Search

Copyright of Digital Education Review is the property of University of Barcelona, Virtual Teaching & Learning Research Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the synthesis and electrochemical study of a composite films biopolymer of cassava starch and polypyrrole (PPy/cassava starch). These composite films biopolymer were prepared by vapor deposition polymerization of pyrrole on cassava starch films. Infrared spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy studies were carried out. The FTIR spectra of plasticized films presented more hydrogen bound hydroxyl groups in the polymer starch chains that the unplasticized films and the PPy/cassava starch spectra evidence possible interactions between PPy and starch biopolymer film. The results obtained from electrochemical impedance spectroscopy indicate that the addition of plasticizer (glycerol) and polypyrrole generate a highest conducting that unplasticized films. Besides, the plasticizer and the polypyrrole incorporation produce electroactivity in the biopolymer films. In conclusion, the composite biopolymer PPy/cassava starch showed interesting electrochemical activity and high conductivity enabling future technological applications. [ABSTRACT FROM AUTHOR]

In this work, a novel one-pot synthesis of polymeric hydrogels (HGs) based on isocyanate click chemistry is proposed and evaluated. In particular, the proposed synthetic route allows to easily and effectively obtain HGs with different types of carbonyl groups, such as urea, urethane, thiourethane, and amide groups, as an approach to impact and modulate the structural, thermal, and functional behavior of the crosslinked networks. To carry out the above, the proposed methodology was employed to prepare HGs from hexamethylene diisocyanate, sorbitol, L-cysteine ​​and water, under moderate conditions (60° C for 24 h). Using FTIR-ATR, FEDS, and solid-state 13C CP/MAS NMR, it was possible to determine the presence and the relative amounts of different carbonyl groups in the obtained HGs, which can be modulated by varying the amounts of diisocyanate, L-cysteine, ​​and sorbitol employed in their synthesis. In addition, TGA and DSC analysis corroborated the influence of these carbonyl groups in the thermal properties of the HGs, i.e., thermal stability and glass transition. It was observed that an increase in L-cysteine and sorbitol amount in the HGs improved their thermal stability (> 200 °C) and increased their Tg values (55–68 °C) due to factors associated with crosslinking degree and intermolecular interactions. On the other hand, in terms of their functional behavior, HGs presented a good water absorption capacity at different pH values ​​(1.0, 7.0 and 12.0), being higher than 300% and enhanced by the presence of L-cysteine and sorbitol in the polymeric structures. Likewise, the HGs were able to retain and release an alkaline medium, in a controlled way, into a neutral and acidic environment, which points to the possibility of implementing this type of HGs in the design and development of novel drug delivery systems. Finally, an inhibitory effect (up to 40%) on the growth of gram-positive bacteria, such as S. aureus, by the HGs reflected their ability to effectively interact with these microorganisms by means of their polymeric structures and functional groups. In this sense, this work represents an important step in the designing and preparation of polymeric HGs based on isocyanate click chemistry, with modulated structural, thermal, and functional properties, that could be applied in different fields, including those of biomedical nature. [ABSTRACT FROM AUTHOR]

El suelo es un sistema altamente complejo, el cual suele definirse de manera más o menos precisa dependiendo de la formación disciplinar de quien lo estudia. Desde un punto de vista amplio el suelo puede conceptualizarse - procurando no inclinar la balanza de su definición a ningún área - como un sistema natural multicomponente, abierto y dinámico. Pero al mismo tiempo, es un recurso no renovable, un soporte biótico, un componente de los sistemas productivos, un reservorio nutricional para las plantas, y desde un enfoque más químico, un intercambiador iónico, un sistema coloidal, un sistema amortiguador, un material híbrido (orgánico-inorgánico), entre otras cosas. Su entendimiento y valoración muchas veces está ligado a la formación de quien lo estudia, por ejemplo, aunque es de naturaleza abiótica en su origen, puede ser considerado un sistema biótico desde el punto de vista ecosistémico, o mientras que, desde el punto de vista de la ingeniería civil se prefiere su compactación, desde el enfoque agrícola se desea todo lo contrario. En este mismo sentido y desde un enfoque más utilitario, en contabilidad es un “activo”, en economía es un recurso, en la Guajira es algo que “falta” y en el Valle del Cauca es algo que “pareciera sobrar”. La importancia de los suelos a lo largo de la historia de la humanidad ha cambiado con la historia misma. Para el hombre primitivo carecía de importancia directa, con el advenimiento de la agricultura y demás actividades pecuarias se convierte en un recurso directamente ligado a la producción de alimentos. Más recientemente, se acuñó el término edafología, siendo el primer edafólogo y padre de dicha disciplina, el científico ruso Vasili Vasílievich Dokucháyev (1846 – 1903). Es él quien introduce el concepto de suelo bajo la concepción de sistema natural de origen geológico en contraposición a la visión estratigráfica que lo define como un sustrato resultante del ciclo geoquímico de las rocas. Con el surgimiento de la edafología en la escuela de San Petersburgo, y el consecuente estudio científico de los suelos desde diferentes disciplinas, hoy por hoy los suelos son considerados un recurso no renovable, o por lo menos con una tasa de renovación muy baja en la escala de tiempo humana, además de que, en algunos círculos científicos existe una mayor conciencia de que los suelos son un recurso finito, heterogéneamente distribuido a nivel global y que de manera progresiva está desapareciendo. Por todo lo anterior, además del día de las madres, del padre, del niño, del trabajo, entre otros tanto días que se celebran en un año habitualmente, se definió el 5 de diciembre como día mundial del suelo por la Organización de la Naciones Unidas para la Alimentación y la Agricultura (FAO), y en el mismo sentido, en el 2015 se celebró el año internacional de los suelos. La conciencia alrededor de la importancia de los suelos debería ser mayor si se analiza la conexión de los suelos con aspectos muy cotidianos y no por ello de poca importancia: la producción de alimentos (los suelos son vitales para la seguridad alimentaria global en un mundo cada vez más poblado), el recurso hídrico (los suelos minimizan las pérdidas por evapotranspiración además de ser un reservorio natural de agua), el cambio climático (los suelos contribuyen con el secuestro de carbono de manera interna y lo promueven mediante), entre otros. La verdad es que hoy por hoy sabemos que los suelos experimentan diferentes tipos de degradación que podemos agrupar en dos categorías: natural y antropomórfica. Siendo más específicos, la degradación puede ser física, química y biológica, y si de buscar culpables se trata, el ser humano es el principal factor asociado a la degradación de los suelos - aunque sin lugar a dudas podemos pensar que, al menos en lo que a la degradación física se refiere, las vacas también tienen algo de culpa, pero en defensa de los bovinos el causante real es la ganadería intensiva e intensificada usada por el hombre para suplir la demanda de alimentos. Aunque la edafología sentó las bases para la tipificación de los suelos como entidades geológicas complejas, a nivel mundial su estudio esta principalmente liderado por enfoques interdisciplinarios principalmente relacionado con las agrociencias. Desde el enfoque químico, aún en muchas investigaciones no se considera el componente dinámico de los mismos y el enfoque conceptual sigue siendo más geológico. Un claro ejemplo de esto es la descripción del contenido de contaminantes en los suelos con base al total y no respecto a la fracción activa. En contraposición, en las ciencias agrícolas, los contenidos de un nutriente (es decir, una sustancia activa) son descritos respecto a la fracción disponible en lugar del total contenido en la muestra de análisis. Es tanto así el enfoque agro de la ciencia del suelo que, en Colombia, las tres principales escuelas en el estudio del suelo se gestaron en la Universidad Nacional sede Palmira, en la Universidad Pedagógica y Tecnológica de Colombia (UPTC) en Tunja y en la Universidad de Córdoba en la Ciudad de Montería, coincidiendo esto tres nodos de alta productividad agrícola del país, y donde se dispone de amplias cantidades en extensión y en profundidad del recurso edafológico. Pero… ¿Es posible recuperar los suelos sin promover su degradación? ¿Al menos, es posible restablecer su capacidad productiva? ¿es posible construir un suelo que sea en sí mismo un sistema de referencia”. Quizás la respuesta a las preguntas anteriores se encuentre en el diseño de estrategias de geotransformación positiva de los suelos (geoingeniería localizada), campo de estudio del Grupo de Investigación en Ciencias con Aplicaciones Tecnológicas (GI-CAT) de la Universidad del Valle y que va direccionada hacia la construcción de sistemas edafológicos artificiales para, entre otros: - Minimizar la expansión de la frontera agrícola - Aumentar el tiempo de uso del suelo - Minimizar el impacto del cambio climático - Recuperar sistemas agrícolas y forestales [ABSTRACT FROM AUTHOR]

[Display omitted] • C. albicans and H. pylori co-existence has been described from stomach. • To advance in the understanding of H. pylori and C. albicans polymicrobial biofilms. • Multiple surface interaction mechanisms were identified • Anchoring, co-aggregation and formation of yeast-bacterium polymicrobial biofilm Polymicrobial biofilms have a significant impact on pathogenesis of infectious microorganisms. Many human diseases are affected by colonization of multi-species communities affecting negatively the treatments and increase the risks for the health. In particular, in the epithelium of the stomach co-existence between C. albicans and H. pylori has been described, which has been associated to a synergistic effect on ulcer pathogenesis. The objective of this work was to advance in the understanding of surface interaction between H. pylori and C. albicans for the formation of polymicrobial biofilms. Studies of microbial surfaces both bacterium, yeast and co-cultures of them were carried out by infrared spectroscopy, deconvolution analysis, transmission and scanning electron microscopies, and optic microscopy. Additional methods were used to contrast the results as dynamic light scattering, contact angle, agarose gel electrophoresis and gene amplification. Several surface interaction mechanisms promote the anchoring of H. pylori on C. albicans , cell co-aggregation, and polymicrobial biofilm formation, main identified interactions were: (i) hydrophobic interactions between non-polar peptide chains and lipid structures, characterized by θ w among 84.9 ± 1.6 (γ = 22.78 mJ/m2 with 95.3 of dispersive contribution) and 76.6 ± 3.8 (γ = 17.34 mJ/m2, 40.2 of dispersive contribution) for C. albicans and H. pylori , respectively, (ii) hydrogen bonds between surface components of yeast and bacterium (e.g., S H⋅⋅⋅NH 2 or S H⋅⋅⋅O CO) and (iii) thiol-mediated surface interactions identified by displacements to lower wavenumbers (Δ v = 5 cm−1). Evidence of internalization and electrostatic interactions were not evidenced. All observations were congruent with the biofilm formation, including the identification of small-size biostructures (i.e., 122–459 nm) associated with extracellular proteins, extracellular DNA, or outer membrane vesicles were observed characteristic of biofilm formation. It is concluded that biofilm is formed by co-aggregation after anchoring of H. pylori on C. albicans. Several surface interactions were associated with the prevalence of H. pylori , the possibility to find C. albicans in the stomach epithelium infected by H. pylori , but also, strength interactions could be interfering in experimental observations associated with bacterial-DNA detection in culture mixtures. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Research of the University of Quindio / Revista de Investigaciones Universidad del Quindio is the property of Journal of Research of the University of Quindio and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The effect of monomer charge on the synthesis of polyelectrolyte hydrogels was studied. • The effect of the monomers were explained by the counterion condensation theory in conjunction with Gibbs-Donnan equilibrium. • Insertion of vinyl side groups favored the formation of the hydrogels with the charged monomers. The objective of this work was to study the effect of the loading of monomers (cationic, anionic and ampholytes) in the preparation of polyelectrolyte hydrogels (PEHG) based on alkylated vinylated chitosan, in order to improve the understanding of the effect of ionic monomers on the polymerization of alkylated vinyl chitosan to obtain PEHGs. To achieve this, sequential synthesis of PEHGs was carried out starting from chitosan, glycidyl methacrylate (GMA) and ionic monomers: sodium 4-styrenesulfonate, [3-(methacryloylamino)propyl]dimethyl(3-sulfopropyl)ammonium hydroxide and 4-(vinylbenzyl)trimethylammonium chloride. The stages of synthesis were (a) chemical modification of the chitosan with N -(3-chloro-2-hydroxypropyl)-trimethylammonium chloride as an alkylating agent to obtain chitosan with positive charges, (b) insertion of vinyl side groups by opening the epoxide ring at pH 3.8 using GMA and (c) in situ polymerization of vinyl monomers in a polyelectrolyte aqueous solution (ACh-vinyl solution). Characterizations of the intermediate and PEHGs were performed. It was concluded that the different solution processes occurring in the reactor can be explained by counterion condensation theory in conjunction with Gibbs-Donnan equilibrium. The water absorption capacities of PEHGs were 144.6, 42.7, and 92.5 g H 2 O/g of dried HG for cationic, ampholyte, and anionic hydrogels, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil conditioners improve the physical–chemical properties of poor or degraded soils. • New geomimetic soil conditioners based on multilayer hybrid composites were developed. • Bentonite and kaolinite surfaces were chemically modified and covered with lignin. • Clay-PAA-Lignin can be used as soil conditioners to mimic the structures and properties of soil. Soil conditioners are products of natural or synthetic origin that aim to improve the physical–chemical properties of poor or degraded soils. Recently, geomimicry has emerged as a novel strategy for obtaining geomimetic materials, which have been designed to imitate the structure and functions of soils, and potentially be used as soil conditioners, by improving their structure, increasing their capacity for water retention (WRC) and cation exchange capacity (CEC), restore the microbiota, etc. Thus, the development of hybrid composites has proven to be an appropriate strategy for obtaining novel materials that combine and improve the properties exhibited by their predecessors; being the systems based on clays and polymers capable of imitating the clay-humin-humic acid structures present in the soil particles and their properties. Therefore, the objective of this work was to develop new geomimetic soil conditioners based on multilayer hybrid composites, MHCs, of clay-PAA-lignin. For this, bentonite and kaolinite surfaces were chemically modified with trichlorovinylsilane to produce surface activation of the clay. Subsequently, chains of poly(acrylic acid), PAA, were inserted into the surface active clay by free radical reactions, in order to generate carboxylic acid groups on the surface. On the other hand, lignin was obtained from sugarcane bagasse by the basic delignification method and was incorporated into the polymeric matrix by urethanization with 4,4 -methylenebis(phenyl isocyanate). By this method, lignin coatings on inorganic particles were obtained using urethane bonds. In addition, different clay-lignin ratios were evaluated. Finally, the material obtained was characterized by infrared spectroscopy, FEDS, nuclear magnetic resonance and thermogravimetric analysis. In addition, their WRC, CEC and bacterial viability properties were evaluated. The results showed that MHCs based on clay-PAA-Lignin can be obtained through the proposed methodology and mimic the structures and properties of soil. The WCR and CEC of the synthesized MHCs were lower than that of their predecessors, produced by the change in hydrophobicity of the materials. In addition, the developed MHCs showed a high microbial viability, >83 %, which suggests a high compatibility with the soil microbiota. [ABSTRACT FROM AUTHOR]

Banana is one of the most consumed and exported fruits worldwide, with Colombia being the fifth biggest exporter. In order to make bananas more attractive to the global market, quality attributes of this climacteric fruit during the ripening process are a topic of deserve. Particularly, the detection of contamination by pesticides are highly interesting given the hazard effects caused in the ecosystems, and even in human health. In this work, the dynamic of the mid-IR spectral signature left by pesticide residues in banana peel during the ripening process for the pesticides Chlorpyrifos, Malathion and Mancozeb is evaluated. This is done by using ATR-FTIR system along FEDS algorithm to analyze the acquired mid spectra for uncontaminated and contaminated green banana peel at different concentrations and their evolution as the banana ripens. The ripening stages of bananas were determined by analyzing the color properties of luminosity, chromaticity, and color angle, and the Loesecke scale. The stages were classified as green, yellow, and yellow with brown flocks. The presence of pesticide signatures in banana peels during different stages of ripening and at varying concentrations is highlighted using a normalization methodology in the spectral range of interest for each pesticide. To quantify the pesticide signatures, the Pearson's correlation coefficient was used by analyzing the correlation between the FEDS spectra of the target and reference pesticide signals; moreover, this coefficient has been successful used to find correlations among the different stages of banana ripening. The study suggests that pesticides like Malathion, which have higher hydrophilicity, smaller particle size, and rapid degradation over time, may pose a challenge for detection in banana peel using the proposed methodology unlike Chlorpyrifos which showed more promising results. Our study found that the degradation of pesticides in banana peel during the ripening can be detected by analyzing the intensity and the behavior of the signal. Interestingly, the ripening process of bananas was found to accelerate this degradation process. Moreover, we found that the yellow ripening stage is particularly noteworthy, as it exhibits the highest changes in r fS-P with concentration and with respect to the control samples, indicating a substantial chemical and physical dynamic during the ripening process at this stage. Finally, the study revealed that residues of Chlorpyrifos and Mancozeb pesticides were detected in banana peels even at the ripeness stage deemed safe for human consumption, raising concerns about their potential health risks and their use in the development of industrial products that may impact living organisms. • Analyzed mid-IR spectral signature of pesticide residues in banana peel during ripening for Chlorpyrifos, Malathion, Mancozeb. • Factors (hydrophilicity, particle size, solubility, degradation) affect pesticide detection in banana peel. • Banana ripening not linear, yellow stage exhibits highest changes in spectral dynamic with concentration. • Pesticide degradation is accelerated during banana ripening, especially at high concentrations, affecting signal intensity. • Study reveals health risks of consuming contaminated bananas & using peel in products. [ABSTRACT FROM AUTHOR]

• Bentonite was modified with trichlorovinylsilane by covalent anchoring. • Polymer composites were synthesized via sequential polymerizations. • Hybrid-composites with CEC and WAC were obtained. • Hybrid-composites were used as bacterial inoculums. The objective of this work was to develop multifunctional hybrid polymers based on bentonite-poly(acrylic acid)-polyesters composites, as potential systems for the development of new strategies for the recovery and improvement of the chemical, physical and biological properties of soils. For this, organoclays with superficial vinyl groups based on bentonite modified by covalent anchoring of trichlorovinylsilane were synthesized. After, polymer composites were synthesized through sequential polymerizations by free radicals with acrylic acid and subsequent polyesterification with citric acid and sorbitol. The hybrid materials were characterized by infrared spectroscopy, nuclear magnetic resonance and thermogravimetric analysis; In addition, the water retention capacity and cationic exchange capacity of the materials were evaluated. Finally, the evaluation of their ability to act as reservoirs of plant growth promoting microorganisms, Azotobacter chroococcum , in dormant state was studied. The results show that these multifunctional hybrid-materials developed in this study can mimic structural and functionally to the soil particles, and even, these can achieve higher water and cation exchange capacities in comparison with natural clays. In addition, the bacterial viability results showed the ability of the Azotobacter chroococcum to encyst, enter in a dormant state under dehydration conditions, conserve itself in the polymer material and maintain the ability to reactivate its metabolism. Our results evidence the multifunctionality of the developed materials, not only contributing potentially to the improvement of the physical and chemical properties of soils, but also allowing the growth of nitrogen-fixing bacteria contributing to their biological restoration. [ABSTRACT FROM AUTHOR]

Dye contamination is a serious environmental issue, particularly affecting water bodies, driving efforts to synthesize adsorbent materials with high dye-removal capacities. In this context, eco-friendly and cost-effective materials derived from bioresidues are being explored to recycle and valorize waste. This study investigates the synthesis, characterization, and application of a biohydrogel made from unripe plantain peel (PP), modified with carboxymethyl groups and crosslinked using varying concentrations of citric acid (CA), an eco-friendly and economical organic acid. The materials were characterized by ATR-FTIR, TGA, and SEM, confirming the successful synthesis of hydrogels, which exhibited rough, irregular surfaces with micropores. Additionally, the materials were analyzed for their pH point of zero charge, swelling capacity, and methylene blue (MB) dye removal efficiency. The results indicate that the biohydrogel formed with 1% CA exhibited the most favorable characteristics for MB removal. Kinetic studies revealed that the adsorption mechanism is pH-dependent, with equilibrium being reached in 720 min. The Freundlich isotherm model provided the best fit for the adsorption data, suggesting a heterogeneous surface and a multilayer adsorption process, with a maximum retention capacity of 600.8 ± 2.1 mg/g at pH 4. These findings contribute to the development of cost-effective and efficient materials for dye removal, particularly from water bodies.

Fertilizers with enhanced efficiency or high-efficiency fertilizers increase the nutrient availability, minimize losses, and reduce costs, thereby increasing crop yields and food production while mitigating environmental impacts. This research evaluates the synthesis of biodegradable hydrogels from cassava starch and citric acid for agrochemical applications. Hydrogels were synthesized using water as the solvent and applied for the controlled release of macronutrients (N and K). Four concentrations of nutrient-containing salts were tested (0.5 to 10.0% w/w). Materials were analyzed using ATR-FTIR spectroscopy and swelling studies. The presence of nutrients reduced both the crosslinking efficacy and the water absorption capacity, with the latter dropping from 183.4 ± 0.6% to 117.9 ± 3.7% and 157.4 ± 25.0% for hydrogels loaded with NH 4 Cl and KCl, respectively. The cumulative release of K and N from the hydrogel was monitored for 144 h and examined using kinetics models, revealing that the releases follow Fickian's diffusion and anomalous diffusion, respectively. Additionally, the material was formed using cassava with peel previously milled to reduce the production costs, and its potential for nutrient-controlled delivery was evaluated, with the finding that this hydrogel decreases the release rate of nitrogen. The results suggest that these biomaterials may have promising applications in the agrochemical industry in the making of high-efficiency fertilizers.

Phosphorous (P) is one the most important elements in several biological cycles, and is a fundamental component of soil, plants and living organisms. P has a low mobility and is quickly adsorbed on clayey soils, limiting its availability and absorption by plants. Here, biodegradable hydrogels based on Cassava starch crosslinked with citric acid (CA) were made and loaded with KH 2 PO 4 and phosphorite to promote the slow release of phosphorus, the storing of water, and the reduction in P requirements during fertilization operations. Crosslinking as a function of CA concentrations was investigated by ATR-FTIR and TGA. The water absorption capacity (WAC) and P release, under different humic acid concentration regimens, were studied by in vitro tests. It is concluded that hydrogel formed from 10% w / w of CA showed the lowest WAC because of a high crosslinking degree. Hydrogel containing 10% w / w of phosphorite was shown to be useful to encouraging the slow release of P, its release behavior being fitted to the Higuchi kinetics model. In addition, P release increased as humic acid contents were increased. These findings suggest that these hydrogels could be used for encouraging P slow release during crop production., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

The aim of this work was to synthesize and study the functional properties of polymer-clay nanocomposite (PCNCs) based on poly(sodium 4-styrene sulfonate) (NaPSS) and two types of clay in the dispersed phase: bentonite and kaolinite, in order to advance in the development of new geomimetic materials for agricultural and environmental applications. In this study, the effect of adding high concentrations of clay (10-20 wt. %) on the structural and functional properties of a polymer-clay nanocomposite was evaluated. The characterization by infrared spectroscopy made it possible to show that the PCNCs had a hybrid nature structure through the identification of typical vibration bands of the clay matrix and NaPSS. In addition, scanning electron microscopy allowed us to verify its hybrid composition and an amorphous particle-like morphology. The thermal characterization showed degradation temperatures higher than ~300 °C with Tg values higher than 100 °C and variables depending on the clay contents. In addition, the PCNCs showed a high water-retention capacity (>2900%) and cation exchange capacity (>112 meq/100 g). Finally, the results demonstrated the ability of geomimetic conditioners to mimic the structure and functional properties of soils, suggesting their potential application in improving soil quality for plant growth.