Furfuryl alcohol/tung oil matrix-based composites reinforced with bacterial cellulose fibres.

Polymeric materials have drastically changed the society in the last century. However, their non-renewable origin, together with their indiscriminate use and disposal, resulted in a huge accumulation of waste in the environment and raised a wide discussion about the emission of greenhouse gases, which must be considerably reduced to minimize global warming. Thus, the establishment of a consolidated production of polymers prioritizing the use of renewable sources of raw materials became a hot research topic. Vegetable oils are protagonists of this initiative, and their carbon-carbon double bonds are convenient reactive sites for chain growth polymerization reactions. However, typical vegetable oil-based homopolymers often do not display competitive thermo-mechanical properties, and the preparation of the corresponding copolymers and composites is therefore an interesting alternative strategy. Herein, the preparation of composites based on a tung oil/furfuryl alcohol co-continuous network reinforced with bacterial cellulose fibers is described. For this purpose, the cellulose nanofibers were suspended in furfuryl alcohol, and different amounts of the ensuing suspension were mixed with tung oil in the presence of trifluoroacetic acid as cationic initiator. Fourier-transform infrared spectroscopy analysis of all samples indicated the association of both tung oil and furfuryl alcohol in the final materials, with peaks belonging to cellulose superposed at the fingerprint regions of composites. Differential scanning calorimetry and thermogravimetry demonstrated an interesting relationship between the composition and the corresponding thermal properties, and the morphology of the materials was assessed by scanning electron microscopy (SEM), which revealed a homogeneous distribution of cellulosic fibers at lower concentrations. The results gathered here contribute to the development of original macromolecular materials exclusively based on the renewable platform.

Monomers and Macromolecular Materials from Renewable Resources: State of the Art and Perspectives.

A progressively increasing concern about the environmental impacts of the whole polymer industry has boosted the design of less aggressive technologies that allow for the maximum use of carbon atoms, and reduced dependence on the fossil platform. Progresses related to the former approach are mostly based on the concept of the circular economy, which aims at a thorough use of raw materials, from production to disposal. The latter, however, has been considered a priority nowadays, as short-term biological processes can efficiently provide a myriad of chemicals for the polymer industry. Polymers from renewable resources are widely established in research and technology facilities from all over the world, and a broader consolidation of such materials is expected in a near future. Herein, an up-to-date overview of the most recent and relevant contributions dedicated to the production of monomers and polymers from biomass is presented. We provide some basic issues related to the preparation of polymers from renewable resources to discuss ongoing strategies that can be used to achieve original polymers and systems thereof.

Multicenter validation study of pathologic response and tumor thickness at the tumor-normal liver interface as independent predictors of disease-free survival after preoperative chemotherapy and surgery for colorectal liver metastases.

BACKGROUND: To validate pathologic markers of response to preoperative chemotherapy as predictors of disease-free survival (DFS) after resection of colorectal liver metastases (CLM). METHODS: One hundred seventy-one patients who underwent resection of CLM after preoperative chemotherapy at 4 centers were studied. Pathologic response-defined as the proportion of tumor cells remaining (complete, 0%; major, <50%; minor, ≥50%) and tumor thickness at the tumor-normal liver interface (TNI) (<0.5 mm, 0.5 to <5 mm, ≥5 mm)-was assessed by a central pathology reviewer and local pathologists. RESULTS: Pathologic response was complete in 8% of patients, major in 49% of patients, and minor in 43% of patients. Tumor thickness at the TNI was <0.5 mm in 21% of patients, 0.5 to <5 mm in 56% of patients, and ≥5 mm in 23% of patients. On multivariate analyses, using either pathologic response or tumor thickness at TNI, pathologic response (P = .002, .009), tumor thickness at TNI (P = 0.015, <.001), duration of preoperative chemotherapy (P = .028, .043), number of CLM (P = .038, . 037), and margin (P = .011, .016) were associated with DFS. In a multivariate analysis using both parameters, tumor thickness at TNI (P = .004, .015), duration of preoperative chemotherapy (P = .025), number of nodules (P = .027), and margin (P = .014) were associated with DFS. Tumor size by pathology examination was the predictor of pathologic response. Predictors of tumor thickness at the TNI were tumor size and chemotherapy regimen. There was near perfect agreement for pathologic response (κ = .82) and substantial agreement (κ = .76) for tumor thickness between the central reviewer and local pathologists. CONCLUSIONS: Pathologic response and tumor thickness at the TNI are valid predictors of DFS after preoperative chemotherapy and surgery for CLM.

Simple green approach to reinforce natural rubber with bacterial cellulose nanofibers.

Natural rubber (NR) is a renewable polymer with a wide range of applications, which is constantly tailored, further increasing its utilizations. The tensile strength is one of its most important properties susceptible of being enhanced by the simple incorporation of nanofibers. The preparation and characterization of natural-rubber based nanocomposites reinforced with bacterial cellulose (BC) and bacterial cellulose coated with polystyrene (BCPS), yielded high performance materials. The nanocomposites were prepared by a simple and green process, and characterized by tensile tests, dynamical mechanical analysis (DMA), scanning electron microscopy (SEM), and swelling experiments. The effect of the nanofiber content on morphology, static, and dynamic mechanical properties was also investigated. The results showed an increase in the mechanical properties, such as Young's modulus and tensile strength, even with modest nanofiber loadings.

High-intensity focused ultrasound (HIFU)-assisted hepatic resection in an animal model.

BACKGROUND: Bleeding is the main cause of postoperative complications of hepatic surgery. To minimize intraoperative bleeding during hepatectomy, resections are generally carried out under hepatic vascular control despite the risk of liver dysfunction in patients with chronic liver disease. This study evaluates the feasibility and safety of high-intensity focused ultrasound (HIFU)-assisted hepatic resection during an open procedure in an animal model. METHODS: Three groups of 12-14-week-old Landrace pigs (n = 7/group) were used to evaluate HIFU-assisted liver resection (group A) vs liver resection with or without portal triad clamping (groups B and C). In each pig, liver resection was performed on the right and left paramedian lobes. The following were evaluated and compared in the 3 groups: total blood loss, blood loss/cm(2) of resection area, clip density, procedure duration, morbidity, and mortality. RESULTS: Median blood loss was significantly lower in group A than in group B (P = .02), and group C (P = .007). Median blood loss/cm(2) of resection area was 4.77 mL/cm² in group A, 11.35 mL/cm² in group B, 12.22 mL/cm² in Group C. Precoagulation resulted in sealing blood vessels <5 mm; therefore, median clip density during liver transection was 0.78 clip/cm² in group A, 1.61 clip/cm(2) in group B, and 1.57 clip/cm(2) in group C. Median duration of the surgical procedure was 12 min in group A, 21 min in group B, and 19 min in group C. CONCLUSIONS: HIFU-assisted hepatic resection during an open procedure in an animal model is safe, reduces bleeding, and allows real-time ultrasound guidance.

A comparative study of patients with and without associated digestive surgery in a two-stage hepatectomy setting.

PURPOSE: The purpose of this study was to compare the feasibility and outcomes of two-stage hepatectomy in patients with or without accompanying digestive surgery. METHODS: We analyzed prospectively data from 56 patients with colorectal liver metastases undergoing two-stage hepatectomy between 1995 and 2009. Patients undergoing associated digestive resection (group I, n = 32) were compared with patients without associated digestive surgery (group II, n = 17). RESULTS: The feasibility rate was 87.5% (49 patients). Neither the type and extent of hepatectomy nor the type of chemotherapy administered differed between the two groups. The median interval between hepatectomies was 1.79 and 2.07 months for groups I and II, respectively (not significant). One patient (group I) died of liver failure after the second hepatectomy. Postoperative morbidity rates were comparable: 37.5% (group I) vs. 35.5% (group II) after the first hepatectomy and 46.9% (group I) vs. 52.9% (group II) after the second hepatectomy. The median hospital stay after the first hepatectomy was longer in group I (13.5 days) than in group II (10 days) (P < 0.01). Median follow-up was 54 months. The median overall survival (OS) was 45.8 months, and 3- and 5-year OS were 58 and 31%, respectively. Median OS was longer for group II (58 months) than for group I (34 months) (P = 0.048). CONCLUSIONS: Digestive tract resection associated with two-stage hepatectomy does not increase postoperative mortality or morbidity nor does it lead to delay in chemotherapy or a reduction in cycles administered. The need for digestive tract surgery should not affect the surgical management of two-stage hepatectomy patients.

A double click strategy applied to the reversible polymerization of furan/vegetable oil monomers.

This investigation describes preliminary results related to the preparation of monomers based on vegetable oil derivatives bearing furan heterocycles appended through thiol-ene click chemistry, and their subsequent polymerization via the Diels-Alder (DA) polycondensation between furan and maleimide complementary moieties, i.e. a second type of click chemistry. Following the optimization of these interactions with model compounds, two basic approaches were considered for these DA polymerizations, namely (i) the use of monomers with two terminal furan rings in conjunction with bismaleimides (AA + BB systems) and (ii) the use of AB monomers incorporating both furan and maleimide end-groups. This ongoing study clearly showed that both approaches were successful, albeit with different outcomes, in terms of the nature of the products. The application of the retro-DA reaction confirmed their thermoreversible character, i.e. the clean-cut return to their respective starting monomers.

The Prospering of Macromolecular Materials Based on Plant Oils within the Blooming Field of Polymers from Renewable Resources.

This paper provides an overview of the recent progress in research and development dealing with polymers derived from plant oils. It highlights the widening interest in novel approaches to the synthesis, characterization, and properties of these materials from renewable resources and emphasizes their growing impact on sustainable macromolecular science and technology. The monomers used include unmodified triglycerides, their fatty acids or the corresponding esters, and chemically modified triglycerides and fatty acid esters. Comonomers include styrene, divinylbenzene, acrylics, furan derivatives, epoxides, etc. The synthetic pathways adopted for the preparation of these materials are very varied, going from traditional free radical and cationic polymerizations to polycondensation reactions, as well as metatheses and Diels-Alder syntheses. In addition to this general appraisal, the specific topic of the use of tung oil as a source of original polymers, copolymers, and (nano)composites is discussed in greater detail in terms of mechanisms, structures, properties, and possible applications.

Copolymers of xylan-derived furfuryl alcohol and natural oligomeric tung oil derivatives.

The utilization of vegetable oils as biological oligomers for the synthesis of macromolecular materials has considerably evolved in the last decades, opening the way for the preparation of sophisticated materials based on synthetic processes for the design of polymers with very specific applications. Tung oil (TO), easily obtained from the seeds of the Asian tung tree (Vernicia fordii), is a relatively cheap commodity that has as its main constituent (~85%) a peculiar natural oligomeric triglyceride structure in which each chain bears three conjugated unsaturations corresponding to α-eleostearic acid. Following a previous study based on the association of TO with furans for the preparation of linear and cross-linked structures based on the Diels-Alder click reaction, the present study deals with the cationic (co) polymerization of xylan-derived furfuryl alcohol (FA) with TO, in order to combine the high intrinsic flexibility of the crosslinked TO polymers with the stiffness of the FA resin, which should lead to fully bio-based crosslinked materials with a tunable glass transition. Three approaches were investigated using trifluoroacetic acid (TFA) in chloroform, viz. (i) combining crude TO and furfuryl alcohol, (ii) combining methyl α-eleostearate and furfuryl alcohol, and (iii) polymerizing furfuryl α-eleostearate itself. The polymerization reactions with varying TFA concentrations were followed by 1H NMR spectroscopy, and it was possible to get valuable information on mechanistic aspects. Also, higher concentrations of TFA were used to synthesize and isolate polymer networks, in order to understand their molecular characteristic as well as access their main thermal properties.

Thermally reversible nanocellulose hydrogels synthesized via the furan/maleimide Diels-Alder click reaction in water.

The study deals with the synthesis of thermally reversible hydrogels from modified cellulose nanofibers via the Diels-Alder "click" reaction in an aqueous medium. "Never-dried" cellulose fibres derived from hardwood were submitted to shearing and surface TEMPO-oxidation before being modified with furfurylamine. The ensuing pendant furan moieties were reacted with a water-soluble bismaleimide via Diels-Alder coupling at 65 °C to produce a hydrogel, whose deconstruction was induced by the corresponding retro-Diels-Alder reaction carried out at 95 °C. Differential scanning calorimetry and rheological measurement were used to characterize the hydrogels. These aqueous cellulosic materials should provide original applications in such areas as strong paper-based artefacts and biocompatible gels.

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.

Enhancing strength and toughness of cellulose nanofibril network structures with an adhesive peptide.

The mechanical properties of cellulose nanofibrils network structure are essential for their applications in functional materials. In this work, an adhesive peptide consisting of just 11 amino acid residues with a hydrophobic core sequence of FLIVI (F - phenylalanine, L - leucine, I - isoleucine, V - valine) flanked by three lysine (K) residues was adsorbed to 2,2,6,6-Tetramethyl-1-piperidinyloxy radical (TEMPO) oxidized cellulose nanofibrils (TO-CNF). Composite films were prepared by solution casting from water suspensions of TO-CNF adsorbed with the adhesive peptide. The nanofibrils network structure of the composite was characterized by atomic force microscopy (AFM). The structure of the peptide in the composites and the interactions between TO-CNF and the peptide were studied by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The mechanical properties of the composites were characterized by tensile tests and dynamic mechanical analysis (DMA). With 6.3wt.% adhesive peptide adsorbed onto TO-CNF, the composite showed a modulus of 12.5±1.4GPa, a tensile strength of 344.5±(15.3)MPa, and a strain to failure of 7.8±0.4%, which are 34.4%, 48.8%, and 23.8% higher than those for neat TO-CNF, respectively. This resulted in significantly improved toughness (work to fracture) for the composite, 77% higher than that for the neat TO-CNF.

Characterization and evaluation of the hydrolytic stability of trifluoroacetylated cellulose fibers.

The controlled heterogeneous modification of cellulose fibers with trifluoroacetic anhydride was investigated. The characterization of the ensuing materials was performed by elemental analysis, FTIR spectroscopy, X-ray diffraction (XRD), thermogravimetry, and surface analysis (XPS, ToF-SIMS, and contact angles measurements). The trifluoroacetylation enhanced significantly the hydrophobic and lipophobic character of the fibers, whereas their thermal stability and cristallinity were only modestly affected by this treatment, except under the most severe conditions for the latter. Their hydrolytic stability to water vapour was also assessed as a function of the air humidity and shown to be lower than that of still liquid water in the case of a saturated atmosphere.

Hydatid cyst of the liver: spontaneous rupture with peritoneal and thoracic involvement. Report of a case.

Hydatidosis due to Echinococcus granulosus is an endemic parasitic disease in Mediterranean countries. The most frequent anatomical locations are the liver and lung and the most significant complication of liver hydatidosis is rupture into the biliary tract. Spontaneous rupture into the free peritoneal cavity associated with thoracic involvement is an unusual complication accompanied by a high mortality rate. An isolated abdominal approach is necessary when peritoneal cavity drainage is required and may be sufficient in cases of contamination of the pleural cavity by scolices without suppurative involvement. An unusual case of spontaneous rupture of a hydatid cyst of the liver into the free peritoneal cavity associated with diaphragmatic and pleural involvement is reported. This complication requires immediate surgical treatment consisting in a combined thoracic and abdominal approach. The isolated abdominal approach not requiring thoracotomy may be satisfactory if there is no intrathoracic damage due to the chronic presence of scolices. Intrabdominal and intrathoracic cyst rupture still remains a serious complication because of the complexity of the lesions which are often difficult to treat in a one-stage operation. The mortality remains high in various series.

Furan-modified natural rubber: A substrate for its reversible crosslinking and for clicking it onto nanocellulose.

The conventional vulcanization process applied to elastomers is irreversible and hinders therefore their useful recycling. We demonstrate here that natural rubber can be reversibly crosslinked via the Diels-Alder coupling of furan and maleimide moieties. The furan-modified natural rubber used in this strategy was also exploited to bind it to maleimide-modified nanocellulose, thus generating a covalently crosslinked composite of these two renewable polymers.

Surface esterification of cellulose fibers: characterization by DRIFT and contact angle measurements.

The surface chemical modification of microcrystalline cellulose and cellulose fibers obtained from different sugar cane bagasse pulping processes, viz. Kraft, organosolv ethanol/water and organosolv/supercritical carbon dioxide, were studied in heterogeneous conditions using modest amounts of octadecanoyl and dodecanoyl chloride. The ensuing surfaces acquired a non-polar character, suitable for incorporating these fibers as reinforcing agents in composite materials based on polymeric matrices. The success of these chemical modifications was assessed by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, elemental analysis, scanning electron microscopy (SEM) and contact angle measurements. In particular, the dynamic and equilibrium contact angle measurements, before and after the treatments, revealed that the value of the polar component (gamma(s)p) of the surface energy had decreased very considerably following the modification.

Reversible hydrophobization and lipophobization of cellulose fibers via trifluoroacetylation.

The surface modification of cellulose fibers with trifluoroacetic anhydride (TFAA) was studied using the heterogeneous cellulose/TFAA/pyridine/toluene system. The degree of substitution (DS) of the ensuing trifluoroacetylated fibers ranged from 0.04 to 0.30. This treatment conferred a high degree of both hydrophobicity and lipophobicity on the fibers' surface, even at low DS values. Both the dispersive and the polar contributions to the surface energy were drastically reduced. However, the original cellulose hydrophilicity could be readily restored through hydrolysis, by treating the modified fibers with neutral water.

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.

Surface grafting of cellulose nanocrystals with natural antimicrobial rosin mixture using a green process.

Surface functionalization of cellulose nanocrystals (CNCs) aims to improve their properties. The main objective of this study was the esterification of the surface of CNCs using nontoxic resin acids, rosin. The structural and morphological modifications of CNC nanorods were characterized by (13)C NMR and Fourier transform infrared spectroscopy, atomic force microscopy, and X-ray diffraction analyses. The properties of functionalized CNCs were evaluated by thermogravimetric analysis and contact-angle measurements. The results indicate that the esterification proceeded from the surface of the CNC. The antimicrobial activities of the modified and neat CNC were investigated; the rosin-grafted CNC exhibited a strong antibacterial activity against Gram-negative bacteria and a modest antibacterial activity against Gram-positive bacteria.