Three dimensional scaffolds based on electroactive polymers for tissue engineering applications

Tese de Doutoramento em Engenharia de MateriaisBiomaterials play an increasingly prominent important role in the development and success of tissue engineering, particularly in the regeneration or reestablishment of tissue functions and organs. The improvement in the understanding of the role of biomaterials in the formation and regeneration of new tissue has promoted faster and more effective developments in this area. Biomaterials based on electroactive polymers have gained special interest in the scientific community for applications in tissue engineering, in particular for mechanosensitive tissues (bone, ligaments/tendons) and electroative tissues (brain cells, heart and muscles). Among them, piezoelectric materials show a strong application potential due to their ability to mimic specific biological environments through electrical stimulation. The main objective of this study was to produce scaffolds with different morphologies (fibers, particles and three-dimensional scaffolds) based on piezoelectric polymers, poly(vinylidene fluoride) (PVDF), poly(hydroxybutyrate) (PHB) and poly(L- lactic acid) (PLLA) for tissue engineering applications. Plasma treatments were also used to modify the wettability of the materials. Thus, PVDF samples were processed by electrospinning technique and plasma treatments were performed under oxygen atmosphere for different times and applied power, in order to modify the wettability of the hydrophobic fiber surface. It was observed that plasma treatments didn´t significantly change the average fiber diameter (~ 400 ± 200 nm) or the physicochemical properties of the membranes, in particularly the β-phase content (~ 80-85 %) and the crystallinity degree (42 ± 2 %), showing that this is a suitable method to obtain superhydrophilic membranes. PVDF microspheres were processed by electrospray technique. Among the different processing parameters, polymer concentration was the one that most influenced the microspheres formation. Microspheres with average diameter ranging between 0.81±0.34 μm and 5.55±2.34 μm with a β-phase content between 63-74 % and a degree of crystallinity between 45 and 55% were obtained from dilute or semi-dilute solutions. Cell viability assays demonstrated the potential of the PVDF microspheres for tissue engineering applications. Three dimensional scaffolds based on PVDF with different porosities were produced using three different methods: solvent casting with sodium chloride (NaCl), solvent casting and freeze extraction using nylon and poly (vinyl alcohol) (PVA) templates. Regardless of the processing method, the scaffolds showed polymer crystallization in the β-phase and a degree of crystallinity of ~ 45%. Mechanical tests demonstrated the suitability of the materials for tissue engineering applications. PHB membranes were processed by electrospinning and the influence of processing parameters on the size and distribution of fibers was studied. It was found that the average fiber diameter of the PHB membranes decreased with decreasing internal diameter of the needle and increased with increasing applied electric field and flow rate up to ~ 2.0 µm. The processing parameters didn´t affect the crystalline phase of the PHB membranes yielding a degree of crystallinity of 53%. Further, cell viability studies proved the suitability of the material for tissue engineering applications. Plasma treatments under argon and oxygen atmospheres were performed with thin films and PLLA membranes obtained by solvent casting and electrospinning, respectively. The average diameter of the fibers didn´t change significantly for argon (866 ± 361 nm) or oxygen (1179 ± 397 nm) treatments. However, it was found an increase of the roughness of the films. Surface wettability studies proved that plasma treatments allowed to obtain superhydrophilic or low contact angles on membranes and films, with no influence on cell viability. PLLA microspheres with sizes between 0.16 and 3.9 μm and a degree of crystallinity of 40% and composite PLLA microspheres with cobalt ferrite nanoparticles (CoFe2O4) in the range of 0.8 to 2.2 μm were produced by emulsifying an oil (PVA solution) in water. PLLA spheres proved to be more stable in alkaline environments compared to magnetic composite PLLA microspheres. Moreover, it was found that the introduction of nanoparticles promoted the amorphous state in PLLA. It was shown that PLLA microspheres with and without CoFe2O4 particles didn´t inhibit cellular viability. In conclusion, it was demonstrated the possibility of processing different electroactive polymers in the form of microspheres, fibers, membranes and three-dimensional scaffolds, as well as evaluated the possibility to modify their wettability. This work represents thus a relevant contribution for increasing the use of these materials in innovative strategies for tissue engineering.Os biomateriais desempenham um papel cada vez mais proeminente no desenvolvimento e sucesso da engenharia de tecidos, nomeadamente na regeneração ou no restabelecimento da função de tecidos/órgãos do corpo humano. Os avanços registados relativamente à compreensão do papel dos biomateriais na formação de novos tecidos e na sua regeneração têm promovido uma maior rapidez e eficácia nos estudos desenvolvidos nesta área. Biomateriais à base de polímeros eletroativos têm despertado especial interesse na comunidade científica, para aplicações em engenharia de tecidos, nomeadamente para tecidos mecano-sensitivos (osso, ligamentos/tendões) e tecidos eletroativos (neurónios, coração e músculos). Em particular, materiais eletroativos à base de polímeros piezoelétricos apresentam uma forte potencialidade por serem capazes de mimetizar o ambiente biológico do tecido através de estímulos eletromecânicos. O principal objetivo do presente trabalho consistiu na produção de scaffolds com diferentes morfologias (fibras, partículas e scaffolds tridimensionais) baseados em polímeros piezoelétricos, o poli(fluoreto de vinilideno) (PVDF), poli(hidroxibutirato) (PHB) e o poli(L-ácido láctico) (PLLA) para aplicações de engenharia de tecidos. Igualmente, foram utilizados tratamentos de plasma para modificar a hidrofobicidade dos materiais. Deste modo, foram processadas membranas de PVDF pela técnica de electrospinning e realizados tratamentos de plasma sobre atmosfera de oxigénio para diferentes tempos de tratamento e potência aplicada de modo a modificar a molhabilidade da superfície hidrofóbica das fibras. Foi observado que o plasma não altera significativamente o diâmetro médio das fibras (~400±200 nm) nem as suas propriedades físico-químicas nomeadamente o conteúdo de fase β (~80-85%) e o seu grau de cristalinidade (42±2 %) demonstrando ser um método eficaz na obtenção de membranas superhidrofílicas. Microesferas de PVDF foram processadas pela técnica de electrospray. De todos os parâmetros estudados (concentração de polímero e parâmetros de processamento) verificou-se que a concentração de polímero é aquela que mais influência a formação de microesferas. Microesferas com diâmetros médios variando entre os 0,81±0,34 μm e 5,55±2,34 μm com um conteúdo de fase β entre os 63-74% e um grau de cristalinidade entre 45 e 55% foram obtidas através de soluções diluídas ou semi-diluídas. Ensaios de viabilidade celular demonstraram a potencialidade destas microesferas para aplicações m engenharia de tecidos. Scaffolds tridimensionais à base de PVDF com diferentes porosidades foram produzidos recorrendo a três métodos distintos: solvent casting – com cloreto de sódio (NaCl), solvent casting e extração a frio utilizando telas de nylon e poli(vinil álcool) (PVA). Independentemente do método de processamento utilizado, os scaffolds apresentam a fase β e um grau de cristalinidade de ~ 45 %. Ensaios mecânicos demostraram a viabilidade dos materiais para a aplicação em causa. Membranas de PHB foram produzidas por electrospinning, realizando-se igualmente um estudo da influência dos parâmetros de processamento no diâmetro e distribuição de fibras. Assim, verificou-se que o diâmetro médio das fibras de PHB diminui com o do diâmetro interno da agulha e aumenta com o aumento do campo elétrico aplicado e taxa de fluxo até ~2,0 μm. Os parâmetros de processamento não influenciaram a fase cristalina das membranas de PHB tendo sido obtido um grau de cristalinidade de 53%. Estudos de viabilidade celular comprovaram a sua potencialidade para aplicações na área de engenharia de tecidos. Tratamentos de plasma sobre atmosferas de árgon e oxigénio foram efetuados em filmes e membranas de PLLA obtidas por solvent casting e por electrospinning, respetivamente. O diâmetro médio das fibras não sofreu uma alteração significativa para o árgon (866±361 nm) nem para o oxigénio (1179±397 nm) tendo-se, no entanto, verificado um aumento da rugosidade dos filmes. Estudos de molhabilidade de superfície demonstraram ser possível obter membranas superhidrofílicas e filmes com um menor valor de ângulo de contacto, não influenciando a viabilidade celular. Microesferas de PLLA com tamanhos compreendidos entre os 0,16 -3,9 μm e um grau de cristalinidade de 40% e microesferas compósitas de PLLA com nanopartículas de ferrita de cobalto (CoFe2O4) na ordem dos 0,8-2,2 μm foram produzidas pelo método de emulsão de um óleo (solução de PVA) em água. Esferas de PLLA demonstraram ser mais estáveis em ambientes alcalinos comparativamente às esferas de PLLA magnéticas. Verificou-se que a introdução de nanopartículas promove o estado amorfo no PLLA. Foi demonstrado que as microesferas de PLLA com e sem partículas de CoFe2O4 não inibem a viabilidade celular. Em conclusão, testou-se a possibilidade de processar diferentes polímeros eletroativos nas formas de microesferas, fibras, membranas e scaffolds tridimensionais, sendo igualmente provada a possibilidade de modificar a sua molhabilidade. Este trabalho representa um contributo relevante para a crescente utilização destes materiais em estratégias inovadoras de engenharia de tecidos

Cellulose nanocrystal and water-soluble cellulose derivative based electromechanical bending actuators

This study reports a versatile method for the development of cellulose nanocrystals (CNCs) and water-soluble cellulose derivatives (methyl cellulose (MC), hydroxypropyl cellulose (HPC), and sodium carboxymethyl cellulose (NaCMC)) films comprising the ionic liquid (IL) 2-hydroxy-ethyl-trimethylammonium dihydrogen phosphate ([Ch][DHP]) for actuator fabrication. The influence of the IL content on the morphology and physico–chemical properties of free-standing composite films was evaluated. Independently of the cellulose derivative, the ductility of the films increases upon [Ch][DHP] incorporation to yield elongation at break values of nearly 15%. An increase on the electrical conductivity as a result of the IL incorporation into cellulosic matrices is found. The actuator performance of composites was evaluated, NaCMC/[Ch][DHP] showing the maximum displacement along the x-axis of 9 mm at 8 Vpp. Based on the obtained high electromechanical actuation performance, together with their simple processability and renewable nature, the materials fabricated here represent a step forward in the development of sustainable soft actuators of high practical relevance.The authors thank FCT - Fundação para a Ciência e Tecnologia - for financial support under the framework of the Strategic Funding UID/FIS/04650/2019 and UID/QUI/50006/2019 and projects PTDC/BTM-MAT/28237/2017, PTDC/EMD-EMD/28159/2017 and PTDC/FIS-MAC/28157/2017. D.M.C. and R.M.M. also acknowledge to FCT by the grants SFRH/BPD/121526/2016 and SFRH/BD/148655/2019. The authors also acknowledge to the funds by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry Department under the ELKARTEK and HAZITEK programs. SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) support is gratefully acknowledged

Shelf-life extension of squid and shrimp skewers through the application of vinegar solutions

info:eu-repo/semantics/publishedVersio

Inhibition of several bacterial species isolated from squid and shrimp skewers by different natural edible compounds

Seafood is an excellent source of nutrients, essential for a healthy diet, ranging from proteins and fatty acids to vitamins and minerals. Seafood products are highly perishable foods due to their nutritional characteristics and composition. The application of nontoxic, natural, and edible preservatives to extend the shelf-life and inhibit bacterial proliferation of several foods has been a hot topic. Consequently, this work aimed to perform the microbiological characterization of squid and shrimp skewers during their shelf-life (five days) and evaluate the susceptibility of randomly isolated microorganisms to several natural edible compounds so that their application for the preservation and shelf-life extension of the product might be analyzed in the future. The product had considerably high total microorganisms loads of about 5 log CFU/g at day zero and 9 log CFU/g at day five. In addition, high bacterial counts of Pseudomonas spp., Enterobacterales, and lactic acid bacteria (LAB) were found, especially on the last day of storage, being Pseudomonas the dominant genus. However, no Escherichia coli or Listeria monocytogenes were detected on the analyzed samples. One hundred bacterial isolates were randomly selected and identified through 16s rRNA sequencing, resulting in the detection of several Enterobacterales, Pseudomonas spp., and LAB. The antibacterial activity of carvacrol, olive leaf extract, limonene, Citrox®, different chitosans, and ethanolic propolis extracts was evaluated by the agar diffusion method, and the minimum inhibitory concentration was determined only for Citrox® since only this solution could inhibit all the identified isolates. At concentrations higher than or equal to 1.69% (v/v), Citrox® demonstrated bacteriostatic and bactericidal activity to 97% and 3% of the isolates, respectively. To our knowledge, there are no available data about the effectiveness of this commercial product on seafood isolates. Although preliminary, this study showed evidence that Citrox® has the potential to be used as a natural preservative in these seafood products, improving food safety and quality while reducing waste. However, further studies are required, such as developing a Citrox®-based coating and its application on this matrix to validate its antimicrobial effect.info:eu-repo/semantics/publishedVersio

Development of poly(l-Lactic Acid)-based bending actuators

This work reports on the development of bending actuators based on poly(l-lactic acid) (PLLA)/ionic liquid (IL) blends, through the incorporation of 40% wt. of the 1-ethyl-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]) IL. The films, obtained by solvent casting at room temperature and 50 °C, were subjected to several post-thermal treatments at 70, 90, 120 and 140 °C, in order to modify the crystallinity of the films. The influence of the drying temperature and of [Emim][TFSI] blending on the morphological, structural, mechanical and electrical properties of the composite materials were studied. The IL induced the formation of a porous surface independently of the processing conditions. Moreover, the [Emim][TFSI] dopant and the post-thermal treatments at 70 °C promoted an increase of the degree of crystallinity of the samples. No significant changes were observed in the degree of crystallinity and Young Modulus for samples with thermal treatment between 70 and 140 °C. The viability of the developed high ionic conductive blends for applications as soft actuators was evaluated. A maximum displacement of 1.7 mm was achieved with the PLLA/[Emim][TFSI] composite prepared at 50 °C and thermally treated at 140 °C, for an applied voltage of 10 Vpp, at a frequency of 100 mHz. This work highlights interesting avenues for the use of PLLA in the field of actuators.The authors thank the FCT—Fundação para a Ciência e Tecnologia—for financial support under the Strategic Funding UID/FIS/04650/2020, and PEST-C/QUI/UIO686/2019, the Associated Laboratory Research Unit for Green Chemistry, Technologies and Clean Processes, LAQV (financed by national funds from FCT/MEC, UID/QUI/50006/2020 and ERDF under the PT2020, POCI-01-0145-FEDER-007265) and projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. DMC and LCF also thank the grants SFRH/BPD/121526/2016 and SFRH/BD/145345/2019, respectively

Multifunctional magnetoelectric sensing and bending actuator response of polymer-based hybrid materials with magnetic ionic liquids

With the evolution of the digital society, the demand for miniaturized multifunctional devices has been increasing, particularly for sensors and actuators. These technological translators allow successful interaction between the physical and digital worlds. In particular, the development of smart materials with magnetoelectric (ME) properties, capable of wirelessly generating electrical signals in response to external magnetic fields, represents a suitable approach for the development of magnetic field sensors and actuators due to their ME coupling, flexibility, robustness and easy fabrication, compatible with additive manufacturing technologies. This work demonstrates the suitability of magnetoelectric (ME) responsive materials based on the magnetic ionic liquid (MIL) 1-butyl-3-methylimidazolium tetrachloroferrate ([Bmim][FeCl4]) and the polymer poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE) for magnetic sensing and actuation device development. The developed sensor works in the AC magnetic field and has frequency-dependent sensitivity. The materials show voltage responses in the mV range, suitable for the development of magnetic field sensors with a highest sensitivity (s) of 76 mV·Oe−1. The high ME response (maximum ME voltage coefficient of 15 V·cm−1·Oe−1) and magnetic bending actuation (2.1 mm) capability are explained by the magnetoionic (MI) interaction and the morphology of the composites.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2020, UID/QUI/00686/2020, LA/P/0008/2020, UIDB/50006/2020 and UIDP/50006/2020. The authors are grateful for funds through FCT under the projects 2022.05932.PTDC, PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017 and grant SFRH/BD/145345/2019 (L.C.F). D.M.C. and P.M. thank FCT—Fundação para a Ciência e Tecnologia for the contract under the Stimulus of Scientific Employment, Individual Support 2020.02915.CEECIND and CEECIND/03975/2017, respectively. This study forms part of the Advanced Materials programme and was supported by MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by the Basque Government under the IKUR program. Funding from the Basque Government Industry Departments under the ELKARTEK program is also acknowledged. Technical and human support provided by IZO-SGI, SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully acknowledged

“Lugar do feminismo é no cotidiano”: : participação nos movimentos feministas e ocupações de mulheres jovens militantes

Given the possibilities for occupational involvement, social activism is characterized as an occupation inseparable from a subject’s identity. The focus of this study is the experiences of women in feminist movements as one of the ways to experience social activism in daily life and aims to understand how involvement in these movements impacts other occupations of young militant women. This was a qualitative research, based on the thematic oral history, with the participation of ten young women who self-identify as current militants of feminist movements. The snowball strategy was used for recruitment and the data was collected through interviews on the Google Meet platform. Six thematic categories are identified, related to the approximation process and the meaning of involvement in feminist movements, the relationship with daily life, social relationships, leisure and work, religion and self-care. The results contribute to the visibility of participation in feminist movements in everyday life and denounce the limitations imposed on women\u27s occupations by the social structures.Frente a las múltiples posibilidades de participación ocupacional, el activismo social se caracteriza como una ocupación inseparable de la identidad de un sujeto. Entre las formas de experimentar la ocupación del activismo social en la vida cotidiana, este estudio se enfoca en aquellas relacionadas con las experiencias de mujeres en movimientos feministas. El objetivo de la investigación es comprender cómo la participación en movimientos feministas impacta en las otras ocupaciones de las jóvenes militantes. Se trata de una investigación cualitativa, del tipo historia oral temática, y contó con la participación de diez mujeres jóvenes que se autorreconocen como militantes actuales de movimientos feministas. Para el reclutamiento se utilizó la técnica de bola de nieve; los datos se recopilaron a través de Google Meet. Se identifican seis categorías temáticas relacionadas con el proceso de aproximación y los significados de involucrarse con los movimientos feministas; la relación con la vida cotidiana en general; las relaciones sociales; el ocio y el trabajo; la religiosidad; el autocuidado. Los resultados contribuyen a dar visibilidad a la participación en movimientos feministas en la cotidianidad y denuncian las limitaciones que las estructuras sociales imponen a las ocupaciones de las mujeres.Diante das múltiplas possibilidades para o envolvimento ocupacional, o ativismo social é caracterizado como uma ocupação indissociável da identidade de um sujeito. Entre as formas de experienciar a ocupação do ativismo social no cotidiano, aquelas relacionadas às vivências de mulheres em movimentos feministas são o foco deste estudo. A pesquisa tem por objetivo compreender como o envolvimento nos movimentos feministas impacta nas outras ocupações de mulheres jovens militantes. Trata-se de uma pesquisa qualitativa, do tipo história oral temática, e teve a participação de dez mulheres jovens, que se auto proclamam como militantes atuais dos movimentos feministas. Foi utilizada a estratégia de bola de neve para o recrutamento e os dados foram coletados por meio de entrevistas via Google Meet. Identificam-se seis categorias temáticas que se relacionam ao processo de aproximação e significados do envolvimento com os movimentos feministas, a relação com o cotidiano em geral, as relações sociais, o lazer e o trabalho, a religiosidade e os cuidados de si. Os resultados contribuem para a visibilidade do envolvimento nos movimentos feministas no cotidiano e denunciam as limitações que as estruturas sociais impõem para as ocupações das mulheres

Electrospun magnetic ionic liquid based electroactive materials for tissue engineering applications

Functional electrospun fibers incorporating ionic liquids (ILs) present a novel approach in the development of active microenviroments due to their ability to respond to external magnetic fields without the addition of magnetic particles. In this context, this work reports on the development of magnetically responsive magneto-ionic fibers based on the electroactive polymer poly(vinylidene fluoride) and the magnetic IL (MIL), bis(1-butyl-3-methylimidazolium) tetrathiocyanatocobaltate ([Bmim]2[(SCN)4Co]). The PVDF/MIL electrospun fibers were prepared incorporating 5, 10 and 15 wt.% of the MIL, showing that the inclusion of the MIL increases the polar β-phase content of the polymer from 79% to 94% and decreases the crystallinity of the fibers from 47% to 36%. Furthermore, the thermal stability of the fibers decreases with the incorporation of the MIL. The magnetization of the PVDF/MIL composite fibers is proportional to the MIL content and decreases with temperature. Finally, cytotoxicity assays show a decrease in cell viability with increasing the MIL content.This research was funded by FCT—Fundação para a Ciência e Tecnologia (FCT) under the scope of the strategic funding of UID/FIS/04650/2020, and project PTDC/BTM-MAT/28237/2017. Moreover, the authors thank FCT for the research grant SFRH/BD/145345/2019 (LMC), SFRH/BD/148655/2019 (RMM), and D.M.C. and CR thank the FCT for the contract under the Stimulus of Scientific Employment 2020.02915.CEECIND and 2020.04163.CEECIND, respectively.The authors acknowledge funding by Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033 and from the Basque Government Industry Departments under the ELKARTEK program. Technical and human support provided by IZO-SGI, SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is gratefully acknowledged

Caracterização fitoquímica e avaliação do potencial acaricida e inseticida do óleo essencial de Hymeneae courbaril L. var. courbaril sobre o ácaro-rajado e o gorgulho do milho

As propriedades inseticidas dos óleos essenciais são geralmente reconhecidas ao longo dos séculos e confirmadas cientificamente nas últimas décadas. Tais produtos podem ser usados na agricultura como uma alternativa para o controle de pragas. O óleo essencial derivado das folhas de Hymenaea courbaril L. var. courbaril foi obtido por hidrodestilação com arraste a vapor e caracterizado fitoquimicamente por cromatografia gasosa/espectrometria de massa (CG/EM); seu potencial acaricida e inseticida foi avaliado contra Tetranychus urticae e Sitophilus zeamais, respectivamente, pragas que ocorrem em uma ampla variedade de culturas economicamente importantes em todo o mundo. Após a análise por CG/EM, foram identificados 36 compostos, sendo 46,42% dos monoterpenos e 51,41% dos sesquiterpenos. Os bioensaios inseticidas avaliaram a interferência do óleo essencial na fisiologia nutricional do gorgulho e no processo de fumigação do ácaro. Os ensaios indicaram que o óleo essencial causou uma mortalidade significativa, promovendo danos fisiológicos ao S. zeamais. O valor de CL50 para T. urticae foi de 35,57 ?L/mL de ar; além disso, também foi observado que a oviposição foi afetada negativamente pelo óleo essencial. O óleo essencial de H. courbaril demonstrou ser um potencial controle de pragas por afetar o metabolismo e a reprodução de ambas as espécies de praga testadas