Application of polysaccharide hydrogels in adsorption and controlled‐extended release of fertilizers processes

This article studied the applicability of poly(acrylamide) and methylcellulose (PAAm‐MC) hydrogels as potential delivery vehicle for the controlled‐extended release of ammonium sulfate (NH₄)₂SO₄ and potassium phosphate (KH₂PO₄) fertilizers. PAAm‐MC hydrogels with different acrylamide (AAm) and MC concentrations were prepared by a free radical polymerization method. The adsorption and desorption kinetics of fertilizers were determined using conductivity measurements based on previously built analytical curve. The addition of MC in the PAAm chains increased the quantities of (NH₄)₂SO₄ and KH₂PO₄ loaded and extended the time and quantities of fertilizers released. Coherently, both loading and releasing processes were strongly influenced by hydrophilic properties of hydrogels (AAm/MC mass proportion). The best sorption (124.0 mg KH₂PO₄/g hydrogel and 58.0 mg (NH₄)₂SO₄/g hydrogel) and desorption (54.9 mg KH₂PO₄/g hydrogel and 49.5 mg (NH₄)₂SO₄/g hydrogel) properties were observed for 6.0% AAm–1.0% MC hydrogels (AAm/MC mass proportion equal 6), indicating that these hydrogels are potentially viable to be used in controlled‐extended release of fertilizers systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

N,N,N-trimethyl chitosan nanoparticles as a vitamin carrier system

There is considerable interest in incorporating stabilized vitamins into biopolymeric nanoparticles, especially in the development of carriers and active systems for pharmaceutical and food applications. Amongst biopolymer, chitosan is highly desirable owing to its good biocompatibility, biodegradability and ability to be chemically modified. In this paper, nanoparticles from three kinds of water-soluble derivative chitosan (N,N,N-trimethyl chitosan, TMC) have successfully been synthesized by ionic gelation with tripolyphosphate (TPP) anions. Combinations of concentrations of TMC and TPP have resulted in nanoparticles with varying sizes for which the capability for loading with vitamins was investigated. Zeta potential measurement and particle size analysis demonstrated that the size of the nanoparticles was optimized (196 ± 8 nm) when the lowest TMC and TPP amounts were used, i.e., 0.86 mg mL⁻¹ and 0.114 mg mL⁻¹ respectively. As the TMC and/or the TPP concentrations increase, the resulting size of the nanoparticles increases considerably. Three different vitamins (B9, B12 and C) were tested as additives and the final system characterized in relation to size, morphology, spectroscopic and zeta potential properties. In general, the incorporation of vitamins increased all the TMC–TPP original nanoparticle sizes, reaching a maximum diameter of 534 ± 20 nm when loaded with vitamin C. The presence of vitamins also decreases the zeta potential, with one exception observed when using vitamin C. The preliminary results of this study suggested that all TMC/TPP nanoparticles can be successfully used as a stable medium to incorporate and transport vitamins, with potential applications in foodstuffs.     

Barrier and Mechanical Properties of Clay-Reinforced Polymeric Nanocomposites

In this work, clay-based nanocomposites films were prepared by addition of clay-Na⁺ natural montmorillonite in pectin and hydroxypropyl methylcellulose (HPMC) matrices. Mechanical (tensile strength, elastic modulus, and elongation) and barrier (Water Vapor Permeability (WVP), and Oxygen permeability (O₂P)) properties were investigated. From results, it was observed that the WVP and O₂P decreased when nanoclay was included into the HPMC and pectin matrix films. Additionally, the incorporation of nanoclay in the films significantly improved the mechanical properties because the reinforcing effect of clay from its high aspect ratio and its enormous surface area. These results are very important in packaging area.     

Release of BSA from porous matrices constituted of alginate–Ca and PNIPAAm-interpenetrated networks

The synthesis of thermosensitive Interpenetrating Polymer Network (IPN) hydrogels and the release of Bovine Serum Albumin (BSA) from the hydrogels were reported. The hydrogels, constituted of poly(N-isopropyl acrylamide) PNIPAAm network interpenetrated in alginate–Ca²⁺ network, were synthesized in a two-stepped process. In the first step, PNIPAAm network was synthesized from an aqueous solution containing N-isopropyl acrylamide (NIPAAm) monomers and N,N′-methylene-bis-acrylamide (MBAAm) co-monomers, and sodium alginate (SA) (1 or 2% w/v). The concentration of NIPAAm monomers in the hydrogel-forming solution was always 2.5, 5.0 or 10.0% (w/v). In the second step, alginate–Ca²⁺ networks were formed by immersion of the membrane, obtained on the first step, in a 1.0% (w/v) aqueous calcium chloride. The IPN hydrogels were characterized as a function of temperature (from 25 to 45 °C) through the following measurements: drop water contact angle (DWCA), compression elastic modulus (E) and cross-linking density (ν_e). The morphology was investigated using scanning electronic microscopy (SEM). In vitro release of BSA from the hydrogels was monitored by UV–Vis spectroscopy at 22 °C and 37 °C. DWCA results showed a decrease in the hydrogel hydrophilicity when the temperature and/or the PNIPAAm amount on hydrogels were increased. PNIPAAm-loader hydrogels are more compacted and presented elevated rigidity, mainly above 35 °C. This trend was attributed to the collapsing of PNIPAAm chains as the hydrogels were warmed above its Lower Critical Solution Temperature (LCST), which in aqueous solution is ca. 32–33 °C. The amount of BSA released from the alginate–Ca²⁺/PNIPAAm hydrogels changes inversely to both amount of PNIPAAm and temperature. The transport of BSA from the hydrogels was evaluated through a conventional model. In the lesser-compacted hydrogels the release occurs mostly by diffusion. In the more compacted ones the chain relaxation contributes to the BSA release. Thus, the alginate–Ca²⁺/PNIPAAm IPN-typed matrixes may be considered as smart hydrogels for the release of BSA, because the amount and rate of BSA released may be tailored by both the NIPAAm concentration in the hydrogel-forming solution and the control of temperature of hydrogel.     

CalcGraph: taming the high costs of deep learning using models

Software and Systems Modeling - Models based on differential programming, like deep neural networks, are well established in research and able to outperform manually coded counterparts in many...     

Photocatalytic and antimicrobial efficacy of PVDF/TiO2 membranes fabricated by solution blow spinning

With its ability to purify water and treat wastewater, photocatalytic membranes have become a promising solution. The membrane's unique properties allow for the separation of solid compounds and the degradation of organic materials through photocatalytic and antibacterial means. Poly(vinylidene fluoride)/titanium oxide (PVDF/TiO₂) composite remain the materials of choice for making these membranes due to their economy, effectiveness, safety, and durability. In this work a photocatalytic membrane reactor (PMR) system was developed using PVDF/TiO₂ membranes fabricated by the solution blow spinning (SBS) process. Obtaining photocatalytic membranes using this method is an efficient and ecological route that overcomes the disadvantage of separating the photocatalyst after the treatment is complete. The results of PMR system showed that the PVDF/TiO₂ membrane could effectively remove total coliforms and E. coli from polluted water. After 10 min of contaminated water circulation through the PMR system, the presence of pathogens was not detected, indicating the efficiency of the obtained membranes.     

Evaluation of the Genotoxicity of Chitosan Nanoparticles for Use in Food Packaging Films

Abstract: The use of nanoparticles in food packaging has been proposed on the basis that it could improve protection of foods by, for example, reducing permeation of gases, minimizing odor loss, and increasing mechanical strength and thermal stability. Consequently, the impacts of such nanoparticles on organisms and on the environment need to be investigated to ensure their safe use. In an earlier study, Moura and others (2008a) described the effect of addition of chitosan (CS) and poly(methacrylic acid) (PMAA) nanoparticles on the mechanical properties, water vapor, and oxygen permeability of hydroxypropyl methylcellulose films used in food packaging. Here, the genotoxicity of different polymeric CS/PMAA nanoparticles (size 60, 82, and 111 nm) was evaluated at different concentration levels, using the Allium cepa chromosome damage test as well as cytogenetic tests employing human lymphocyte cultures. Test substrates were exposed to solutions containing nanoparticles at polymer mass concentrations of 1.8, 18, and 180 mg/L. Results showed no evidence of DNA damage caused by the nanoparticles (no significant numerical or structural changes were observed), however the 82 and 111 nm nanoparticles reduced mitotic index values at the highest concentration tested (180 mg/L), indicating that the nanoparticles were toxic to the cells used at this concentration. In the case of the 60 nm CS/PMAA nanoparticles, no significant changes in the mitotic index were observed at the concentration levels tested, indicating that these particles were not toxic. The techniques used show promising potential for application in tests of nanoparticle safety envisaging the future use of these materials in food packaging.     

Polyacrylamide and methylcellulose hydrogel as delivery vehicle for the controlled release of paraquat pesticide

PAAm–MC hydrogels as a potential delivery vehicle for the controlled release of paraquat pesticide was investigated, as they play an essential role to use hydrogels in controlled release technology. The release kinetics of paraquat was determined using UV–Vis measurements. The release mechanism of paraquat from PAAm–MC hydrogels was investigated through a semi-empirical model proposed by Ritger and Peppas. In general, the initial rate of paraquat release was fast, decreasing after several days, hence indicating that paraquat on the surface (or close to) of hydrogels diffused rapidly after the initial swelling of the gel. Later, the cumulative release occurred in a very controlled and sustained manner, with the paraquat concentration maintaining constant from 15 to 46 days. The paraquat release capacity was dependent on the swelling of the matrix and the density of the network chains. The curves obtained from Peppas’s model presented good linearity (R ² ≥ 0.999), indicating that such model can be applicable to analyze the systems. The n values for the pesticide release from hydrogels indicate that paraquat release has Fickian and non-Fickian diffusion, depending of hydrogel formulation. The values of k showed that the release of paraquat becomes slower when the MC and AAm concentration increases. Finally, to the best of our knowledge, we report a hydrogel-based vehicle (first carrier) that is able to prolong the sustained release of paraquat pesticide up to 45 days, which is essential for its application in controlled release systems.     

Physicochemical and morphological properties of poly(acrylamide) and methylcellulose hydrogels: Effects of monomer,crosslinker and polysaccharide compositions

This article describes the physicochemical (mechanical and swelling) and morphological characterization of poly(acrylamide) and methylcellulose (PAAm‐MC) hydrogels synthesized with different formulations by the free radical polymerization method. The structure‐property relationship of the PAAm‐MC hydrogels is very important for application of these materials in different fields. Results showed that the properties of the PAAm‐MC hydrogels can be controlled by varying the acrylamide (AAm) and N′,N‐methylene‐bis‐acrylamide (MBAAm) concentrations and methylcellulose (MC) content. Increase of AAm and MBAAm concentrations causes a pronounced decrease in swelling degree (SD) values and porosity, and an increase in mechanical properties. Increasing the MC concentration caused an increase in SD values and porosity, but decrease in maximum load and modulus of elasticity because of the increase in the hydrogel hydrophilicity due to incorporation of hydroxyl groups from MC chains. PAAm‐MC hydrogels are excellent candidates for several applications, such as matrices for cell transplantation, controlled release (agrochemicals and drugs), tissue repair and regeneration. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Combining Cupuassu (Theobroma grandiflorum) Puree,Pectin, and Chitosan Nanoparticles into Novel Edible Films for Food Packaging Applications

Every year, the residues generated by the disposal of packaging materials produced from fossil fuels have been growing, denoting a major environmental problem that can be mitigated by the development of biodegradable materials from natural polymers, particularly edible films. This work aimed at the development of pectin films added by cupuassu puree and chitosan nanoparticles and to evaluate the improvement of the physical–mechanical performance of the composite films. The nanostructures displayed an average size of 110 nm and a zeta potential of approximately +40 mV. The films were produced by casting, and they exhibited manageability, homogeneity, and continuity. Based upon the mechanical analysis of maximum stress and elongation, it was concluded that the nanoparticles functioned as fillers, increasing the toughness of the pectin films. Water vapor permeability assays demonstrated that the nanostructured films containing cupuassu exhibited improved barrier properties. The glass transition temperature of the films was not strongly affected by the addition of nanoparticles. Conversely, the initial degradation temperature decreased with the addition of nanoparticles and cupuassu puree. The outcomes of this research pave a new route for the development of nonconventional food packaging materials.