Nanostructured composites obtained by ATRP sleeving of bacterial cellulose nanofibers with acrylate polymers.

Novel nanostructured composite materials based on bacterial cellulose membranes (BC) and acrylate polymers were prepared by in situ atom transfer radical polymerization (ATRP). BC membranes were functionalized with initiating sites, by reaction with 2-bromoisobutyryl bromide (BiBBr), followed by atom transfer radical polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA), catalyzed by copper(I) bromide and N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA), using two distinct initiator amounts and monomer feeds. The living characteristic of the system was proven by the growth of PBA block from the BC-g-PMMA membrane. The BC nanofiber sleeving was clearly demonstrated by SEM imaging, and its extent can be tuned by controlling the amount of initiating sites and the monomer feed. The ensuing nanocomposites showed high hydrophobicity (contact angles with water up to 134°), good thermal stability (initial degradation temperature in the range 241-275 °C), and were more flexible that the unmodified BC membranes.

Supercritical fluid extraction of Eucalyptus globulus bark-A promising approach for triterpenoid production.

Eucalyptus bark contains significant amounts of triterpenoids with demonstrated bioactivity, namely triterpenic acids and their acetyl derivatives (ursolic, betulinic, oleanolic, betulonic, 3-acetylursolic, and 3-acetyloleanolic acids). In this work, the supercritical fluid extraction (SFE) of Eucalyptus globulus deciduous bark was carried out with pure and modified carbon dioxide to recover this fraction, and the results were compared with those obtained by Soxhlet extraction with dichloromethane. The effects of pressure (100-200 bar), co-solvent (ethanol) content (0, 5 and 8% wt), and multistep operation were studied in order to evaluate the applicability of SFE for their selective and efficient production. The individual extraction curves of the main families of compounds were measured, and the extracts analyzed by GC-MS. Results pointed out the influence of pressure and the important role played by the co-solvent. Ethanol can be used with advantage, since its effect is more important than increasing pressure by several tens of bar. At 160 bar and 40 °C, the introduction of 8% (wt) of ethanol greatly improves the yield of triterpenoids more than threefold.

Effect of cationization pretreatment on the properties of cationic Eucalyptus micro/nanofibrillated cellulose.

Micro/nanofibrillated celluloses (M/NFCs) have attracted considerable research interest over the past few decades, with various pretreatments being used to reduce energy consumption and/or increase fibrillation. To date, few studies have considered cationization as a pretreatment for their preparation. In this work, quaternary ammonium groups were attached to cellulose fibers by a direct reaction with 2,3-epoxypropyltrimethylammonium chloride or by a two-step method (periodate oxidation + Girard's reagent T). The cationic fibers with degrees of substitution (DS) between 0.02 and 0.36, were subjected to homogenization treatment. The morphological properties, chemical composition, and rheological behavior were evaluated to assess the effect of DS and the effect of the cationization method (for samples with similar DS). The two-step cationization resulted in significant degradation of the cellulose structure, leading to the formation of short fibrils and solubilization of the material, ranging from 6% to almost complete solubilization at a DS of 0.36. Direct cationization resulted in longer fibrils with an average diameter of 1 µm, and no significant cellulose degradation was observed, leading to a more cohesive gel-like material (at 1 wt%). These observations clearly show the strong influence of the cationization method on the final properties of the cationic cellulosic materials.

Assessment of the Performance of Cationic Cellulose Derivatives as Calcium Carbonate Flocculant for Papermaking.

Cationic polyacrylamides (CPAMs) are usually used as filler retention agents in papermaking formulations. However, increasing environmental restrictions and their non-renewable origin have driven research into bio-based alternatives. In this context, cationic lignocellulosic derivatives have been attracting considerable research interest as a potential substitute. In this work, distinct cationic celluloses with degrees of substitution of between 0.02 and 1.06 and with distinct morphological properties were synthesized via the cationization of bleached eucalyptus kraft pulp, using a direct cationization with (3-chloro-2-hydroxypropyl) trimethylammonium chloride (CHPTAC) or a two-step cationization, where the cellulose was first oxidized to form dialdehyde cellulose and was then made to react with Girard's reagent T (GT). Fibrillated samples were produced by subjecting some samples to a high-pressure homogenization treatment. The obtained samples were evaluated regarding their potential to flocculate and retain precipitated calcium carbonate (PCC), and their performance was compared to that of a commercial CPAM. The cationic fibrillated celluloses, with a degree of substitution of ca. 0.13-0.16, exhibited the highest flocculation performance of all the cationic celluloses and were able to increase the filler retention from 43% (with no retention agent) to ca. 61-62% (with the addition of 20 mg/g of PCC). Although it was not possible to achieve the performance of CPAM (filler retention of 73% with an addition of 1 mg/g of PCC), the results demonstrated the potential of cationic cellulose derivatives for use as bio-based retention agents.

Cytotoxic activity of lignans from Hibiscus cannabinus.

The antimicrobial and cytotoxic activities of six lignans isolated from the core and bark acetone extracts of Hibiscus cannabinus have been investigated. Two compounds (2 and 3) showed strong cytotoxic activity against HeLa, Hep-2 and A-549 cell lines while compound 5 showed moderate activity on HeLa cells when they were in advanced stage of cellular division. The compounds did not exhibit antimicrobial activity.

Structural differentiation of uronosyl substitution patterns in acidic heteroxylans by electrospray tandem mass spectrometry.

The structures of two oligomers of acidic xylo-oligosaccharides (XOS) of the same molecular weight (634 Da), Xyl(2)MeGlcAHex and Xyl(2)GlcA(2) were differentiated by electrospray tandem mass spectrometry (ESI-MS/MS). These oligomers were present in a mixture of XOS obtained by acid hydrolysis of heteroxylans extracted from Eucalyptus globulus wood (Xyl(2)MeGlcAHex) and Olea europaea olive fruit (Xyl(2)GlcA(2)). In the ESI-MS spectra of the XOS, ions at m/z 657 and 652 were observed and assigned to [M + Na](+) and [M + NH(4)](+), respectively. The ESI-MS/MS spectrum of [M + Na](+) ion of Xyl(2)MeGlcAHex showed the loss of Hex residue from the reducing end followed by the loss of MeGlcA moiety. Simultaneously, the loss of a Xyl residue from either the reducing or the non-reducing ends was detected. On the other hand, the fragmentation of Xyl(2)GlcA(2) occurs mainly by the loss of one and two GlcA residues or by the loss of the GlcAXyl moiety, due to the glycosidic bond cleavage between the two Xyl residues. Loss of one and two CO(2) molecules was only observed for this oligomer, where the GlcA are in vicinal Xyl residues. The ESI-MS/MS spectra of [M + NH(4)](+) of both oligomers showed the loss of NH(3), resulting in the protonated molecule, where the presence of ions assigned as protonated molecules of aldobiuronic acid residues, [MeGlcA - Xyl + H](+) and [GlcA - Xyl + H](+), are diagnostic ions of the presence of MeGlcA and GlcA moieties in XOS. Since these structures occur in small amounts in complex acidic XOS mixtures and are very difficult, if possible, to isolate, tandem mass spectrometry revealed to be a powerful tool for the characterization of these types of substitution patterns present in heteroxylans.

Do bacterial cellulose membranes have potential in drug-delivery systems?

INTRODUCTION: Bacterial cellulose (BC) is an extremely pure form of cellulose, which, due to its unique properties, such as high purity, water-holding capacity, three-dimensional nanofibrilar network, mechanical strength, biodegradability and biocompatibility, shows a high potential as nanomaterial in a wide range of high-tech domains including biomedical applications, and most notably in controlled drug-delivery systems. AREAS COVERED: This appraisal is intended to cover the major characteristics of BC, followed by the key aspects of BC production both in static and agitated conditions, and a glance of the major applications of BC, giving some emphasis to biomedical applications. Finally, a detailed discussion of the different applications of BC in controlled drug-delivery systems will be put forward, with focus on topical and oral drug-delivery systems, using either native BC or composite materials thereof. EXPERT OPINION: The limited number of studies carried out so far demonstrated that BC, or materials prepared from it, are interesting materials for drug-delivery systems. There is, however, a large field of systematic research ahead to develop new and more selectively responsive materials and eventually to conjugate them with other biomedical applications of BC under development.

Electrospray tandem mass spectrometry of underivatised acetylated xylo-oligosaccharides.

Acetylated neutral (Xyl(n)Ac(m)) and acidic xylo-oligosaccharides (Xyl(n)Ac(m)MeGlcA, and Xyl(n)Ac(m)MeGlcAHex) obtained by partial acid hydrolysis of Eucalyptus globulus wood glucuronoxylans and fractionated by preparative ligand exchange/size-exclusion chromatography were identified by electrospray ionisation mass spectrometry (ESI-MS). Low molecular weight acetylated xylo-oligosaccharides were studied by ESI-tandem mass spectrometry (MS/MS). All the acetylated xylo-oligosaccharides showed an abundant ion due to the neutral loss of 60 Da (CH(3)CO(2)H) in the MS/MS spectra. The presence of diacetylated xylo-oligosaccharides was confirmed by the ions formed by loss of two molecules of acetic acid. Furthermore, characteristic [Xyl(res)Ac(2)+Na](+) and [XylAc(2)+Na](+) ions, and ions due to loss of XylAc(2), indicate that both acetyl groups are located in the same Xyl residue. On the other hand, losses of Xyl(res)Ac and XylAc are also observed as well as [Xyl(res)Ac+Na](+) and [XylAc+Na](+) , indicating the location of both acetyl groups in different Xyl residues, in some cases even in adjacent xyloses. The MS/MS spectra of triacetylated xylo-oligosaccharides were complex due to the presence of different isobaric xylo-oligosaccharides containing the acetyl groups at different locations in the xylo-oligosaccharide backbone. In the MS/MS spectra of acidic xylo-oligosaccharides, the ion at m/z 387, [Xyl(res)AcMeGlcA+Na](+), indicates that the acetyl groups are preferentially linked to Xyl substituted with MeGlcA. However, acidic xylo-oligosaccharides with the acetyl and 4-O-methylglucuronic acid groups in different Xyl residues were also identified. In neutral and in acidic xylo-oligosaccharides several possible locations of the acetyl groups were identified, namely at terminal positions. In summary, ESI-MS/MS is shown to be a powerful tool for the characterisation of acetylated patterns in complex mixtures of oligosaccharides.