From Polyester Plastics to Diverse Monomers via Low-Energy Upcycling

Polyester plastics, constituting over 10% of the total plastic production, are widely used in packaging, fiber, single-use beverage bottles, etc. However, their current depolymerization processes face challenges such as non-broad spectrum recyclability, lack of diversified high-value-added depolymerization products, and crucially high energy consumption. Herein, an efficient strategy is developed for dismantling the compact structure of polyester plastics to achieve diverse monomer recovery. Polyester plastics undergo swelling and decrystallization with a low depolymerization energy barrier via synergistic effects of polyfluorine/hydrogen bonding, which is further demonstrated via density functional theory calculations. The swelling process is elucidated through scanning electron microscopy analysis. Obvious destruction of the crystalline region is demonstrated through X-ray crystal diffractometry curves. PET undergoes different aminolysis efficiently, yielding nine corresponding high-value-added monomers via low-energy upcycling. Furthermore, four types of polyester plastics and five types of blended polyester plastics are closed-loop recycled, affording diverse monomers with exceeding 90% yields. Kilogram-scale depolymerization of real polyethylene terephthalate (PET) waste plastics is successfully achieved with a 96% yield.

Influences of Recycled Polyethylene Terephthalate Microplastic on the Hygrothermal and Mechanical Performance of Plasterboard with Polymethylhydrosiloxane Content

New composites produced with recycled waste are needed to manufacture more sustainable construction materials. This paper aimed to analyze the hygrothermal and mechanical performance of plasterboard with a polymethylhydrosiloxane (PMHS) content, incorporating recycled PET microplastic waste and varying factors such as PMHS dose, homogenization time, and drying temperature after setting. A cube-centered experimental design matrix was performed. The crystal morphology, porosity, fluidity, water absorption, flexural strength, and thermal conductivity of plasterboards were measured. The results showed that incorporating recycled PET microplastics does not produce a significant difference in the absorption and flexural strength of plasterboards. However, the addition of recycled PET reduced the thermal conductivity of plasterboards by around 10%.

Application of Infrared Pyrolysis and Chemical Post-Activation in the Conversion of Polyethylene Terephthalate Waste into Porous Carbons for Water Purification

In this study, we compared the conversion of polyethylene terephthalate (PET) into porous carbons for water purification using pyrolysis and post-activation with KOH. Pyrolysis was conducted at 400-850 °C, followed by KOH activation at 850 °C for samples pyrolyzed at 400, 650, and 850 °C. Both pyrolyzed and post-activated carbons showed high specific surface areas, up to 504.2 and 617.7 m2 g-1, respectively. As the pyrolysis temperature increases, the crystallite size of the graphite phase rises simultaneously with a decrease in specific surface area. This phenomenon significantly influences the final specific surface area values of the activated samples. Despite their relatively high specific surface areas, pyrolyzed PET-derived carbons prove unsuitable as adsorbents for purifying aqueous media from methylene blue dye. A sample pyrolyzed at 650 °C, with a surface area of 504.2 m2 g-1, exhibited a maximum adsorption value of only 20.4 mg g-1. We propose that the pyrolyzed samples have a surface coating of amorphous carbon poor in oxygen groups, impeding the diffusion of dye molecules. Conversely, post-activated samples emerge as promising adsorbents, exhibiting a maximum adsorption capacity of up to 127.7 mg g-1. This suggests their potential for efficient dye removal in water purification applications.

An Atomic-Level Perspective on the interactions between Organic Pollutants and PET particles: A Comprehensive Computational Investigation

Microplastics (MPs) have recently attracted a lot of attention worldwide due to their abundance and potentially harmful effects on the environment and on human health. One of the factors of concern is their ability to adsorb and disperse other harmful organic pollutants in the environment. To properly assess the adsorption capacity of MP for organic pollutants in different environments, it is pivotal to understand the mechanisms of their interactions in detail at the atomic level. In this work, we studied interactions between polyethylene terephthalate (PET) MP and small organic pollutants containing different functional groups within the framework of density functional theory (DFT). Our computational outcomes show that organic pollutants mainly bind to the surface of a PET model via weak non-bonding interactions, mostly hydrogen bonds. The binding strength between pollutant molecules and PET particles strongly depends on the adsorption site while we have found that the particle size is of lesser importance. Specifically, carboxylic sites are able to form strong hydrogen bonds with pollutants containing hydrogen bond donor or acceptor groups. On the other hand, it is found that in such kind of systems π-π interactions play a minor role in adsorption on PET particles.

Engineering microbiomes to transform plastics

The design and study of active microbial consortia able to degrade plastics represent an exciting area of research toward the development of bio-based alternatives to efficiently transform plastic waste. This forum article discusses concepts and mechanisms to inform emerging strategies for engineering microbiomes to transform plastics under controlled settings.

Thermophilic bacteria from Peruvian hot springs with high potential application in environmental biotechnology

Hot springs are extreme environments in which well-adapted microorganisms with biotechnological applications can thrive naturally. These thermal environments across Peruvian territory have, until now, remained poorly investigated. In this study, two hot springs, El Tragadero and Quilcate, located in Cajamarca (Peru) were selected in order to investigate the biotechnological potential of indigenous thermophilic bacteria. Enrichment and isolation processes were carried out using microbial mats, sediments, biofilms, and plastic polymers as samples. Screening for biosurfactants and siderophores production, as well as for polyethylene terephthalate (PET) hydrolysis was done using culture-dependent techniques. After molecular identification, Bacillus was found as the most abundant genus in both hot springs. Bacillus velezensis was found producing biosurfactants under high-level temperature. Anoxybacillus species (A. salavatliensis and A. gonensis) are here reported as siderophore-producing bacteria for the first time. Additionally, Brevibacillus and the less-known bacterium Tistrella mobilis were found demonstrating PET hydrolysis activity. Our study provides the first report of thermophilic bacteria isolated from Peruvian hot springs with biotechnological potential for the bioremediation of oil-, metal- and plastic-polluted environments.

Inhalable Textile Microplastic Fibers Impair Airway Epithelial Differentiation

Rationale: Microplastics are a pressing global concern, and inhalation of microplastic fibers has been associated with interstitial and bronchial inflammation in flock workers. However, how microplastic fibers affect the lungs is unknown. Objectives: Our aim was to assess the effects of 12 × 31 μm nylon 6,6 (nylon) and 15 × 52 μm polyethylene terephthalate (polyester) textile microplastic fibers on lung epithelial growth and differentiation. Methods: We used human and murine alveolar and airway-type organoids as well as air-liquid interface cultures derived from primary lung epithelial progenitor cells and incubated these with either nylon or polyester fibers or nylon leachate. In addition, mice received one dose of nylon fibers or nylon leachate, and, 7 days later, organoid-forming capacity of isolated epithelial cells was investigated. Measurements and Main Results: We observed that nylon microfibers, more than polyester, inhibited developing airway organoids and not established ones. This effect was mediated by components leaching from nylon. Epithelial cells isolated from mice exposed to nylon fibers or leachate also formed fewer airway organoids, suggesting long-lasting effects of nylon components on epithelial cells. Part of these effects was recapitulated in human air-liquid interface cultures. Transcriptomic analysis revealed upregulation of Hoxa5 after exposure to nylon fibers. Inhibiting Hoxa5 during nylon exposure restored airway organoid formation, confirming Hoxa5's pivotal role in the effects of nylon. Conclusions: These results suggest that components leaching from nylon 6,6 may especially harm developing airways and/or airways undergoing repair, and we strongly encourage characterization in more detail of both the hazard of and the exposure to microplastic fibers.

Effect of Abiotic Treatments on Agricultural Plastic Waste: Efficiency of the Degradation Processes

In this study, four different plastic materials usually used in the agricultural sector (polystyrene film (PS), polyethylene terephthalate film (PET), low-density polyethylene film (LDPE) and linear low-density polyethylene film (LLDPE)) were subjected to different abiotic treatments, including photo-oxidation (ultraviolet and e-beam radiation) and thermochemical treatments, to enhance polymer degradation. The extensive use of these polymers leads to large amounts of plastic waste generation, including small plastic pieces, known as microplastics, which affect the quality of the agricultural environment, including soil fertility and quality. Therefore, polymer degradation strategies are needed to effectively reduce plastic waste to protect the agricultural sector. The degree of polymer degradation was assessed by the use of thermal and spectroscopic analyses, such as TGA and FTIR. In addition, efficiency, cost-benefits, and potential side-effects were also evaluated to propose the optimal degradation strategy to reduce plastic waste from the point of view of efficiency. The results obtained showed that the pre-treatments based on photo-oxidation (ultraviolet B and C and e-beam radiation) were more efficient and had a better cost-benefit for the degradation of the polymers studied in relation to the thermochemical treatments. Specifically, ultraviolet photo-oxidation worked well for PS and PET, requiring low energy and medium times. However, e-beam radiation was recommended for PE (LDPE and LLDPE) degradation, since high energy and long times were needed when ultraviolet energy was applied to this polymer. Furthermore, the overall efficiency of the plastic degradation of pre-treatments should be studied using a multicriteria approach, since FTIR assessments, in some cases, only consider oxidation processes on the plastic surface and do not show the potential integrity changes on the plastic probes.

Green Synthesis of CoZn-Based Metal-Organic Framework (CoZn-MOF) from Waste Polyethylene Terephthalate Plastic As a High-Performance Anode for Lithium-Ion Battery Applications

The recycling of discarded polyethylene terephthalate (PET) plastics produced metal-organic frameworks can effectively minimize environmental pollution and promote sustainable economic development. In this study, we developed a method using NaOH in alcohol and ether solvent environments to degrade PET plastics for synthesizing terephthalic acid. The method achieved a 97.5% degradation rate of PET plastics under a reaction temperature of 80 °C for 60 min. We used terephthalic acid as a ligand from the degradation products to successfully synthesize two types of monometallic and bimetallic CoZn-MOF materials. We investigated the impact of different metal centers and solvents on the electrochemical performance of the MOF materials. The result showed that the MOF-DMF/H2O material maintained a specific capacity of 1485.5 mAh g-1 after 100 cycles at a current density of 500 mA g-1, demonstrating excellent rate capability and cycling stability. In addition, our finding showed that the performance difference might be attributed to the synergistic effect of bimetallic Co2+ and Zn2+ in MOF-DMF/H2O, rapid lithium-ion diffusion and electron transfer rates, and the absence of coordinating solvents. Additionally, the non-in situ X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis results showed that lithium storage in the MOF-DMF/H2O electrode mainly depended on the aromatic C6 ring and carboxylate portions of the organic ligands in different charge and discharge states. Lithium ions can be reversibly inserted/removed into/from the electrode material. The physical adsorption on the MOF surface through electrostatic interactions enhanced both capacity and cycling stability. This research provides valuable insight for mitigating solid waste pollution, promoting sustainable economic development, and advancing the extensive applications of MOF materials in lithium-ion batteries.

Polyethylene Terephthalate Hydrolases in Human Gut Microbiota and Their Implications for Human Health

Polyethylene terephthalate (PET), primarily utilized for food and beverage packaging, consistently finds its way into the human gut, thereby exerting adverse effects on human health. PET hydrolases, critical for the degradation of PET, have been predominantly sourced from environmental microbial communities. Given the fact that the human gut harbors a vast and intricate consortium of microorganisms, inquiry into the presence of potential PET hydrolases within the human gut microbiota becomes imperative. In this investigation, we meticulously screened 22,156 homologous sequences that could potentially encode PET hydrolases using the hidden Markov model (HMM) paradigm, drawing from 4984 cultivated genomes of healthy human gut bacteria. Subsequently, we methodically validated the hydrolytic efficacy of five selected candidate PET hydrolases on both PET films and powders composed of micro-plastics (MPs). Notably, our study also unveiled the influence of both diverse PET MP powders and their resultant hydrolysates on the modulation of cytokine expression in macrophages. In summary, our research underscores the ubiquitous prevalence and considerable potential of the human gut microbiota in PET hydrolysis. Furthermore, our study significantly contributes to the holistic evaluation of the potential health hazards posed by PET MPs to human well-being.

Applicability of Electron-Beam and Hybrid Plasmas for Polyethylene Terephthalate Processing to Obtain Hydrophilic and Biocompatible Surfaces

The applicability of beam-plasma chemical reactors generating cold hybrid plasma for the production of noncytotoxic polymeric surfaces with high hydrophilicity and good biocompatibility with human fibroblast culture and human red blood cells was studied. Oxygen hybrid plasma was excited by the joint action of a continuous scanning electron beam and a capacity-coupled RF-gas discharge. Experiments showed that hybrid plasma treatment caused polar oxygen-containing functional group formation in the surface layer of poly (ethylene terephthalate) films. No thermal or radiative damage in tested polymer samples was found. The plasma-modified polymers turned out to be noncytotoxic and revealed good biocompatibility with human fibroblasts BJ-5ta as well as lower hemolytic activity than untreated poly (ethylene terephthalate). Experiments also demonstrated that no phenomena caused by the electrostatic charging of polymers occur in hybrid plasma because the electron beam component of hybrid plasma eliminates the item charge when it is treated. The electron beam can effectively control the reaction volume geometry as well as the fluxes of active plasma particles falling on the item surface. This provides new approaches to the production of abruptly structured patterns or smooth gradients of functionalities on a plane and 3D polymeric items of complicated geometry.

Seek and you shall find-news on the quest for novel PET-degrading enzymes

Plastic-degrading enzymes hold immense potential for eco-friendly recycling methods. However, the catalytic rates of current enzymes do not stack up against the mammoth task of degrading millions of tons of plastic waste per year. In the quest for more efficient polyethylene terephthalate (PET)-degrading enzymes, Zhang et al. report the discovery and characterization of PET40, a versatile PET-hydrolyzing esterase that is divergent from most characterized PETases. While PET40 has comparably low hydrolytic activity on PET, Zhang et al. demonstrate its broad activity on an expanded substrate pool. This sheds light on the potential ecological role of these esterases and suggests that PET might be only a recent addition to their substrate spectrum.

Computation-Based Design of Salt Bridges in PETase for Enhanced Thermostability and Performance for PET Degradation

Polyethylene terephthalate (PET) is one of the most widely used plastics, and the accumulation of PET poses a great threat to the environment. IsPETase can degrade PET rapidly at moderate temperatures, but its application is greatly limited by the low stability. Herein, molecular dynamics (MD) simulations combined with a sequence alignment strategy were adopted to introduce salt bridges into the flexible region of IsPETase to improve its thermal stability. In the designed variants, the Tm values of IsPETaseI168R/S188D and IsPETaseI168R/S188E were 7.4 and 8.7 °C higher than that of the wild type, respectively. The release of products degraded by IsPETaseI168R/S188E was 4.3 times that of the wild type. Tertiary structure characterization demonstrated that the structure of the variants IsPETaseI168R/S188D and IsPETaseI168R/S188E became more compact. Extensive MD simulations verified that a stable salt bridge was formed between the residue R168 and D186 in IsPETaseI168R/S188D , while in IsPETaseI168R/S188E an R168-D186-E188 salt bridge network was observed. These results confirmed that the proposed computation-based salt bridge design strategy could efficiently generate variants with enhanced thermal stability for the long-term degradation of PET, which would be helpful for the design of enzymes with improved stability.

On the Effect of Non-Thermal Atmospheric Pressure Plasma Treatment on the Properties of PET Film

The aim of the work was to investigate the effect of non-thermal plasma treatment of an ultra-thin polyethylene terephthalate (PET) film on changes in its physicochemical properties and biodegradability. Plasma treatment using a dielectric barrier discharge plasma reactor was carried out in air at room temperature and atmospheric pressure twice for 5 and 15 min, respectively. It has been shown that pre-treatment of the PET surface with non-thermal atmospheric plasma leads to changes in the physicochemical properties of this polymer. After plasma modification, the films showed a more developed surface compared to the control samples, which may be related to the surface etching and oxidation processes. After a 5-min plasma exposure, PET films were characterized by the highest wettability, i.e., the contact angle decreased by more than twice compared to the untreated samples. The differential scanning calorimetry analysis revealed the influence of plasma pretreatment on crystallinity content and the melt crystallization behavior of PET after soil degradation. The main novelty of the work is the fact that the combined action of two factors (i.e., physical and biological) led to a reduction in the content of the crystalline phase in the tested polymeric material.

Ligand-Aided Glycolysis of PET Using Functionalized Silica-Supported Fe2O3 Nanoparticles

The development of efficient catalysts for the chemical recycling of poly(ethylene terephthalate) (PET) is essential to tackling the global issue of plastic waste. There has been intense interest in heterogeneous catalysts as a sustainable catalyst system for PET depolymerization, having the advantage of easy separation and reuse after the reaction. In this work, we explore heterogeneous catalyst design by comparing metal-ion (Fe3+) and metal-oxide nanoparticle (Fe2O3 NP) catalysts immobilized on mesoporous silica (SiO2) functionalized with different N-containing amine ligands. Quantitative solid-state nuclear magnetic resonance (NMR) spectroscopy confirms successful grafting and elucidates the bonding mode of the organic ligands on the SiO2 surface. The surface amine ligands act as organocatalysts, enhancing the catalytic activity of the active metal species. The Fe2O3 NP catalysts in the presence of organic ligands outperform bare Fe2O3 NPs, Fe3+-ion-immobilized catalysts and homogeneous FeCl3 salts, with equivalent Fe loading. X-ray photoelectron spectroscopy analysis indicates charge transfer between the amine ligands and Fe2O3 NPs and the electron-donating ability of the N groups and hydrogen bonding may also play a role in the higher performance of the amine-ligand-assisted Fe2O3 NP catalysts. Density functional theory (DFT) calculations also reveal that the reactivity of the ion-immobilized catalysts is strongly correlated to the ligand-metal binding energy and that the products in the glycolysis reaction catalyzed by the NP catalysts are stabilized, showing a significant exergonic character compared to single ion-immobilized Fe3+ ions.

Two-Step Chemo-Microbial Degradation of Post-Consumer Polyethylene Terephthalate (PET) Plastic Enabled by a Biomass-Waste Catalyst

Polyethylene terephthalate (PET) pollution has significant environmental consequences; thus, new degradation methods must be explored to mitigate this problem. We previously demonstrated that a consortium of three Pseudomonas and two Bacillus species can synergistically degrade PET in culture. The consortium more readily consumes bis(2-hydroxyethyl) terephthalate (BHET), a byproduct created in PET depolymerization, compared to PET, and can fully convert BHET into metabolically usable monomers, namely terephthalic acid (TPA) and ethylene glycol (EG). Because of its crystalline structure, the main limitation of the biodegradation of post-consumer PET is the initial transesterification from PET to BHET, depicting the need for a transesterification step in the degradation process. Additionally, there have been numerous studies done on the depolymerization reaction of PET to BHET, yet few have tested the biocompatibility of this product with a bacterial consortium. In this work, a two-step process is implemented for sustainable PET biodegradation, where PET is first depolymerized to form BHET using an orange peel ash (OPA)-catalyzed glycolysis reaction, followed by the complete degradation of the BHET glycolysis product by the bacterial consortium. Results show that OPA-catalyzed glycolysis reactions can fully depolymerize PET, with an average BHET yield of 92% (w/w), and that the reaction product is biocompatible with the bacterial consortium. After inoculation with the consortium, 19% degradation of the glycolysis product was observed in 2 weeks, for a total degradation percentage of 17% when taking both steps into account. Furthermore, the 10-week total BHET degradation rate was 35%, demonstrating that the glycolysis products are biocompatible with the consortium for longer periods of time, for a total two-step degradation rate of 33% over 10 weeks. While we predict that complete degradation is achievable using this method, further experimentation with the consortium can allow for a circular recycling process, where TPA can be recovered from culture media and reused to create new materials.

Research on the Development of a Way to Modify Asphalt Mixtures with PET Recyclates

Due to the growing need to recycle plastics, new possibilities for their reuse are intensively sought. In the Asian market, waste polymers are increasingly used to modify road bitumen. This solution is beneficial in many aspects, especially in economic and ecological terms. In this work, recycled poly(ethylene terephthalate) (RPET), obtained from storage points located in Lesser Poland, was subjected to material recycling, and its properties were examined using three analyses: differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and Fourier transform infrared spectroscopy (FTIR). The most important point of this research was the selection of conditions for obtaining modified asphalt mixtures through the addition of RPET. Subsequently, the effect of the polymer on the properties of road bitumens was assessed on the basis of penetration tests, softening point, elastic recovery, and structure. In the last stage of our research work, asphalt mixtures with the addition of modified waste PET (PMA) containing mineral filler in the form of basalt dust were obtained. The properties of the obtained mineral-polymer-asphalt mixtures were compared in terms of frost resistance, structure, and abrasion resistance with the properties of mineral-asphalt mixtures that were taken from damaged road surfaces in four points in the city of Tarnów (Lesser Poland) in the winter of 2022. It has been shown that the modification of road bitumen with the use of recyclate and mineral filler has a significant impact on its performance properties.

Toxicological Profile of Polyethylene Terephthalate (PET) Microplastic in Ingested Drosophila melanogaster (Oregon R+) and Its Adverse Effect on Behavior and Development

Microplastics are readily available in the natural environment. Due to the pervasiveness of microplastic pollution, its effects on living organisms necessitate further investigation. The size, time of exposure, and amount of microplastic particles appear to be the most essential factor in determining their toxicological effects, either organismal or sub-organismal. For our research work, we preferred to work on a terrestrial model organism Drosophila melanogaster (Oregon R+). Therefore, in the present study, we characterized 2-100 µm size PET microplastic and confirmed its accumulation in Drosophila, which allowed us to proceed further in our research work. At larger dosages, research on locomotory activities such as climbing, jumping, and crawling indicated a decline in physiological and neuromuscular functions. Our studies also determined retarded development in flies and decreased survival rate in female flies after exposure to the highest concentration of microplastics. These experimental findings provide insight into the possible potential neurotoxic effects of microplastics and their detrimental effects on the development and growth of flies.

Engineering the catalytic activity of an Antarctic PET-degrading enzyme by loop exchange

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.

HY-75

Polyethylene terephthalate (PET) is a plastic material that is widely used in beverage bottles, food packaging, and other consumer products, which is highly resistant to biodegradation. In this study, we investigated the effects of two insect gut symbionts, Xanthomonas sp. HY-74 and Bacillus sp. HY-75, during PET biodegradation. Both strains degraded PET-containing agar plates, and the sole nutrition source assay showed that HY-74 had different degradation rates depending on the presence of specific carbon and nitrogen sources, whereas HY-75 exhibited comparable degradation across all tested conditions. The two strains biodegraded the PET film with 1.57 ± 0.21% and 1.42 ± 0.46% weight loss after 6 weeks, respectively. Changes in the morphology and structure of the PET films, such as erosion, scratching, and surface roughening, were determined using scanning electron microscopy (SEM). Further, the two strains biodegraded PET powder, broke it into its degradation products, and changed the surface functional groups. This is the first study to investigate the biodegradation of PET by Hymenoptera gut-derived microbes and offers promising insights into the potential applications of insect gut symbionts in PET waste management.

Utilizing Polyethylene Terephthalate PET in Concrete: A Review

In general, plastic waste has been growing remarkably. Numerous waste plastic products are generated by manufacturing processes, service industries, and municipal solid waste (MSW). The increase in plastic waste increases concern about the environment and how to dispose of the generated waste. Thus, recycling plastic waste becomes an alternative technique to the disposal of plastic waste in a limited landfill. One of the solutions is to use plastic waste as recycled material in concrete construction to produce what is called green concrete. This research illustrates a summary of studies that utilized polyethylene terephthalate (PET) in concrete as a volume ratio or concrete aggregate replacement. It presents data with regard to mixing design and concrete behavior when PET is used. Moreover, using PET in concrete industries may reduce environmental pollution such as the emission of carbon dioxide and plastic waste disposal problems.

Special Packaging Materials from Recycled PET and Metallic Nano-Powders

The European methodology for plastics, as a feature of the EU's circular economy activity plan, ought to support the decrease in plastic waste. The improvement of recycled plastics' economics and quality is one important part of this action plan. Additionally, achieving the requirement that all plastic packaging sold in the EU by 2030 be recyclable or reusable is an important objective. This means that food packaging materials should be recycled in a closed loop at the end. One of the most significant engineering polymers is polyethylene terephthalate (PET), which is widely used. Due to its numerous crucial qualities, it has a wide variety of applications, from packaging to fibers. The thermoplastic polyolefin, primarily polyethylene and polypropylene (PP), is a popular choice utilized globally in a wide range of applications. In the first phase of the current experiment, the materials were obtained by hot pressing with the press machine. The reinforcer is made of Al nanopowder 800 nm and Fe nanopowder 790 nm and the quality of the recycled polymer was examined using Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). From DSC variation curves as a function of temperature, the values from the transformation processes (glass transition, crystallization, and melting) are obtained. SEM measurements revealed that the polymer composites with Al have smooth spherical particles while the ones with Fe have bigger rough spherical particles.

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics

Polymer composites with various recycled poly(ethylene terephthalate)-based (PET-based) polyester matrices (poly(ethylene terephthalate), copolyesters, and unsaturated polyester resins), similar in properties to the primary ones, can be obtained based on PET glycolysis products after purification. PET glycolysis allows one to obtain bis(2-hydroxyethyl) terephthalate and oligo(ethylene terephthalates) with various molecular weights. A kinetic model of poly(ethylene terephthalate) homogeneous glycolysis under the combined or separate action of oligo(ethylene terephthalates), bis(2-hydroxyethyl) terephthalate, and ethylene glycol is proposed. The model takes into account the interaction of bound, terminal, and free ethylene glycol molecules in the PET feedstock and the glycolysis agent. Experimental data were obtained on the molecular weight distribution of poly(ethylene terephthalate) glycolysis products and the content of bis(2-hydroxyethyl) terephthalate monomer in them to verify the model. Homogeneous glycolysis of PET was carried out at atmospheric pressure in dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) solvents with catalyst based on antimony trioxide (Sb₂O₃) under the action of different agents: ethylene glycol at temperatures of 165 and 180 °C; bis(2-hydroxyethyl) terephthalate at 250 °C; and oligoethylene terephthalate with polycondensation degree 3 at 250 °C. Homogeneous step-by-step glycolysis under the successive action of the oligo(ethylene terephthalate) trimer, bis(2-hydroxyethyl) terephthalate, and ethylene glycol at temperatures of 250, 220, and 190 °C, respectively, was also studied. The composition of products was confirmed using FTIR spectroscopy. Molecular weight characteristics were determined using gel permeation chromatography (GPC), the content of bis(2-hydroxyethyl) terephthalate was determined via extraction with water at 60 °C. The developed kinetic model was found to be in agreement with the experimental data and it could be used further to predict the optimal conditions for homogeneous PET glycolysis and to obtain polymer-based composite materials with desired properties.

Effect of Aging on Physicochemical Properties and Size Distribution of PET Microplastic: Influence on Adsorption of Diclofenac and Toxicity Assessment

Microplastics (MPs) are detected in the water, sediments, as well as biota, mainly as a consequence of the degradation of plastic products/waste under environmental conditions. Due to their potentially harmful effects on ecosystems and organisms, MPs are regarded as emerging pollutants. The highly problematic aspect of MPs is their interaction with organic and inorganic pollutants; MPs can act as vectors for their further transport in the environment. The objective of this study was to investigate the effects of ageing on the changes in physicochemical properties and size distribution of polyethylene terephthalate (PET), as well as to investigate the adsorption capacity of pristine and aged PET MPs, using pharmaceutical diclofenac (DCF) as a model organic pollutant. An ecotoxicity assessment of such samples was performed. Characterization of the PET samples (bottles and films) was carried out to detect the thermooxidative aging effects. The influence of the temperature and MP dosage on the extent of adsorption of DCF was elucidated by employing an empirical modeling approach using the response surface methodology (RSM). Aquatic toxicity was investigated by examining the green microalgae Pseudokirchneriella subcapitata. It was found that the thermooxidative ageing process resulted in mild surface changes in PET MPs, which were reflected in changes in hydrophobicity, the amount of amorphous phase, and the particle size distribution. The fractions of the particle size distribution in the range 100-500 μm for aged PET are higher due to the increase in amorphous phase. The proposed mechanisms of interactions between DCF and PET MPs are hydrophobic and π-π interactions as well as hydrogen bonding. RSM revealed that the adsorption favors low temperatures and low dosages of MP. The combination of MPs and DCF exhibited higher toxicity than the individual components.

[Engineering the plastic degradation enzyme Ple629 from marine consortium to improve its thermal stability]

Petrochemical-derived polyester plastics such as polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) have been widely used. However, the difficulty to be degraded in nature (PET) or the long biodegradation cycle (PBAT) resulted in serious environmental pollution. In this connection, treating these plastic wastes properly becomes one of the challenges of environment protection. From the perspective of circular economy, biologically depolymerizing the waste of polyester plastics and reusing the depolymerized products is one of the most promising directions. Recent years have seen many reports on polyester plastics degrading organisms and enzymes. Highly efficient degrading enzymes, especially those with better thermal stability, will be conducive to their application. The mesophilic plastic-degrading enzyme Ple629 from the marine microbial metagenome is capable of degrading PET and PBAT at room temperature, but it cannot tolerate high temperature, which hampers its potential application. On the basis of the three-dimensional structure of Ple629 obtained from our previous study, we identified some sites which might be important for its thermal stability by structural comparison and mutation energy analysis. We carried out transformation design, and performed expression, purification and thermal stability determination of the mutants. The melting temperature (T_m) values of mutants V80C and D226C/S281C were increased by 5.2 ℃ and 6.9 ℃, respectively, and the activity of mutant D226C/S281C was also increased by 1.5 times compared with that of the wild-type enzyme. These results provide useful information for future engineering and application of Ple629 in polyester plastic degradation.

Bacterial sulfidogenic community from the surface of technogenic materials in vitro: composition and biofilm formation

Microbial biofilms of sulfate-reducing bacteria Desulfovibrio oryzae SRB1 and SRB2 were evaluated on polyethylene terephthalate in mono- and associative bacterial cultures. Bacillus velesensis strains C1 and C2b suppressed both the formation of biofilm and reduced the number of sulfate-reducing bacteria in the biofilm on the polyethylene terephthalate during the 50-day experiment. A decrease in the number of sulfate-reducing bacteria compared to the monoculture was also noted in association of D. oryzae SRB1 + Sat1 (bacterium-satellite of the sulfate-reducing bacteria). The strain Sat1 was identified as Anaerotignum (Clostridium) propionicum based on some microbiological, physiological and biochemical, genetic features. The importance of studying existing interactions between microorganisms in the ferrosphere and plastisphere is emphasized.

Combined Toxicities of Di-Butyl Phthalate and Polyethylene Terephthalate to Zebrafish Embryos

The increasing concern for the ecological risks of microplastics (MPs) as carriers of hydrophobic organic contaminants is evident. Di-butyl phthalate (DBP) is extensively utilized as an additive in plastic products, and both DBP and MPs are widespread in the environment. However, the combined toxicity of these substances remains uncertain. In this study, zebrafish embryos were employed to assess the toxic effects of polyethylene terephthalate (PET, MPs) and DBP, with a focus on the DBP toxicities influenced by PET. The embryonic chorion was partially covered by PET particles, and PET led to a delayed hatching of zebrafish embryos without inducing death or teratogenesis. On the other hand, exposure to DBP considerably inhibited the hatching of embryos, leading to severe lethal and teratogenic effects. The most common phenotypes induced by DBP exposure were delayed yolk sac absorption and pericardial edema. The mortality increased in co-treatment with 100 particles/mL PET and 2 mg/L DBP at 24 hpf and 48 hpf. The malformation phenotype, bent notochord, and delayed yolk sac absorption became more severe in 1 mg/L DBP exposition with the co-exposure of 100 particles/mL PET at 72 hpf. PET might act as a carrier that enhances the bioavailability of ambient DBP.

PET Waste Recycling into BTX Fraction Using In Situ Obtained Nickel Phosphide

The annual production of plastic waste is a serious ecological problem as it causes substantial pollution of the environment. Polyethylene terephthalate, a material usually found in disposable plastic bottles, is one of the most popular material used for packaging in the world. In this paper, it is proposed to recycle polyethylene terephthalate waste bottles into benzene-toluene-xylene fraction using a heterogeneous nickel phosphide catalyst formed in situ during the polyethylene terephthalate recycling process. The catalyst obtained was characterized using powder X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. The catalyst was shown to contain a Ni₂P phase. Its activity was studied in a temperature range of 250-400 °C and a H₂ pressure range of 5-9 MPa. The highest selectivity for benzene-toluene-xylene fraction was 93% at quantitative conversion.

Rheology of Recycled PET

Polyethylene terephthalate (PET) is a thermoplastic material that is widely used in many application fields, such as packaging, construction and household products. Due to the relevant contribution of PET to global yearly solid waste, the recycling of such material has become an important issue. Disposed PET does not maintain the mechanical properties of virgin material, as exposure to water and other substances can cause multiple chain scissions, with subsequent degradation of the viscoelastic properties. For this reason, chain extension is needed to improve the final properties of the recycled product. Chain extension is generally performed through reactive extrusion. As the latter involves structural modification and flow of PET molecules, rheology is a relevant asset for understanding the process and tailoring the mechanical properties of the final products. This paper briefly reviews relevant rheological studies associated with the recycling of polyethylene terephthalate through the reactive extrusion process.

A Multitool for Circular Economy: Fast Ring-Opening Polymerization and Chemical Recycling of (Bio)polyesters Using a Single Aliphatic Guanidine Carboxy Zinc Catalyst

A new aliphatic hybrid guanidine N,O-donor ligand (TMGeech) and its zinc chloride complex ([ZnCl₂ (TMGeech)]) are presented. This complex displays high catalytic activity for the ring-opening polymerization (ROP) of lactide in toluene, exceeding the toxic industry standard tin octanoate by a factor of 10. The high catalytic activity of [ZnCl₂ (TMGeech)] is further demonstrated under industrially preferred melt conditions, reaching high lactide conversions within seconds. To bridge the gap towards a sustainable circular (bio)economy, the catalytic activity of [ZnCl₂ (TMGeech)] for the chemical recycling of polylactide (PLA) by alcoholysis in THF is investigated. Fast production of different value-added lactates at mild temperatures is demonstrated. Selective PLA degradation from mixtures with polyethylene terephthalate (PET) and a polymer blend, catalyst recycling, and a detailed kinetic analysis are presented. For the first time, chemical recycling of post-consumer PET producing different value-added materials is demonstrated using a guanidine-based zinc catalyst. Therefore, [ZnCl₂ (TMGeech)] is a promising, highly active multitool, not only to implement a circular (bio)plastics economy, but also to tackle today's ongoing plastics pollution.

Degradation of PET Bottles by an Engineered Ideonella sakaiensis PETase

Extensive plastic production has become a serious environmental and health problem due to the lack of efficient treatment of plastic waste. Polyethylene terephthalate (PET) is one of the most used polymers and is accumulating in landfills or elsewhere in nature at alarming rates. In recent years, enzymatic degradation of PET by Ideonella sakaiensis PETase (IsPETase), a cutinase-like enzyme, has emerged as a promising strategy to completely depolymerize this polymer into its building blocks. Here, inspired by the architecture of cutinases and lipases homologous to IsPETase and using 3D structure information of the enzyme, we rationally designed three mutations in IsPETase active site for enhancing its PET-degrading activity. In particular, the S238Y mutant, located nearby the catalytic triad, showed a degradation activity increased by 3.3-fold in comparison to the wild-type enzyme. Importantly, this structural modification favoured the function of the enzyme in breaking down highly crystallized (~31%) PET, which is found in commercial soft drink bottles. In addition, microscopical analysis of enzyme-treated PET samples showed that IsPETase acts better when the smooth surface of highly crystalline PET is altered by mechanical stress. These results represent important progress in the accomplishment of a sustainable and complete degradation of PET pollution.

Chemical Recycling Processes of Waste Polyethylene Terephthalate Using Solid Catalysts

Polyethylene terephthalate (PET) is a non-degradable single-use plastic and a major component of plastic waste in landfills. Chemical recycling is one of the most widely adopted methods to transform post-consumer PET into PET's building block chemicals. Non-catalytic depolymerization of PET is very slow and requires high temperatures and/or pressures. Recent advancements in the field of material science and catalysis have delivered several innovative strategies to promote PET depolymerization under mild reaction conditions. Particularly, heterogeneous catalysts assisted depolymerization of post-consumer PET to monomers and other value-added chemicals is the most industrially compatible method. This review includes current progresses on the heterogeneously catalyzed chemical recycling of PET. It describes four key pathways for PET depolymerization including, glycolysis, pyrolysis, alcoholysis, and reductive depolymerization. The catalyst function, active sites and structure-activity correlations are briefly outlined in each section. An outlook for future development is also presented.

Can Superhydrophobic PET Surfaces Prevent Bacterial Adhesion?

Prevention of bacterial adhesion is a way to reduce and/or avoid biofilm formation, thus restraining its associated infections. The development of repellent anti-adhesive surfaces, such as superhydrophobic surfaces, can be a strategy to avoid bacterial adhesion. In this study, a polyethylene terephthalate (PET) film was modified by in situ growth of silica nanoparticles (NPs) to create a rough surface. The surface was further modified with fluorinated carbon chains to increase its hydrophobicity. The modified PET surfaces presented a pronounced superhydrophobic character, showing a water contact angle of 156° and a roughness of 104 nm (a considerable increase comparing with the 69° and 4.8 nm obtained for the untreated PET). Scanning Electron Microscopy was used to evaluate the modified surfaces morphology, further confirming its successful modification with nanoparticles. Additionally, a bacterial adhesion assay using an Escherichia coli expressing YadA, an adhesive protein from Yersinia so-called Yersinia adhesin A, was used to assess the anti-adhesive potential of the modified PET. Contrarily to what was expected, adhesion of E. coli YadA was found to increase on the modified PET surfaces, exhibiting a clear preference for the crevices. This study highlights the role of material micro topography as an important attribute when considering bacterial adhesion.

Environmental Sustainable Cement Mortars Based on Polyethylene Terephthalate from Recycling Operations

The building and construction industry is a key sector behind the ecological transition in that it is one of the main responsible factors in the consumption of natural resources. Thus, in line with circular economy, the use of waste aggregates in mortars is a possible solution to increase the sustainability of cement materials. In the present paper, polyethylene terephthalate (PET) from bottle scraps (without chemical pretreatment) was used as aggregate in cement mortars to replace conventional sand aggregate (20%, 50% and 80% by weight). The fresh and hardened properties of the innovative mixtures proposed were evaluated through a multiscale physical-mechanical investigation. The main results of this study show the feasibility of the reuse of PET waste aggregates as substitutes for natural aggregates in mortars. The mixtures with bare PET resulted in less fluid than the specimens with sand; this was ascribed to the higher volume of the recycled aggregates with respect to sand. Moreover, PET mortars showed a high tensile strength and energy absorption capacity (with Rf = 1.9 ÷ 3.3 MPa, Rc = 6 ÷ 13 MPa); instead, sand samples were characterized by a brittle rupture. The lightweight specimens showed a thermal insulation increase ranging 65-84% with respect to the reference; the best results were obtained with 800 g of PET aggregate, characterized by a decrease in conductivity of approximately 86% concerning the control. The properties of these environmentally sustainable composite materials may be suitable for non-structural insulating artifacts.

p-Xylene Oxidation to Terephthalic Acid: New Trends

Large-scale terephthalic acid production from the oxidation of p-xylene is an especially important process in the polyester industry, as it is mainly used in polyethylene terephthalate (PET) manufacturing, a polymer that is widely used in fibers, films, and plastic products. This review presents and discusses catalytic advances and new trends in terephthalic acid production (since 2014), innovations in terephthalic acid purification processes, and simulations of reactors and reaction mechanisms.

Killing two birds with one stone: chemical and biological upcycling of polyethylene terephthalate plastics into food

Most polyethylene terephthalate (PET) plastic waste is landfilled or pollutes the environment. Additionally, global food production must increase to support the growing population. This article explores the feasibility of using microorganisms in an industrial system that upcycles PET into edible microbial protein powder to solve both problems simultaneously. Many microorganisms can utilize plastics as feedstock, and the resultant microbial biomass contains fats, nutrients, and proteins similar to those found in human diets. While microbial degradation of PET is promising, biological PET depolymerization is too slow to resolve the global plastic crisis and projected food shortages. Evidence reviewed here suggests that by coupling chemical depolymerization and biological degradation of PET, and using cooperative microbial communities, microbes can efficiently convert PET waste into food.

Overview of Polyethylene Terephthalate Foils Patterned Using 10 MeV Carbon Ions for Realization of Micromembranes

Polymer membranes are conventionally prepared using high-energy particles from radioactive decay or by the bombardment of hundreds of MeVs energy ions. In both circumstances, tracks of damage are produced by particles/ions passing through the polymer, and successively, the damaged material is removed by chemical etching to create narrow pores. This process ensures nanosized pore diameter but with random placement, leading to non-uniform local pore density and low membrane porosity, which is necessary to reduce the risk of their overlapping. The present study is focused on the use of polyethylene terephthalate (PET) foils irradiated by 10.0 MeV carbon ions, easily achievable with ordinary ion accelerators. The ion irradiation conditions and the chemical etching conditions were monitored to obtain customized pore locations without pore overlapping in PET. The quality, shape, and size of the pores generated in the micromembranes can have a large impact on their applicability. In this view, the Scanning Transmission Ion Microscopy coupled with a computer code created in our laboratory was implemented to acquire new visual and quantitative insights on fabricated membranes.

Counter-intuitive enhancement of degradation of polyethylene terephthalate through engineering of lowered enzyme binding to solid plastic

Degradation of solid polyethylene terephthalate (PET) by leaf branch compost cutinase (LCC) produces various PET-derived degradation intermediates (DIs), in addition to terephthalic acid (TPA), which is the recyclable terminal product of all PET degradation. Although DIs can also be converted into TPA, in solution, by LCC, the TPA that is obtained through enzymatic degradation of PET, in practice, is always contaminated by DIs. Here, we demonstrate that the primary reason for non-degradation of DIs into TPA in solution is the efficient binding of LCC onto the surface of solid PET. Although such binding enhances the degradation of solid PET, it depletes the surrounding solution of enzyme that could otherwise have converted DIs into TPA. To retain a subpopulation of enzyme in solution that would mainly degrade DIs, we introduced mutations to reduce the hydrophobicity of areas surrounding LCC's active site, with the express intention of reducing LCC's binding to solid PET. Despite the consequent reduction in invasion and degradation of solid PET, overall levels of production of TPA were ~3.6-fold higher, due to the partitioning of enzyme between solid PET and the surrounding solution, and the consequent heightened production of TPA from DIs. Further, synergy between such mutated LCC (F125L/F243I LCC) and wild-type LCC resulted in even higher yields, and TPA of nearly ~100% purity.

Efficacy of sodium chlorite in inactivating Vibrio parahaemolyticus attached to polyethylene terephthalate surfaces

The inactivation of Vibrio parahaemolyticus cells attached to a polyethylene terephthalate (PET) disc in a sodium chlorite (NaClO2) solution was kinetically studied in a weakly acidic pH range of 4.0 - 6.5. The logarithmic reduction in the survival ratio depended on the concentration-time product. All inactivation curves showed a linear reduction phase, and the reduction in viable cells was greater than 4-log. No significant desorption of attached cells was observed during the inactivation treatment. The first-order inactivation rate constant (k) increased by approximately 4.5-fold for every 1.0 unit fall in pH. At all pH values, the k values calculated for the attached cells were approximately half of those for the unattached cells. These findings indicate that a weakly acidic NaClO2 solution is effective in inactivating bacteria attached to hard surfaces.

Silver Nanoparticles Loaded on Polyethylene Terephthalate Films Grafted with Chitosan

Currently, polyethylene terephthalate (PET) is one of the most widely used polymeric materials in different sectors such as medicine, engineering, and food, among others, due to its benefits, including biocompatibility, mechanical resistance, and tolerance to chemicals and/or abrasion. However, despite all these excellent characteristics, it is not capable of preventing the proliferation of microorganisms on its surface. Therefore, providing this property to PET remains a difficult challenge. Fortunately, different strategies can be applied to remove microorganisms from the PET surface. In this work, the surface of the PET film was functionalized with amino groups and later with a dicarboxylic acid, allowing a grafting reaction with chitosan chains. Finally, the chitosan coating was loaded with silver nanoparticles with an average size of 130 ± 37 nm, presenting these materials with an average cell viability of 80%. The characterization of these new PET-based materials showed considerable changes in surface morphology as well as increased surface hydrophilicity without significantly affecting their mechanical properties. In general, the implemented method can open an alternative pathway to design new PET-based materials due to its good cell viability with possible bacteriostatic activity due to the biocidal properties of silver nanoparticles and chitosan.

Enhanced Adsorption of Bromoform onto Microplastic Polyethylene Terephthalate Exposed to Ozonation and Chlorination

This paper selected microplastic polyethylene terephthalate (PET), commonly found in water/wastewater plant effluent, to investigate the changes of PET oxidized under ozonation (designated as ozonized PET), followed by sodium hypochlorite oxidation (designated as ozonized-chlorinated PET) and studied their influence on the adsorption of the disinfection by-product bromoform (TBM). Fragmentation and cracks appeared on the oxidized PET surface. As the oxidation degree increased, the contact angle decreased from 137° to 128.90° and 128.50°, suggesting hydrophilicity was enhanced. FTIR and XPS analyses suggested that carbonyl groups increased on the surface of ozonized PET and ozonized-chlorinated PET, while the formation of intermolecular halogen bonds was possible when PET experienced dual oxidation. These physiochemical changes enhanced the adsorption of TBM. The adsorption capacity of TBM followed the order of ozonized-chlorinated PET (2.64 × 10−6 μg/μg) > ozonized PET (2.58 × 10−6 μg/μg) > pristine PET (2.43 × 10−6 μg/μg). The impact of raw water characteristics on the adsorption of TBM onto PETs, such as the pH, and the coexistence of inorganic ions and macromolecules (humic acid, surfactant, and bovine serum albumin) were studied. A different predominant adsorption mechanism between TBM and pristine PET or oxidized PETs was proposed.

Migration Modeling as a Valuable Tool for Exposure Assessment and Risk Characterization of Polyethylene Terephthalate Oligomers

Polyethylene terephthalate (PET) is one of the most widely used food contact materials due to its excellent mechanical properties and recyclability. Migration of substances from PET and assessment of compliance are usually determined by experimental testing, which can be challenging depending on the migrants of interest. Low concentrations and missing reference standards, among other factors, have led to inadequate investigation of the migration potential of PET oligomers. Migration modeling can overcome such limitations and is therefore a suitable starting point for exposure and risk assessment. In this study, the activation energy-based (E_A) model and the A_P model were used to systematically evaluate the migration potential of 52 PET oligomers for 12 different application scenarios. Modeling parameters and conditions were evaluated to investigate their impact and relevance on the assessment of realistic exposures. Obtained results were compared with safety thresholds known from the concept of toxicological thresholds of concern. This allowed the evaluation and identification of oligomers and/or applications where migration or exposure levels may be associated with a potential risk because they exceed these safety thresholds. Overall, this study demonstrated that migration modeling can be a high-throughput, fast, flexible, and suitable approach for comprehensive exposure assessment.

Biodegradable and Non-Biodegradable Biomaterials and Their Effect on Cell Differentiation

Biomaterials for tissue scaffolds are key components in modern tissue engineering and regenerative medicine. Targeted reconstructive therapies require a proper choice of biomaterial and an adequate choice of cells to be seeded on it. The introduction of stem cells, and the transdifferentiation procedures, into regenerative medicine opened a new era and created new challenges for modern biomaterials. They must not only fulfill the mechanical functions of a scaffold for implanted cells and represent the expected mechanical strength of the artificial tissue, but furthermore, they should also assure their survival and, if possible, affect their desired way of differentiation. This paper aims to review how modern biomaterials, including synthetic (i.e., polylactic acid, polyurethane, polyvinyl alcohol, polyethylene terephthalate, ceramics) and natural (i.e., silk fibroin, decellularized scaffolds), both non-biodegradable and biodegradable, could influence (tissue) stem cells fate, regulate and direct their differentiation into desired target somatic cells.

Evaluation of chemicals leached from PET and recycled PET containers into beverages

The use of recycled polyethylene terephthalate (rPET) containers, a recent shift in the beverage industry, poses new potential human health concerns including contamination from the original container; use of additives, detergents, and catalysts during recycling; and improper recycling practices. The purpose of this analysis was to evaluate available data regarding: (1) chemicals leached from PET and rPET in bottle form; (2) concentration of these chemicals; and (3) trends between rPET percent and concentration of chemicals leached. This analysis identified 211 scientific articles related to recycled plastic and leachables. Three articles met the inclusion criteria: (1) plastic was in bottle form; (2) plastic was made of PET or rPET; and (3) the study analyzed both PET and rPET using the same methods. This evaluation demonstrated that only nine compounds - benzene, styrene, acetaldehyde, 2-methyl-1,3-dioxolane, furan, bisphenol A (BPA), 2-buta-none, acetone, and limonene - have been studied. Notably, the leachable concentration of benzene, styrene, and BPA increased as the percent of recycled content increased from 0 to 100%. However, 2-methyl-1,3-dioxolane and furan implied a reverse trend, where the leachable concentration decreased as the percent of recycled content increased from 0 to 100%. The concentrations of 2-butanone, acetone, and limonene did not follow any suggested trend. Evidently, recycling PET can lead to changes in the leachables profile. This analysis further identified key areas of research, including testing a variety of liquid types, that need to be addressed to adequately conduct a human health risk assessment.

Surface Properties of the Polyethylene Terephthalate (PET) Substrate Modified with the Phospholipid-Polypeptide-Antioxidant Films: Design of Functional Biocoatings

Surface properties of polyethylene terephthalate (PET) coated with the ternary monolayers of the phospholipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), the immunosuppressant cyclosporine A (CsA), and the antioxidant lauryl gallate (LG) were examined. The films were deposited, by means of the Langmuir-Blodgett (LB) technique, on activated by air low temperature plasma PET plates (PET_air). Their topography and surface chemistry were determined with the help of atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS), respectively, while wettability was evaluated by the contact angle measurements. Then, the surface free energy and its components were calculated from the Lifshitz-van der Waals/Acid-Base (LWAB) approach. The AFM imaging showed that the Langmuir monolayers were transferred effectively and yielded smoothing of the PET_air surface. Mass spectrometry confirmed compatibility of the quantitative and qualitative compositions of the monolayers before and after the transfer onto the substrate. Moreover, the molecular arrangement in the LB films and possible mechanisms of DOPC-CsA-LG interactions were determined. The wettability studies provided information on the type and magnitude of the interactions that can occur between the biocoatings and the liquids imitating different environments. It was found that the changes from open to closed conformation of CsA molecules are driven by the hydrophobic environment ensured by the surrounding DOPC and LG molecules. This process is of significance to drug delivery where the CsA molecules can be released directly from the biomaterial surface by passive diffusion. The obtained results showed that the chosen techniques are complementary for the characterization of the molecular organization of multicomponent LB films at the polymer substrate as well as for designing biocompatible coatings with precisely defined wettability.

Decoration of Ultramicrotome-Cut Polymers with Silver Nanoparticles: Effect of Post-Deposition Laser Treatment

Today, ultramicrotome cutting is a practical tool, which is frequently applied in the preparation of thin polymeric films. One of the advantages of such a technique is the decrease in surface roughness, which enables an effective recording of further morphological changes of polymeric surfaces during their processing. In view of this, we report on ultramicrotome-cut polymers (PET, PEEK) modified by a KrF excimer laser with simultaneous decoration by AgNPs. The samples were immersed into AgNP colloid, in which they were exposed to polarized laser light. As a result, both polymers changed their surface morphology while simultaneously being decorated with AgNPs. KrF laser irradiation of the samples resulted in the formation of ripple-like structures on the surface of PET and worm-like ones in the case of PEEK. Both polymers were homogeneously covered by AgNPs. The selected area of the samples was then irradiated by a violet semiconductor laser from the confocal laser scanning microscope with direct control of the irradiated area. Various techniques, such as AFM, FEGSEM, and CLSM were used to visualize the irradiated area. After irradiation, the reverse pyramid was formed for both types of polymers. PET samples exhibited thicker transparent reverse pyramids, whereas PEEK samples showed thinner brownish ones. We believe that his technique can be effectively used for direct polymer writing or the preparation of stimuli-responsive nanoporous membranes.

Investigation of the halophilic PET hydrolase PET6 from Vibrio gazogenes

The handling of plastic waste and the associated ubiquitous occurrence of microplastic poses one of the biggest challenges of our time. Recent investigations of plastic degrading enzymes have opened new prospects for biological microplastic decomposition as well as recycling applications. For polyethylene terephthalate, in particular, several natural and engineered enzymes are known to have such promising properties. From a previous study that identified new PETase candidates by homology search, we chose the candidate PET6 from the globally distributed, halophilic organism Vibrio gazogenes for further investigation. By mapping the occurrence of Vibrios containing PET6 homologs we demonstrated their ubiquitous prevalence in the pangenome of several Vibrio strains. The biochemical characterization of PET6 showed that PET6 has a comparatively lower activity than other enzymes but also revealed a superior turnover at very high salt concentrations. The crystal structure of PET6 provides structural insights into this adaptation to saline environments. By grafting only a few beneficial mutations from other PET degrading enzymes onto PET6, we increased the activity up to three-fold, demonstrating the evolutionary potential of the enzyme. MD simulations of the variant helped rationalize the mutational effects of those mutants and elucidate the interaction of the enzyme with a PET substrate. With tremendous amounts of plastic waste in the Ocean and the prevalence of Vibrio gazogenes in marine biofilms and estuarine marshes, our findings suggest that Vibrio and the PET6 enzyme are worthy subjects to study the PET degradation in marine environments.

Analysis of Elastic Properties of Al/PET Isotropic Composite Materials Using Finite Element Method

This study uses the finite element method and numerical analysis to develop an eco-friendly composite material with shielding capabilities. A preliminary study was performed to predict the mechanical properties of the composite material. Polyethylene terephthalate and aluminum powder (AP) were selected as the matrix and enhancer, respectively. The particles of AP are spherical, with a diameter of 1 μm. Material properties were investigated as the AP volume fraction (VF) increased from 5-70%. The FEM results show that the physical properties for AP VFs improve by up to 40%, but there is no significant change in the elastic modulus, shear modulus, and Poisson's ratio at an AP VF of 50-70%. However, the numerical analysis models show that the elastic properties for AP VFs improve by up to 70%. The mechanical properties improved as the VF increased, and the FEM predicted values were reliable for VFs up to 40%. However, it was confirmed that 40% is the limit of AP VF in the FEM. In addition, the FEM and numerical analysis predictions showed that the most similar numerical analysis model was the Halpin-Tsai model. The predictions of the Halpin-Tsai model allowed prediction of the maximum VF above the FEM limit. If the correction coefficients of the FEM and numerical analysis models are derived based on the predictions of this study and future experimental results, reliable predictions can be obtained for the physical properties of composite materials.

Ion Lithography of Single Ions Irradiation for Spatially Regular Arrays of Pores in Membranes of Polyethylene Terephthalate

Routinely, in membrane technology, the decay from radioactive particles or the bombardment of ions with MeV energy per nucleon have been employed for the production of narrow and long pores in membranes. Presently, the ion lithography is proposed to make the fabrication cost more affordable. It is prospective for the use of medium capacity accelerators making more feasible the fabrication of customized membranes. Thin polyethylene terephthalate foils have been patterned using 12 MeV O⁵⁺ ions and then processed to obtain good aspect ratio ion track pores in membranes. Pores of micrometric diameter with the following profiles were fabricated in the membranes: truncated cone, double conical, ideal cone, and cylindrical. Monitoring of the shape and size of pores has been attempted with a combination of Scanning Transmission Ion Microscope and a newly designed simulation program. This study is focused on the use of low-energy ions, accomplished in all laboratories, for the fabrication of membranes where the pores are not randomly traced and exhibit higher surface density and negligible overlapping than in membranes commonly manufactured. The good reproducibility and the ordered pore locations can be potentially utilized in applications such as microfluidics and organ-on-chip microsystems, where cells growing over porous substrates are used in simulation of biological barriers and transport processes.

The Physicochemical Characterization of New "Green" Epoxy-Resin Hardener Made from PET Waste

"Green" thermally stable hardener was synthesized from a PET waste. The rigid molecular linear structure of the new hardener suggests that it will provide the polymer matrix with the necessary physical and mechanical characteristics. It also allows the expectation that cured matrix based on this hardener can provide increased toughness. New hardener was used as a curing agent for three epoxy resins-tetraglycidyl methylenedianiline (TGDMA, 111-117 EEW), diglycidylether of bisphenol A (DGEBA, 170-192 EEW) and solid epoxy resin (SER)-with a medium molecular weight (860-930 EEW) based on DGEBA. The mixtures were found to have the highest T_g for the DGEBA resin, and high of that for TGDMA and SER. According to the DMA analysis for two cured matrices, the hardener proved to be no worse than the standard ones, and made it possible to obtain cured matrices with excellent mechanical properties, which allows us to hope for further application of new hardener cured epoxy matrices in appropriate composite materials at high temperatures.