In situ synthesis of bacterial cellulose/polycaprolactone blends for hot pressing nanocomposite films production.

A series of bacterial cellulose (BC)/polycaprolactone (PCL) nanocomposite films were successfully prepared by supplementation of the BC culture medium with variable amounts of PCL powder followed by hot-pressing of the BC/PCL mixtures obtained after incubation. PCL powder was fully incorporated into the BC network during its production and did not change the BC network morphology. The obtained films showed a homogenous distribution of PCL throughout the BC network, as well as good thermal stability (up to 200 °C) and improved mechanical properties, when compared to pristine PCL. In addition, the intrinsic biodegradability and biocompatibility of the nanocellulose fibers and PCL opens the possibility of using this novel nanocomposite in the biomedical field and food packaging. The BC biosynthetic approach combined with the hot-pressing proved successful for the sustainable development of nanocomposites combining hydrophobic thermoplastic matrices and hydrophilic nanocellulose fibers, without the use of harmful organic solvents commonly used to dissolve this type of polymeric matrices.

Unveiling the chemistry behind the green synthesis of metal nanoparticles.

Nanobiotechnology has emerged as a fundamental domain in modern science, and metallic nanoparticles (NPs) are one of the largest classes of NPs studied because of their wide spectrum of possible applications in several fields. The use of plant extracts as reducing and stabilizing agents in their synthesis is an interesting and reliable alternative to conventional methodologies. However, the role of the different components of such extracts in the reduction/stabilization of metal ions has not yet been understood clearly. Here we studied the behavior of the main components of a Eucalyptus globulus Labill. bark aqueous extract during metal-ion reduction followed by advanced chromatographic techniques, which allowed us to establish their specific role in the process. The obtained results showed that phenolic compounds, particularly galloyl derivatives, are mainly responsible for the metal-ion reduction, whereas sugars are essentially involved in the stabilization of the NPs.

Protein-based materials: from sources to innovative sustainable materials for biomedical applications.

Proteins display an essential role in numerous natural systems due to their structural and biological properties. Given their unique properties, proteins have been thoroughly investigated in the last few decades, offering a myriad of solutions for the development of innovative biomaterials, including films, foams, composites and gels, in particular for biomedical applications such as drug delivery systems, biosensors and scaffolds for tissue regeneration. In this context, this review intends to give a general overview of the potential of protein based materials within the sustainable polymers context, covering aspects ranging from protein types, selection/isolation to properties of protein based (nano)materials and biomedical applications, passing through preparation methodologies of materials.

Biocompatible bacterial cellulose-poly(2-hydroxyethyl methacrylate) nanocomposite films.

A series of bacterial cellulose-poly(2-hydroxyethyl methacrylate) nanocomposite films was prepared by in situ radical polymerization of 2-hydroxyethyl methacrylate (HEMA), using variable amounts of poly(ethylene glycol) diacrylate (PEGDA) as cross-linker. Thin films were obtained, and their physical, chemical, thermal, and mechanical properties were evaluated. The films showed improved translucency compared to BC and enhanced thermal stability and mechanical performance when compared to poly(2-hydroxyethyl methacrylate) (PHEMA). Finally, BC/PHEMA nanocomposites proved to be nontoxic to human adipose-derived mesenchymal stem cells (ADSCs) and thus are pointed as potential dry dressings for biomedical applications.

Antibacterial activity of nanocomposites of copper and cellulose.

The design of cheap and safe antibacterial materials for widespread use has been a challenge in materials science. The use of copper nanostructures combined with abundant biopolymers such as cellulose offers a potential approach to achieve such materials though this has been less investigated as compared to other composites. Here, nanocomposites comprising copper nanofillers in cellulose matrices have been prepared by in situ and ex situ methods. Two cellulose matrices (vegetable and bacterial) were investigated together with morphological distinct copper particulates (nanoparticles and nanowires). A study on the antibacterial activity of these nanocomposites was carried out for Staphylococcus aureus and Klebsiella pneumoniae, as pathogen microorganisms. The results showed that the chemical nature and morphology of the nanofillers have great effect on the antibacterial activity, with an increase in the antibacterial activity with increasing copper content in the composites. The cellulosic matrices also show an effect on the antibacterial efficiency of the nanocomposites, with vegetal cellulose fibers acting as the most effective substrate. Regarding the results obtained, we anticipate the development of new approaches to prepare cellulose/copper based nanocomposites thereby producing a wide range of interesting antibacterial materials with potential use in diverse applications such as packaging or paper coatings.

Formation of oligomeric alkenylperoxides during the oxidation of unsaturated fatty acids: an electrospray ionization tandem mass spectrometry study.

This study reports the identification of oligomeric alkenylperoxides by electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS(2)), during the oxidation of oleic, linoleic and linolenic acids with Fenton's (Fe(2+)/H(2)O(2)) and Fe(2+)/O(2) systems. The reactions were followed by ferrous oxidation-xylenol orange method together with GC-MS and GC-FID, allowing to observe that both oxidation systems are different in terms of hydroperoxide evolution, probably due to the presence of different intermediate reactive species: perferryl ion and OH(·) radical responsible for the decomposition of lipid hydroperoxides and formation of new compounds. The analysis of ESI-MS in the negative mode, obtained after oxidation of each fatty acid, confirmed the presence of the monomeric oxidation products together with other compounds at high mass region above m/z 550. These new ions were attributed to oligomeric structures, identified by the fragmentation pathways observed in the tandem mass spectra.

Characterization of phenolic components in polar extracts of Eucalyptus globulus Labill. bark by high-performance liquid chromatography-mass spectrometry.

High-performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS) and tandem mass spectrometry (MS(n)) were used to investigate the phenolic constituents in methanol, water, and methanol/water extracts of Eucalyptus globulus Labill. bark. Twenty-nine phenolic compounds were identified, 16 of them referenced for the first time as constituents of E. globulus bark, namely, quinic, dihydroxyphenylacetic, and caffeic acids, bis(hexahydroxydiphenoyl (HHDP))-glucose, galloyl-bis(HHDP)-glucose, galloyl-HHDP-glucose, isorhamentin-hexoside, quercetin-hexoside, methylellagic acid (EA)-pentose conjugate, myricetin-rhamnoside, isorhamnetin-rhamnoside, mearnsetin, phloridzin, mearnsetin-hexoside, luteolin, and a proanthocyanidin B-type dimer. Digalloylglucose was identified as the major compound in the methanol and methanol/water extracts, followed by isorhamnetin-rhamnoside in the methanol extract and by catechin in the methanol/water extract, whereas in the water extract catechin and galloyl- HHDP-glucose were identified as the predominant components. The methanol/water extract was shown be the most efficient to isolate phenolic compounds identified in E. globulus bark.

Preparation of highly hydrophobic and lipophobic cellulose fibers by a straightforward gas-solid reaction.

This work describes a very simple, rapid, and efficient approach to the hydrophobization and lipophobization of cellulose fibers through their reaction with gaseous trichloromethylsilane (TCMS). The characterization of the modified surface involved FTIR-ATR and solid-state (29)Si NMR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements with different liquids. The modification generated an inorganic coating around the fibers, associated with the construction of a three-dimensional network of Si-O-Si bridges partly bound to the polysaccharide macromolecules. This coating conferred both a high hydrophobicity and a lipophobicity to the samples even when the treatments applied modest TCMS quantities and reaction times as short as 30 s. The green connotation of this novel process constitutes an additional positive feature.

Suberin of potato (Solanum tuberosum var. Nikola): comparison of the effect of cutinase CcCut1 with chemical depolymerization.

Chemical and enzymatic depolymerizations of suberin isolated from potato peel ( Solanum tuberosum var. Nikola) were performed under various conditions. Enzymatic hydrolysis with cutinase CcCut1 and chemical methanolysis with NaOMe of suberin yielded monomeric fragments, which were identified as TMS derivatives with GC-MS and GC-FID. The solid, hydrolysis-resistant residues were analyzed with solid state (13)C CPMAS NMR, FT-IR, and microscopic methods. Methanolysis released more CHCl(3)-soluble material than the cutinase treatment when determined gravimetrically. Interestingly, cutinase-catalyzed hydrolysis produced higher proportions of aliphatic monomers than hydrolysis with the NaOMe procedure when analyzed by GC in the form of TMS derivatives. Monomers released by the two methods were mainly alpha,omega-dioic acids and omega-hydroxy acids, but the ratios of the detected monomers were different, at 40.0 and 32.7% for methanolysis and 64.6 and 8.2% for cutinase, respectively. Thus, cutinase CcCut1 showed higher activity toward ester bonds of alpha,omega-dioic acids than toward the bonds of omega-hydroxy acids. The most abundant monomeric compounds were octadec-9-ene-1,18-dioic acid and 18-hydroxyoctadec-9-enoic acid, which accounted for ca. 37 and 28% of all monomers, respectively. The results of the analyses of the chemical and enzymatic hydrolysis products were supported by the spectroscopic analyses with FT-IR and CPMAS (13)C NMR together with the analysis of the microstructures of the hydrolysis residues by light and confocal microscopy.

Determination of the hydroxy and carboxylic acid groups in natural complex mixtures of hydroxy fatty acids by 1H nuclear magnetic resonance spectroscopy.

The use of trichloroacetyl isocyanate (TAI) to mark both hydroxyl and carboxyl groups borne by the hydrolysis or methanolysis of suberin fragments (a complex mixture of hydroxy fatty acids), allowed the quantitative assessment of the ratio between carboxyl and hydroxy groups, as well as the ratio between primary and secondary hydroxy groups, to be carried out reliably by 1H nuclear magnetic resonance (NMR) spectroscopy. All the samples thus analyzed displayed an excess of CO2H (or CO2CH3) functions with respect to the OH counterparts, albeit to a variable extent, depending on the procedure adopted to isolate the suberin fragments. The precise knowledge of the molar ratio of these two reactive moieties is fundamental for the correct utilization of suberin monomers in polymerization reactions leading to aliphatic polyesters.

Synthesis and characterization of novel biopolyesters from suberin and model comonomers.

The synthesis of novel polyesters from model long-chain aliphatic monomers and from suberin reactive aliphatic fragments was conducted using mild polycondensation or polytransesterification conditions. The ensuing polyesters were characterized by means of various techniques. When mixtures of simple suberin-like monomers were used, the ensuing polyesters had very regular structures, with melting temperatures around 80 degrees C and glass transitions below room temperature. This first systematic study of the exploitation of suberin as a precursor to novel aliphatic polyesters confirmed the huge potential of using this abundant renewable resource to prepare macromolecular materials for promising applications.

What is the real value of chitosan's surface energy?

Because of conflicting reports and unrealistic literature values, a systematic study of the surface energy of chitin, chitosan, and their respective monomeric counterparts was carried out using contact angle measurements on films and pellets, before and after different purification procedures. All the commercial samples of these polymers were shown to contain nonpolar impurities that gave rise to enormous errors in the determination of the polar component of their surface energy. After their thorough removal, the value of the total surface energy (gamma(s)), and particularly of its polar component, increased considerably and reached the classical polysaccharide figures of gamma(s)d approximately 30 and gamma(s)p approximately 30 mJ/m2. The characterization of the impurities by gas chromatography/mass spectrometry analysis indicated the presence of significant amounts of higher alkanes, fatty acids, and alcohols and sterols.

Highly hydrophobic biopolymers prepared by the surface pentafluorobenzoylation of cellulose substrates.

New highly hydrophobic/lipophobic biopolymers were prepared by the controlled heterogeneous pentafluorobenzoylation of cellulose substrates, i.e., plant and bacterial cellulose fibers. The characterization of the modified fibers was performed by elemental analysis, FTIR spectroscopy, X-ray diffraction, thermogravimetry, and surface analysis (XPS, ToF-SIMS, and contact angle measurements). The degree of substitution of the ensuing pentafluorobenzoylated fibers ranged from 0.014 to 0.39. The hydrolytic stability of these perfluorinated cellulose derivatives was also evaluated and showed that they were quite water stable, although of course the fluorinated moieties could readily be removed by hydrolysis in an aqueous alkaline medium.

Triterpenic and other lipophilic components from industrial cork byproducts.

The detailed chemical composition of the lipophilic extractives of cork and cork byproducts generated throughout industrial processing has been investigated by gas chromatography-mass spectrometry. Triterpenes (cerine, friedeline, and betulinic acid) were the major components detected. Betulinic acid is the main triterpene (11.7 g/kg) identified in industrial cork powder, whereas in black condensates friedeline (95.3 g/kg), betuline (13.1 g/kg), and betulinic acid (12.1 g/kg) are the main triperpenes. Significant fractions of alpha-hydroxy fatty acids (115.1 g/kg) and alpha,omega-dicarboxylic acids (21.2 g/kg) were also detected in black condensate after alkaline hydrolysis. The results demonstrate that these two industrial byproducts can be considered as promising sources of bioactive chemicals or chemical intermediates for the synthesis of polymeric materials.

Surface characterization by XPS, contact angle measurements and ToF-SIMS of cellulose fibers partially esterified with fatty acids.

The topochemistry of the controlled heterogeneous esterification of cellulose fibers with fatty acid chlorides of different chain length, both in swelling and non-swelling media, was assessed by X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and contact angle measurements. On the one hand, the results provided by the combined use of these three powerful techniques showed unambiguously the occurrence of the reaction at the fibers' surface and, on the other hand, the XPS results showed that the surface coverage with the fatty acid moieties increased with their chain length, but was only modestly affected by the degree of substitution (DS), suggesting that when the esterification yield was increased (higher DS values), an in-depth reaction also occurred, particularly when DMF was used as a cellulose swelling medium, involving the OH groups buried below the fibers' surface.

Effect of oxygen, ozone and hydrogen peroxide bleaching stages on the contents and composition of extractives of Eucalyptus globulus kraft pulps.

The effects of oxygen (O), ozone (Z) and hydrogen peroxide (P) bleaching stages on the composition and total amount of Eucalyptus globulus kraft pulp lipophilic extractives was studied. These bleaching stages led to the partial removal and to several oxidative transformations of fatty acids and sterols, the main lipophilic extractives found in the unbleached pulp. Unsaturated extractives were found to be partially degraded while saturated ones were, in general, stable. The oxygen and hydrogen peroxide bleaching stages were more effective than ozone in removing fatty acids from pulp, by dissolution in the liquid phase. On the other hand, the ozone stage was more effective in the oxidative degradation of sterols. Oxygen and hydrogen peroxide bleaching stages were also effective in sterols removal, but led to the formation of sterol oxidation derivatives, previously shown to be involved in the formation of pitch that accumulates in the bleaching filtrates.

Chemical composition of the epicuticular wax from the fruits of Eucalyptus globulus.

The chemical composition of the epicuticular wax from the fruits of Eucalyptus globulus was studied by GC-MS before and after alkaline hydrolysis. The wax had two main components, ursolic acid and tritriacontan-16,18-dione, together with several other triterpenic acids. After alkaline hydrolysis, a large increase in the amounts of triterpenic acids and fatty acids (particularly in hexadecanoic acid) was observed, suggesting that these components were present predominantly in esterified forms in the fruit wax. Six compounds were isolated from the fruits by preparative chromatography, and were identified as 8-desmethyleucalyptin, sesamin, tritriacontan-16,18-dione, ursolic acid, 3beta-hydroxyurs-11-en-13beta(28)-olide (ursolic acid lactone) and 3beta,11alpha-dihydroxyurs-12-en-28-oic acid, the latter of which was identified for the first time.

Chemical composition and structural features of the macromolecular components of plantation Acacia mangium wood.

The wood of Acacia mangium, a prominent fast-growing plantation species used in the pulp-and-paper industry and, so far, poorly investigated for its chemical structure, was submitted to a detailed characterization of its main macromolecular components. Lignin (28% wood weight) isolated by mild acidolysis and characterized by permanganate oxidation, 1H and 13C NMR, and GPC, showed a very low content of syringylpropane-derived units (S:G:H of 48:49:3), a high degree of condensation, a low content of beta-O-4 ( approximately 0.40-0.43 per C6) structures, and a Mw of 2230. Glucuronoxylan (14% wood weight) isolated by alkaline (KOH) or by dimethyl sulfoxide extraction was characterized by methylation analysis, 1H NMR, and GPC. About 10% of the xylopyranose (Xylp) units constituting the linear backbone were substituted at O-2 with 4-O-methylglucuronic acid residues. Almost half of the Xylp units (45%) were O-2 (18%), O-3 (24%) or O-2,3 (3%) acetylated. X-ray diffraction analysis of cellulose (46% wood weight), isolated according to the Kürschner-Hoffer method, showed a degree of crystallinity of 67.6%.

Identification of delta7 phytosterols and phytosteryl glucosides in the wood and bark of several Acacia species.

The wood and bark of four Acacia species growing in Portugal, namely, A. longifolia, A. dealbata, A. melanoxylon, and A. retinodes, were investigated for their sterol content. The lipids fractions of the different wood and bark samples were isolated, and the sterols were identified and quantified by GC-MS. Two delta7 sterols, specifically, spinasterol and dihydrospinasterol, were the main sterols found in considerable amounts, particularly in wood tissues (more than 0.5 g/kg of dry wood in the case of A. melanoxylon and A. retinodes). The corresponding unusual steryl glucosides were also identified in significant amounts in the wood and bark extracts.