Sonochemical Formation of Iodohydrin and Epoxide from Cyclohexene

Ultrasonic irradiation substantially improves the reaction of cyclohexene with I₂ in aqueous dioxane in the presence of Cu(OAc)₂ · H₂O to generate the expected iodohydrin in high yield. The product undergoes cyclization to the epoxide by biphasic treatment with either Na₂CO₃ or KOH in a sonication‐sensitive step.     

Thermal and photochemical effects on the structure,morphology, thermal and optical properties of PVA/Ni0.04Zn0.96O and PVA/Fe0.03Zn0.97O nanocomposite films

Ni_0.04Zn_0.96O and Fe_0.03Zn_0.97O with average diameter of 23 and 19 nm, respectively, have been synthesized by a modified sol–gel method to be used in the preparation of (100 − x)/x poly(vinyl alcohol)/oxide nanocomposite films, with x = 0, 1, 3 and 5 (in wt.%). A 125 W-Hg vapor lamp with emission above 254 nmwas used to irradiate PVA/Ni_0.04Zn_0.96O and PVA/Fe_0.03Zn_0.97O films. The effect on their structural, thermal, morphological and optical properties was studied by TG, DSC, DRX, AFM, UV–vis and PL spectrophotometry. The Ni_0.04Zn_0.96O addition on PVA films decreases the thermal stability of the polymer in inert and in oxidative atmosphere. In contrast, the Fe_0.03Zn_0.97O presence in the PVA films seems to increase the thermal stability of the polymer. The characteristic peak of the crystalline phase of PVA and wurtzite phase of the zinc oxide were identified through X-ray diffraction in both films. The crystallinity of the PVA film increases with UV irradiation and with the presence of Ni_0.04Zn_0.96O and Fe_0.03Zn_0.97O. The roughness of the PVA film was not modified by the addition of the doped oxides; however, it increases after UV irradiation, more significantly in the films containing the oxides. The PVA film exhibits absorption around 280 nm characteristic of π–π^∗ transitions related to carbonyl groups from residuals acetate, while the 95/05 PVA/Ni_0.04Zn_0.96O and 95/05 PVA/Fe_0.03Zn_0.97O nanocomposite films show absorption at the visible region which is characteristics of the band gap reduction of the doped oxides. The photoluminescence of PVA was modified by the presence of the oxides in the film. These nanocomposite films are interesting due to their thermal, mechanical (flexible) properties and low cost of production. In addition they are also able to exhibit peculiar optical properties showing potential to be used in photonic devices, gas sensors and organic solar cell applications.     

Radiolabeling of low molecular weight d-galactose-based glycodendrimer with technetium-99m and biodistribution studies

Glycodendrimers are neoglycoconjugates that can be considered as bioisosters of glycoproteins, since they can mimic the multivalent interactions of lectin-carbohydrate. The ability of glycodendrimers to present multivalent interactions with lectins as compared to a monovalent ligand is referred to as “cluster effect”. It is expected that, because of the cluster effect, glycodendrimers would result in a better association with lectins than mono-carbohydrate anchored systems. Radioisotopes are useful to evaluate biodistribution of molecules. This study is important to obtain information about molecule–receptor interactions. Indeed, such study can provide an exquisite tool to evaluate the affinity of certain molecules to specific areas in the body, leading to the development of new radiopharmaceuticals and/or drug delivery systems. Herein, we describe a d-galactose coated low molecular weight PAMAM G0 dendrimer that was successfully radiolabeled with technetium-99m. Biodistribution studies and scintigraphic images were performed in healthy mice. It was observed high liver uptake which was significantly reduced in blocking studies, indicating hepatic specificity. Therefore, low molecular weight glycodendrimer can be considered as useful platform for selective targeting of drugs to the liver and to assess hepatic function.     

The Effect of Biomass Immobilization Support Material and Bed Porosity on Hydrogen Production in an Upflow Anaerobic Packed-Bed Bioreactor

The aim of this study was to investigate the effect of the support material used for biomass attachment and bed porosity on the potential generation of hydrogen gas in an anaerobic bioreactor treating low-strength wastewater. For this purpose, an upflow anaerobic packed-bed (UAPB) reactor fed with sucrose-based synthetic wastewater was used. Three reactors with various support materials (expanded clay, vegetal coal, and low-density polyethylene) were operated for hydraulic retention time (HRT) of 0.5 and 2 h. Based on the results obtained, three further reactors were operated with low-density polyethylene as a material support using various bed porosities (91, 75, and 50 %) for an HRT of 0.5 h. The UAPB reactor was found to be a feasible technology for hydrogen production, reaching a maximum substrate-based hydrogen yield of 7 mol H₂ mol^?1 sucrose for an HRT of 0.5 h. The type of support material used did not affect hydrogen production or the microbial population inside the reactor. Increasing the bed porosity to 91 % provided a continuous and cyclic production of hydrogen, whereas the lower bed porosities resulted in a reduced time of hydrogen production due to biomass accumulation, which resulted in a decreasing working volume.     

Enzymatic syntheses of unsaturated polyesters based on isosorbide and isomannide

The search for materials produced from renewable sources aiming at the substitution of petroleum‐based derivates is an area of intense investigation. In this work, the enzymatic copolymerization of isosorbide or isomannide with diethyl adipate and fractions of different unsaturated diesters (diethyl itaconate, diethyl fumarate, diethyl glutaconate, and diethyl hydromuconate) were examined using CAL‐B as catalyst. The polyesters prepared using one‐step syntheses were characterized by SEC, NMR, and MALDI‐TOF MS. In addition, syntheses with linear diols were carried out in bulk to evaluate the reactivity of cyclic diols in producing unsaturated polyesters using enzymatic catalysis, as well as to evaluate the occurrence of addition side reactions on the double bonds. Isosorbide and isomannide yielded unsaturated polymers with values in the order of 4,000‐16,000 when fumarate or glutaconate esters were added in 5 mol % ratio against adipate. In all cases MALDI‐TOF confirmed the presence of unsaturated units. Although these polyesters have unreacted double bonds they are prone to crosslinking and ready to further functionalization, like anchoring bioactive molecules. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3881–3891     

The role of nanocellulose fibers, starch and chitosan on multipolysaccharide based films

Thin nanocomposite films of thermoplastic starch, chitosan and cellulose nanofibers (bacterial cellulose or nanofibrillated cellulose) were prepared for the first time by solvent casting of water based suspensions of the three polysaccharides. The role of the different bioploymers on the final properties (thermal stability, transparency, mechanical performance and antimicrobial activity) of the films was related with their intrinsic features, contents and synergic effects resulting from the establishment of interactions between them. Thermoplastic starch displays an important role on the thermal stability of the films because it is the most stable polysaccharide; however it has a negative impact on the mechanical performance and transparency of the films. The addition of chitosan improves considerably the transparency (up to 50 % transmittance for 50 % of chitosan, in respect to the amount of starch), mechanical performance and antimicrobial properties (at least 25 % of chitosan and no more than 10 % of cellulose nanofibers are required to observe bacteriostatic or bactericidal activity) but decrease their thermal stability. The incorporation of cellulose nanofibers had the strongest positive impact on the mechanical properties of the materials (increments of up to 15 and 30 MPa on the Young′s modulus and Tensile strength, respectively, for films with 20 % of BC or NFC). Nonetheless, the impact in thermal stability and mechanical performance of the films, promoted by the addition of chitosan and cellulose nanofibres, respectively, was higher than the expected considering their percentage contents certainly because of the establishment of strong and complex interactions between the three polysaccharides.     

Chemical Strategies for Dendritic Magneto-plasmonic Nanostructures Applied to Surface-Enhanced Raman Spectroscopy

Chemical analyses in the field using surface-enhanced Raman scattering (SERS) protocols are expected to be part of several analytical procedures applied to water quality monitoring. To date, these endeavors have been supported by developments in SERS substrate nanofabrication, instrumentation portability, and the internet of things. Here, we report distinct chemical strategies for preparing magneto-plasmonic (Fe₃O₄ : Au) colloids, which are relevant in the context of trace-level detection of water contaminants due to their inherent multifunctionality. The main objective of this research is to investigate the role of poly(amidoamine) dendrimers (PAMAMs) in the preparation of SERS substrates integrating both functionalities into single nanostructures. Three chemical routes were investigated to design magneto-plasmonic nanostructures that translate into different ways for assessing SERS detection by using distinct interfaces. Hence, a series of magneto-plasmonic colloids have been characterized and then assessed for their SERS activity by using a model pesticide (thiram) dissolved in aqueous samples.     

Antiprotozoal and Antibacterial Activity of Ravenelin,a Xanthone Isolated from the Endophytic Fungus Exserohilum rostratum

The natural compound ravenelin was isolated from the biomass extracts of Exserohilum rostratum fungus, and its antimicrobial, antiplasmodial, and trypanocidal activities were evaluated. Ravenelin was isolated by column chromatography and HPLC and identified by NMR and MS. The susceptibility of Gram-positive and Gram-negative bacteria strains to ravenelin was determined by microbroth dilution assay. Cytotoxicity was evaluated in hepatocarcinoma cells (HepG2) and BALB/c peritoneal macrophages by using MTT. SYBR Green I-based assay was used in the asexual stages of Plasmodium falciparum. Trypanocidal activity was tested against the epimastigote and intracellular amastigote forms of Trypanosoma cruzi. Ravenelin was active against Gram-positive bacteria strains, with emphasis on Bacillus subtilis (MIC value of 7.5 µM). Ravenelin’s antiparasitic activities were assessed against both the epimastigote (IC₅₀ value of 5 ± 1 µM) and the intracellular amastigote forms of T. cruzi (IC₅₀ value of 9 ± 2 µM), as well as against P. falciparum (IC₅₀ value of 3.4 ± 0.4 µM). Ravenelin showed low cytotoxic effects on both HepG2 (CC₅₀ > 50 µM) and peritoneal macrophage (CC₅₀ = 185 ± 1 µM) cells with attractive selectivity for the parasites (SI values > 15). These findings indicate that ravenelin is a natural compound with both antibacterial and antiparasitic activities, and considerable selectivity indexes. Therefore, ravenelin is an attractive candidate for hit-to-lead development.