Novel methods for the characterization of water-soluble polymers

The liquid chromatography of four water-soluble polymers [pullulan, polyacrylamide, poly(ethylene glycol), and poly(ethylene oxide)] have been investigated and used to categorize separation processes which couple enthalpic and entropic mechanisms. Experiments were carried out with a binary mobile phase which combined a thermodynamically good solvent (water or aqueous 0.02M Na₂SO₄) and nonsolvent (methanol). The polymer solute was injected in a good solvent. By varying the solvent–nonsolvent ratio in the eluent, conditions could be obtained where the free energies of exclusion and solvation were balanced. This has been given the nomenclature “liquid chromatography under limiting conditions of solubility” (LC-LCS) since the polymer elutes just in front of the system peak at the “limit” of its solubility. Conditions can also be identified where exclusion is balanced with adsorption (“liquid chromatography under limiting conditions of adsorption,” or LC-LCA). To our knowledge, these are the first experimental reports of LC-LCS for any polymer and the first LC-LCA observation on water-soluble macromolecules. All measurements were carried out over a poly(hydroxymethylacrylate) sorbent. Cloud point curves were found to generally distinguish the regions where LC-LCA or LC-LCS dominate. The data illustrate the need to consider the polymer when analyzing LC-LCA. Conversely, polymer adsorption may play an important role in LC-LCS. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2549–2557, 1998     

Effect of Cobalt and Chromium Ions on the Chlorhexidine Digluconate as Seen by Intermolecular Diffusion

Metal ions such as cobalt (II) and chromium (III) might be present in the oral cavity, as a consequence of the corrosion of Co-Cr dental alloys. The diffusion of such metal ions into the organism, carried by saliva, can cause health problems as a consequence of their toxicity, enhanced by a cumulative effect in the body. The effect of the chlorhexidine digluconate, which is commonly used in mouthwash formulations, on the transport of these salts is evaluated in this paper by using the Taylor dispersion technique, which will allow an assessment of how the presence of chlorhexidine digluconate (either in aqueous solution or in a commercial formulation) may affect the diffusion of metal ions. The ternary mutual diffusion coefficients of metal ions (Co and Cr) in the presence of chlorhexidine digluconate, in an artificial saliva media, were measured. Significant coupled diffusion of CoCl₂ (and CrCl₃) and chlorhexidine digluconate is observed by analysis of the non-zero values of the cross-diffusion coefficients, D₁₂ and D₂₁. The observed interactions between metal ions and chlorhexidine digluconate suggest that the latter might be considered as an advantageous therapeutic agent, once they contribute to the reduction of the concentration of those ions inside the mouth.     

Gene Expression Data Mining Reveals the Involvement of GPR55 and Its Endogenous Ligands in Immune Response,Cancer, and Differentiation

G protein-coupled receptor 55 (GPR55) is a recently deorphanized lipid- and peptide-sensing receptor. Its lipidic endogenous agonists belong to lysoglycerophospholipids, with lysophosphatidylinositol (LPI) being the most studied. Peptide agonists derive from fragmentation of pituitary adenylate cyclase-activating polypeptide (PACAP). Although GPR55 and its ligands were implicated in several physiological and pathological conditions, their biological function remains unclear. Thus, the aim of the study was to conduct a large-scale re-analysis of publicly available gene expression datasets to identify physiological and pathological conditions affecting the expression of GPR55 and the production of its ligands. The study revealed that regulation of GPR55 occurs predominantly in the context of immune activation pointing towards the role of the receptor in response to pathogens and in immune cell lineage determination. Additionally, it was revealed that there is almost no overlap between the experimental conditions affecting the expression of GPR55 and those modulating agonist production. The capacity to synthesize LPI was enhanced in various types of tumors, indicating that cancer cells can hijack the motility-related activity of GPR55 to increase aggressiveness. Conditions favoring accumulation of PACAP-derived peptides were different than those for LPI and were mainly related to differentiation. This indicates a different function of the two agonist classes and possibly the existence of a signaling bias.     

PPAR-Gamma Activation May Inhibit the In Vivo Degeneration of Bioprosthetic Aortic and Aortic Valve Grafts under Diabetic Conditions

Background: We aimed to examine the anti-calcification and anti-inflammatory effects of pioglitazone as a PPAR-gamma agonist on bioprosthetic-valve-bearing aortic grafts in a rat model of diabetes mellitus (DM). Methods: DM was induced in male Wistar rats by high-fat diet with an intraperitoneal streptozotocin (STZ) injection. The experimental group received additional pioglitazone, and controls received normal chow without STZ (n = 20 each group). Cryopreserved aortic donor grafts including the aortic valve were analyzed after 4 weeks and 12 weeks in vivo for analysis of calcific bioprosthetic degeneration. Results: DM led to a significant media proliferation at 4 weeks. The additional administration of pioglitazone significantly increased circulating adiponectin levels and significantly reduced media thickness at 4 and 12 weeks, respectively (p = 0.0002 and p = 0.0107, respectively). Graft media calcification was highly significantly inhibited by pioglitazone after 12 weeks (p = 0.0079). Gene-expression analysis revealed a significant reduction in relevant chondro-osteogenic markers osteopontin and RUNX-2 by pioglitazone at 4 weeks. Conclusions: Under diabetic conditions, pioglitazone leads to elevated circulating levels of adiponectin and to an inhibition of bioprosthetic graft degeneration, including lower expression of chondro-osteogenic genes, decreased media proliferation, and inhibited graft calcification in a small-animal model of DM.     

Transcriptome Analysis of Cells Exposed to Actinomycin D and Nutlin-3a Reveals New Candidate p53-Target Genes and Indicates That CHIR-98014 Is an Important Inhibitor of p53 Activity

Co-treatment with actinomycin D and nutlin-3a (A + N) strongly activates p53. Previously we reported that CHIR-98014 (GSK-3 kinase inhibitor), acting in cells exposed to A + N, prevents activation of TREM2-an innate immunity and p53-regulated gene associated with Alzheimer’s disease. In order to find novel candidate p53-target genes and genes regulated by CHIR-98014, we performed RNA-Seq of control A549 cells and the cells exposed to A + N, A + N with CHIR-98014 or to CHIR-98014. We validated the data for selected genes using RT-PCR and/or Western blotting. Using CRISPR/Cas9 technology we generated p53-deficient cells. These tools enabled us to identify dozens of candidate p53-regulated genes. We confirmed that p53 participates in upregulation of BLNK, APOE and IRF1. BLNK assists in activation of immune cells, APOE codes for apolipoprotein associated with Alzheimer’s disease and IRF1 is activated by interferon gamma and regulates expression of antiviral genes. CHIR-98014 prevented or inhibited the upregulation of a fraction of genes stimulated by A + N. Downregulation of GSK-3 did not mimic the activity of CHIR-98014. Our data generate the hypothesis, that an unidentified kinase inhibited by CHIR-98014, participates in modification of p53 and enables it to activate a subset of its target genes, e.g., the ones associated with innate immunity.     

Polymer track membranes as a trap support for reagent in fiber optic sensors

The article presents a new idea of the application of polymer track membranes (PTM) for immobilization of a reagent in fiber optic chemical sensors. PTM was made of a poly(ethylene terephthalate) foil (10 μm in thickness, pores of 0.2 μm in diameter). The usefulness of membranes additionally covered by poly(vinyl chloride) was tested in a fiber optic redox titrator. The titrator utilized N,N′-diphenylbenzidine as a reagent which changes its absorbance in dependence on the redox potential. The measuring system is based on a lightemitting diode and a silicon photodiode connected to a bifurcated fiber optic bundle. The gain is in price and availability of the membrane. © 1996 John Wiley & Sons, Inc.     

Optimization of Novel Human Acellular Dermal Dressing Sterilization for Routine Use in Clinical Practice

Gamma rays and electrons with kinetic energy up to 10 MeV are routinely used to sterilize biomaterials. To date, the effects of irradiation upon human acellular dermal matrices (hADMs) remain to be fully elucidated. The optimal irradiation dosage remains a critical parameter affecting the final product structure and, by extension, its therapeutic potential. ADM slides were prepared by various digestion methods. The influence of various doses of radiation sterilization using a high-energy electron beam on the structure of collagen, the formation of free radicals and immune responses to non-irradiated (native) and irradiated hADM was investigated. The study of the structure changes was carried out using the following methods: immunohistology, immunoblotting, and electron paramagnetic resonance (EPR) spectroscopy. It was shown that radiation sterilization did not change the architecture and three-dimensional structure of hADM; however, it significantly influenced the degradation of collagen fibers and induced the production of free radicals in a dose-dependent manner. More importantly, the observed effects did not disrupt the therapeutic potential of the new transplants. Therefore, radiation sterilization at a dose of 35kGy can ensure high sterility of the dressing while maintaining its therapeutic potential.     

Sewage sludge-to-energy approaches based on anaerobic digestion and pyrolysis: Brief overview and energy efficiency assessment

Energy recovery from sewage sludge offers an opportunity for sustainable management of sewage sludge and energy. Anaerobic digestion and pyrolysis are among the most promising processes applicable for sewage sludge-to-energy conversion. Anaerobic digestion of sewage sludge forms methane-rich biogas, which can be utilized as fuel to offset heat and electricity consumption of the wastewater treatment sector. However, the digestion process has the limitation that it cannot sufficiently extract the energy in sewage sludge. The digested sludge is still energy profitable in that it contains considerable organic matter, but poor in biodegradability. Sludge pyrolysis is an innovative process that can convert both raw and digested sludge into useful bioenergy in the form of oil and gas, forming biochar as a byproduct that is environmentally resistant and holds potential for carbon sequestration and soil conditioning. It is expectable that sludge pyrolysis would step into practical deployment in the near future.This paper presents a brief overview of anaerobic digestion and pyrolysis in the application to bioenergy production from sewage sludge. An assessment of energy conversion efficiency of two parallel sludge-to-energy pathways is also presented. One pathway relies on an exclusive pyrolysis process (fed with raw sludge) while the other is based on anaerobic digestion followed by pyrolysis (fed with the digested sludge). The pathway via the combination of anaerobic digestion and pyrolysis could achieve higher energy efficiency compared to the pathway employing the pyrolysis alone.     

Revealing the Role of Anchoring Groups in the Electrical Conduction Through Single‐Molecule Junctions

A combined experimental and theoretical study is presented revealing the influence of metal–molecule coupling on electronic transport through single‐molecule junctions. Transport experiments through tolane molecules attached to gold electrodes via thiol, nitro, and cyano anchoring groups are performed. By fitting the experimental current–voltage characteristics to a single‐level tunneling model, we extract both the position of the molecular orbital closest to the Fermi energy and the strength of the metal–molecule coupling. The values found for these parameters are rationalized with the help of density‐functional‐theory‐based transport calculations. In particular, these calculations show that the anchoring groups determine the junction conductance by controlling not only the strength of the coupling to the metal but also the position of the relevant molecular energy levels.     

Applying process design software for capacity increase and revamp of distillation units

The paper presents the results of feasibility study for increase of crude processing capacity and improves of energy efficiency of crude oil distillation units. Results introduce that boosting up the distillation capacity was solved while keeping the flexibility of units for processing different type crude oils. Analysis of heat exchanger network resulted significant reduction in fuel consumption and in CO₂ emission (93 × 10⁶ GJ year⁻¹ and 3,030 tCO₂ year⁻¹, respectively). Modification of furnace of one of the distillation units showed 63 GJ kt_crude⁻¹ saving in energy and 4.5 tCO₂ kt_crude⁻¹ decrease in emission.