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Production of polymers by cyanobacteria grown in wastewater: Current status, challenges and future perspectives.
Arias, DM, García, J, Uggetti, E
New biotechnology. 2020;:46-57
Abstract
Cyanobacteria are prokaryotic oxygenic phototrophs receiving attention in a wide variety of technological applications such as food and feed supplements and production of valuable polymers. Among these, carbohydrates (e.g. glycogen) and polyhydroxyalkanoates (PHAs) are of increasing interest due to their potential as a biofuel substrate and bioplastics, respectively. However, biofuels and bioplastics from cyanobacteria have seen many years of effort towards commercialization with only limited success. Their main limitation for polymer production is the high cost of the nutrient source; wastewater, as an inexpensive and widely available alternative, may overcome this bottleneck. Though cyanobacteria have demonstrated a capacity to treat wastewater effluents, their cultivation in such a variable environment involves certain challenges of which the chief one is linked to contamination by other species, especially green algae. This would represent a serious drawback during cyanobacterial biomass production and affect further PHA and carbohydrate production. The present study reviews the potential of cyanobacteria to grow in wastewater effluents from different sources. Conditions favoring them in mixed-culture reactors are described, focusing on nutritional and operational aspects. Current advances and future prospects in PHA and carbohydrate production are explored and discussed.
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Review of Chitosan-Based Polymers as Proton Exchange Membranes and Roles of Chitosan-Supported Ionic Liquids.
Rosli, NAH, Loh, KS, Wong, WY, Yunus, RM, Lee, TK, Ahmad, A, Chong, ST
International journal of molecular sciences. 2020;(2)
Abstract
Perfluorosulphonic acid-based membranes such as Nafion are widely used in fuel cell applications. However, these membranes have several drawbacks, including high expense, non-eco-friendliness, and low proton conductivity under anhydrous conditions. Biopolymer-based membranes, such as chitosan (CS), cellulose, and carrageenan, are popular. They have been introduced and are being studied as alternative materials for enhancing fuel cell performance, because they are environmentally friendly and economical. Modifications that will enhance the proton conductivity of biopolymer-based membranes have been performed. Ionic liquids, which are good electrolytes, are studied for their potential to improve the ionic conductivity and thermal stability of fuel cell applications. This review summarizes the development and evolution of CS biopolymer-based membranes and ionic liquids in fuel cell applications over the past decade. It also focuses on the improved performances of fuel cell applications using biopolymer-based membranes and ionic liquids as promising clean energy.
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Polymer - Metal Nanocomplexes Based Delivery System: A Boon for Agriculture Revolution.
Kaur, P, Choudhary, R, Pal, A, Mony, C, Adholeya, A
Current topics in medicinal chemistry. 2020;(11):1009-1028
Abstract
Metal nanoparticles are well known for their antimicrobial properties. The use of metalbased nanoparticles in the agricultural field has considerably increased globally by both direct and indirect means for the management of plant diseases. In this context, the development of controlled delivery systems for slow and sustained release of metal nanoparticles is crucial for prolonged antimicrobial activity. Polymers have emerged as a valuable carrier for controlled delivery of metal nanoparticles as agrochemicals because of their distinctive properties. The most significant benefits of encapsulating metal nanoparticles in a polymer matrix include the ability to function as a protector of metal nanoparticles and their controlled release with prolonged efficacy. This review focuses on loading strategies and releasing behavior of metal nanoparticles in the polymer matrix as antimicrobial agents for plant diseases. The Polymer-metal nanocomplexes (PMNs) comprise a biocompatible polymeric matrix and metal nanoparticles as active components of an antimicrobial agent, pesticides and plant growth regulators used to enhance the crop productivity.
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Let Them Eat Healthy: Can Emerging Potassium Binders Help Overcome Dietary Potassium Restrictions in Chronic Kidney Disease?
Sussman, EJ, Singh, B, Clegg, D, Palmer, BF, Kalantar-Zadeh, K
Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation. 2020;(6):475-483
Abstract
Potassium-rich foods might provide many health benefits even to people who have declining renal function. The barrier to obtaining these health benefits has long been the concern over hyperkalemia. There are new and novel treatment options available which may enable patients with chronic kidney disease to obtain the health benefits of eating a diet that contains foods such as fruits and vegetables which are high in potassium while reducing the risk of hyperkalemia. We conclude by emphasizing the need for clinical trials with patients on hemodialysis to directly compare the current standard of care, including a potassium-restricted diet, to a potassium-liberalized diet with a potassium binder. The outcome measures would be serum potassium (<5.3 mmol/L), assessments of acidosis, blood pressure, constipation, glycemic control, overhydration, and azotemia, all of which might change in a favorable direction with vegetarian diets as well as quality of life and satisfaction.
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5.
The Hot Spring Hypothesis for an Origin of Life.
Damer, B, Deamer, D
Astrobiology. 2020;(4):429-452
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Abstract
We present a testable hypothesis related to an origin of life on land in which fluctuating volcanic hot spring pools play a central role. The hypothesis is based on experimental evidence that lipid-encapsulated polymers can be synthesized by cycles of hydration and dehydration to form protocells. Drawing on metaphors from the bootstrapping of a simple computer operating system, we show how protocells cycling through wet, dry, and moist phases will subject polymers to combinatorial selection and draw structural and catalytic functions out of initially random sequences, including structural stabilization, pore formation, and primitive metabolic activity. We propose that protocells aggregating into a hydrogel in the intermediate moist phase of wet-dry cycles represent a primitive progenote system. Progenote populations can undergo selection and distribution, construct niches in new environments, and enable a sharing network effect that can collectively evolve them into the first microbial communities. Laboratory and field experiments testing the first steps of the scenario are summarized. The scenario is then placed in a geological setting on the early Earth to suggest a plausible pathway from life's origin in chemically optimal freshwater hot spring pools to the emergence of microbial communities tolerant to more extreme conditions in dilute lakes and salty conditions in marine environments. A continuity is observed for biogenesis beginning with simple protocell aggregates, through the transitional form of the progenote, to robust microbial mats that leave the fossil imprints of stromatolites so representative in the rock record. A roadmap to future testing of the hypothesis is presented. We compare the oceanic vent with land-based pool scenarios for an origin of life and explore their implications for subsequent evolution to multicellular life such as plants. We conclude by utilizing the hypothesis to posit where life might also have emerged in habitats such as Mars or Saturn's icy moon Enceladus. "To postulate one fortuitously catalyzed reaction, perhaps catalyzed by a metal ion, might be reasonable, but to postulate a suite of them is to appeal to magic." -Leslie Orgel.
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Polymers with antiviral properties: A brief review.
Zmonarski, S, Stojanowski, J, Zmonarska, J
Polimery w medycynie. 2020;(2):79-82
Abstract
Viruses that are pathogenic to humans and livestock pose a serious epidemiological threat and challenge the world's population. The SARS-CoV-2/COVID-19 pandemic has made the world aware of the scale of the threat. The surfaces of various materials can be a source of viruses that remain temporarily contagious in the environment. Few polymers have antiviral effects that reduce infectivity or the presence of a virus in the human environment. Some of the effects are due to certain physical properties, e.g., high hydrophobicity. Other materials owe their antiviral activity to a modified physicochemical structure favoring the action on specific virus receptors or on their biochemistry. Current research areas include: gluten, polyvinylidene fluoride, polyimide, polylactic acid, graphene oxide, and polyurethane bound to copper oxide. The future belongs to multi-component mixtures or very thin multilayer systems. The rational direction of research work is the search for materials with a balanced specificity in relation to the most dangerous viruses and universality in relation to other viruses.
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Veverimer: An Emerging Potential Treatment Option for Managing the Metabolic Acidosis of CKD.
Adrogué, HJ, Madias, NE
American journal of kidney diseases : the official journal of the National Kidney Foundation. 2020;(6):861-867
Abstract
Sodium bicarbonate is the mainstay treatment of the metabolic acidosis of chronic kidney disease but associated concerns center on administering sodium to patients with hypertension and sodium-retentive states. Veverimer (formerly referred to as TRC101), a drug candidate for which Tricida, Inc is seeking approval from the US Food and Drug Administration, is a novel nonabsorbable polymer that binds hydrogen cations and chloride anions in the gastrointestinal tract and then is excreted fecally, thereby increasing serum bicarbonate concentration without administering sodium. We examine the published evidence on the investigational use of veverimer in patients with chronic kidney disease and metabolic acidosis. We highlight the achieved increase in serum bicarbonate concentration without coadministering sodium, effects on physical functioning, and the safety record of the drug. We also scrutinize certain unanticipated findings: a lack of dose dependency in the increase in serum bicarbonate concentration observed and that despite the presumed large hydrogen chloride losses in feces, veverimer induces an isochloremic increase in serum bicarbonate concentration that is accompanied by a decrease in serum anion gap. We propose likely explanations for these puzzling findings and raise questions about veverimer's mode of action and its potential interaction with colonic bacterial flora. Additional work is required to fill these knowledge gaps that could have important clinical implications.
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8.
Nanotheranostics: Their role in hepatocellular carcinoma.
Malla, RR, Kumari, S, Kgk, D, Momin, S, Nagaraju, GP
Critical reviews in oncology/hematology. 2020;:102968
Abstract
Hepatocellular carcinoma (HCC) is the fifth most prevalent malignancy worldwide. Despite advances in imaging techniques, early diagnosis and management remain very poor. The early diagnosis of HCC requires diagnostic and imaging technologies with high sensitivity and precise quantification ability and with no tissue penetration limit. Nanotechnology-based cancer imaging is a rapidly emerging research area with significant applications in the diagnosis and treatment of cancer, which we review here with application to HCC. Furthermore, we discuss the combination of functional nanotheranostics and magnetic resonance imaging (MRI) for targeted delivery of phytochemical therapeutics, chemotherapeutic drugs, RNAi-based therapeutics, and vaccinations. Finally, this review presents the importance of MRI biomarkers for monitoring HCC treatment response. The use of advanced nanotheranostics as MRI contrast agents for imaging, diagnosis and drug delivery may enhance HCC management and provide a new area of research in tumor imaging technology.
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9.
Potassium Binders for Hyperkalemia in Chronic Kidney Disease-Diet, Renin-Angiotensin-Aldosterone System Inhibitor Therapy, and Hemodialysis.
Palmer, BF
Mayo Clinic proceedings. 2020;(2):339-354
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Abstract
Hyperkalemia is a potentially life-threatening complication of chronic kidney disease (CKD). The management of CKD requires balancing the benefits of specific treatments, which may exacerbate the potential for hyperkalemia, with the risks of hyperkalemia itself. Renin-angiotensin-aldosterone system (RAAS) inhibitors, which slow CKD progression and improve cardiovascular outcomes, are often discontinued if hyperkalemia develops. Patients with hyperkalemia are frequently advised to restrict dietary potassium (K+), depriving these patients of many heart-healthy foods. Patients receiving hemodialysis are particularly susceptible to hyperkalemia during long interdialytic intervals, and managing this risk without causing hypokalemia can be challenging. Recently, 2 K+-binding agents were approved for the treatment of hyperkalemia: sodium zirconium cyclosilicate and patiromer. These agents offer alternatives to sodium polystyrene sulfonate, which is associated with serious gastrointestinal adverse effects. For this review, PubMed was searched for English-language articles published in 2014-2018 using the terms patiromer, sodium zirconium cyclosilicate, sodium polystyrene sulfonate, hyperkalemia, renin-angiotensin-aldosterone, diet, and dialysis. In randomized controlled studies of patients with hyperkalemia, sodium zirconium cyclosilicate and patiromer effectively reduced serum K+ and were generally well tolerated. Furthermore, patients in these studies could maintain RAAS inhibitor therapy and, in some studies, were not required to limit dietary K+. There may also be a role for these agents in preventing hyperkalemia in patients receiving hemodialysis. Thus, K+-binding agents may allow patients with CKD at risk for hyperkalemia to optimize RAAS inhibitor therapy, receive benefits of a K+-rich diet, and experience improved hemodialysis outcomes. Additional long-term studies are necessary to confirm these effects.
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10.
Phenols and Melanoidins as Natural Antioxidants in Beer. Structure, Reactivity and Antioxidant Activity.
Martinez-Gomez, A, Caballero, I, Blanco, CA
Biomolecules. 2020;(3)
Abstract
Beer is one of the most consumed drinks around the world, containing a variety of compounds that offer both appreciated sensorial characteristics and health advantages. Important healthy compounds in beer are those with antioxidant properties that attenuate the content of free radicals produced as by-products in the human metabolism, exerting an appreciable effect against cancers or cardiovascular diseases. This work details a study of antioxidant compounds present in beer, focusing on the two main groups: phenols (including polyphenolic forms) and melanoidins, formed specifically during brewing as Maillard products. The fundaments of the most important methods to evaluate beer antioxidant activity, the main antioxidant compounds present in beer-especially those with healthy properties-and the new trends to increase beer antioxidant activity are also discussed.