Natural Science Hub Search function
Type your keywords and we will find the results

-
Radially and Axially Oriented Ammonium Alginate Aerogels Modified with Clay/Tannic Acid and Crosslinked with Glutaraldehyde.
- Date:
- Author: De la Cruz LG  |  Abt T  |  León N  |  Sánchez-Soto M  | 
Lightweight materials that combine high mechanical strength, insulation, and fire resistance are of great interest to many industries. This work explores the properties of environmentally friendly alginate aerogel composites as potential sustainable alternatives to petroleum-based materials. This study analyzes the effects of two additives (tannic acid and montmorillonite clay), the orientation that results during casting, and the crosslinking of the biopolymer with glutaraldehyde on the properties of the aerogel composites. The prepared aerogels exhibited high porosities between 90% and 97% and densities in the range of 0.059-0.191 g/cm. Crosslinking increased the density and resulted in excellent performance under loading conditions. In combination with axial orientation, Young's modulus and yield strength reached values as high as 305 MPa·cm/g and 7 MPa·cm/g, respectively. Moreover, the alginate-based aerogels exhibited very low thermal conductivities, ranging from 0.038 W/m·K to 0.053 W/m·K. Compared to pristine alginate, the aerogel composites' thermal degradation rate decreased substantially, enhancing thermal stability. Although glutaraldehyde promoted combustion, the non-crosslinked aerogel composites demonstrated high fire resistance. No flame was observed in these samples under cone calorimeter radiation, and a minuscule peak of heat release of 21 kW/m was emitted as a result of their highly efficient graphitization and fire suppression. The combination of properties of these bio-based aerogels demonstrates their potential as substituents for their fossil-based counterparts.
Read More on PubMed -
The Interphase Gas-Solid Synthesis of Ammonium Alginate-The Comparison of Two Synthesis Methods and the Effect of Low Molecular Weight Electrolyte Presence.
- Date:
- Author: Tarzynska N  |  Bednarowicz A  |  Pabjanczyk-Wlazlo E  |  Draczyński Z  | 
This paper presents a method for the synthesis of ammonium alginate by interphase gas-solid reaction. It was confirmed by FTIR ATR spectroscopy analysis that a full substitution of acid groups by ammonium groups on the surface of powdered alginic acid was performed. Comparative studies on the properties of ammonium alginate solutions obtained by interphase reaction with those prepared by the classical method of dissolving alginic acid in an ammonia solution showed that the rheological properties of the solutions from these two derivatives do not differ significantly. Moreover, it was shown that aqueous solutions of ammonium alginate are more stable over time than solutions of sodium alginate. It was confirmed that ammonium alginate and sodium alginate are typical polyelectrolytes, as the addition of a low molecular weight electrolyte to their solutions resulted in a decrease in viscosity.
Read More on PubMed -
Alginates as food ingredients absorb extra salt in sodium chloride-treated mice.
- Date:
- Author: Fujiwara Y  |  Maeda R  |  Takeshita H  |  Komohara Y  | 
Many patients with impaired renal function undergoing dialysis are subject to severe dietary restrictions. Especially overdose of salt is related to crisis of their life, so their meals are basically salt-free or low salt. Therefore, their quality of life is declined due to their yearning for salty taste. In the present study, we searched new salt-adsorbing food materials in dietary fibers to develop food ingredients preventing salt-sensitive hypertension and kidney dysfunction. As a result, calcium alginate and ammonium alginate possessed sodium-binding capacity without releasing potassium which causes a problem in chronic kidney injury. Furthermore, the administration of those fibers inhibited blood NaCl concentration and induced NaCl excretion in mice model. Therefore, calcium alginate and ammonium alginate are new candidate materials as salt-adsorbing materials, thus indicating that the health foods and/or health supplements containing those fibers may be a potentially new tool for prevention of salt-sensitive hypertension and kidney dysfunction.
Read More on PubMed -
Fabrication of membranes with high antifouling and self-cleaning ability is a long-term pursuit of research community. For this purpose, the current work proposed a strategy to use an external magnetic field to arrange the magnetic TiO@Ni particles (MNPs) onto the polymeric polyether sulfone (PES) membrane surface. The characterization results clearly indicated that the MNPs were successfully embedded onto the membrane surface instead of uniformly distributing into the membrane bulk. Because of this superficial distribution, the prepared composite membrane exhibited a flux of 871.2 ± 2.9 L·m·h·bar, which was 5 times flux of the pristine PES membrane. Meanwhile, it remained a rejection of 95.85% bovine serum albumin (BSA), which was also better than that of the pristine PES membrane. The cycle filtration experiments verified that the composite membrane possessed promoted antifouling ability for filtrating BSA, yeast extract fermentation (YEF), ammonium alginate (SA) and humic acid (HA) solutions. The antifouling mechanism was analyzed by the total interaction energies (ΔG), which were quantitatively evaluated by using the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory. Moreover, it was interestingly found that the composite membrane possessed a self-cleaning property under radiation of UV light and sunlight. The optimal membrane after self-cleaning presented flux recovery ratio (FRR) of 75.4%, 99.56%, 92.11% and 98.26% for BSA, YEF, SA and HA solutions, respectively. This work demonstrated a novel way to fabricate membranes with high antifouling and self-cleaning ability for water treatment.
Read More on PubMed -
The Relation between the Rheological Properties of Gels and the Mechanical Properties of Their Corresponding Aerogels.
- Date:
- Author: Sun M  |  Sun H  |  Wang Y  |  Sánchez-Soto M  |  Schiraldi DA  | 
A series of low density, highly porous clay/poly(vinyl alcohol) composite aerogels, incorporating ammonium alginate, were fabricated via a convenient and eco-friendly freeze drying method. It is significant to understand rheological properties of precursor gels because they directly affect the form of aerogels and their processing behaviors. The introduction of ammonium alginate impacted the rheological properties of colloidal gels and improved the mechanical performance of the subject aerogels. The specific compositions and processing conditions applied to those colloidal gel systems brought about different aerogel morphologies, which in turn translated into the observed mechanical properties. The bridge between gel rheologies and aerogel structures are established in the present work.
Read More on PubMed -
Re-evaluation of alginic acid and its sodium, potassium, ammonium and calcium salts (E 400-E 404) as food additives.
- Date:
- Author:  |  Younes M  |  Aggett P  |  Aguilar F  |  Crebelli R  |  Filipič M  |  Frutos MJ  |  Galtier P  |  Gott D  |  Gundert-Remy U  |  Kuhnle GG  |  Lambré C  |  Leblanc JC  |  Lillegaard IT  |  Moldeus P  |  Mortensen A  |  Oskarsson A  |  Stankovic I  |  Waalkens-Berendsen I  |  Woutersen RA  |  Wright M  |  Brimer L  |  Lindtner O  |  Mosesso P  |  Christodoulidou A  |  Horváth Z  |  Lodi F  |  Dusemund B  | 
The present opinion deals with the re-evaluation of alginic acid and its sodium, potassium, ammonium and calcium salts (E 400-E 404) when used as food additives. Alginic acid and its salts (E 400-E 404) are authorised food additives in the EU in accordance with Annex II and Annex III to Regulation (EC) No 1333/2008. Following the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010, the Panel concluded that there was no need for a numerical Acceptable Daily Intake (ADI) for alginic acid and its salts (E 400, E 401, E 402, E 403 and E 404), and that there was no safety concern at the level of the refined exposure assessment for the reported uses of alginic acid and its salts (E 400, E 401, E 402, E 403 and E 404) as food additives. The Panel further concluded that exposure of infants and young children to alginic acid and its salts (E 400, E 401, E 402, E 403 and E 404) by the use of these food additives should stay below therapeutic dosages for these population groups at which side-effects could occur. Concerning the use of alginic acid and its salts (E 400, E 401, E 402, E 403 and E 404) in 'dietary foods for special medical purposes and special formulae for infants' (Food category 13.1.5.1) and 'in dietary foods for babies and young children for special medical purposes as defined in Directive 1999/21/EC' (Food category 13.1.5.2), the Panel further concluded that the available data did not allow an adequate assessment of the safety of alginic acid and its salts (E 400, E 401, E 402, E 403 and E 404) in infants and young children consuming the food belonging to the categories 13.1.5.1 and 13.1.5.2.
Read More on PubMed -
Nonflammable materials based on renewable ammonium alginate and nano fillers (nanoscale magnesium hydroxide, nanoscale aluminum hydroxide, layered double hydroxide, sodium montmorillonite, and Kaolin) were fabricated through a simple, environmentally friendly freeze-drying process, in which water was used as a solvent. A simple and economic post-cross-linking method was used to obtain homogeneous samples. The microstructure of the cross-linked alginate aerogels show three-dimensional networks. These materials exhibit low densities (0.064-0.116 g cm(-3)), low thermal conductivities (0.024-0.046 W/m K), and useful mechanical strengths (0.7-3.5 MPa). The aerogels also exhibit high thermal stabilities and achieve inherent nonflammability with limiting oxygen indexes (LOI) higher than 60. Related properties were conducted and analyzed by cone calorimeter (CC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). These results combine to suggest promising prospects for use of these aerogel nanocomposites in a range of applications.
Read More on PubMed -
Facile preparation of ammonium alginate-derived nanofibers carrying diverse therapeutic cargo.
- Date:
- Author: Pegg CE  |  Jones GH  |  Athauda TJ  |  Ozer RR  |  Chalker JM  | 
Alginic acid was converted to a variety of ammonium alginate derivatives carrying diverse chemical cargo such as analgesics, antibiotics, and enzymes. These functional polymers could be fashioned into nanofibrous mats by electrostatic spinning. The therapeutic payload could be released in functional form by a simple ion exchange mechanism. Prospects in wound healing are discussed.
Read More on PubMed -
Preparation of porous yttrium oxide microparticles by gelation of ammonium alginate in aqueous solution containing yttrium ions.
- Date:
- Author: Kawashita M  |  Matsui N  |  Li Z  |  Miyazaki T  | 
Porous Y2O3 microparticles 500 microm in size were obtained, when 1 wt%-ammonium alginate aqueous solution was dropped into 0.5 M-YCl3 aqueous solution by a Pasteur pipette and the resultant gel microparticles were heat-treated at 1100 degrees C. Small pores less than 1 microm were formed in the microparticles by the heat treatment. The bulk density of the heat-treated microparticle was as low as 0.66 g cm(-3). The chemical durability of the heat-treated microparticles in simulated body fluid at pH = 6 and 7 was high enough for clinical application of in situ radiotherapy. Although the size of the microparticles should be decreased to around 25 microm using atomizing device such as spray gun for clinical application, we found that the porous Y2O3 microparticles with high chemical durability and low density can be obtained by utilizing gelation of ammonium alginate in YCl3 aqueous solution in this study.
Read More on PubMed -
Cytocompatibility and hemocompatibility of a novel chitosan-alginate gel system.
- Date:
- Author: Notara M  |  Scotchford CA  |  Grant DM  |  Weston N  |  Roberts GA  | 
Two chitosan-alginate gel systems in the form of membranes were produced and evaluated. The first membrane was produced by a novel gel system formed after blending N-(methylsulfonic acid) chitosan with ammonium alginate (CAG1) and the second was an N-(methylsulfonic acid) chitosan-sodium alginate blend cross-linked with glutaraldehyde and calcium chloride (CAG2). The cytocompatibility and hemocompatibility of the gels were examined by assessing the cell viability of 3T3 Swiss mouse fibroblasts, whole blood hemolysis, and platelet activation. Cell viability was not significantly different by exposure to these gels compared to the controls. Both gel types had minimal effect on hemolysis of whole heparinized rabbit blood after 1-h exposure. Further platelet activation by the surfaces was also minimal. These results indicate that these novel gels merit further investigation for blood contact applications.
Read More on PubMed