A novel electrospun, hydrophobic, and elastomeric styrene-butadiene-styrene membrane for membrane distillation applications

© 2017 In this study, a novel hydrophobic, microporous membrane was fabricated from styrene-butadiene-styrene (SBS) polymer using electrospinning and evaluated for membrane distillation applications. Compared to a commercially available polytetrafluoroethylene (PTFE) membrane, the SBS membrane had larger membrane pore size and fiber diameter and comparable membrane porosity. The fabricated SBS showed slightly lower water flux than the PTFE membrane because it was two times thicker. However, the SBS membrane had better salt rejection and most importantly could be fabricated via a simple process. The SBS membrane was also more hydrophobic than the reference PTFE membrane. In particular, as temperature of the reference water liquid increased to 60 °C, the SBS membrane remained hydrophobic with a contact angle of 100° whereas the PTFE became hydrophilic with a contact angle of less than 90°. The hydrophobic membrane surface prevented the intrusion of liquid into the membrane pores, thus improving the salt rejection of the SBS membrane. In addition, the SBS membrane had superior mechanical strength over the PTFE membrane. Using the SBS membrane, stable water flux was achieved throughout an extended MD operation period of 120 h to produce excellent quality distillate (over 99.7% salt rejection) from seawater

Cell adhesion and proliferation of skeletal muscle cells on piezoelectric poly(vinylidene fluoride) membranes

Several body tissues, including bone and muscle, are subjected to electromechanical solicitations during their functional activity [1-3]. Thus, the use of electroactive polymers as active scaffolds shows innovative large potential for tissue engineering applications as it offers functional resemblance to biological clues [2]. In particular, piezoelectric polymers have shown suitability for tissue engineering due to their ability to vary surface charge when a mechanical load is applied [4] and their possibility to be processed in form of films, porous 2D and 3D membranes and scaffolds and fiber mats. The influence of poling state and morphology (film or fiber morphology) of piezoelectric poly(vinylidene fluoride) (PVDF) on the adhesion and morphology of myoblast cells was studied. Non-poled, ‘‘poled +’’ and “poled-’’ !-PVDF films were prepared by solvent casting followed by corona poling. Further, random and aligned electrospun !-PVDF fiber mats were also prepared. It is demonstrated that negatively charged surfaces improve cell adhesion and proliferation and that the directional growth of the myoblast cells can be achieved by culturing the cell on aligned fibers. Therefore, the potential application of electroative materials for muscle regeneration is demonstrated

Electrical response of β-PVDF in a constant uniaxial strain rate deformation

The microstructure of β-PVDF has great influence on its piezo- and pyroelectric responses. The microstructure of β-PVDF drastically changes upon a mechanical deformation perpendicular to the preferred chain orientation, mainly above the yielding point. The voltage (open-circuit response) developed in β-PVDF films was monitored while the material is subjected to a constant strain rate programFundação para a Ciência e Tecnologia (FCT) - POCTI/CTM/33501/99

α - to - β transformation on PVDF films obtained by uniaxial stretch

The α to β phase transformation of PVDF through the stretching process at different temperatures was investigated. The optimum stretching conditions were studied and characterised by infrared spectroscopy and differential scanning calorimetry. The maximum β−phase content was achieved at 80ºC and a stretch ratio of 5. Accompanying the phase transformation, a orientation of the polymer chains and a packing of the crystalline structure is observed. The stretch ratio does not significantly affect the degree of crystallinity.GRICES/FAPESP (Proc. 4.1.3/FAPESP).EU-ALFA project Plastinet.Fundação para a Ciência e a Tecnologia (FCT) - Grants POCTI/CTM/33501/99, POCI/CTM/59425/2004

Antibacterial performance of bovine lactoferrin-fish gelatine electrospun nanocomposites

Antibacterial performance of bovine lactoferrin-fish gelatine electrospun nanocomposites The alarming increase of antibiotic resistant microorganisms urged the development and synthesis of novel antimicrobial biomaterials, to be employed in a broad range of applications, ranging from food casings to medical devices [1 – 3]. This work describes the processing and characterization of an innovative fully biobased eletrctrospun nanocomposite material displaying antibacterial properties. Its composition is exclusively comprised of proteins, with fish gelatine as the structural matrix and bovine lactoferrin as the antimicrobial agent. Mainly obtained from the inedible components of the fishery processed catch, fish gelatine (FG) represents a viable alternative source for this highly demanded protein [4]. Electrospun fish gelatine possesses highly interesting properties, such as resilience, biocompatibility, and is stable in aqueous solutions after crosslinking through exposure to glutaraldehyde or genipin atmosphere [5, 6]. Bovine lactoferrin is a wide spectrum antimicrobial protein, exerting its action in numerous virus, bacteria and prokaryotic parasites. Moreover, lactoferrin bears immunoregulatory properties and anti-tumour activity. Specifically, the antibacterial activity of lactoferrin consists of several mechanisms, namely through deprivation of environmental iron, destabilization of Gram negative lipopolysaccharide outer membrane via calcium chelation, and surface charge disruption of Gram positive [7]. In order to confirm the bovine lactoferrin bactericidal efficiency, the minimal inhibitory concentration was determined using clinical isolates of Escherichia coli and Staphylococcus aureus, through microtitre broth dilution test. Two distinctive methods were used to incorporate lactoferrin into the fish gelatine nanofibers: i. as a filler in the electrospinning formulation using concentrations of 2, 5 and 10 (%wt), and ii. through adsorption in a solution with 40 mg mL-1 of lactoferrin. Fourier transform spectroscopy analysis revealed that the structure of both nanocomposite proteins remained intact through the electrospinning blending and crosslinking procedure. The increase in the concentration of lactoferrin as a filler diminished in approximately 50% the size of the fibres when compared to pristine gelatine. The electrospun material with adsorbed LF displayed an antimicrobial activity similar to the fish gelatine fibres without LF, most likely due to the low uptake of LF. The nanocomposites bearing 5% of LF as a filler showed a bacterial reduction of approximately 90% when compared to the control (electrospun FG). In addition, films containing 10% of LF revealed a notable antibacterial performance, with 100% of contact killing capacity, representing a > 6 log reduction in E. coli and S. aureus bacterial populations. Keywords: electrospinning; fish gelatine; lactoferrin; bactericidal; nanocomposite References [1] Silver, L.L., Challenges of antibacterial discovery. Clinical Microbiology Reviews, 2011. 24(1): p.71-109 [2] Fukuda, K., Antimicrobial resistance – global report on surveillance. World Health Organization, 2014 [3] Hancock, R.E.W. and Lehrer, R., Cationic peptides: a new source of antibiotics. Trends in Biotechnology, 1998. 16(2): p.82-88 [4] Karim, A.A. and Bhat, R., Fish gelatin: properties, challenges, and prospects as an alternative to mammalian gelatins. Food Hydrocholloids, 2009. 23(3): p.563-576 [5] Correia, D.M., et al., Thermal and hydrolytic degradation of electrospun fish gelatine membranes. Polymer Testing, 2013. 32(5): p. 995-1000 [6] Padrão, J., et al., Modifying fish electrospun membranes for biomedical applications: cross-linking and swelling behavior. Soft Materials, 2014. 12(3): p.247-252 [7] Jennsen, H. and Hancock, R.E.W., Antimicrobial properties of lactoferrin. Biochimie, 2009. 91(1): p. 19-2

Enhanced proliferation of pre-osteoblastic cells by dynamic piezoelectric stimulation

[EN] This work reports on the influence of the polarization of electroactive poly(vinylidene fluoride), PVDF, on the biological response of cells cultivated under static and dynamic conditions. Non-poled and "poled +" beta-PVDF with and without a titanium layer were thus prepared. A thin titanium layer was deposited on PVDF films in order to obtain a more homogeneous surface charge. The MC3T3-E1 osteoblast cell culture exhibited different responses in the presence of PVDF films. The positively charged beta-PVDF films promote higher osteoblast adhesion and proliferation, which is higher under dynamic conditions on poled samples, showing that the surface charge under mechanical stimulation improves the osteoblast growth. Therefore, electroactive membranes and scaffolds can provide the necessary electrical stimuli for the growth and proliferation of specific cells.JLGR acknowledge the support of the Spanish Ministry of Education through project No. MAT2010-21611-C03-01 (including the FEDER financial support) and project EUI2008-00126.Ribeiro, C.; Moreira, S.; Correia, V.; Sencadas, V.; Rocha, JG.; Gama, FM.; Gómez Ribelles, JL.... (2012). Enhanced proliferation of pre-osteoblastic cells by dynamic piezoelectric stimulation. RSC Advances. 2(30):11504-11509. https://doi.org/10.1039/c2ra21841k115041150923

Magnetoelectric CoFe2O4/polyvinylidene fluoride electrospun nanofibres.

Magnetoelectric 0-1 composites comprising CoFe2O4 (CFO) nanoparticles in a polyvinylidene fluoride (PVDF) polymer-fibre matrix have been prepared by electrospinning. The average diameter of the electrospun composite fibres is ∼325 nm, independent of the nanoparticle content, and the amount of the crystalline polar β phase is strongly enhanced when compared to pure PVDF polymer fibres. The piezoelectric response of these electroactive nanofibres is modified by an applied magnetic field, thus evidencing the magnetoelectric character of the CFO/PVDF 0-1 composites.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/UI607/2014 and PTDC/CTM NAN/112574/2009. R. G., P. M., V. S., G. B. and S. L. M. acknowledge support from “Matepro – Optimizing Materials and Processes” (ref. NORTE-07-0124-FEDER-000037), co funded by “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte, QREN, FEDER). P. M. and R. Gonçalves acknowledges also support from FCT (SFRH/BPD/96227/2013 and SFRH/BD/88397/2012 grants respectively). X. M. acknowledges support from the Ramón y Cajal (RYC) Programme (Spanish MEC) and the Royal Society.This is the accepted manuscript. The final version is available at http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/c5nr00453e#!divAbstract

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

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