From the Lab to the Field: Organic Materials for Industrial Applications and Environmental Remediation.

Many new developments for different industries have their origin in basic science. In recent years, this trend has gained attention due to the increasing interaction between academic science and industry. This article presents some rational materials for chemical modifications that were developed by the basic science, then transferred to the productive sector. Conducting hydrophobic coatings for aerospace applications, hydrogels for the oil and gas industry, as well as polymers for removal of heavy metal, were some of the topics approached in the lab to solve industrial problems. Many times, nature is a great source of inspiration to produce new materials. In this sense, superhydrophobicity and superhydrophilicity (concepts closely related to our everyday life) were the bioinspiration for the development of membranes. These membranes were able to separate hydrocarbons and water, which found application in the treatment of subterranean water for the oil and gas industry.

Hemicelluloses hydrogel: Synthesis, characterization, and application in dye removal.

Novel materials using biowaste as adsorbents in wastewater treatment have been allocated considerable interest. Herein, we present the synthesis of different hydrogels of crosslinked polyacrylamide in presence of hemicelluloses with/ without bentonite, using a soft reaction condition. The structure of new hydrogels was characterized by spectroscopic, thermal and microscopic experiments. The semi-interpenetrated network with hemicelluloses: 10 %; acrylamide 79 %; bentonite 10 %; N,N,N',N'-tetramethylethylenediamine: 1 % allows reducing 20 % the use of non-renewable acrylamide, without changing its decomposition temperatures and keeping its water absorption capacity. This hydrogel was applied to dye removals, such as rhodamine B, methylene red and methylene blue in aqueous solutions. In the case of methylene blue, highest removal is observed with maximum adsorption of qmax = 140.66 mg/g, compared to material without hemicelluloses that only a qmax = 88.495 mg/g. The adsorption kinetics and equilibrium adsorption isotherms are in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model, respectively. The developed hydrogel from hemicelluloses represents a potential alternative adsorbent for a sustainable system of sewage treatment.

Biofilm Formation of Two Different Marine Bacteria on Modified PDMS Surfaces is Affected by Surface Roughness and Topography.

Different strategies were tested to reduce biofilm formation of the model marine bacteria Cobetia marina and Marinobacter hydrocarbonoclasticus on cross-linked polydimethylsiloxane (PDMS) coated aluminum and cellulose acetate surfaces modified by addition of multi-walled carbon nanotubes (MWCNT) or exposure of the surfaces to bromine vapors in the presence and absence of UV irradiation. The three surface modifications explored led to important reductions in biofilm formation for the two marine bacteria, up to 30% in the case of exposure to Br2(g). Biofouling reduction could be correlated to surface properties in all cases through the introduction of a quantitative theoretical model based on an effective roughness parameter, Raeff, that accounted for the different morphological changes observed. The model considers the possibility of bacterial inclusion into large surface wells, as observed by AFM in the case of Br2(g) + UV light treatment. In addition, a linear relationship was observed between biofouling reduction and the Raeff effective roughness parameter.

Liquid-Polymer Contact Electrification: Modeling the Dependence of Surface Charges and ξ-Potential on pH and Added-Salt Concentration.

Here, a mathematical model is presented, which accounts for the dependence of the surface electrical charge density (σ) on pH and the concentration of added salts (Cs), generated when a water drop rolls or slides on the surface of a hydrophobic polymer, a process known as liquid-polymer contact electrification (LPCE). The same model was successfully applied to fit the isotherms of ξ-potential as a function of pH, reported in the literature by other authors for water-poly(tetrafluoroethylene) (PTFE) interfaces. Hence, the dependence of σ and ξ on pH was described using the same concept: acid-base equilibria at the water-polymer interface. Equilibrium constants were estimated by fitting experimental isotherms. The experimental results and the model are consistent with a number of 10-100 acid-base sites/µm2. The model predicts the increase of |σ| and |ξ| with pH in the range of 2-10 and the existence of a zero-charge point at pHzcp ≅ 3 for PTFE (independent of Cs). Excellent fits were obtained with Ka/Kb ∼ 9 × 107, where Ka and Kb are the respective acid and base equilibrium constants. On the other hand, the observed decrease in |σ| and |ξ| with Cs at fixed pH is quantitatively described by introducing an activity factor associated with the quenching of water activity by the salt ions at the polymer-water interface, with quenching constant Kq. Additionally, the quenching predicts a decrease in |σ| and |ξ| at extreme pH, where I > (1/Kq) (I: ionic strength), in agreement with literature reports.

Application of Crosslinked Polybenzimidazole-Poly(Vinyl Benzyl Chloride) Anion Exchange Membranes in Direct Ethanol Fuel Cells.

Crosslinked membranes have been synthesized by a casting process using polybenzimidazole (PBI) and poly(vinyl benzyl chloride) (PVBC). The membranes were quaternized with 1,4-diazabicyclo[2.2.2]octane (DABCO) to obtain fixed positive quaternary ammonium groups. XPS analysis has showed insights into the changes from crosslinked to quaternized membranes, demonstrating that the crosslinking reaction and the incorporation of DABCO have occurred, while the 13C-NMR corroborates the reaction of DABCO with PVBC only by one nitrogen atom. Mechanical properties were evaluated, obtaining maximum stress values around 72 MPa and 40 MPa for crosslinked and quaternized membranes, respectively. Resistance to oxidative media was also satisfactory and the membranes were evaluated in single direct ethanol fuel cell. PBI-c-PVBC/OH 1:2 membrane obtained 66 mW cm-2 peak power density, 25% higher than commercial PBI membranes, using 0.5 bar backpressure of pure O2 in the cathode and 1 mL min-1 KOH 2M EtOH 2 M aqueous solution in the anode. When the pressure was increased, the best performance was obtained by the same membrane, reaching 70 mW cm-2 peak power density at 2 bar O2 backpressure. Based on the characterization and single cell performance, PBI-c-PVBC/OH membranes are considered promising candidates as anion exchange electrolytes for direct ethanol fuel cells.

Liquid-polymer triboelectricity: chemical mechanisms in the contact electrification process.

Liquid-polymer contact electrification between sliding water drops and the surface of polytetrafluoroethylene (PTFE) was studied as a function of the pH and ionic strength of the drop as well as ambient relative humidity (RH). The PTFE surface was characterized by using SEM, water-contact-angle measurements, FTIR spectroscopy, XPS, and Raman spectroscopy. The charge acquired by the drops was calculated by detecting the transient voltage induced on a specifically designed capacitive sensor. It is shown that water drops become positively charged at pH > pHzch (pHzch being the zero charge point of the polymer) while they become negatively charged for pH < pHzch. The addition of non-hydrolysable salts (NaCl or CaCl2) to water decreases the electrical charge induced in the drop. The charge also decreases with increasing RH. These results suggest proton or hydroxyl transfer from the liquid to the hydrophobic polymer surface. A proposed thermodynamic model for the ion transfer process allows explaining the observed effects of RH, pH and ionic strength.

Synthesis and antiviral activity of some imidazo[1,2-b][1,3,4]thiadiazole carbohydrate derivatives.

Herein we describe the synthesis of imidazo[2,1-b][1,3,4]thiadiazoles from carbohydrates with D-ribo and D-xylo configuration. The antiviral activity of these compounds was tested against Junín virus (the etiological agent of Argentine hemorrhagic fever). The p-chlorophenyl derivatives showed antiviral activity in a range of micromolar concentration.

Modified ribavirin analogues as antiviral agents against Junín virus.

In this work, several ribavirin analogues were synthesized and incorporated into a multivalent arrangement. Both were subsequently modified by the addition of polyhydroxylated residues. Their antiviral activity was tested against Junín virus, etiological agent responsible of Argentine hemorrhagic fever. Some compounds inhibited Junín virus in the range of 13.2-389.1 µM. Two modified ribavirin analogues presented an effective concentration comparable to ribavirin but with a higher selectivity index.

Synthesis and in vitro antiproliferative activities of (5-aryl-1,2,4-oxadiazole-3-yl) methyl d-ribofuranosides.

The emergence of multidrug resistance cell lines is one of the major obstacles in the success of cancer chemotherapeutic treatment. Therefore, it remains a big challenge the development of new and effective drugs to defeat cancer. The presence of nitrogen heterocycles in the architectural design of drugs has led to the discovery of new leading compounds. Herein, we report the synthesis, characterization and in vitro antiproliferative activity against six cancer cell lines of d-ribofuranoside derivatives bearing a 1,2,4-oxadiazolic ring, with the aim of developing new active compounds. Most of these derivatives exhibit significant antiproliferative activities in the micromolar range. Noteworthy, the most potent compound of the series showed better selectivity towards the more resistant colon cancer cell line WiDr.

High-Energy Dissipation Performance in Epoxy Coatings by the Synergistic Effect of Carbon Nanotube/Block Copolymer Conjugates.

Hierarchical assembly of hard/soft nanoparticles holds great potential as reinforcements for polymer nanocomposites with tailored properties. Here, we present a facile strategy to integrate polystyrene-grafted carbon nanotubes (PSgCNT) (0.05-0.3 wt %) and poly(styrene-b-[isoprene-ran-epoxyisoprene]-b-styrene) block copolymer (10 wt %) into epoxy coatings using an ultrasound-assisted noncovalent functionalization process. The method leads to cured nanocomposites with core-shell block copolymer (BCP) nanodomains which are associated with carbon nanotubes (CNT) giving rise to CNT-BCP hybrid structures. Nanocomposite energy dissipation and reduced Young's Modulus (E*) is determined from force-distance curves by atomic force microscopy operating in the PeakForce QNM imaging mode and compared to thermosets modified with BCP and purified carbon nanotubes (pCNT). Remarkably, nanocomposites bearing PSgCNT-BCP conjugates display an increase in energy dissipation of up to 7.1-fold with respect to neat epoxy and 53% more than materials prepared with pCNT and BCP at the same CNT load (0.3 wt %), while reduced Young's Modulus shows no significant change with CNT type and increases up to 25% compared to neat epoxy E* at a CNT load of 0.3 wt %. The energy dissipation performance of nanocomposites is also reflected by the lower wear coefficients of materials with PSgCNT and BCP compared to those with pCNT and BCP, as determined by abrasion tests. Furthermore, scanning electron microscopy (SEM) images taken on wear surfaces show that materials incorporating PSgCNT and BCP exhibit much more surface deformation under shear forces in agreement with their higher ability to dissipate more energy before particle release. We propose that the synergistic effect observed in energy dissipation arises from hierarchical assembly of PSgCNT and BCP within the epoxy matrix and provides clues that the CNT-BCP interface has a significant role in the mechanisms of energy dissipation of epoxy coating modified by CNT-BCP conjugates. These findings provide a means to design epoxy-based coatings with high-energy dissipation performance.

Improving bone cement toughness and contrast agent confinement by using acrylic branched polymers.

A new biomedical material to be used as part of acrylic bone cement formulations is described. This new material is tough, its Young's Modulus is similar to the one of poly (methylmethacrylate) and the contrast agent, usually employed in acrylic bone cements, is homogeneously distributed among the polymeric matrix. Additionally, its wear coefficient is 66% lower than the one measured in poly(methyl methacrylate). The developed material is a branched polymer with polyisoprene backbone and poly(methyl methacrylate) side chains, which are capable of retaining barium sulphate nanoparticles thus avoiding their aggregation. The grafting reaction was carried out in presence of the nanoparticles, using methyl methacrylate as solvent. From the (1)H-NMR spectra it was possible to determine the average number of MMA units per unit of isoprene (3.75:1). The ability to retain nanoparticles (about 8wt.%), attributed to their interaction with the polymer branches, was determined by thermogravimetric analysis and confirmed by FTIR and microscopy techniques. By SEM microscopy it was also possible to determine the homogeneous spatial distribution of the barium sulphate nanoparticles along the polymer matrix.

Antiviral activity of an N-allyl acridone against dengue virus.

BACKGROUND: Dengue virus (DENV), a member of the family Flaviviridae, is at present the most widespread causative agent of a human viral disease transmitted by mosquitoes. Despite the increasing incidence of this pathogen, there are no antiviral drugs or vaccines currently available for treatment or prevention. In a previous screening assay, we identified a group of N-allyl acridones as effective virus inhibitors. Here, the antiviral activity and mode of action targeted to viral RNA replication of one of the most active DENV-2 inhibitors was further characterized. RESULTS: The compound 10-allyl-7-chloro-9(10H)-acridone, designated 3b, was active to inhibit the in vitro infection of Vero cells with the four DENV serotypes, with effective concentration 50% (EC50) values in the range 12.5-27.1 µM, as determined by virus yield inhibition assays. The compound was also effective in human HeLa cells. No cytotoxicity was detected at 3b concentrations up to 1000 µM. Mechanistic studies demonstrated that virus entry into the host cell was not affected, whereas viral RNA synthesis was strongly inhibited, as quantified by real time RT-PCR. The addition of exogenous guanosine together with 3b rescued only partially the infectivity of DENV-2. CONCLUSIONS: The acridone derivative 3b selectively inhibits the infection of Vero cells with the four DENV serotypes without a direct interaction with the host cell or the virion but interfering specifically with the intracellular virus multiplication. The mode of antiviral action for this acridone apparently involves the cellular enzyme inosine-monophospahe dehydrogenase together with another still unidentified target related to DENV RNA synthesis.

Differential effect of heterocyclic D-ribofuranoside derivatives on human prostate cancer cell viability and cell cycle progression.

New d-ribofuranoside derivatives containing two five membered heterocycles, isoxazole and triazole or two triazole rings, were synthesized. The final products as well as the synthetic precursors were physically and spectroscopically characterized. These new diheterocyclic derivatives together with other d-riboside compounds were assessed for their impact on PC3 cell line viability. We found that exposure of prostate cancer cells to some of these compounds caused a significant inhibition of cell growth and a G0/G1 cell cycle arrest, which was concomitant with alterations in the expression of proteins involved in cell cycle progression. Furthermore, the inhibitory activity was improved in di-heterocycles when the carbohydrate moiety was protected with a cyclopentylidene group compared to the isopropylidene analogues.

Acrylic bone cements: the role of nanotechnology in improving osteointegration and tunable mechanical properties.

Nanotechnology is an extremely powerful emerging technology, which is expected to have a substantial impact on biomedical technology, especially in tissue engineering and drug delivery. The use of nanocompounds and nanoparticles in the synthesis of improved bone cements to be applied in vertebroplasty/kyphoplasty and arthroplasty, is of great interest due to the increasing incidence of osteoporosis and osteoarthritis. This review reports new advances in the development of acrylic bone cements, using different radio-opalescent nanomaterials taking into consideration their influence on the mechanical behavior and biocompatibility of the resulting acrylic bone cement. Furthermore, other non-radiopaque nanoparticles capable of mechanically reinforcing the bone cement as well as induce osteointegration, are also reviewed. Additionally, nanoparticles used to improve the controlled release of antibiotics contained in acrylic bone cements are briefly described.

Inhibition of Junin virus RNA synthesis by an antiviral acridone derivative.

There are no specific approved drugs for the treatment of agents of viral hemorrhagic fevers (HF) and antiviral therapies against these viruses are urgently needed. The present study characterizes the potent and selective antiviral activity against the HF causing arenavirus Junin virus (JUNV) of the compound 10-allyl-6-chloro-4-methoxy-9(10H)-acridone, designated 3f. The effectiveness of 3f to inhibit JUNV multiplication was not importantly affected by the initial multiplicity of infection, with similar effective concentration 50% (EC(50)) values in virus yield inhibition assays performed in Vero cells in the range of 0.2-40 plaque forming units (PFU)/cell. Mechanistic studies demonstrated that 3f did not affect the initial steps of adsorption and internalization. The subsequent process of viral RNA synthesis was strongly inhibited, as quantified by real time RT-PCR in compound-treated cells relative to non-treated cells. The addition of exogenous guanosine rescued the infectivity and RNA synthesis of JUNV in 3f-treated cells in a dose-dependent manner, but the reversal was partial, suggesting that the reduction of the GTP pool contributed to the antiviral activity of 3f, but it was not the main operative mechanism. The comparison of 3f with two other viral RNA inhibitors, ribavirin and mycophenolic acid, showed that ribavirin did not act against JUNV through the cellular enzyme inosine monophosphate dehydrogenase (IMPDH) inhibition whereas the anti-JUNV activity of mycophenolic acid was mainly targeted at this enzyme.

1,2,4-Triazole D-ribose derivatives: design, synthesis and antitumoral evaluation.

Herein we report the design, synthesis and characterization of novel 1,2,4-triazole d-ribose derivatives, as well as their synthetic precursors. The antitumoral activity against T cell lymphoma cell line of these products was studied. Structures containing a 1,2,4-triazolic ring linked by sulfur to the carbohydrate moiety showed a moderate antiproliferative activity. The presence of the second heterocyclic ring did not show significant changes in their biological activity. Meanwhile, structures with 3-thiobenzyl-5-substituted-1,2,4-triazole ring linked by nitrogen leads to compounds with a biphasic behavior, stimulating cell proliferation at low concentrations and inhibiting it at higher ones. An increment in the polarity was associated with a decrease in the activity of the evaluated compounds. A preliminary antitumoral screening pointed the 1,2,4-triazolic structures linked to protected sugars as promising leaders for further studies.

Imidazo[2,1-b]thiazole carbohydrate derivatives: Synthesis and antiviral activity against Junin virus, agent of Argentine hemorrhagic fever.

Herein, we describe the syntheses of 3,5-disubstituted imidazo[2,1-b]thiazole. The cyclization step was performed in two different conditions by using either thermal or microwave heating. Comparing the results of both methodologies, we found that the microwave assistance is an improved alternative to obtain this family of heterocyclic compound. Compounds were first evaluated for cytotoxicity in Vero cells by MTT method and then, the antiviral activity was assayed by a virus yield inhibition assay in the range of concentrations lower than the corresponding CC(50), using JUNV strain IV4454 as the model system. The most active compounds (3 and 4), showed a level of antiviral activity against JUNV in monkey Vero cells better than the reference substance ribavirin. Then, they are promising lead compound for further analysis and characterization to establish their therapeutic potential against hemorrhagic fever viruses.

In vitro effect of a new cinnamic acid derivative against the epimastigote form of Trypanosoma cruzi.

An intensive effort has been directed toward finding alternative drugs for treatment of Chagas' disease, caused by Trypanosoma cruzi (T. cruzi), and prophylaxis of blood in endemic areas. The preparation and in vitro evaluation as potential anti-protozoal agent of (2E)-N-(1,3-benzothiazol-2-yl)-3-(2,5-dimethoxyphenyl)-2-propenamide (CAD-1) is presented. The results show that 0.05 mM CAD-1 induced 58.1% of T. cruzi epimastigotes death; mainly by apoptosis. The diminution in the transmembrane mitochondrial electrical potential together with the increase in the intracellular generation/accumulation of reactive oxygen species, suggest the parasites mitochondria as the main target for CAD-1-induced death. The concentration of 0.05 mM CAD-1 is not low enough to consider it as a potent tripanocydal agent. However the novel mechanism that induces T. cruzi death, together with the novelty of its chemical structure, point out CAD-1 as a head group compound that could serve as a template to obtain new, more potent anti-Chagas disease agents.

Effect of energy density on color stability in dental resin composites under accelerated aging.

The effects of the energy density that is used for polymerization on properties of dental resin composites are well known. However, few studies relate color stability to this factor. The aim of this study was to assess color changes (deltaE*), in vitro, in terms of accelerated aging under UV exposure of specimens prepared with different energy densities. Four commercial dental resin composites were included in the study. Thirty six specimens were prepared for each one of them, following the procedure established by ISO 4049 Standard, and assigned to three groups: A (3.75 J/cm2), B (9 J/cm2), C (24 J/cm2). Each group was further subdivided into four subgroups: 1 (no aging), 2 (500 hours aging), 3 (1000 hours aging) and 4 (1500 hours aging). The results were analyzed by means of ANOVA and Tukey's test (alpha = 0.05) to determine the effect of the factors. Correlation was performed in order to determine the possible relationship among variables. Energy density is not a significant factor in color stability. However aging is directly proportional to color changes. deltaE* depends on filler size; hybrid material presented deltaE* of 2.1(0.5), 2.4(0.6) and 3.3(0.3) at 500, 1000 and 1500 hours of accelerated aging respectively, and nanofilled material showed deltaE* of 3.0(0.6), 4.5(1.2) and 5.9(0.6) at the same times respectively. It can be concluded that deltaE* does not depend on energy density; however other factors are involved in color change. Further studies in this area are warranted.

Synthesis and antiviral activity of azoles obtained from carbohydrates.

Herein we describe the synthesis of 1,2,4-triazolyl-3-thione;1,3,4-oxadiazole, and imidazo[2,1-b]thiazole derivatives from carbohydrates. The antiviral activity of these compounds was tested against Dengue and Junin virus (the etiological agent of Argentine hemorrhagic fever). The 3-(p-bromobenzoyl)-5-(1,2-O-isopropylidene-3-O-methyl-alpha-d-xylofuranos-5-ulos-5-yl)imidazo[2,1-b]thiazole was able to inhibit the replication of both viruses in Vero cells at concentration significantly lower than the CC(50).