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

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

Characterization Of The Crotalus Durissus Terrificus Venom By Atomic Force Microscopy

A preliminary analysis of the morphology of crude CDT venom was performed using atomic force microscopy (AFM). As a result, a direct measurement of the forces between the surface of the venom crystals and a sharp probe tip was achieved.20413171321Azevedo Marques, M.M., Cupo, P., Coimbra, T.M., Hering, S.E., Rossi, M.A., Laure, C.J., (1985) Toxicon, 23, p. 631Sanchez, E.E., Soliz, L.A., Susana Ramirez, M., Perez, J.C., (2001) Toxicon, 39, p. 523Soares, A.M., Mancin, A.C., Cecchini, A.L., Arantes, E.C., Franca, S.C., Gutierrez, J.M., Giglio, J.R., (2001) Int. J. Biochem. Cell Biol., 33, p. 877Choumet, V., Lafaye, P., Demangel, C., Bon, C., Mazie, J.C., (1999) Biol. Chem., 380, p. 561Sanchez, S.A., Chen, Y., Muller, J.D., Gratton, E., Hazlett, T.L., (2001) Biochemistry, 40, p. 6903Sharma, S., Jabeen, T., Singh, J.K., Bredhorst, R., Vogel, C.W., Betzel, C., Singh, T.P., (2001) Acta Crystallogr., Sect. D: Biol. Crystallogr., 57, p. 596Nonato, M.C., Garrat, R.C., Mascarenhas, Y.P., Jesus, W.D.P., Assakura, M.T., Serrano, S.M.T., Oliva, G., (2001) Biol. Crystallogr., D, 57, p. 599Arni, R.K., Ward, R.J., (1996) Toxicon, 34, p. 827Souza, D.H.F., Selistre-deAraujo, H.S., Garratt, R.C., (2000) Toxicon, 38, p. 1307Binning, G., Coate, C.F., Gerber, G., (1986) Phys. Rev. Lett., 56, p. 930Baranauskas, V., Vidal, B.C., Parizotto, N.A., (1998) Appl. Biochem. Biotechnol., 69, p. 91Baranauskas, V., Garavello-Freitas, I., Jingguo, Z., Cruz-Hofling, M.A., (2001) J. Vac. Sci. Technol. A, 19, p. 104

Input of sugarcane post-harvest residues into the soil

Sugarcane (Saccharum spp.) crops provide carbon (C) for soil through straw and root system decomposition. Recently, however, sugarcane producers are considering straw to be removed for electricity or second generation ethanol production. To elucidate the role of straw and root system on the carbon supply into the soil, the biomass inputs from sugarcane straw (tops and dry leaves) and from root system (rhizomes and roots) were quantified, and its contribution to provide C to the soil was estimated. Three trials were carried out in the State of Sao Paulo, Brazil, from 2006 to 2009. All sites were cultivated with the variety SP81 3250 under the green sugarcane harvest. Yearly, post-harvest sugarcane residues (tops, dry leaves, roots and rhizomes) were sampled; weighted and dried for the dry mass (DM) production to be estimated. On average, DM root system production was 4.6 Mg ha-1 year-1 (1.5 Mg C ha-1 year-1) and 11.5 Mg ha-1 year-1 (5.1 Mg C ha-1 year-1) of straw. In plant cane, 35 % of the total sugarcane DM was allocated into the root system, declining to 20 % in the third ratoon. The estimate of potential allocation of sugarcane residues to soil organic C was 1.1 t ha-1 year-1; out of which 33 % was from root system and 67 % from straw. The participation of root system should be higher if soil layer is evaluated, a deeper soil layer, if root exudates are accounted and if the period of higher production of roots is considered

Growth of pea plants (Pisum sativum L.) subjected to different soil water potentials : physiological indexes

A ervilha é cultivada no Brasil Central, durante o inverno seco, exigindo para o pleno êxito da cultura o uso da irrigação. Assim, o presente trabalho se propõe a avaliar os efeitos do potencial da água no solo nos índices fisiológicos da análise quantitativa de crescimento de plantas de ervilha (Pisum sativum L.). O experimento foi montado em casa de vegetação, em solos de textura argilosa, com delineamento experimental inteiramente casualizado, com quatro tratamentos decorrentes de potenciais mínimos da água no solo (-33, -100, -200 e -1500 kPa) em três repetições, cada qual contendo duas plantas de ervilha, cultivar Caprice. Os resultados obtidos evidenciaram que a redução do potencial água no solo, induziu o decréscimo na área foliar, sem interferir no comportamento da razão de massa foliar, razão de área foliar, taxa assimilatória líquida e taxa de crescimento relativo. _________________________________________________________________________________________ ABSTRACT: Peas are cultivated in the central region of Brazil, during the dry winter, demanding for the complete success the use of irrigation. Therefore, the present work has the aim of evaluating soil water potential effects on the indexes of physiological growth analysis of peas (Pisum sativum L.). The experiment was carried out in a greenhouse using soils of clayey texture, in a fully randomized design, with four treatments, based on minimum soil water potentials (-33, -100, -200 and -1500 kPa) in three replicates, each one containing two pea plants Caprice cultivar. The results obtained indicate that the reduction of soil water potential induced the decrease of leaf area, but did not interfer on the behaviour of leaf weight ratio, leaf area ratio, net assimilation rate and relative growth rate