Processing and characterization of alpha-elastin electrospun membranes

Elastin isolated from fresh bovine ligaments was dissolved in a mixture of 1,1,1,3,3,3-Hexafluoro-2-propanol and water and electrospun into fiber membranes under different processing conditions. Fiber mats of randomly and aligned fibers were obtained with fixed and rotating ground collectors and fibrils were composed by thin ribbons whose width depends on electrospinning conditions; fibrils with 721 nm up to 2.12 m width were achieved. After cross-linking with glutaraldehyde, -elastin can uptake as much as 1700 % of PBS solution and a slight increase on fiber thickness was observed. The glass transition temperature of electrospun fiber mats was found to occur at ~ 80 ºC. Moreover, -Elastin showed to be a perfect elastomeric material, and no mechanical hysteresis was found in cycle mechanical measurements. The elastic modulus obtained for oriented and random fibers mats in a PBS solution was 330 ± 10 kPa and 732 ± 165 kPa, respectively. Finally, the electrospinning and cross-linking process does not inhibit MC-3T3-E1 cell adhesion. Cell culture results showed good cell adhesion and proliferation in the cross-linked elastin fiber mats.

Electrospun silk-elastin-like fiber mats for tissue engineering applications

Protein-based polymers are present in a wide variety of organisms fulfilling structural and mechanical roles. Advances in protein engineering and recombinant DNA technology allow the design and production of recombinant protein-based polymers (rPBPs) with an absolute control of its composition. Although the application of recombinant proteins as biomaterials is still an emerging technology, the possibilities are limitless and far superior to natural or synthetic materials, as the complexity of the structural design can be fully customized. In this work, we report the electrospinning of two new genetically engineered silk-elastin-like proteins (SELPs) consisting of alternate silk- and elastin-like blocks. Electrospinning was performed with formic acid and aqueous solutions at different concentrations without addition of further agents. The size and morphology of the electrospun structures was characterized by scanning electron microscopy showing to be dependent of concentration and solvent used. Treatment with air saturated with methanol was employed to stabilize the structure and promote water insolubility through a time-dependent conversion of random coils into β-sheets (FTIR). The resultant methanol-treated electrospun mats were characterized for swelling degree (570-720%), water vapour transmission rate (1083 g/m2/day) and mechanical properties (modulus of elasticity of ~126 MPa). Furthermore, the methanol-treated SELP fiber mats showed no cytotoxicity and were able to support adhesion and proliferation of normal human skin fibroblasts. Adhesion was characterized by a filopodia-mediated mechanism. These results demonstrate that SELP fiber mats can provide promising solutions for the development of novel biomaterials suitable for tissue engineering applications.

A Wireless EEG Acquisition Platform based on Embedded Systems

This paper proposes a wireless EEG acquisition platform based on Open Multimedia Architecture Platform (OMAP) embedded system. A high-impedance active dry electrode was tested for improving the scalp- electrode interface. It was used the sigma-delta ADS1298 analog-to-digital converter, and developed a “kernelspace” character driver to manage the communications between the converter unit and the OMAP’s ARM core. The acquired EEG signal data is processed by a “userspace” application, which accesses the driver’s memory, saves the data to a SD-card and transmits them through a wireless TCP/IP-socket to a PC. The electrodes were tested through the alpha wave replacement phenomenon. The experimental results presented the expected alpha rhythm (8-13 Hz) reactiveness to the eyes opening task. The driver spends about 725 μs to acquire and store the data samples. The application takes about 244 μs to get the data from the driver and 1.4 ms to save it in the SD-card. A WiFi throughput of 12.8Mbps was measured which results in a transmission time of 5 ms for 512 kb of data. The embedded system consumes about 200 mAh when wireless off and 400 mAh when it is on. The system exhibits a reliable performance to record EEG signals and transmit them wirelessly. Besides the microcontroller-based architectures, the proposed platform demonstrates that powerful ARM processors running embedded operating systems can be programmed with real-time constrains at the kernel level in order to control hardware, while maintaining their parallel processing abilities in high level software applications.

Guimarães residents’ perceptions towards tourism impacts: a cluster analysis

The present study was designed to assess and segment local residents with respect to their perceived impacts of Guimarães tourism development. The residents of this municipality (located in the northern part of Portugal) are quite strong in their support to tourism. However, they do not keep a homogeneous perception of tourism impacts. A clusters analysis using data from a survey of 400 Guimarães residents’ has revealed the existence of three clusters, according the different degrees of perceived tourism impacts: the Skeptics - moderate in relation to the benefits (averages range from 2.89-3.74) and the ones more concerned with its costs (averages range from 2.86-3.74); the Moderately optimistic - very optimistic about the benefits of tourism (averages range from 3.74-4.51) and conscious of the costs (averages range from 2.71-3.49); the Enthusiasts - very optimistic about tourism benefits (averages range from 2.92-4.52) and little worried about its costs (averages range from 1.78-3.26). Following the data from the survey, the findings are discussed and a few conclusions are extracted.

Turismo como estratégia integradora dos recursos locais: o caso do Minho-Lima (palestra)

O turismo tem vindo a ganhar um espaço crescente nas propostas de desenvolvimento do mundo rural, constituindo, no caso de certas regiões mais remotas e deprimidas, um dos sectores melhor colocados para alcançar esse objectivo. Este papel tem que ver com a possibilidade de tirar partido dos recursos endógenos desses territórios. Esta investigação pretendeu contribuir para clarificar o papel do turismo no desenvolvimento de um território eminentemente rural, o Minho-Lima, tendo-se desenvolvido em três etapas. Numa primeira etapa, procedeu-se à inventariação e avaliação dos recursos turísticos dos municípios da sub-região, bem como à análise dos elementos complementares e dos factores externos relacionados com a imagem de destino. Numa segunda fase, procurou-se ter a perspectiva dos actores envolvidos, do lado da oferta (agentes institucionais e proprietários de restaurantes) e do lado da procura (turistas). Finalmente, elaborou-se um diagnóstico da situação existente e um conjunto de propostas de política para o desenvolvimento turístico da sub-região. Com o diagnóstico realizado e as recomendações de política propostas pretende-se contribuir para o desenvolvimento sustentado do turismo na sub-região em estudo.

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 a reduction of 100 % and 99.69 % against E. coli and S. aureus were achieved, respectively.

Effect of filler content on morphology and physical-chemical characteristics of poly(vinylidene fluoride)/NaY-zeolite filled membranes

Poly(vinylidene fluoride) electrospun membranes have been prepared with different NaY zeolite contents up to 32%wt. Inclusion of zeolites induces an increase of average fiber size from ~200 nm in the pure polymer up to ~500 nm in the composite with 16%wt zeolite content. For higher filler contents, a wider distribution of fibers occurs leading to a broader size distributions between the previous fiber size values. Hydrophobicity of the membranes increases from ~115º water contact angle to ~128º with the addition of the filler and is independent on filler content, indicating a wrapping of the zeolite by the polymer. The water contact angle further increases with fiber alignment up to ~137º. Electrospun membranes are formed with ~80 % of the polymer crystalline phase in the electroactive  phase, independently on the electrospinning processing conditions or filler content. Viability of MC3T3-E1 cells on the composite membranes after 72 h of cell culture indicates the suitability of the membranes for tissue engineering applications.

Modifying fish gelatin electrospun membranes for biomedical applications: cross- linking and swelling behavior

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)/(m2.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.

Effect of neutralization and cross-linking on the thermal degradation of chitosan electrospun membranes

Thermal degradation of as electrospun chitosan membranes and samples subsequently treated with ethanol and cross-linked with glutaraldehyde (GA) have been studied by thermogravimetry (TG) coupled with an infrared spectrometer (FTIR). 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 ºC, loss of side groups formed between the amine groups of chitosan and trifluoroacetic acid between 150 – 270 ºC and chitosan thermal degradation that starts around 250 ºC and goes up to 400 ºC. 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.

Avaliação do Impacto dos Fundos do QREN no Desempenho Económico e Financeiro das PME: Estudo de Caso da Indústria Transformadora do Concelho de Barcelos

A União Europeia é composta por regiões com diferentes níveis de desenvolvimento económico. O instrumento financeiro FEDER – Fundo Europeu de Desenvolvimento Regional surgiu com o objetivo de corrigir alguns dos desequilíbrios regionais, nomeadamente através da atribuição de fundos ao tecido empresarial, destinados a investimentos produtivos e geradores de emprego, fomentando a coesão entre vários Estados Membros. Ao longo dos tempos as empresas adquiriram uma importância crescente no âmbito da Política Regional Europeia, uma vez que a competitividade das regiões depende diretamente dos níveis de competitividade do seu tecido empresarial. Dada a importância desta temática, a presente investigação tem como objeto de estudo uma análise ao tecido empresarial a posteriori da atribuição dos fundos comunitários. Concretamente, o presente trabalho constitui um estudo empírico ao impacto dos sistemas de incentivo atribuídos às empresas no contexto do território Português. Tem como foco principal o estudo da influência do Quadro de Referencia Estratégico Nacional (QREN) no desempenho económico e financeiro das micro, pequenas e médias empresas (PME) do setor da indústria transformadora no período 2007-2013. A análise económica e financeira constitui um instrumento quantitativo de avaliação de desempenho empresarial, o qual, quando comparado com um padrão perfil, mede a competitividade. O estudo de caso consiste na análise de indicadores económicos e financeiros de uma amostra de 56 PME, que beneficiaram de apoios do QREN no âmbito do Programa Operacional Fatores de Competitividade, sediadas no concelho de Barcelos, assim como a aplicação de um questionário dirigido aos seus diretores financeiros de forma a avaliar a sua perceção sobre a importância dos projetos implementados, os seus impactos e perspetivas para projetos futuros. Da análise aos resultados quantitativos podemos concluir que, de uma forma geral, os indicadores económicos como volume de negócios, exportações, valor acrescentado bruto e produtividade tiveram crescimentos substanciais e resultados estatisticamente significativos. Quanto à perceção por parte das empresas, de acordo com o questionário aplicado, encontram-se satisfeitas com os apoios comunitários na concretização dos seus projetos, assim como salientam a existência de melhorias nos indicadores económicos, principalmente nos indicadores de crescimento, medidos em volume de negócios e exportações. Concluiu-se ainda que, na inexistência do apoio dos fundos estruturais, as empresas implementariam o mesmo investimento produtivo, no entanto a um ritmo mais lento, traduzindo uma dinâmica e flexibilidade por parte das empresas.