Kinetic study of thermal degradation of chitosan as a function of deacetylation degree

[EN] Thermal degradation of chitosan with varying deacetylation degree (DD) ranging between 50 and 85% was analyzed by dynamic thermogravimetric analysis at different heating rates. The present study focused on the temperature range between 500 and 800 K, above water evaporation. Thermal degradation showed a main degradation stage in this temperature interval with a second stage that appeared in the weight derivative curves as a shoulder in the high temperature side of the main peak with increasing intensity as the DD decreased. The Kissinger and isoconversional Ozawa-Flynn-Wall models were employed to evaluate the Ea of both thermal degradation processes. Different kinetic models were tested to computer simulate the thermogravimetric traces calculating the model parameters with a non-linear least squares fitting routine. The Sestack-Berggren model allowed reproducing accurately the overlapping of the two degradation mechanisms and calculating the mass fraction lost in each of them revealing the coupling between the two degradation mechanisms.Thermal degradation of chitosan with varying deacetylation degree (DD) ranging between 50 and 85% was analyzed by dynamic thermogravimetric analysis at different heating rates. The present study focused on the temperature range between 500 and 800 K, above water evaporation. Thermal degradation showed a main degradation stage in this temperature interval with a second stage that appeared in the weight derivative curves as a shoulder in the high temperature side of the main peak with increasing intensity as the DD decreased. The Kissinger and isoconversional Ozawa-Flynn-Wall models were employed to evaluate the Ea of both thermal degradation processes. Different kinetic models were tested to computer simulate the thermogravimetric traces calculating the model parameters with a non-linear least squares fitting routine. The Sestack-Berggren model allowed reproducing accurately the overlapping of the two degradation mechanisms and calculating the mass fraction lost in each of them revealing the coupling between the two degradation mechanisms.Gamiz-Gonzalez, MA.; Correia, D.; Lanceros-Mendez, S.; Sencadas, V.; Gómez Ribelles, JL.; Vidaurre, A. (2017). Kinetic study of thermal degradation of chitosan as a function of deacetylation degree. Carbohydrate Polymers. 167:52-58. https://doi.org/10.1016/j.carbpol.2017.03.020S525816

Therapeutic Hypothermia for Neonatal Encephalopathy Results in Improved Microstructure and Metabolism in the Deep Gray Nuclei

BACKGROUND AND PURPOSE: Therapeutic hypothermia has reduced morbidity and mortality and is associated with a lower burden of lesions on conventional imaging in NE. However, its effects on brain microstructure and metabolism have not been fully characterized. We hypothesized that therapeutic hypothermia improves measures of brain microstructure and metabolism. MATERIALS AND METHODS: Forty-one neonates with moderate/severe NE (29 treated with hypothermia, 12 nontreated) and 12 healthy neonates underwent MR imaging, DTI, and (1)H-MR spectroscopy. MR imaging scans were scored by the predominant pattern of brain injury: normal, watershed, and BG/thalamus. ADC, FA, Lac:NAA, and NAA:Cho values from bilateral BG and thalamus ROIs were averaged. T test and linear regression analysis were used to determine the association between hypothermia and MR imaging quantitative measures. RESULTS: Conventional MR imaging findings were normal in 41% of treated neonates; all nontreated neonates had brain injury. Values of MR imaging metrics were closer to normal in treated neonates compared with nontreated neonates: ADC was 63% higher in the BG and 116% higher in the thalamus (both P < .05), and Lac:NAA was 76% lower (P = .04) in the BG. Treated neonates with normal MR imaging findings had normal (1)H-MR spectroscopy metabolites, and ADC was higher by 35% in the thalamus (P = .03) compared with healthy neonates. CONCLUSIONS: Therapeutic hypothermia may reduce disturbances of brain metabolism and preserve its microstructure in the setting of NE, possibly by minimizing cytotoxic edema and cell death. Long-term follow-up studies are required to determine whether early post-treatment DTI and (1)H-MR spectroscopy will be useful biomarkers of treatment response

Different proportion of root cutting and shoot pruning influence the growth of citronella plants

Environment concern, sustainable products demand, and natural components conscious are currently global movement factors. Related to the global movement factors, citronella grass (Cymbopogon nardus L.) is being widely used in folk medicine, and has insect repellent activity, fungal and bactericidal action. Its essential oil has high content of citronellal, citronellol, geraniol. The essential oil is mostly extracted from leaves which turns this plant with high commercial demand. However, to obtain the best therapeutic quality and productivity of medicinal plants, which culminates in greater quantity and quality of the active compounds, the proper management of the crop is fundamental, as several factors can interfere during its growth and development. Thus, we analyzed the growth of citronella plants submitted to different levels of shoot and root cuts. Five different proportions of root pruning (0, 25, 50, 75, 100%), after 145 days of seedling planting and four cuttings in the shoots: blunt; a cut at 145 DAP (days after planting) along with the root cut; a cut at 228 DAP; and cuts at 145 and 228 DAP (two cuts). Four harvesting for dry matter accumulation and photoassimilate partition data were performed. The treatment with 100% root cut, but without leaf cut, increased the total dry mass accumulation of the plant in relation to the other treatments, for the last analysis period, demonstrating a recovery. Thus, the application of two leaf cuts or no leaf cutting within the 100% root cut treatment for leaf dry mass accumulation is more effective when compared to the blunt root treatment

Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture

[EN] The use of piezoelectric materials in tissue engineering has grown considerably since inherent bone piezoelectricity was discovered. Combinations of piezoelectric polymers with magnetostrictive nanoparticles (MNP) can be used to magnetoelectrically stimulate cells by applying an external magnetic field which deforms the magnetostrictive nanoparticles in the polymer matrix, deforming the polymer itself, which varies the surface charge due to the piezoelectric effect. Poly(vinylidene) fluoride (PVDF) is the piezoelectric polymer with the largest piezoelectric coefficients, being a perfect candidate for osteogenic differentiation. As a first approach, in this paper, we propose PVDF membranes containing magnetostrictive nanoparticles and a biomimetic heparin/ collagen layer-by-layer (LbL) coating for mesenchymal stem cell culture. PVDF membranes 20% (w/v) with and without cobalt ferrite oxide (PVDF-CFO) 10% (w/w) were produced by non-solvent induced phase separation (NIPS). These membranes were found to be asymmetric, with a smooth surface, crystallinity ranging from 65% to 61%, and an electroactive beta-phase content of 51.8% and 55.6% for PVDF and PVDF-CFO, respectively. Amine groups were grafted onto the membrane surface by an alkali treatment, confirmed by ninhydrin test and X-ray photoelectron spectroscopy (XPS), providing positive charges for the assembly of heparin/collagen layers by the LbL technique. Five layers of each polyelectrolyte were deposited, ending with collagen. Human mesenchymal stem cells (hMSC) were used to test cell response in a short-term culture (1, 3 and 7 days). Nucleus cell counting showed that LbL favored cell proliferation in PVDF-CFO over non-coated membranes.This work has been funded by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the PID2019-106099RB-C41/AEI/10.13039/501100011033 and PID2019-106099RB-C43/AEI/10.13039/501100011033 projects and the Associate Laboratory for Green Chemistry-LAQV financed by national funds from FCT/MCTES (UIDB/50006/2020). Maria GuillotFerriols acknowledges the Spanish Government funding of her doctoral thesis through a BES-2017-080398 FPI Grant. The CIBER-BBN (CB06/01/1026) initiative is funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund. D.M.C is also grateful to the FCT-Fundacao para a Ciencia e Tecnologia for grant SFRH/BPD/121526/2016. Finally, the authors acknowledge funding from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively, also Dr. Carlos Sa (CEMUP) for assistance with the XPS analyses.Guillot-Ferriols, MT.; Rodriguez-Hernandez, J.; Correia, D.; Carabineiro, S.; Lanceros-Méndez, S.; Gómez Ribelles, JL.; Gallego Ferrer, G. (2020). Poly(vinylidene) fluoride membranes coated by heparin/collagen layer-by-layer, smart biomimetic approaches for mesenchymal stem cell culture. Materials Science and Engineering C: Materials for Biological Applications (Online). 117:1-12. https://doi.org/10.1016/j.msec.2020.111281112117Jacob, J., More, N., Kalia, K., & Kapusetti, G. (2018). Piezoelectric smart biomaterials for bone and cartilage tissue engineering. Inflammation and Regeneration, 38(1). doi:10.1186/s41232-018-0059-8Fukada, E., & Yasuda, I. (1957). On the Piezoelectric Effect of Bone. 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The effect of electrostatic heparin/collagen layer-by-layer coating degradation on the biocompatibility. Applied Surface Science, 362, 281-289. doi:10.1016/j.apsusc.2015.11.227Zhang, K., Huang, D., Yan, Z., & Wang, C. (2017). Heparin/collagen encapsulating nerve growth factor multilayers coated aligned PLLA nanofibrous scaffolds for nerve tissue engineering. Journal of Biomedical Materials Research Part A, 105(7), 1900-1910. doi:10.1002/jbm.a.36053Ferreira, A. M., Gentile, P., Toumpaniari, S., Ciardelli, G., & Birch, M. A. (2016). Impact of Collagen/Heparin Multilayers for Regulating Bone Cellular Functions. ACS Applied Materials & Interfaces, 8(44), 29923-29932. doi:10.1021/acsami.6b09241Castilla-Casadiego, D. A., García, J. R., García, A. J., & Almodovar, J. (2019). Heparin/Collagen Coatings Improve Human Mesenchymal Stromal Cell Response to Interferon Gamma. 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M., & Lanceros-Mendez, S. (2010). Nucleation of electroactive β-phase poly(vinilidene fluoride) with CoFe2O4 and NiFe2O4 nanofillers: a new method for the preparation of multiferroic nanocomposites. Applied Physics A, 103(1), 233-237. doi:10.1007/s00339-010-6003-7Qi, L., Knapton, E. K., Zhang, X., Zhang, T., Gu, C., & Zhao, Y. (2017). Pre-culture Sudan Black B treatment suppresses autofluorescence signals emitted from polymer tissue scaffolds. Scientific Reports, 7(1). doi:10.1038/s41598-017-08723-2Young, T.-H., Cheng, L.-P., Lin, D.-J., Fane, L., & Chuang, W.-Y. (1999). Mechanisms of PVDF membrane formation by immersion-precipitation in soft (1-octanol) and harsh (water) nonsolvents. Polymer, 40(19), 5315-5323. doi:10.1016/s0032-3861(98)00747-2Cheng, L.-P. (1999). Effect of Temperature on the Formation of Microporous PVDF Membranes by Precipitation from 1-Octanol/DMF/PVDF and Water/DMF/PVDF Systems. 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Effect of Preparation Methods on Crystallization Behavior and Tensile Strength of Poly(vinylidene fluoride) Membranes. Membranes, 3(4), 389-405. doi:10.3390/membranes3040389ZHANG, M., ZHANG, A., ZHU, B., DU, C., & XU, Y. (2008). Polymorphism in porous poly(vinylidene fluoride) membranes formed via immersion precipitation process. Journal of Membrane Science, 319(1-2), 169-175. doi:10.1016/j.memsci.2008.03.029Xiao, L., Davenport, D. M., Ormsbee, L., & Bhattacharyya, D. (2015). Polymerization and Functionalization of Membrane Pores for Water Related Applications. Industrial & Engineering Chemistry Research, 54(16), 4174-4182. doi:10.1021/ie504149tDuca, M. D., Plosceanu, C. L., & Pop, T. (1998). Effect of X-rays on poly(vinylidene fluoride) in X-ray photoelectron spectroscopy. Journal of Applied Polymer Science, 67(13), 2125-2129. doi:10.1002/(sici)1097-4628(19980328)67:133.0.co;2-gCorreia, D. M., Ribeiro, C., Sencadas, V., Botelho, G., Carabineiro, S. A. C., Ribelles, J. L. G., & Lanceros-Méndez, S. (2015). Influence of oxygen plasma treatment parameters on poly(vinylidene fluoride) electrospun fiber mats wettability. Progress in Organic Coatings, 85, 151-158. doi:10.1016/j.porgcoat.2015.03.019Kehrer, M., Duchoslav, J., Hinterreiter, A., Cobet, M., Mehic, A., Stehrer, T., & Stifter, D. (2019). XPS investigation on the reactivity of surface imine groups with TFAA. Plasma Processes and Polymers, 16(4), 1800160. doi:10.1002/ppap.201800160Morales-Román, R. M., Guillot-Ferriols, M., Roig-Pérez, L., Lanceros-Mendez, S., Gallego-Ferrer, G., & Gómez Ribelles, J. L. (2019). Freeze-extraction microporous electroactive supports for cell culture. European Polymer Journal, 119, 531-540. doi:10.1016/j.eurpolymj.2019.07.011Camacho, N. P., West, P., Torzilli, P. A., & Mendelsohn, R. (2000). FTIR microscopic imaging of collagen and proteoglycan in bovine cartilage. Biopolymers, 62(1), 1-8. doi:10.1002/1097-0282(2001)62:13.0.co;2-oRibeiro, C., Panadero, J. 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The cellular magnetic response and biocompatibility of biogenic zinc- and cobalt-doped magnetite nanoparticles. Scientific Reports, 7(1). doi:10.1038/srep3992

Ionic and conformational mobility in poly(vinylidene fluoride)/ionic liquid blends: Dielectric and electrical conductivity behavior

[EN] The glass transition dynamics and the charge transport for blends composed of poly(vinylidene fluoride) (PVDF) and the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [Emim] [TESI] have been investigated as a function of different IL content (0, 10, 25 and 40 % wt) by differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA) and broadband dielectric relaxation spectroscopy (BDS) in wide frequency and temperature ranges (0.1 Hz-1 MHz and -120 to 150 degrees C, respectively). The inclusion of the IL in the polymer matrix affected the main relaxation process (beta-relaxation) of the amorphous phase of the polymer matrix detected with all the techniques employed. It is demonstrated, that the chain segments of PVDF and the IL are mixed at the nanometer range. The blends were homogeneous regardless of the amount of IL and the glass transition temperature (Tg) shifted to lower temperatures as the IL content was increased. A good agreement between the Tg measured by BDS and DSC was observed for all PVDF/IL samples. The conductivity formalism revealed significant contributions of the IL concentration to the conductivity behavior of the blends in that is described by charge motion and electrode polarization effects. The activation energy of all the PVDF/IL samples, calculated by Dyre model, decreased with IL addition with respect to that of neat PVDF. (C) 2018 Elsevier Ltd. All rights reserved.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013. The authors thank FEDER funds through the COMPETE 2020 Programme and National Funds through FCT under the projects PTDC/CTM-ENE/5387/2014, PTDC/EEI-SII/5582/2014 and UID/CTM/50025/2013 and Grants SFRH/BPD/121526/2016 (D.M.C.), SFRH/BPD/112547/2015 (C.M.C.). Financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) (including the FEDER financial support) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs is also acknowledged. CIBER-BBN is an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program. CIBER Actions are financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund.Correia, D.; Sabater I Serra, R.; Gómez-Tejedor, JA.; De Zea Bermudez, V.; Andrio Balado, A.; Meseguer Dueñas, JM.; Gómez Ribelles, JL.... (2018). Ionic and conformational mobility in poly(vinylidene fluoride)/ionic liquid blends: Dielectric and electrical conductivity behavior. Polymer. 143:164-172. https://doi.org/10.1016/j.polymer.2018.04.019S16417214

Induction melt thermoforming of advanced multi-axial thermoplastic composite laminates

The viability of using induction heating to facilitate the wrinkle-free forming of multi-axial pre-consolidated advanced thermoplastic composites over complex geometries is explored. The research focuses on the use of tin as a medium to both heat and lubricate the forming laminate. Initial tests demonstrate the viability of the fundamental ideas of the process; induction heating is used to melt the tin sheet, which is then shown to melt the matrix phase of carbon-nylon composite laminates when stacked in a hybrid composite/tin layup. A novel low-cost reconfigurable multi-step forming tool is used to demonstrate how most of the tin can be squeezed out of the layup prior to consolidation. The multi-step tool can be augmented with segmented tooling to rapidly manufacture composite parts of high geometric complexity. In this investigation, a 'ripple' geometry containing three 'cavities' is used to demonstrate the technique. Tests demonstrated that at least three sheets of inter-laminar tin can be simultaneously melted using the induction heating system. Initial results indicate complex geometries can be formed with minimal wrinkling while removing interlaminar tin

The EU societal awareness of landscape indicator: a review of its meaning, utility and performance across different scales

There is increasing recognition that agricultural landscapes meet multiple societal needs and demands beyond provision of economic and environmental goods and services. Accordingly, there have been significant calls for the inclusion of societal, amenity and cultural values in agri-environmental landscape indicators to assist policy makers in monitoring the wider impacts of land-based policies. However, capturing the amenity and cultural values that rural agrarian areas provide, by use of such indicators, presents significant challenges. The EU social awareness of landscape indicator represents a new class of generalized social indicator using a top-down methodology to capture the social dimensions of landscape without reference to the specific structural and cultural characteristics of individual landscapes. This paper reviews this indicator in the context of existing agri-environmental indicators and their differing design concepts. Using a stakeholder consultation approach in five case study regions, the potential and limitations of the indicator are evaluated, with a particular focus on its perceived meaning, utility and performance in the context of different user groups and at different geographical scales. This analysis supplements previous EU-wide assessments, through regional scale assessment of the limitations and potentialities of the indicator and the need for further data collection. The evaluation finds that the perceived meaning of the indicator does not vary with scale, but in common with all mapped indicators, the usefulness of the indicator, to different user groups, does change with scale of presentation. This indicator is viewed as most useful when presented at the scale of governance at which end users operate. The relevance of the different sub-components of the indicator are also found to vary across regions

PHB-PEO electrospun fiber membranes containing chlorhexidine for drug delivery applications

Fiber meshes of poly(hydroxybutyrate) (PHB) and poly(hydroxybutyrate)/poly(ethylene oxide) (PHB/PEO) with different concentrations of chlorhexidine (CHX) were prepared by electrospinning for assessment as a polymer based drug delivery system. The electrospun fibers were characterized at morphological, molecular and mechanical levels. The bactericidal potential of PHB and PHB/PEO electrospun fibers, with and without CHX, was investigated against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) by disk diffusion susceptibility tests. Electrospun fibers containing CHX exhibited bactericidal activity. PHB/PEO-1%CHX displayed higher CHX release levels and equivalent antibacterial activity when compared to PHB/PEO with 5 and 10 wt% CHX. Bactericidal performance of samples with 1 wt% CHX was assessed by Colony Forming Units (CFU), where reductions of 100% and 99.69% against E. coli and S. aureus were achieved, respectively.This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011 and PEST-C/QUI/UIO686/2011. The authors also thank funding from Matepro - Optimizing Materials and Processes", ref. NORTE-07-0124-FEDER-000037", co-funded by the "Programa Operacional Regional do Norte" (ON.2 - O Novo Norte), under the "Quadro de Referencia Estrategico Nacional" (QREN), through the "Fundo Europeu de Desenvolvimento Regional" (FEDER). D.M.C, JP and VS thanks the FCT for the, SFRH/BD/82411/2011, SFRH/BD/64901/2009 and SFRH/BPD/63148/2009 grants respectively. The authors also thank support from the COST Action MP1003, 2010 'European Scientific Network for Artificial Muscles' and to the COST Action MP1206 'Electrospun Nano-fibres for Bio inspired Composite Materials and Innovative Industrial Applications'. The authors also thank prof. Jose Luis Gomez Ribelles from the Unversidad Politecnica de Valencia, Spain, for interesting discussions on these issues

Thermal and hydrolytic degradation of electrospun fish gelatin membranes

The thermal and hydrolytic degradation of electrospun gelatin membranes cross-linked with glutaraldehyde in vapor phase has been studied. In vitro degradation of gelatin membranes was evaluated in phosphate buffer saline solution at 37 °C. After 15 days under these conditions, a weight loss of 68% was observed, attributed to solvation and depolymerization of the main polymeric chains. Thermal degradation kinetics of the gelatin raw material and as-spun electrospun membranes showed that the electrospinning processing conditions do not influence polymer degradation. However, for cross-linked samples a decrease in the activation energy was observed, associated with the effect of glutaraldehyde cross-linking reaction in the inter- and intra-molecular hydrogen bonds of the protein. It is also shown that the electrospinning process does not affect the formation of the helical structure of gelatin chainsThis work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011 and by projects project references NANO/NMed-SD/0156/2007 and PTDC/CTM-NAN/112574/2009. The authors also thank support from the COST Action MP1003, 2010 'European Scientific Network for Artificial Muscles'. DMC, JP and VS would like to acknowledge the FCT for the SFRH/BD/82411/2011, SFRH/BD/64901/2009 and SFRH/BPD/64958/2009 grants respectively

Mitochondria are required for pro-ageing features of the senescent phenotype

Cell senescence is an important tumour suppressor mechanism and driver of ageing. Both functions are dependent on the development of the senescent phenotype, which involves an overproduction of pro‐inflammatory and pro‐oxidant signals. However, the exact mechanisms regulating these phenotypes remain poorly understood. Here, we show the critical role of mitochondria in cellular senescence. In multiple models of senescence, absence of mitochondria reduced a spectrum of senescence effectors and phenotypes while preserving ATP production via enhanced glycolysis. Global transcriptomic analysis by RNA sequencing revealed that a vast number of senescent‐associated changes are dependent on mitochondria, particularly the pro‐inflammatory phenotype. Mechanistically, we show that the ATM, Akt and mTORC1 phosphorylation cascade integrates signals from the DNA damage response (DDR) towards PGC‐1β‐dependent mitochondrial biogenesis, contributing to a ROS‐mediated activation of the DDR and cell cycle arrest. Finally, we demonstrate that the reduction in mitochondrial content in vivo, by either mTORC1 inhibition or PGC‐1β deletion, prevents senescence in the ageing mouse liver. Our results suggest that mitochondria are a candidate target for interventions to reduce the deleterious impact of senescence in ageing tissues