CO), and recycled poly(ethylene terephthalate) (rPET), were used to add value to renewable raw materials and to a recycled polymer produced worldwide, producing mats composed of fibers on the nano- and submicrometric (ultrathin) scales through a sustainable process. Bio-based electrospun mats composed of aligned (rotary collector) and nonaligned (static collector) nanofibers/ultrathin fibers were produced from the electrospinning of solutions prepared from rPET (mixed with CO, CNCs, or CNCs/CO). The contact angle results showed that the CNC mat surfaces composed of nonaligned fibers were hydrophilic, and in contrast, these surfaces were hydrophobic when composed of aligned fibers. Among the mats composed of nonaligned fibers, PET/CO/CNC exhibited storage and Young's moduli approximately eleven and ten times, respectively, better than those of neat rPET. The PET/CO/CNC mat showed both modulus and tensile strength values higher than those of PET/CNC, when characterized in the preferential direction of fiber alignment. Electrospun mats were obtained from environmentally sound raw materials with diversified properties, which were modulated by the type of collector used, as well as whether CO and CNC were mixed with rPET, and have the potential for use in applications such as membrane separation processes and biomedical applications.
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Aceite de Ricino/química , Celulosa/química , Nanofibras/química , Nanopartículas/química , Tereftalatos Polietilenos/química , Fenómenos Químicos , Fenómenos Mecánicos , Nanocompuestos , Nanofibras/ultraestructura , Nanopartículas/ultraestructura , Resistencia a la TracciónRESUMEN
Recalcitrant characteristics and insolubility in water make the disposal of synthetic polymers a great environmental problem to be faced by modern society. Strategies towards the recycling of post-consumer polymers, like poly (ethylene terephthalate, PET) degradation/depolymerization have been studied but still need improvement. To contribute with this purpose, 100 fungal strains from hydrocarbon-associated environments were screened for lipase and esterase activities by plate assays and high-throughput screening (HTS), using short- and long-chain fluorogenic probes. Nine isolates were selected for their outstanding hydrolytic activity, comprising the genera Microsphaeropsis, Mucor, Trichoderma, Westerdykella, and Pycnidiophora. Two strains of Microsphaeropsis arundinis were able to convert 2-3% of PET nanoparticle into terephthalic acid, and when cultured with two kinds of commercial PET bottle fragments, they also promoted weight loss, surface and chemical changes, increased lipase and esterase activities, and led to PET depolymerization with release of terephthalic acid at concentrations above 20.0 ppm and other oligomers over 0.6 ppm. The results corroborate that hydrocarbon-associated areas are important source of microorganisms for application in environmental technologies, and the sources investigated revealed important strains with potential for PET depolymerization.
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Hongos/metabolismo , Tereftalatos Polietilenos/metabolismo , Biodegradación Ambiental , Esterasas/metabolismo , Proteínas Fúngicas/metabolismo , Hongos/enzimología , Hidrocarburos/química , Hidrocarburos/metabolismo , Lipasa/metabolismo , Tereftalatos Polietilenos/química , PolimerizacionRESUMEN
The aim of this study was to evaluate the physical-mechanical and morphological properties of polyethylene terephthalate (PET), for a new application as a prosthetic component for overdentures implant-retained, compared with different polymers. Were prepared 20 specimens for each material: Polyethylene terephthalate (PET), Polyacetal, Polytetrafluoroethylene (PTFE) and Polyethylene, for analysis of roughness and hardness surface, compressive strength and pull out test. For fatigue strength test, a total of 200 capsules (nâ¯=â¯40) were captured in pairs with acrylic resin and subjected to 2900 insertion/removal cycles, simulating 24â¯months of overdenture use. In this test, a group was added (o-ring Intra-Lock System) as a standard of comparison. The morphological and structural analysis were realized by stereomicroscopy, scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD). All specimens in this study were analyzed before and after thermocycling (5-55⯰C, for 10,000â¯cycles). Two-way ANOVA with repeated measurements and Tukey test were used (αâ¯=â¯0.05). For roughness, difference was observed only between the materials, with lowest averages for Polyacetal and PET (pâ¯<â¯0.001). For the hardness there was no statistically significant difference between the materials (pâ¯>â¯0.001). For compressive strength, Polyacetal, followed by PET (pâ¯<â¯0.001) presented the highest values independent of thermocycling. In the pullout test, PET and polyacetal presented, the highest values (pâ¯=â¯0.033). In the fatigue test, for 24â¯months analysis, difference was observed before and after thermocycling for O-ring group (pâ¯=â¯0.010) and polyacetal (pâ¯=â¯0.002), PET also presented higher values of resistance in relation to the o-ring (pâ¯<â¯0.001). The thermocycling did not alter the polyethylene surface through SEM images as well as the structure of all the materials analyzed by FTIR and DRX. In this study, the PET presented results compatible with those expected, which suggests its application for making retention capsules for implant-retained overdentures.
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Prótesis Dental de Soporte Implantado , Prótesis de Recubrimiento , Tereftalatos Polietilenos/química , Resinas Acrílicas/química , Fuerza Compresiva , Dureza , Ensayo de Materiales , Espectroscopía Infrarroja por Transformada de Fourier , Difracción de Rayos XRESUMEN
Cardiovascular disease is the leading cause of mortality in the United States. Peripheral artery disease (PAD) affects a substantial portion of the elderly population (>70 years). PAD can be symptomatic or asymptomatic, and treatment is directed towards improving functional vessel patency and limb salvage. Revascularization surgical treatments are needed in some cases, and it is not always possible to use autologous veins for vascular grafting. In this case, synthetic materials may be used. Synthetic materials such as expanded polytetrafluoroethylene (ePTFE) and poly (ethylene terephthalate) (Dacron) have been used. These materials are much stiffer compared to normal arterial vessels so developing alternative materials is an active area of research. One such potential material is a pâolyvinyl alcohol cryogel reinforced arterial model (PRAM). In this study we used shear wave elastography (SWE) techniques to compare the mechanical behavior of excised aortas and anastomoses formed between the aortas and the Dacron, ePTFE, and PRAM materials. Different initial longitudinal strains (0%-40%) and transmural pressures (20-180 mmHg) were used to test a wide range of parameters that are within physiological ranges. We found that the PRAM materials had similar mechanical behavior in terms of group velocity measured in the vessel wall with respect to the excised aortas compared to the Dacron and ePTFE that had higher values of group velocity. The ratios of the group velocity for the PRAM material with respect to the aortas ranged from 0.83 to 1.13 where the Dacron and ePTFE had ranges of 1.12-2.22 and 1.91-3.10 for the same stretch and pressure ranges. The PRAM materials provide an alternative vascular material with better mechanical matching with excised aortas.
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Prótesis Vascular/normas , Diagnóstico por Imagen de Elasticidad , Tereftalatos Polietilenos/química , Politetrafluoroetileno/química , Anciano , Anastomosis Quirúrgica/instrumentación , Anastomosis Quirúrgica/métodos , Aorta/cirugía , Arteria Femoral/cirugía , Humanos , Masculino , Tereftalatos Polietilenos/efectos adversos , Politetrafluoroetileno/efectos adversos , Grado de Desobstrucción VascularRESUMEN
The current knowledge about the role terrestrial ornamental plants play in constructed wetlands (CWs) has scarcely been evaluated. Likewise, little attention has been given towards the use of new support or fill media for subsurface flow CWs, which may result in the reduction of costs when implemented on a large scale. This study evaluated, during nine months, the effect of three terrestrial ornamental plants and two substrates on the elimination of pollutants in wastewaters by using fill-and-drain vertical subsurface flow CWs (FD-CWs). Sixteen microcosms were used, nine filled with polyethylene terephthalate (PET) and nine with porous river stone (PRS). For each type of substrate, duplicates of microcosms were used, utilizing Anthurium sp., Zantedeschia aethiopica, and Spathiphyllum wallisii as vegetation and two other CWs without vegetation as controls. The environmental conditions, number of flowers, and height of the plants were registered. The results revealed that both substrates in the FD-CWs were efficient in removing pollutants. The average removal of pollutants in systems with vegetation revealed a positive effect on the reduction of the biochemical oxygen demand (55â»70%), nitrates (28â»44%), phosphates (25â»45%), and fecal coliforms (52â»65%). Meanwhile, in units without vegetation, the reduction of pollutants was nearly 40â»50% less than in those with vegetation. The use of PET as a filling substrate in CWs did not affect the growth and/or the flowering of the species; therefore, its use combined with the species studied in CWs may be replicated in villages with similar wastewater problems. This may represent a reduction in implementation costs when utilizing PET recycled wastes and PRS as substrates in these systems in comparison with the typical substrates used in CWs. More studies are needed to better understand the interactions among these novel support media and the commercial terrestrial ornamental plants.
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Araceae/metabolismo , Entorno Construido , Eliminación de Residuos Líquidos/métodos , Contaminantes Químicos del Agua/aislamiento & purificación , Humedales , Araceae/clasificación , Biodegradación Ambiental , Minerales/química , Tereftalatos Polietilenos/química , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/metabolismoRESUMEN
The characteristics of the electron-mirror effect (EME) image depend on both the scanning electron microscope parameters and the sample's physical properties. The behavior of human tooth (dentin and enamel) and synthetic hydroxyapatite samples submitted to the EME procedure is presented in this work. Polyethylene terephthalate (PET) and epoxy resin, two good EME producers, were used for comparison. A distorted EME image was observed in the obtained dentin's surface, but enamel and synthetic hydroxyapatite surfaces did not produce the EME. After ex situ calcination treatments of the teeth at 700 and 1,200°C, the EME was observed in dentin, enamel, and synthetic hydroxyapatite, but highly deformed EME images were produced. We show that these last observations are the result of the well-known charge-edge effect. After EME analysis, the calculated dielectric constant was 8.7 for dentin and 3.8 for PET. RESEARCH HIGHLIGHTS: Electron-mirror effect (EME) was observed in dentin but not in enamel or synthetic hydroxyapatite. Highly deformed EME images are produced in all samples after calcination at above 700°C. For dentin the calculated dielectric constant was 8.7 and for PET is was 3.8.
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Esmalte Dental/ultraestructura , Dentina/ultraestructura , Durapatita/química , Resinas Compuestas/química , Esmalte Dental/química , Dentina/química , Durapatita/síntesis química , Humanos , Microscopía Electrónica de Rastreo , Tereftalatos Polietilenos/química , TemperaturaRESUMEN
This work describes the synthesis of catalysts based on red mud/polyethylene terephthalate (PET) composites and their subsequent heat treatment under N2 atmosphere. The materials were characterized by scanning electron microscopy (SEM), temperature programmed reduction (TPR), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric (TG) analysis and N2 adsorption/desorption. The catalysts were evaluated in the oxidative desulfurization reaction of dibenzothiophene (DBT) in a biphasic system. The results indicated that the PET impregnation on red mud increased the affinity of the catalyst with the nonpolar phase (fuel), in which the contaminant was dissolved, allowing a higher conversion (up to 80%) and selectivity to the corresponding dibenzothiophene sulfone. The sulfone compound is more polar than DBT and diffused into the polar solvent as indicated by the data obtained via gas chromatography-mass spectrometry (GC-MS).
Asunto(s)
Modelos Químicos , Tereftalatos Polietilenos/química , Adsorción , Catálisis , Oxidación-Reducción , Espectroscopía Infrarroja por Transformada de Fourier , TiofenosRESUMEN
Biofilm Formation is a survival strategy for microorganisms to adapt to their environment. Microbial cells in biofilm become tolerant and resistant to antibiotics and immune responses, increasing the difficulties for the clinical treatment of microbial infections. The surface chemistry and the micro/nano-topography of solid interfaces play a major role in mediating microorganism activity and adhesion. The effect of the surface chemical composition and topography on the adhesion and viability of Pseudomonas aeruginosa was studied. Polymeric (polyethylene terephthalate) surfaces were covered with a conducting polymer (polyaniline, PANI) film by in-situ polymerization and microstructured by Direct Laser Interference Patterning (DLIP). The viability of Pseudomonas aeruginosa on the different surfaces was investigated. The physicochemical properties of the surfaces were characterized by water contact angle measurements, scanning electron microscopy and atomic force microscopy. Bacterial biofilms were imaged by atomic force and scanning electron microscopies. The bacterial viability decreased on PANI compared with the substrate (polyethylene terephthalate) and it decreased even more upon micro-structuring the PANI films. In addition, the biofilm reduction could be improved using polymers with different chemical composition and/or the same polymer with different topographies. Both methods presented diminish the bacterial attachment and biofilm formation. These findings present a high impact related to materials for biomedical engineer applications regarding medical devices, as prostheses or catheters.
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Compuestos de Anilina/química , Biopelículas , Pseudomonas aeruginosa/fisiología , Adhesión Bacteriana , Materiales Biocompatibles/química , Catéteres , Farmacorresistencia Bacteriana , Equipos y Suministros , Violeta de Genciana/química , Microscopía de Fuerza Atómica , Microscopía Electrónica de Rastreo , Microscopía Fluorescente , Tereftalatos Polietilenos/química , Propiedades de SuperficieRESUMEN
Human antithrombin is a blood derivative widely used in the treatment of coagulation dysfunction. Affinity chromatography using heparin (HEP) derivatives is usually used for antithrombin purification. In this study, an affinity procedure based on a magnetic Dacron-HEP composite is proposed. Dacron was firstly converted to Dacron-hydrazide and magnetised by co-precipitation with of Fe2+/Fe3+ (mDAC). HEP was activated by carbodiimide and N-hydroxysuccinimide and covalently linked to mDAC (mDAC-HEP). EDX and infrared spectra analyses confirmed each synthesis step of mDAC-HEP. This composite exhibited superparamagnetism behaviour. Human plasma was incubated with mDAC-HEP (fresh and stored over a long period) and washed with phosphate buffer containing increasing concentrations of NaCl. Human plasma antithrombin activity was reduced by approximately 20% in the presence of the 1.0M NaCl fraction, and this eluate was able to prolong coagulation time (aPTT) using both preparations. Electrophoresis of the eluates revealed bands corresponding to the expected size of antithrombin (58kDa). The mDAC-HEP particles are reusable. This method presents the following advantages: easy, low-cost synthesis of the composite, magnet-based affinity purification steps, and reusability.
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Antitrombinas/sangre , Antitrombinas/aislamiento & purificación , Cromatografía de Afinidad/métodos , Heparina/química , Imanes/química , Tereftalatos Polietilenos/química , Humanos , Tiempo de Tromboplastina ParcialRESUMEN
The leaching of antimony (Sb) from polyethylene terephthalate (PET) bottling material was assessed in twelve brands of bottled water purchased in Mexican supermarkets by atomic fluorescence spectrometry with a hydride generation system (HG-AFS). Dowex® 1X8-100 ion-exchange resin was used to preconcentrate trace amounts of Sb in water samples. Migration experiments from the PET bottle material were performed in water according to the following storage conditions: 1) temperature (25 and 75°C), 2) pH (3 and 7) and 3) exposure time (5 and 15days), using ultrapure water as a simulant for liquid foods. The test conditions were studied by a 2(3) factorial experimental design. The Sb concentration measured in the PET packaging materials varied between 73.0 and 111.3mg/kg. The Sb concentration (0.28-2.30µg/L) in all of the PET bottled drinking water samples examined at the initial stage of the study was below the maximum contaminant level of 5µg/L prescribed by European Union (EU) regulations. The parameters studied (pH, temperature, and storage time) significantly affected the release of Sb, with temperature having the highest positive significant effect within the studied experimental domain. The highest Sb concentration leached from PET containers was in water samples at pH7 stored at 75°C for a period of 5days. The extent of Sb leaching from the PET ingredients for different brands of drinking water can differ by as much as one order of magnitude in experiments conducted under the worst-case conditions. The chronic daily intake (CDI) caused by the release of Sb in one brand exceeded the Environmental Protection Agency (USEPA) regulated CDI value of 400ng/kg/day, with values of 514.3 and 566.2ng/kg/day for adults and children. Thus, the appropriate selection of the polymer used for the production of PET bottles seems to ensure low Sb levels in water samples.
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Antimonio/análisis , Agua Potable/química , Contaminación de Alimentos/análisis , Tereftalatos Polietilenos/química , Contaminantes Químicos del Agua/análisis , Antimonio/química , Embalaje de Alimentos , Temperatura , Contaminantes Químicos del Agua/química , Calidad del AguaRESUMEN
This work presents the modeling and simulation of the mechanical response of a Dacron graft in the pressurization test and its clinical application in the analysis of an end-to-end anastomosis. Both problems are studied via an anisotropic constitutive model that was calibrated by means of previously reported uniaxial tensile tests. First, the simulation of the pressurization test allows the validation of the experimental material characterization that included tests carried out for different levels of axial stretching. Then, the analysis of an end-to-end anastomosis under an idealized geometry is proposed. This case consists in evaluating the mechanical performance of the graft together with the stresses and deformations in the neighborhood of the Dacron with the artery. This research contributes important data to understand the functioning of the graft and the possibility of extending the analysis to complex numerical cases like its insertion in the aortic arch.
Asunto(s)
Prótesis Vascular , Tereftalatos Polietilenos/química , Estrés Mecánico , Anastomosis Quirúrgica , Anisotropía , Aorta Torácica , Fenómenos Biomecánicos , Simulación por Computador , HumanosRESUMEN
Experimental and numerical analyses focused on the mechanical characterisation of a woven Dacron vascular graft are presented. To that end, uniaxial tensile tests under different orientations have been performed to study the anisotropic behaviour of the material. These tests have been used to adjust the parameters of a hyperelastic anisotropic constitutive model which is applied to predict through numerical simulation the mechanical response of this material in the ring tensile test. The obtained results show that the model used is capable of representing adequately the nonlinear elastic region and, in particular, it captures the progressive increase of the rigidity and the anisotropy due to the stretching of the Dacron. The importance of this research lies in the possibility of predicting the graft׳s mechanical response under generalized loading such as those that occur under physiological conditions after surgical procedures.