Hydrolysis effects on the water uptake of starch-g-glycidyl methacrylate (GMASt)/dimethylacrylamide (DMAAm)-based hydrogels for potential agricultural purposes.

This work assessed the effect of different hydrolysis periods on the properties of hydrogels based on 75 % w w-1 of N,N'-dimethyl acrylamide (DMAAm) and 25 % w w-1 of starch-g-(glycidyl methacrylate) (GMASt). FTIR results confirmed the conversion of ester groups into carboxylic acids and carboxylates, besides forming a keto-enol tautomer due to the peeling reaction of starch. For DMAAm, the hydrolysis mostly converted amide into carboxylate groups. The morphology, thermal stability, and the mechanical properties of the predominantly amorphous matrices (as confirmed by XRD results) did not drastically change even after 10 days of hydrolysis in alkali media. However, the thermogravimetric analysis results suggested that DMAAm partially protected GMASt from the hydrolysis. The swelling degree of the matrix increased from (10.1 ± 2.1) g g-1 to (61.9 ± 2.6) g g-1 after 1 day of hydrolysis, but no statistical differences (at 95 % of significance) were observed for the matrices hydrolyzed for longer periods, confirming that the maximum hydrolysis occurred within 24 h. The results confirmed that the hydrolysis increased the water uptake of the GMASt/DMAAm-based matrices, making appealing for uses as a water retentor for agricultural purposes.

A conventional and chemometric analytical approach to solving urea determination with accuracy and precision.

Urea is an essential molecule usually detected using spectroscopy, particularly ultraviolet and visible spectroscopy (UV-vis). However, its detection represents a not always fully acknowledged issue. Its concentration dependency has raised questions about the reliability of the UV-vis results. Derivatization reactions, common alternatives to achieve accuracy and precision with UV-vis measurements, still represent an additional step in the measurement process. Besides the problems mentioned earlier, urea forms complex mixtures in aqueous mediums. Therefore, this work proposes to investigate the accuracy and precision of urea determination by UV-vis spectroscopy in the pure form and derivatized with para-dimethylaminobenzaldehyde. The results show that UV-vis spectroscopy could not quantify urea in both forms with precision and accuracy. On the other hand, when applying multivariate curve resolution with alternating least squares (MCR-ALS) to the UV-vis data, the pure urea analytical signal is mathematically separated. Then, those parameters of merit were successfully achieved.

A comparative study of starch-g-(glycidyl methacrylate)/synthetic polymer-based hydrogels.

Chemical modification reactions and blending formation are two alternatives used to improve the properties of starch-based materials. This work used both approaches to evaluate how they would affect the properties of hydrogels. The hydrogels were based on corn starch (St), modified with glycidyl methacrylate (GMA; starch-g-GMA; GMASt), and blended with N,N'-dimethylacrylamide (DMAAm; GMAStxDMAAmy) or sodium acrylate (SA; GMAStxSAy). The results confirmed that the pure GMASt matrix had a low swelling degree (≈3 g g-1), but when blended with the synthetic polymers, this value reached ≈10 g g-1 (sample GMASt25DMAAm75). All matrices showed responsiveness towards pH variations. In general, they swelled more at pH 5 than at pH 7. While DMAAm had more influence on the swelling degree, SA was more efficient as a mechanical enhancer. Increasing 25 % of the amount of SA in the blend increased Young's Modulus by a factor of ≈10 times. It confirmed that both polymers effectively change the properties of GMASt, but in different ways.

Magnetic chitosan microgels: Synthesis, characterization, and evaluation of magnetic field effect over the drug release behavior.

Magnetic microgels based on chitosan, modified with glycidyl methacrylate (GMA) and activated with folic acid (FA), and cobalt ferrite nanoparticles, modified with GMA (GMACoFe2O4), were synthesized by emulsion polymerization. The size of the round-shaped microgels, with and without GMACoFe2O4, ranged from (1.62 ± 0.38) µm to (1.71 ± 0.61) µm, respectively. Their release behavior was evaluated in the presence and absence of a magnetic field (MF), using vitamin-B12 as a model drug. In the absence of MF, at pH 7.4, a fast release was observed, reaching the equilibrium after 30 min. In the MF presence, the alignment of the chains to it promoted an initial fast release, followed by a more controlled one, lasting for 50 min at pH 7.4. This type of release is attractive for the treatment of gastric wounds, which is improved by the presence of FA, conferring anti-oxidative and anti-secretory properties to the microgels.

Chitosan hybrid microgels for oral drug delivery.

In the present work, hybrid microgels based on chitosan and SiO2 nanoparticles (NPs) were synthesized. Both chitosan and the SiO2 NPs were submitted to chemical modification reactions to having vinyl groups incorporated into their structures. The microgels were synthesized by emulsion polymerization. SEM analysis indicated a high dispersity of diameter for the microgels, ranging between (18.7 ±â€¯12.3) µm for the samples without SiO2-VTS and (11.3 ±â€¯8.07) µm for the microgels with SiO2-VTS. The material showed pH-responsiveness, especially in acidic pHs. The longest release lasted 45 min and large amounts of drugs were released as soon as the material was added to the release medium. It is interesting for oral drug delivery systems, especially for gastric wound treatment. The fast release of high amounts of drugs promotes an immediate relief of the pain and the following controlled release allows the gradual recovery of the damaged area.

Curcumin and silver nanoparticles carried out from polysaccharide-based hydrogels improved the photodynamic properties of curcumin through metal-enhanced singlet oxygen effect.

Colorectal cancer (CRC) has a high incidence and resistance to conventional treatments. Curcumin (CUR) is a promising natural product in the treatment of CRC with excellent in vitro results. However, its low bioavailability is a limiting factor in clinical applications. To overcome, CUR was incorporated into hydrogels constituted by chitosan (CHT) and chondroitin sulfate (CS), natural biopolymers, capable of controlled release. Hydrogels were synthesized in ionic liquids (ILs, [Hmim][HSO4]) improving the solubility of CHT and the hydrogel properties. Furthermore, CUR was combined with silver nanoparticles (AgNPs) and visible light by Photodynamic Therapy (PDT), which, through the MEO effect (Metal-Enhanced Singlet Oxygen), leads to cell death. It is highlighted the green synthesis of AgNPs using an ultrasound bath. The CHT/CS hydrogels loaded with CUR/AgNPs were properly characterized. Cellular assays showed that the hydrogels (CHT/CS) were not cytotoxic to healthy tissues. However, PDT selective illumination led to inhibition of Caco-2 human colon cancer cells by the CHT/CS/CUR-AgNPs (CC50 = 91.5 µg mL-1 of hydrogel). The cellular uptake assays showed, in addition to the therapeutic action, that the CUR can works as a diagnostic fluorescence probe (theranostic system). Finally, we highlight our commitment to work with reagents, solvents, and methodologies aiming at the principles of green chemistry.

Activity and Cell-Death Pathway in Leishmania infantum Induced by Sugiol: Vectorization Using Yeast Cell Wall Particles Obtained From Saccharomyces cerevisiae.

Visceral leishmaniasis, caused by Leishmania infantum, is a neglected tropical disease, to which efforts in the innovation of effective and affordable treatments remain limited, despite the rising incidence in several regions of the world. In this work, the antileishmanial effects of sugiol were investigated in vitro. This compound was isolated from the bark of Cupressus lusitanica and showed promising activity against L. infantum. In spite of the positive results, it is known that the compound is a poorly water-soluble diterpene molecule, which hinders further investigation, especially in preclinical animal studies. Thus, in an alternative delivery method, sugiol was entrapped in glucan-rich particles obtained from Saccharomyces cerevisiae yeast cell walls (YCWPs). To evaluate the activity of sugiol, the experiments were divided into two parts: (i) the in vitro investigation of antileishmanial activity of free sugiol against L. infantum promastigotes after 24, 48, and 72 h of treatment and (ii) the evaluation of antileishmanial activity of sugiol entrapped in glucan-rich particles against intracellular L. infantum amastigotes. Free sugiol induced the cell-death process in promastigotes, which was triggered by enhancing cytosolic calcium level and promoting the autophagy up to the first 24 h. Over time, the presence of autophagic vacuoles became rarer, especially after treatment with lower concentrations of sugiol, but other cellular events intensified, like ROS production, cell shrinkage, and phosphatidylserine exposure. Hyperpolarization of mitochondrial membrane potential was found at 72 h, induced by the mitochondria calcium uptake, causing an increase in ROS production and lipid peroxidation as a consequence. These events resulted in the cell death of promastigotes by secondary necrosis. Sugiol entrapped in glucan-rich particles was specifically recognized by dectin-1 receptor on the plasma membrane of macrophages, the main host cell of Leishmania spp. Electron micrographs revealed particles containing sugiol within the infected macrophages and these particles were active against the intracellular L. infantum amastigotes without affecting the host cell. Therefore, the YCWPs act like a Trojan horse to successfully deliver sugiol into the macrophage, presenting an interesting strategy to deliver water-insoluble drugs to parasitized cells.

In vitro anti-Leishmania activity of T6 synthetic compound encapsulated in yeast-derived ß-(1,3)-d-glucan particles.

The objective of this study was to encapsulate a synthetic compound, the 4-[(2E)-N'-(2,2'-bithienyl-5-methylene)hydra-zinecarbonyl]-6,7-dihydro-1-phenyl-1H-pyrazolo[3,4-d]pyridazin-7-one (T6) in glucan-rich particles mainly composed by the cell wall of Saccharomyces cerevisiae (GPs) and to study their individual and combined activity on Leishmania infantum. The possible mechanism of action of T6 was also investigated. Our results showed the activity of T6 compound in both promastigote (IC50 = 2.5 µg/mL) and intracellular amastigote (IC50 = 1.23 µg/mL) forms. We also found activity against intracellular amastigote forms (IC50 = 8.20 µg/mL) when the T6 compound was encapsulated in GPs. Another interesting finding was the fact that T6 encapsulated in GPs showed a significant decrease in J774A1 macrophage toxicity (CC50 ≥ 18.53 µg/mL) compared to the T6 compound alone (IC50 = 2.27 µg/mL). Through electron microscopy and biochemical methodologies, we verified that the activity of T6 in promastigote forms of L. infantum was characterized by events of cell death by apoptosis like increased ROS production, cell shrinkage, phosphatidylserine exposure and DNA fragmentation. We conclude that T6 can be considered a promising anti-Leishmania compound, and that the use of GPs for drug encapsulation is an interesting approach to the development of new effective and less toxic formulations.

Physical-chemical properties of dental composites and adhesives containing silane-modified SBA-15.

The aim of this study was to synthesize and characterize mesoporous materials SBA-15 and SBA-15 modified with 3-(methacryloxy)-propyl-trimethoxysilane (MPS) to be used as inorganic filler in restorative dental composites and adhesives, and evaluate the main physical-chemical properties of the resulting material. The SBA-15 and SBA-15/MPS were characterized by FTIR, BET and X-Ray and combined with TEGDMA, bis-GMA and commercial spherical silica to produce dental composites. Afterwards, the mesoporous materials were combined with TEGDMA, bis-GMA and HEMA to make adhesives. To compare the results, composites and adhesives containing only commercial spherical silica were investigated. Some physical-chemical properties such as degree of conversion (DC), flexural strength (FS) and modulus (FM), water sorption and solubility (Wsp and Wsl), specific area (BET), and the leachable components were evaluated. The SBA-15/MPS can be used to prepare dental restorative materials, with some foreseeable advantages compared with pure SBA-15 dental materials and with improved properties compared with commercial spherical silica dental materials. An important improvement was that the dental materials based on modified SBA-15 presented a reduction of approximately 60% in leaching of unreacted monomers extracted by solvent compared to the control group.

Generating nanoparticles containing a new 4-nitrobenzaldehyde thiosemicarbazone compound with antileishmanial activity.

Thiosemicarbazones are an important class of compounds that have been extensively studied in recent years, mainly because of their broad profile of pharmacological activity. A new 4-nitrobenzaldehyde thiosemicarbazone compound (BZTS) that was derived from S-limonene has been demonstrated to have significant antiprotozoan activity. However, the hydrophobic characteristic of BZTS limits its administration and results in low oral bioavailability. In the present study, we proposed the synthesis of nanoparticle-based block copolymers that can encapsulate BZTS, with morphological evaluation of the nanoparticle suspensions being performed by transmission and cryo-transmission electronic microscopy. The mean particle sizes of the nanoparticle suspensions were determined by static light and dynamic light scattering (SLS/DLS), and the hydrodynamic radius (Rh) was determined using the Stokes-Einstein equation. The zeta potential (ζ) and polydispersity index (PDI) were also determined. The entrapment encapsulation efficiency of the BZTS nanoparticles was measured by ultraviolet spectrophotometry. In vitro activity of BZTS nanoparticle suspensions against intracellular amastigotes of Leishmania amazonensis and cytotoxic activity were also evaluated. The results showed the production of spherical nanoparticles with varied sizes depending on the hydrophobic portion of the amphiphilic diblock copolymers used. Significant concentration-dependent inhibitory activity against intracellular amastigotes was observed, and low cytotoxic activity was demonstrated against macrophages.

Resíduos de pesticidas organoclorados em amostras ambientais (águas e solos) do Município de Maringá - PR / Residues of organochloric pesticides in environmental samples (water and soils) in Maringá - PR

This paper describes the concentration of organochloric pesticides found in water and soils. The samples were gathered in several places of Maringa, State of Parana, Brasil. In all surfgace samples analysed, there were found high concentrations of organochloric pesticides. This high level of pesticides was found in wells, mines, and almost all samples analysed. It may not be recomended for human consumption