Theoretical Studies on the Quantitative Structure-Toxicity Relationship of Polychlorinated Biphenyl Congeners Reveal High Affinity Binding to Multiple Human Nuclear Receptors.

Polychlorinated biphenyls (PCBs) are organic chemicals consisting of a biphenyl structure substituted with one to ten chlorine atoms, with 209 congeners depending on the number and position of the chlorine atoms. PCBs are widely known to be endocrine-disrupting chemicals (EDCs) and have been found to be involved in several diseases/disorders. This study takes various molecular descriptors of these PCBs (e.g., molecular weight) and toxicity endpoints as molecular activities, investigating the possibility of correlations via the quantitative structure-toxicity relationship (QSTR). This study then focuses on molecular docking and dynamics to investigate the docking behavior of the strongest-binding PCBs to nuclear receptors and compares these to the docking behavior of their natural ligands. Nuclear receptors are a family of transcription factors activated by steroid hormones, and they have been investigated to consider the impact of PCBs on humans in this context. It has been observed that the docking affinity of PCBs is comparable to that of the natural ligands, but they are inferior in terms of stability and interacting forces, as shown by the RMSD and total energy values. However, it is noted that most nuclear receptors respond to PCBs similarly to how they respond to their natural ligands-as shown in the RMSF plots-the most similar of which are seen in the ER, THR-ß, and RAR-α. However, this study is performed purely in silico and will need experimental verification for validation.

Dopamine-Induced Surface Zwitterionization of Expanded Poly(tetrafluoroethylene) for Constructing Thermostable Bioinert Materials.

Although energy-demanding, the surface modification of polytetrafluoroethylene (PTFE) for biomedical applications is mandatory to mitigate irreversible biofouling that occurs whenever PTFE comes into contact with biological fluids. Here, we propose to take advantage of the adhesive properties of dopamine (DA) and of the antifouling ability of various zwitterionic monomers (sulfobetaine methacrylate (SBMA), sulfobetaine methacrylamide (SBAA), sulfobetaine acrylamide (SBAA'), and 4-vinylpyridine propylsulfobetaine (4VPPS)) and form antifouling coatings by copolymerization on the surface of expanded PTFE membranes. This simple, low-energy, and one-step coating procedure arises in significant biofouling mitigation. All zwitterionic coatings led to important reduction of biofouling by red blood cell conentrate (88-94%), platelet conentrate (70-90%), whole blood (40-66%), or bacteria (83-96%). Also, it is shown that the interactions of polydopamine with ePTFE are stable even at high temperatures. However, the zwitterionic monomers are differently affected. While the performance of SBMA coatings decreased (as SBMA is prone to hydrolysis), those of SBAA, SBAA', and 4VPPS coatings were generally maintained. All in all, this study illustrates that efficient and stable antifouling zwitterionic coatings can be generated onto PTFE membranes for biomedical applications, without the use of conventional high-energy-demanding surface modification processes.

Infusion of Silver-Polydopamine Particles into Polyethersulfone Matrix to Improve the Membrane's Dye Desalination Performance and Antibacterial Property.

The advancement in membrane science and technology, particularly in nanofiltration applications, involves the blending of functional nanocomposites into the membranes to improve the membrane property. In this study, Ag-polydopamine (Ag-PDA) particles were synthesized through in situ PDA-mediated reduction of AgNO3 to silver. Infusing Ag-PDA particles into polyethersulfone (PES) matrix affects the membrane property and performance. X-ray photoelectron spectroscopy (XPS) analyses confirmed the presence of Ag-PDA particles on the membrane surface. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) describe the morphology of the membranes. At an optimum concentration of Ag-PDA particles (0.3 wt % based on the concentration of PES), the modified membrane exhibited high water flux 13.33 L∙m-2∙h-1 at 4 bar with high rejection for various dyes of >99%. The PESAg-PDA0.3 membrane had a pure water flux more than 5.4 times higher than that of a pristine membrane. Furthermore, in bacterial attachment using Escherichia coli, the modified membrane displayed less bacterial attachment compared with the pristine membrane. Therefore, immobilizing Ag-PDA particles into the PES matrix enhanced the membrane performance and antibacterial property.

Surface Zwitterionization of Expanded Poly(tetrafluoroethylene) via Dopamine-Assisted Consecutive Immersion Coating.

Expanded polytetrafluoroethylene (ePTFE) is one of the materials widely used in the biomedical field, yet its application is being limited by adverse reactions such as thrombosis when it comes in contact with blood. Thus, a simple and robust way to modify ePTFE to be biologically inert is sought after. Modification of ePTFE without high-energy pretreatment, such as immersion coating, has been of interest to researchers for its straightforward process and ease in scaling up. In this study, we utilized a two-step immersion coating to zwitterionize ePTFE membranes. The first coating consists of the co-deposition of polyethylenimine (PEI) and polydopamine (PDA) to produce amine groups in the surface of the ePTFE for further functionalization. These amine groups from PEI will be coupled with the epoxide group of the zwitterionic copolymer, poly(GMA-co-SBMA) (PGS), via a ring-opening reaction in the second coating. The coated ePTFE membranes were physically and chemically characterized to ensure that each step of the coating is successful. The membranes were also tested for their thrombogenicity via quantification of the blood cells attached to it during contact with biological solutions. The coated membranes exhibited around 90% reduction in attachment with respect to the uncoated ePTFE for both Gram-positive and Gram-negative strains of bacteria (Staphylococcus aureus and Escherichia coli). The coating was also able to resist blood cell attachment from human whole blood by 81.57% and resist red blood cell attachment from red blood cell concentrate by 93.4%. These ePTFE membranes, which are coated by a simple immersion coating, show significant enhancement of the biocompatibility of the membranes, which shows promise for future use in biological devices.

Enhanced recovery of aluminum from wastewater using a fluidized bed homogeneously dispersed granular reactor.

The recovery of aluminum from wastewater is one of the main environmental issues that need to be addressed in the aluminum finishing industry. A new technique of converting a soft slurry into hard granules using the homogeneous granulation process in the fluidized-bed reactor (FBR) can respond to this problem. It is a better method of remediation than producing a slurry containing 70% water. This study deals with the recovery of aluminum from aqueous solutions using Fluidized-bed homogeneous granulation process (FBHGP) without seeds. The hydraulic operating conditions were optimized using Box-Behnken Design (BBD) to attain the optimum aluminum removal (AR%) and granulation ratio (GR%). Optimum values of AR% = 98.8% and GR% = 96.9% were attained at the following conditions: influent aluminum concentration, 334.1 mg L-1; precipitant pH, 10.4; molar ratio (MR) of precipitant to metal [OH-]in/[Al3+]in, 2.5. The characteristics of the granules were comparable with those of orthorhombic structure of aluminum oxide (Al2.66O4). FBHGP was proven to be effective as dictated by the reaction mechanism in the recovery of aluminum from aluminum-rich aqueous solutions.

Effects of acidified aqueous glycerol and glycerol carbonate pretreatment of rice husk on the enzymatic digestibility, structural characteristics, and bioethanol production.

Rice husk as an abundant biomass was used in this study, and it contained 30.1% glucan and 13.5% xylan, 22.4% lignin. The pretreated rice husk with glycerol carbonate and acidified aqueous glycerol (10% water) at 90°C and 130°C for 60min had the maximum yield of glucan digestibility which was 78.2% and 69.7% respectively, using cellulase for 72h. The simultaneous saccharification and fermentation was conducted anaerobically at 37°C with Saccharomyces cerevisiae, 5% w/v glucan and 10FPU/g glucan of cellulase. 11.58 and 8.84g/L was the highest ethanol concentration after 3days of incubation form pretreated rice husk with glycerol carbonate and acidified aqueous glycerol respectively.

Correlating PSf Support Physicochemical Properties with the Formation of Piperazine-Based Polyamide and Evaluating the Resultant Nanofiltration Membrane Performance.

Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200⁻35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L·m-2·h-1, RNa2SO4 = 91.1% ± 1.8%, and RNaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance.

Factors affecting degradation of polyethylene terephthalate (PET) during pre-flotation conditioning.

In general, plastics are exposed to different degrading agents in every procedure involved in their recovery from waste mixture and from subsequent recycling. In this study, two methods of pre-flotation conditioning were used to determine how these methods affect the general properties of the pre-conditioned PET particles to be recovered from the PET-PVC mixture. The first method comprised the conditioning of PET samples using an alkaline solution of nonionic surfactant (Triton X-100) based on the patent by the Goodyear Tire and Rubber Company. The second method, developed in this study, was a conditioning process which used an alkali-less solution of the same nonionic surfactant (Triton X-100) used in the first method. The following analytical methods were used to characterize properties of the pre-conditioned PET samples that were correlated to relative degradation of the samples: differential scanning calorimetry (DSC), for thermal behavior of the samples; FT-IR spectroscopy, for functional groups present in the samples; and, Pohl's method, for carboxyl end-group concentration count. Results show that in addition to water the presence of NaOH in the conditioning solution contributes to the further degradation of the polymer.