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This work evaluated the effect of acetylated bacterial cellulose (ABC) substrates coated with urinary bladder matrix (UBM) on the behavior of retinal pigment epithelium (RPE), as assessed by cell adhesion, proliferation and development of cell polarity exhibiting transepithelial resistance and polygonal shaped-cells with microvilli. Acetylation of bacterial cellulose (BC) generated a moderate hydrophobic surface (around 65°) while the adsorption of UBM onto these acetylated substrates did not affect significantly the surface hydrophobicity. The ABS substrates coated with UBM enabled the development of a cell phenotype closer to that of native RPE cells. These cells were able to express proteins essential for their cytoskeletal organization and metabolic function (ZO-1 and RPE65), while showing a polygonal shaped morphology with microvilli and a monolayer configuration. The coated ABC substrates were also characterized, exhibiting low swelling effect (between 1.5-2.0 swelling/mm3), high mechanical strength (2048MPa) and non-pyrogenicity (2.12EU/L). Therefore, the ABC substrates coated with UBM exhibit interesting features as potential cell carriers in RPE transplantation that ought to be further explored.

This work evaluated the effect of acetylated bacterial cellulose (ABC) substrates coated with urinary bladder matrix (UBM) on the behavior of retinal pigment epithelium (RPE), as assessed by cell adhesion, proliferation and development of cell polarity exhibiting transepithelial resistance and polygonal shaped-cells with microvilli. Acetylation of bacterial cellulose (BC) generated a moderate hydrophobic surface (around 65°) while the adsorption of UBM onto these acetylated substrates did not affect significantly the surface hydrophobicity. The ABS substrates coated with UBM enabled the development of a cell phenotype closer to that of native RPE cells. These cells were able to express proteins essential for their cytoskeletal organization and metabolic function (ZO-1 and RPE65), while showing a polygonal shaped morphology with microvilli and a monolayer configuration. The coated ABC substrates were also characterized, exhibiting low swelling effect (between 1.5-2.0 swelling/mm3), high mechanical strength (2048MPa) and non-pyrogenicity (2.12EU/L). Therefore, the ABC substrates coated with UBM exhibit interesting features as potential cell carriers in RPE transplantation that ought to be further explored.

This work evaluated the effect of acetylated bacterial cellulose (ABC) substrates coated with urinary bladder matrix (UBM) on the behavior of retinal pigment epithelium (RPE), as assessed by cell adhesion, proliferation and development of cell polarity exhibiting transepithelial resistance and polygonal shaped-cells with microvilli. Acetylation of bacterial cellulose (BC) generated a moderate hydrophobic surface (around 65°) while the adsorption of UBM onto these acetylated substrates did not affect significantly the surface hydrophobicity. The ABS substrates coated with UBM enabled the development of a cell phenotype closer to that of native RPE cells. These cells were able to express proteins essential for their cytoskeletal organization and metabolic function (ZO-1 and RPE65), while showing a polygonal shaped morphology with microvilli and a monolayer configuration. The coated ABC substrates were also characterized, exhibiting low swelling effect (between 1.5-2.0 swelling/mm3), high mechanical strength (2048MPa) and non-pyrogenicity (2.12EU/L). Therefore, the ABC substrates coated with UBM exhibit interesting features as potential cell carriers in RPE transplantation that ought to be further explored.

This work evaluated the effect of acetylated bacterial cellulose (ABC) substrates coated with urinary bladder matrix (UBM) on the behavior of retinal pigment epithelium (RPE), as assessed by cell adhesion, proliferation and development of cell polarity exhibiting transepithelial resistance and polygonal shaped-cells with microvilli. Acetylation of bacterial cellulose (BC) generated a moderate hydrophobic surface (around 65°) while the adsorption of UBM onto these acetylated substrates did not affect significantly the surface hydrophobicity. The ABS substrates coated with UBM enabled the development of a cell phenotype closer to that of native RPE cells. These cells were able to express proteins essential for their cytoskeletal organization and metabolic function (ZO-1 and RPE65), while showing a polygonal shaped morphology with microvilli and a monolayer configuration. The coated ABC substrates were also characterized, exhibiting low swelling effect (between 1.5-2.0 swelling/mm3), high mechanical strength (2048MPa) and non-pyrogenicity (2.12EU/L). Therefore, the ABC substrates coated with UBM exhibit interesting features as potential cell carriers in RPE transplantation that ought to be further explored.

Bacterial cellulose (BC) films from two distinct sources (obtained by static culture with Gluconacetobacter xylinus ATCC 53582 (BC1) and from a commercial source (BC2)) were modified by bovine lactoferrin (bLF) adsorption. The functionalized films (BC + bLF) were assessed as edible antimicrobial packaging, for use in direct contact with highly perishable foods, specifically fresh sausage as a model of meat products. BC + bLF films and sausage casings were characterized regarding their water vapour permeability (WVP), mechanical properties, and bactericidal efficiency against two food pathogens, Escherichia coli and Staphylococcus aureus. Considering their edibility, an in vitro gastrointestinal tract model was used to study the changes occurring in the BC films during passage through the gastrointestinal tract. Moreover, the cytotoxicity of the BC films against 3T3 mouse embryo fibroblasts was evaluated.BC1 and BC2 showed equivalent density, WVP and maximum tensile strength. The percentage of bactericidal efficiency of BC1 and BC2 with adsorbed bLF (BC1. +. bLF and BC2. +. bLF, respectively) in the standalone films and in inoculated fresh sausages, was similar against E. coli (mean reduction 69% in the films per se versus 94% in the sausages) and S. aureus (mean reduction 97% in the films per se versus 36% in the case sausages). Moreover, the BC1. +. bLF and BC2. +. bLF films significantly hindered the specific growth rate of both bacteria. Finally, no relevant cytotoxicity against 3T3 fibroblasts was found for the films before and after the simulated digestion. BC films with adsorbed bLF may constitute an approach in the development of bio-based edible antimicrobial packaging systems.

Magnetoelectric microspheres based on piezoelectric poly(vinylidene fluoride) (PVDF) and magnetostrictive CoFe2O4 (CFO), a novel morphology for polymer-based ME materials, have been developed by an electrospray process. The CFO nanoparticle content in the (3-7 mm diameter) microspheres reaches values up to 27 wt%, despite their concentration in the starting solution reaching values up to 70 wt%. Additionally, the inclusion of magnetostrictive nanoparticles into the polymer spheres has no relevant effect on the piezoelectric b-phase content (z60%), crystallinity (40%) and the onset degradation temperature (460-465 C) of the polymer matrix. The multiferroic microspheres show a maximum piezoelectric response |d33| z 30 pC N1, leading to a magnetoelectric response of D|d33| z 5 pC N1 obtained when a 220 mT DC magnetic field was applied. It is also shown that the interface between CFO nanoparticles and PVDF (from 0 to 55%) has a strong influence on the ME response of the microspheres. The simplicity and the scalability of the processing method suggest a large application potential of this novel magnetoelectric geometry in areas such as tissue engineering, sensors and actuators.

Electrospun poly(vinylidene fluoride) (PVDF) fiber mats found applications in an increasing number of areas, such as battery separators, filtration and detection membranes, due to their excellent properties. However, there are limitations due to the hydrophobic nature and low surface energy of PVDF. In this work, oxygen plasma treatment has been applied in order to modify the surface wettability of PVDF fiber mats and superhydrophilic PVDF electrospun membranes have been obtained. Further, plasma treatment does not significantly influences fiber average size (~400 ± 200 nm), morphology, electroactive B-phase content (~80-85%) or the degree of crystallinity (Xc of 42 ± 2%), allowing to maintain the excellent physic-chemical characteristics of PVDF. Plasma treatment mainly induces surface chemistry modifications, such as the introduction of oxygen and release of fluorine atoms that significantly changes polymer membrane wettability by a reduction of the contact angle of the polymer fibers and an overall decrease of the surface tension of the membranes.

Titanium dioxide (TiO2) in different forms such as films, fibers or particles are being extensively studied for removal of contaminants from aquatic environments due to its outstanding photocatalytic activity. This work reports the development of TiO2-polyamide 12 electrospun fiber mats. A systematic study on the influence of electrospun processing parameters on polymer fiber morphology was performed. It was observed that the average fiber diameter is mainly influenced by polymer concentration and average fiber diameters between 404 ± 82 nm and 1442 ± 360 nm were obtained. Polyamide-12 (PA-12) was used as a polymer matrix and electrospun with 0, 10 and 20 wt% of TiO2. It was observed that the filler does not change the average fiber diameter, being similar to that observed for neat PA-12 fibers processed under the same experimental conditions. The TiO2 were particles dispensed not only in the bulk of the polymeric matrix but also on the surface of the fibers, especially for the samples with higher filler contents. Neat and nanocomposite electrospun samples show a hydrophobic behavior and a degree of crystallinity of ~25%. The photocatalytic performance of the processed samples was measured by following the degradation capability of a chosen dye, methylene blue (MB). Results show that the nanocomposite samples have a remarkable photocatalytic activity, especially the one with a higher load of TiO2 particles (20 wt%), with all MB being removed from the solution after 100 min.

Polymeric scaffolds used in regenerative therapies are implanted in the damaged tissue and submitted to repeated loading cycles. In the case of articular cartilage engineering, an implanted scaffold is typically subjected to long-term dynamic compression. The evolution of the mechanical properties of the scaffold during bioresorption has been deeply studied in the past, but the possibility of failure due to mechanical fatigue has not been properly addressed. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. In this work fatigue studies of polycaprolactone scaffolds were carried by subjecting the scaffold to repeated compression cycles in conditions simulating the scaffold implanted in the articular cartilage. The behavior of the polycaprolactone sponge with the pores filled with a poly(vinyl alcohol) gel simulating the new formed tissue within the pores was compared with that of the material immersed in water. Results were analyzed with Morrow's criteria for failure and accurate fittings are obtained just up to 200 loading cycles. It is also shown that the presence of poly(vinyl alcohol) increases the elastic modulus of the scaffolds, the effect being more pronounced with increasing the number of freeze/thawing cycles.

Tissue engineering often rely on scaffolds for supporting cell differentiation and growth. Novel paradigms for tissue engineering include the need of active or smart scaffolds in order to properly regenerate specific tissues. In particular, as electrical and electromechanical clues are among the most relevant ones in determining tissue functionality in tissues such as muscle and bone, among others, electroactive materials and, in particular, piezoelectric ones, show strong potential for novel tissue engineering strategies, in particular taking also into account the existence of these phenomena within some specific tissues, indicating their requirement also during tissue regeneration. This referee reports on piezoelectric materials used for tissue engineering applications. The most used materials for tissue engineering strategies are reported together with the main achievements, challenges and future needs for research and actual therapies. This review provides thus a compilation of the most relevant results and strategies and a start point for novel research pathways in the most relevant and challenging open questions.

The 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 packaging to medical devices. This work describes the production and characterization of a protein-based electrospun fibrous membranes bearing antimicrobial properties. Its composition is exclusively comprised of proteins, with fish gelatine as structural matrix and bovine lactoferrin (bLF) as the active antimicrobial agent. The bLF bactericidal effect was determined against clinical isolates of Escherichia coli and Staphylococcus aureus through microdilution assays. Two distinctive methods were used to incorporate bLF into the fish gelatine nanofibres: (i) as a filler in the electrospinning formulation with concentrations of 2, 5 and 10 (wt%), and cross-linked with glutaraldehyde vapour, in order to achieve stability in aqueous solution; and (ii) through adsorption in a solution with 40mgmL-1 bLF. Fourier transform infrared spectroscopy analysis showed that the structure of both proteins remained intact through the electrospinning blending and cross-linking procedure. Remarkable antibacterial properties were obtained with membranes containing 5% and 10% bLF with a bacterial reduction of approximately 90% and 100%, respectively.

The variation of the physical properties of four different carbon nanofibers (CNFs), based-polymer nanocomposites incorporated in the same polypropylene (PP) matrix by twin-screw extrusion process was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviors as function of CNF's content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyrolitically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal stability. Further, CNF's incorporation into the polymer increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the CNFs' clusters in PP was analyzed by transmitted light optical microscopy, and grayscale analysis (GSA). The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol% above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that for tailoring the physical properties of CNF based-polymer nanocomposites, both adequate CNFs structure and content have to be chosen.

Thermal degradation of as-electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde has been studied by thermogravimetry (TG) coupled with an infrared spectrometer. The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 °C, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 and 270 °C and chitosan thermal degradation that starts around 250 °C and goes up to 400 °C. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

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.

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.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

The variation of the physical properties of four different carbon nanofibers (CNFs), based-polymer nanocomposites incorporated in the same polypropylene (PP) matrix by twin-screw extrusion process was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviors as function of CNF's content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyrolitically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal stability. Further, CNF's incorporation into the polymer increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the CNFs' clusters in PP was analyzed by transmitted light optical microscopy, and grayscale analysis (GSA). The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol% above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that for tailoring the physical properties of CNF based-polymer nanocomposites, both adequate CNFs structure and content have to be chosen.

Thermal degradation of as-electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde has been studied by thermogravimetry (TG) coupled with an infrared spectrometer. The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 °C, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 and 270 °C and chitosan thermal degradation that starts around 250 °C and goes up to 400 °C. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

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.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

The variation of the physical properties of four different carbon nanofibers (CNFs), based-polymer nanocomposites incorporated in the same polypropylene (PP) matrix by twin-screw extrusion process was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviors as function of CNF's content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyrolitically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal stability. Further, CNF's incorporation into the polymer increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the CNFs' clusters in PP was analyzed by transmitted light optical microscopy, and grayscale analysis (GSA). The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol% above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that for tailoring the physical properties of CNF based-polymer nanocomposites, both adequate CNFs structure and content have to be chosen.

Thermal degradation of as-electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde has been studied by thermogravimetry (TG) coupled with an infrared spectrometer. The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 °C, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 and 270 °C and chitosan thermal degradation that starts around 250 °C and goes up to 400 °C. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

The variation of the physical properties of four different carbon nanofibers (CNFs), based-polymer nanocomposites incorporated in the same polypropylene (PP) matrix by twin-screw extrusion process was investigated. Nanocomposites fabricated with CNFs with highly graphitic outer layer revealed electrical isolation-to-conducting behaviors as function of CNF's content. Nanocomposites fabricated with CNFs with an outer layer consisting on a disordered pyrolitically stripped layer, in contrast, revealed better mechanical performance and enhanced thermal stability. Further, CNF's incorporation into the polymer increased the thermal stability and the degree of crystallinity of the polymer, independently on the filler content and type. In addition, dispersion of the CNFs' clusters in PP was analyzed by transmitted light optical microscopy, and grayscale analysis (GSA). The results showed a correlation between the filler concentration and the variance, a parameter which measures quantitatively the dispersion, for all composites. This method indicated a value of 1.4 vol% above which large clusters of CNFs cannot be dispersed effectively and as a consequence only slight changes in mechanical performance are observed. Finally, this study establishes that for tailoring the physical properties of CNF based-polymer nanocomposites, both adequate CNFs structure and content have to be chosen.

Thermal degradation of as-electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde has been studied by thermogravimetry (TG) coupled with an infrared spectrometer. The influence of the electrospinning process and cross-linking in the electrospun chitosan thermal stability was evaluated. Up to three degradation steps were observed in the TG data, corresponding to water dehydration reaction at temperatures below 100 °C, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 and 270 °C and chitosan thermal degradation that starts around 250 °C and goes up to 400 °C. The Kissinger model was employed to evaluate the activation energies of the electrospun membranes during isothermal experiments and revealed that thermal degradation activation energy increases for the samples processed by electrospinning and subsequent neutralization and cross-linking treatments with respect to the neat chitosan powder.

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.

Different copolymers of styrene-butadiene-styrene (SBS) and hydrogenated SBS, styrene-ethylene/butylene-styrene (SEBS) were processed by electrospinning with micrometers fiber diameters. The effect of butadiene/styrene ratio, linear or radial block structure, hydrogenation, and carbon nanotube (CNT) loading on the overall material properties is reported. SEBS has higher initial modulus and mechanical hysteresis when compared to SBS. The mechanical hysteresis decreases with the number of applied cycles. The inclusion of CNTs increases the nanocomposites mechanical hysteresis and electrical conductivity independently on the copolymer matrix. The amount of styrene monomer within the samples is within the range allowed for food packaging applications. Finally, SBS and SEBS pristine samples and SEBS composites do not show cytotoxicity.

Polypyrrole (PPy) has been synthesized as an homogeneous layer on the fibers of electroactive poly(vinylidene fluoride) (PVDF) electrospun mats via in-situ polymerization of pyrrole (Py). A core-sheath structure was obtained, the electrical conductivity depending on synthesis time, which influences the morphology and thickness of PPy layer. An overall dc conductivity of 70 ± 4 S m-1 was obtained for the sample with a PPy layer of 160 ± 25 nm. Further, the thermal coefficient of resistivity obtained for the sample after 120 min in-situ polymerization is almost twice the one calculated for the sample with 5 min synthesis time. The temperature dependence of the electrical dc conductivity of the PPy/PVDF membranes gives evidence of a transport mechanism based on Mott's variable range hopping model. Using this model, values for the density of states, hopping energy and distance were assessed.

Development of suitable membranes is a fundamental requisite for tissue and biomedical engineering applications. This work presents fish gelatin random and aligned electrospun membranes cross-linked with glutaraldehyde (GA). It was observed that the fiber average diameter and the morphology is not influenced by the GA exposure time and presents fibers with an average diameter around 250 nm. Moreover, when the gelatin mats are immersed in a phosphate buffered saline solution (PBS), they can retain as much as 12 times its initial weight of solution almost instantaneously, but the material microstructure of the fiber mats changes from the characteristic fibrous to an almost spherical porous structure. Cross-linked gelatin electrospun fiber mats and films showed a water vapor permeability of 1.37 ± 0.02 and 0.13 ± 0.10 (g.mm)/(m 2.h.kPa), respectively. Finally, the processing technique and cross-linking process does not inhibit MC-3T3-E1 cell adhesion. Preliminary cell culture results showed good cell adhesion and proliferation in the cross-linked random and aligned gelatin fiber mats.

Electroactive materials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidene fluoride), PVDF, have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.

Electroactive materials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidene fluoride), PVDF, have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.

Electroactive materials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidene fluoride), PVDF, have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.

Electroactive materials can be taken to advantage for the development of sensors and actuators as well as for novel tissue engineering strategies. Composites based on poly(vinylidene fluoride), PVDF, have been evaluated with respect to their biological response. Cell viability and proliferation were performed in vitro both with Mesenchymal Stem Cells differentiated to osteoblasts and Human Fibroblast Foreskin 1. In vivo tests were also performed using 6-week-old C57Bl/6 mice. It was concluded that zeolite and clay composites are biocompatible materials promoting cell response and not showing in vivo pro-inflammatory effects which renders both of them attractive for biological applications and tissue engineering, opening interesting perspectives to development of scaffolds from these composites. Ferrite and silver nanoparticle composites decrease osteoblast cell viability and carbon nanotubes decrease fibroblast viability. Further, carbon nanotube composites result in a significant increase in local vascularization accompanied an increase of inflammatory markers after implantation.

Poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) membranes are evaluated for lithium-ion battery separator applications. Some of the main parameters affecting separator performance such as porosity, dehydration of lithium ions, and processing technique (Li-ion uptake versus composite formation) are investigated. The polymer characteristics, as determined by infrared spectroscopy, do not change as a function of porosity, dehydration of lithium ions in the electrolyte solution, or processing technique. The electrochemical impedance spectroscopy represented through the Nyquist plot, Bode plot, and the ionic conductivity as a function of temperature strongly depends on the aforementioned parameters. The membrane that exhibits the highest ionic conductivity is a porous membrane without dehydration of lithium ions and prepared by the uptake technique. The performance of the membrane for battery applications are, therefore, strongly influenced both by porosity and processing technique.

Battery separators based on electrospun membranes of poly(vinylidene fluoride) (PVDF) have been prepared in order to study the effect of fiber alignment on the performance and characteristics of the membrane. The prepared membranes show an average fiber diameter of ~272 nm and a degree of porosity of ~87 %. The gel polymer electrolytes are prepared by soaking the membranes in the electrolyte solution. The alignment of the fibers improves the mechanical properties for the electrospun membranes. Further, the microstructure of the membrane also plays an important role in the ionic conductivity, being higher for the random electrospun membrane due to the lower tortuosity value. Independently of the microstructure, both membranes show good electrochemical stability up to 5.0 V versus Li/Li+. These results show that electrospun membranes based on PVDF are appropriate for battery separators in lithium-ion battery applications, the random membranes showing a better overall performance.

Thermoplastic elastomer/carbon nanotube composites are studied for sensor applications due to their excellent mechanical and electrical properties. Piezoresisitive properties of tri-block copolymer styrene-butadiene-styrene (SBS)/carbon nanotubes (CNT) prepared by solution casting have been investigated. The initial elastic modulus of the SBS/CNT composites increases with increasing the CNT filler content present in the samples, without losing the high deformation capability of the polymer matrix (∼1500%). Furthermore, above the percolation threshold these materials are unique for the development of large deformation sensors due to the strong piezoresistive response. Piezoresistive properties evaluated by uniaxial stretching in tensile mode and 4-point bending showed gauge factors up to 120. The linearity obtained between strain and electrical resistance makes these composites interesting for large strain piezoresistive sensors applications.

The success of artificial prosthetic replacements depends on the fixation of the artificial prosthetic component after being implanted in the thighbone. This work shows a smart prosthesis based on highly sensitive silicon thin-film piezoresistive sensors attached to a hip prosthesis. The performance of the sensors for this application is studied and compared to commercial strain gauge sensors. Mechanical stress-strain experiments were performed in compressive mode, during 10,000 cycles and data was acquired at mechanical vibration frequencies of 0.5 Hz, 1 Hz and 5 Hz, and sent to a computer by means of a wireless link. The results show that there is a decrease in sensitivity of the thin-film silicon piezoresistive (n-type nanocrystalline Si) sensors when they are attached to the prosthesis, however this decrease does not compromise its monitoring performance. The sensitivity, compared to that of commercial strain gauges, is much larger due to their higher gauge factor (-23.5), when compared to the gage factor of commercial sensors (2).

Poly[(vinylidene fluoride)-co-trifluoroethylene] membranes doped with different lithium perchlorate trihydrate contents have been produced by solvent evaporation at different temperatures in order to tailor membrane morphology and characterized by infrared spectroscopy, thermal and mechanical analysis techniques. Electrochemical properties of the composite membranes for battery applications were determined through complex impedance spectroscopy and cyclic voltammetry. The polymer phase and molecular main features of the polymer do not depend on lithium ion content and crystallization temperature. Higher crystallization temperatures allow obtaining more porous polymer microstructures which strongly influences the electrical response. The degree of crystallinity and ionic conductivity, on the other hand, are related to lithium ion content. The obtained ionic conductivity determined by impedance spectroscopy increases with increasing lithium ion content. The most conducting electrolyte composition, PVDF-TrFE 1.5LiClO4.3H2O exhibits 2.3 x 10- 6 S cm- 1 and corresponds to the membrane crystallized at room temperature, i.e. the most porous membrane.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature for lithium ion battery separator applications. Microporous membranes with varying pore size and overall porosity are obtained and the thermal, mechanical and electrical properties of the membranes were evaluated before and after liquid uptake of an electrolyte solution of 1M LiClO 4-PC.The electrolyte solution does not change the phase of the polymer and the membranes separators exhibited good thermal and mechanical properties until 100. °C. The electrolyte solution improves the ionic conductivity of the microporous membranes with the ionic conductivity decreasing with increasing degree of porosity of the membranes. The electrical results obtained for the membranes were compared to the ones obtained for Celgard separators.

Biodegradable poly(L-lactide acid) (PLLA) nanofiber membranes were prepared by electrospinning of PLLA and poly(ethylene oxide) (PEO). The selective removal of PEO by water allows to obtain smaller fiber diameters and to increase the porosity of the membranes in comparison to PLLA membranes obtained under the same electrospinning conditions. After removal of PEO membranes with fiber sizes of 260 nm and average porosity close to 80% are obtained. Thermal and infrared results confirm the poor miscibility of PLLA and PEO, with the PEO randomly distributed along the PLLA fibers. On the other, PLLA and PEO mixing strongly affect their respective degradation temperatures. The influence of the PEO in the electrospinning process is discussed and the results are correlated to the evolution of the PLLA fiber diameter.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature. The morphology of the membranes reveals an interconnected porous structure with porosity ranging from 72% up to 80%. The conductivity of the membranes and the LiClO 4 uptake increases with increasing porosity. After uptake, the increase of the electrical conductivity is larger for the less porous membranes and the thermal stability of the electrical conductivity is increased.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature. The morphology of the membranes reveals an interconnected porous structure with porosity ranging from 72% up to 80%. The conductivity of the membranes and the LiClO 4 uptake increases with increasing porosity. After uptake, the increase of the electrical conductivity is larger for the less porous membranes and the thermal stability of the electrical conductivity is increased.

Biodegradable poly(L-lactide acid) (PLLA) nanofiber membranes were prepared by electrospinning of PLLA and poly(ethylene oxide) (PEO). The selective removal of PEO by water allows to obtain smaller fiber diameters and to increase the porosity of the membranes in comparison to PLLA membranes obtained under the same electrospinning conditions. After removal of PEO membranes with fiber sizes of 260 nm and average porosity close to 80% are obtained. Thermal and infrared results confirm the poor miscibility of PLLA and PEO, with the PEO randomly distributed along the PLLA fibers. On the other, PLLA and PEO mixing strongly affect their respective degradation temperatures. The influence of the PEO in the electrospinning process is discussed and the results are correlated to the evolution of the PLLA fiber diameter.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature for lithium ion battery separator applications. Microporous membranes with varying pore size and overall porosity are obtained and the thermal, mechanical and electrical properties of the membranes were evaluated before and after liquid uptake of an electrolyte solution of 1M LiClO 4-PC.The electrolyte solution does not change the phase of the polymer and the membranes separators exhibited good thermal and mechanical properties until 100. °C. The electrolyte solution improves the ionic conductivity of the microporous membranes with the ionic conductivity decreasing with increasing degree of porosity of the membranes. The electrical results obtained for the membranes were compared to the ones obtained for Celgard separators.

Poly[(vinylidene fluoride)-co-trifluoroethylene] membranes doped with different lithium perchlorate trihydrate contents have been produced by solvent evaporation at different temperatures in order to tailor membrane morphology and characterized by infrared spectroscopy, thermal and mechanical analysis techniques. Electrochemical properties of the composite membranes for battery applications were determined through complex impedance spectroscopy and cyclic voltammetry. The polymer phase and molecular main features of the polymer do not depend on lithium ion content and crystallization temperature. Higher crystallization temperatures allow obtaining more porous polymer microstructures which strongly influences the electrical response. The degree of crystallinity and ionic conductivity, on the other hand, are related to lithium ion content. The obtained ionic conductivity determined by impedance spectroscopy increases with increasing lithium ion content. The most conducting electrolyte composition, PVDF-TrFE 1.5LiClO4.3H2O exhibits 2.3 x 10- 6 S cm- 1 and corresponds to the membrane crystallized at room temperature, i.e. the most porous membrane.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature for lithium ion battery separator applications. Microporous membranes with varying pore size and overall porosity are obtained and the thermal, mechanical and electrical properties of the membranes were evaluated before and after liquid uptake of an electrolyte solution of 1M LiClO 4-PC.The electrolyte solution does not change the phase of the polymer and the membranes separators exhibited good thermal and mechanical properties until 100. °C. The electrolyte solution improves the ionic conductivity of the microporous membranes with the ionic conductivity decreasing with increasing degree of porosity of the membranes. The electrical results obtained for the membranes were compared to the ones obtained for Celgard separators.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature. The morphology of the membranes reveals an interconnected porous structure with porosity ranging from 72% up to 80%. The conductivity of the membranes and the LiClO 4 uptake increases with increasing porosity. After uptake, the increase of the electrical conductivity is larger for the less porous membranes and the thermal stability of the electrical conductivity is increased.

Biodegradable poly(L-lactide acid) (PLLA) nanofiber membranes were prepared by electrospinning of PLLA and poly(ethylene oxide) (PEO). The selective removal of PEO by water allows to obtain smaller fiber diameters and to increase the porosity of the membranes in comparison to PLLA membranes obtained under the same electrospinning conditions. After removal of PEO membranes with fiber sizes of 260 nm and average porosity close to 80% are obtained. Thermal and infrared results confirm the poor miscibility of PLLA and PEO, with the PEO randomly distributed along the PLLA fibers. On the other, PLLA and PEO mixing strongly affect their respective degradation temperatures. The influence of the PEO in the electrospinning process is discussed and the results are correlated to the evolution of the PLLA fiber diameter.

Poly[(vinylidene fluoride)-co-trifluoroethylene] membranes doped with different lithium perchlorate trihydrate contents have been produced by solvent evaporation at different temperatures in order to tailor membrane morphology and characterized by infrared spectroscopy, thermal and mechanical analysis techniques. Electrochemical properties of the composite membranes for battery applications were determined through complex impedance spectroscopy and cyclic voltammetry. The polymer phase and molecular main features of the polymer do not depend on lithium ion content and crystallization temperature. Higher crystallization temperatures allow obtaining more porous polymer microstructures which strongly influences the electrical response. The degree of crystallinity and ionic conductivity, on the other hand, are related to lithium ion content. The obtained ionic conductivity determined by impedance spectroscopy increases with increasing lithium ion content. The most conducting electrolyte composition, PVDF-TrFE 1.5LiClO4.3H2O exhibits 2.3 x 10- 6 S cm- 1 and corresponds to the membrane crystallized at room temperature, i.e. the most porous membrane.

Poly(vinylidene fluoride-trifluorethylene) porous membranes were prepared by solvent evaporation at room temperature for lithium ion battery separator applications. Microporous membranes with varying pore size and overall porosity are obtained and the thermal, mechanical and electrical properties of the membranes were evaluated before and after liquid uptake of an electrolyte solution of 1M LiClO 4-PC.The electrolyte solution does not change the phase of the polymer and the membranes separators exhibited good thermal and mechanical properties until 100. °C. The electrolyte solution improves the ionic conductivity of the microporous membranes with the ionic conductivity decreasing with increasing degree of porosity of the membranes. The electrical results obtained for the membranes were compared to the ones obtained for Celgard separators.