Surface-ATRP of PEGMA onto polydimethyl siloxane for biomedical applications

Silicone rubber (poly(dimethyl siloxane; PDMS)), is extensively used for biomedical implants due to its low toxicity, flexible processing techniques, long-term endurance and good blood compatibility. However, the presence of low molecular weight organic molecules and catalyst residues that cause host systemic inflammatory reactions. The hydrophobic nature of PDMS also allows microbial adhesion followed by infection. Hydrophilic PDMS surfaces would be of great value in inhibiting biofilm formation thus prolonging the lifetime of the implants. This could be obtained by surface-initiated atom transfer radical polymerization (ATRP). The robustness and versatility of ATRP allow the preparation of functional bioactive surfaces, including antifouling, antibacterial, stimuliresponsive, biomolecule-coupled and micropatterned surfaces.[1-3] We aim at establishing the experimental conditions allowing the surface-grafting of polyethylene glycol methacrylate (PEGMA) by surface attaching an initiator (1- trichlorosilyl-2-(chloromethylphenyl)ethane) onto PDMS (Sylgard ® 184). Here, cooper is being used as a metal catalyst and 2,2'-Bipyridine as a ligant. Polymerizations are being assayed in aqueous media. The native smooth and transparent surface of the PDMS could be preserved following polymerization (as confirmed by SEM). FTIR-ATR also showed the presence of PEGMA polymer chains. By contact angle measurement, a change in the surface hydrophobicity was observed, the values changing from 114º to 60º, following 30h polymerization. Work is in progress to optimize the modification of PDMS by PEGMA surface-ATRP. This implies following up the polymer chain growth kinetics, surface characterization by XPS, FTIR-ATR, SEM and contact angle measurements. Static and dynamic microbial adhesion, as well as biocompatibility studies are also envisaged

Evaluation of phenolic compounds and antioxidant activity of blueberries and modelization by artificial neural networks

The study aimed at evaluating the influence of different production conditions, conservation and extraction procedures on the total phenolic compounds and antioxidant activity of blueberries by DPPH and ABTS methods. The production factors considered were origin, altitude of the farm location and age of the bushes. The conservation conditions considered were freezing as opposed to the fresh product. The extraction procedures included two different solvents and two orders of extraction. The data analysis was carried out by training artificial neural networks to model the data and extract information from the model. The results obtained revealed that the type of extract and the order of extraction influenced the concentrations of phenolic compounds as well as the antioxidant activity of the different samples studied. Also the origin of the farms from where the blueberries were harvested significantly influence those properties, showing that the blueberries from Oliveira do Hospital had less phenolic compounds and lower antioxidant activity. Also older bushes at higher altitudes seem to produce berries richer in these properties. Regarding conservation, no influence was observed for phenols but a slight influence could be detected for antioxidant activity.info:eu-repo/semantics/publishedVersio

Die Optimierung von Poly(Dimethylsiloxan) für biomedizinische Anwendungen durch oberflächeninitiierte Atom-Transferradikal-Polymerisation

Project BIOSURFA ref. PTDC/SAU-BEB/73498/200

Secagens convectivas de pêra S. Bartolomeu em túnel.

Foram realizadas em Agosto dos anos de 2007 e 2008 secagens de pêra São Bartolomeu em túnel, com circulação de ar forçada. Estes ensaios foram realizados, como alternativa às técnicas convencionais de secagem solar, em regime contínuo. Nos anos de 2007 e 2008 foram utilizadas temperaturas de sacagem de 40ºC. Em 2007 foi realizada também uma secagem a 30ºC. Foram utilizados diversos caudais de ar nos dois anos. Os resultados obtidos permitiram constatar que a temperatura desempenha um papel fulcral ao nível da velocidade de secagem, quando comparada com o factor velocidade do ar. As secagens a 40ºC revelaram-se vantajosas ao nível da rapidez, aliada a uma maior segurança alimentar do processo, quando comparadas com a mesma operação a 30ºC. As secagens convectivas efectuadas em regime contínuo mostraram ser uma alternativa a considerar relativamente à secagem tradicional de pêra São Bartolomeu, por permitir uma maior rapidez de secagem e controlo do processo. Contudo a ausência de algumas características organolépticas, nomeadamente ao nível da coloração do produto final, apresenta-se como uma condicionante a ser minimizada

Comparação de secagens convectivas em túnel, em regime contínuo e descontínuo.

A secagem convectiva, em túnel, de pêra São Bartolomeu, pode ser efectuada em modo contínuo com equipamentos que imponham valores pré- escolhidos para a temperatura e velocidade do ar de secagem, tornando o processo independente das condições meteorológicas, modo este que não é análogo ao verificado numa secagem solar tradicional, inerentemente descontínua (suspensão do processo nos períodos nocturnos). O presente estudo comparou as eventuais vantagens e desvantagens da utilização de uma metodologia de secagem descontínua, convectiva e forçada em túnel, mais próxima das condições habituais de secagem por via solar, quando comparada com uma secagem contínua, para valores análogos da temperatura e velocidade do ar de secagem. Os resultados demonstram que o tempo total de secagem em modo contínuo é mais curto (um decréscimo de cerca de 28 horas). Contudo, em modo descontínuo, a ventilação e o aquecimento estiveram desligados 67,5 horas, correspondentes a 55,8% do tempo total do ensaio. Foi também verificado que a remoção de água no modo descontínuo foi sempre superior em cada reactivação do sistema de termo ventilação quando comparada com o instante imediatamente anterior à pausa nocturna. Os resultados obtidos evidenciam que o modo descontínuo apresenta reduções substanciais da energia gasta, se bem que à custa de um aumento, em todo o caso relativamente pouco significativo, do tempo total de secagem, o que é um resultado muito interessante do ponto de vista da poupança energética em processos desta natureza

Artificial neural network modelling of the antioxidant activity and phenolic compounds of bananas submitted to different drying treatments

Bananas (cv. Musa nana and Musa cavendishii) fresh and dried by hot air at 50 and 70 °C and lyophilisation were analysed for phenolic contents and antioxidant activity. All samples were subject to six extractions (three with methanol followed by three with acetone/water solution). The experimental data served to train a neural network adequate to describe the experimental observations for both output variables studied: total phenols and antioxidant activity. The results show that both bananas are similar and air drying decreased total phenols and antioxidant activity for both temperatures, whereas lyophilisation decreased the phenolic content in a lesser extent. Neural network experiments showed that antioxidant activity and phenolic compounds can be predicted accurately from the input variables: banana variety, dryness state and type and order of extract. Drying state and extract order were found to have larger impact in the values of antioxidant activity and phenolic compounds

Interaction of wine mannoproteins and arabinogalactans with anthocyanins

Wine polymeric material (WPM), which includes polysaccharides, proteins, and polyphenolic compounds, interacts with anthocyanins. To determine the contribution of polysaccharides in these interactions, the diffusion performance of anthocyanins along a dialysis membrane was determined in the presence and absence of isolated mannoproteins (MP) and arabinogalactans (AG) from WPM. Furthermore, to estimate the extent of the interaction between WPM and polyphenolic compounds, the activation energy (Ea) required for their diffusion in the presence of WPM was determined. AG, generally more abundant than MP in wine, interact in a greater extent with anthocyanins, showing their relevant contribution for WPM/anthocyanins interactions. The Ea for the diffusion of polyphenolic compounds in presence of WPM indicated the occurrence of interactions with relative weak to strong intensities (2.6–50.8 kJ/mol). As not all polyphenolic compounds were able to be released from WPM, stronger interactions, possibly by covalent linkages, are involved, providing new insights on WPM/polyphenolic compounds relationships.info:eu-repo/semantics/acceptedVersio

Unraveling the ecotoxicity of deep eutectic solvents using the mixture toxicity theory

The interest on deep eutectic solvents (DES) has been increasing. However, the ecotoxicological profile of DES is scarcely known. Also, despite previous studies showed that DES components dissociate in water, none assessed DES toxicity using the classical and adequate models for mixture toxicity prediction - concentration addition (CA) and independent action (IA). This study evaluates the ecotoxicological profile of DES based on [N1111]Cl, [N2222]Cl and [N3333]Cl as hydrogen bond acceptors (HBA) combined with hydrogen-bond donors (HBD) vis. ethylene glycol and 1-propanol, through the Microtox® Acute Toxicity Test. CA and IA with deviations describing synergism/antagonism, dose-ratio and dose-level effects were fitted to the toxicity data. Neither the starting materials nor DES were found hazardous to Aliivibrio fischeri, in this specific case agreeing with the claimed "green character" of DES. Among the starting materials, ethylene glycol was the least toxic, whereas [N3333]Cl was the most toxic (30 min-EC50 = 96.49 g L-1 and 0.5456 g L-1, respectively). DES toxicity followed the same trend as observed for the salts: [N1111]Cl-based DES < [N2222]Cl-based DES < [N3333]Cl-based DES. The IA model, with specific deviations, adjusted better in 5 out of 6 DES. Antagonism was observed for [N1111]Cl-based DES, and synergism for [N3333]Cl-based DES and for 1-propanol:[N2222]Cl. The application of the mixture toxicity models represents a breakthrough in the problematic of assessing the toxicity of the countless number of DES that can be created with the same starting materials, since they provide the expected toxicity of any virtual combination between HBA and HBD.publishe

Diretiva Quadro da Água: o instrumento legal para a avaliação da qualidade ecológica da água, em rios, na União Europeia

A Diretiva Quadro da Água (DQA) foi implementada na União Europeia em 2000 e gradualmente transposta para a legislação nacional dos Estados Membros. A DQA constituiu um importante avanço na proteção dos ecossistemas aquáticos superficiais, águas de transição e subterrâneas, tendo como objetivo atualmente que todas as massas de água atinjam a Boa qualidade ecológica, até 2027. No entanto, os procedimentos que permitem a monitorização e classificação das massas de água no âmbito da DQA são complexos e morosos. O presente artigo apresenta o enquadramento e a aplicação das metodologias de monitorização e classificação das massas de água de natureza lótica (p.ex. rios) de uma forma simplificada, contribuindo para melhorar a acessibilidade da sociedade em geral a esta informação, e consequentemente favorecendo a disseminação dos princípios e metodologias de monitorização associados à DQA. Este trabalho está focado especificamente em sistemas lóticos. Uma vez que a avaliação da qualidade da água sensu DQA considera a monitorização de comunidades biológicas e que as comunidades biológicas de maior importância indicadora são distintas entre diferentes tipos de ecossistemas aquáticos (p.ex. entre rios e albufeiras ou lagos), o enfoque foi definido para tornar o documento mais conciso. A informação aqui disponibilizada poderá servir como um suporte relevante para o desenvolvimento de estratégias de envolvimento da sociedade na implementação da DQA em Portugal, que se encontra ainda aquém do desejável.publishe

A 45° saw-dicing process applied to a glass substrate for wafer-level optical splitter fabrication for optical coherence tomography

This paper reports on the development of a technology for the wafer-level fabrication of an optical Michelson interferometer, which is an essential component in a micro optoelectromechanical system (MOEMS) for a miniaturized optical coherence tomography (OCT) system. The MOEMS consists on a titanium dioxide/silicon dioxide dielectric beam splitter and chromium/gold micro-mirrors. These optical components are deposited on 45° tilted surfaces to allow the horizontal/vertical separation of the incident beam in the final microintegrated system. The fabrication process consists of 45° saw dicing of a glass substrate and the subsequent deposition of dielectric multilayers and metal layers. The 45° saw dicing is fully characterized in this paper, which also includes an analysis of the roughness. The optimum process results in surfaces with a roughness of 19.76 nm (rms). The actual saw dicing process for a high-quality final surface results as a compromise between the dicing blade’s grit size (#1200) and the cutting speed (0.3mm s−1). The proposed wafer-level fabrication allows rapid and low-cost processing, high compactness and the possibility of wafer-level alignment/ assembly with other optical micro components for OCT integrated imagingThis work is supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 - Programa Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio