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Geomimetic materials (GEOMI) are composite materials based on polymer and clays, able to imitate structural and functional properties of soils, including their structure, cationic exchange capability (CEC), water uptake capability (WUC), pH buffering ability, immobilizing of substances, among other. Because they can be used to develop of fertilizer slow-release systems, they have been identified as a novel approach to advance toward a most sustainable agriculture. The aim of this work was to study the effect of GEOMI on the plant growth in degraded soils. For this, GEOMI-1.0 was synthesized using poly(acrylic acid) as model of humic substances and bentonite modified with trichlorovinylsilane as mineral fraction model. Materials were characterized by different techniques. GEOMI-1.0 showed a hybrid, homogeneous, and amorphous structure. In addition, it was thermally stable at below ⁓200 °C with a Tg about 49.3 °C, showed a high WUC (⁓1384 g of water per 100 g of material). Likewise, it was verified that GEOMI-1.0 can decreases the pH values and increases the CEC of degraded soils depending on the added amount of geomaterial; but also, the electric conductivity values showed no dependence on the added amount of GEOMI-1.0. By correlation analysis, an exponential dependence of CEC was observed respect to pH changes, the relative amount added of GEOMI-1.0 and the initial CEC. Finally, using Brachiaria Brizantha cv. Marandúas plant model, the increase in the biomass content of roots and leaves, and the number of germinated seeds, were observed when GEOMI-1.0 was used for restoration of in-lab degraded soils.

Purpose: Controlled release systems are an efficient alternative for the effective use of agricultural supplies. Among the most versatile controlled release systems are intelligent or stimulus-sensitive polymeric materials, since these materials are multipurpose and adaptable alternatives that offer great adaptability for agricultural applications. The objective of this work was to develop stimulus-sensitive polyurethanes (PUs) based on cationic aminoglycosides (CAG) to be used as an active phase for the manufacture of systems for the controlled release of phytohormones such as naphthalene acetic acid (NAA). Design/methodology/approach: The synthesis of stimulus-sensitive PUs was carried out by a polycondensation reaction using CAGs and methylene diphenyl isocyanate (MDI) as precursors. The NAA retention and release experiments were performed at different pH values and ionic forces to include the acidity and salinity of agricultural soils. Findings: The results demonstrate that PUs can be obtained from CAG and MDI using the one-step method. The retention of NAA increased as the CAG content increased in the polymer structure, while it is seen that the effect of pH is weak compared to the effect of ionic strength. On the other hand, the release of NAA from cationic PUs can be accomplished by small changes in ionic strength that are mainly affected by the composition of the PU and the pH. The results suggest that, for developed systems, retention and release of NAA is affected by other interaction mechanisms that could probably be related to p-aromatic interactions. Research limitations/implications: Findings are limited to controlled conditions and the expanding of results to extensive crops should be analyzed in next research studies. Practical implications: The practical implications of this study are improving of control for the dosage of phytohormones in stake propagation crops, greenhouse crops, optimization of reseeding operations, among others. Social implications: The social implication of this study is reduction of pollution by addition of excess of NAA, in consequence, production costs are decreased. Originality/value: Originality and value of this research is the use of PUs based on CAG, and in consequence, the possibility to build novel environment-friendly systems for phytohormone dosage.

Background: Polyphenols are secondary metabolites of plants which are generally associated with the protection against ultraviolet radiation and aggression by pathogens. Epidemiological studies suggest that long term consumption of diets rich in plant polyphenols offer protection against different diseases with positive effects in the context of human health. Objective: The objective of this work was to develop biodegradable polymer hydrogels (HGs) based in sorbitol and citric acid for controlled release of bioactive substances from plants (specifically strictinin). Method: HGs were synthesized at two relation sorbitol:citric acid (1:1 and 1:2) and characterized by ATRFTIR. In addition, it was determined its water absorption capacity by tea bag method. Hydrolysis of strictinin was studied at different pH and release of strictinin was monitored by UV-vis. Antimicrobial activity of strictinin in solution and in the HGs was tested against E. coli and S. aureus. Results: HGs can be synthesized from sorbitol and citric acid by free-solvent synthesis. These HGs can be used for the release of strictinin at acid pH without changes in its chemical structure; at alkaline pH, hydrolysis processes affect its strictinin chemical structure. Diffusion of strictinin is slower in HG 1:1 than HG 1:2, being the released quantity by diffusion in both cases are the same. In addition, only 29.8 % of strictinin can be release by diffusion and, in consequence, the remaining strictinin must be released by other mechanism. Conclusion: Results evidence that E. coli and S. aureus are sensitive to low strictinin concentrations (2.43 mgL-1) released from HGs.

Background: Nanostructured hybrid antibiotics (NHAs) are a new class of substances with a high potential in the development of novel alternatives for antimicrobial treatments. This strategy is based on the building of synergy between biologically-active organic and inorganic substances. Objective: The aim of this study was to develop hydrogels based in cassava starch for controlled release systems with antibacterial and antibiofilm properties using nanostructured hybrid systems. Method: For that, hydrogels were synthesized from cassava starch and poly(acrylic acid) (PAA) by esterification reaction. Silver nanoparticles were synthesized by chemical reduction using NaBH4 as reducing agent and citrate as capping agent. Nanostructured hybrid systems were prepared from silver nanoparticles (AgNPs) and cysteamine (cysa) by ligand exchange reaction; these systems were characterized (Fourier transform infrared, dynamic light scattering, elemental analysis) and evaluated against Escherichia coli and Staphylococcus aureus using Tryptic Soy Broth as liquid phase. Conclusion: Hydrogels can be used as controlled-release systems of substance with antibacterial activity (AgNPs, cysa and AgNPs-cysa). Antibacterial effect against Escherichia coli and Staphylococcus aureus was seen to be relatively low at studied concentrations; however, the charge of antimicrobial activity can be controlled as a result of high water absorption capacity. Inhibition percent for hybrid systems (AgNPs-cysa) was seen to be most effective against Escherichia coli and very similar to the observed effect for AgNPs.

Nanoparticles (NPs) with antimicrobial properties recently have emerged as an interesting study area. Different types of inorganic NPs (metal, oxide, alloy and mixture) have been synthesized and studied against Gram-positive and Gram-negative bacteria. Factors associated with the antimicrobial activity of NPs can be associated with the microorganism (e.g., bacterial cell wall, biofilm formation, etc) and with NPs (e.g., size, shape, chemical compositions). Here, we reviewed recent advances in relation with the interaction mechanisms of inorganic NPs with biomolecular systems of microorganism’s cells. In particular, we analyzed the action mechanisms of AgNPs and the interaction of NPs with specific cell components. Factors associated with the antimicrobial activity of NPs can be associated with the microorganism (e.g., bacterial cell wall, biofilm formation, etc) and with NPs (e.g., size, shape, chemical compositions). NP can modify the secondary, tertiary and quaternary structures of polymer biomolecules as proteins and therefore its biological function can be affected. Results suggest that an initial point to understand the interaction of bacterial biomolecules with inorganic NPs is the nature of NPs (bulk and surface composition).

The aim of this work is to give the theoretical background of liquid-phase polymer-based retention (LPR) technique, provide a complete model of separation process, and evaluate its application for the removal of pollutant inorganic ions (PIIs) from aqueous solution. Thus, fundaments of LPR modeling by washing method from the ion distribution in active and passive zones are specified and its application was evaluated for cadmium removal using poly(sodium styrene sulfonate) as water-soluble polymer (WSP). LPR simulations were performed using a semiempirical description from data of concentration, filtration factorm, and retention coefficients. It is concluded that semiempirical simulation of PII retention by WSP can be performed from a small amount of experimental data using the described modeling. In addition, new approximations associated with molecular structure of polymer should be performed and linked to parameters of LPR experiments.