Browsing by Author "Rodrigues, Raquel Oliveira"
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- Avaliação da produtividade e qualidade de tomate produzido no solo e em hidroponia na região Noroeste de PortugalPublication . Mourão, Isabel; Brito, Luís Miguel; Moura, Luísa; Rodrigues, Raquel OliveiraA cultura hidropónica de tomate na região NW de Portugal poderá substituir o sistema de produção convencional no solo, na época de primavera/verão, se o aumento de produtividade e a qualidade dos frutos compensar os custos de produção adicionais. Com este objectivo as cultivares de tomate Durinta (tipo cacho) e Romana (tipo chucha) foram produzidas na Póvoa de Varzim, para comparar culturas convencionais produzidas em solo de textura arenosa, com culturas hidropónicas em substrato de fibra de coco, no interior de estufas sem aquecimento. A plantação e a colheita de tomate hidropónico ocorreram um mês antes da cultura produzida no solo. A produtividade e as características de qualidade dos frutos (calibre, cor, firmeza, pH, sólidos solúveis totais, acidez total e concentração de N, P, K, Ca, Mg e Fe dos frutos) foram avaliadas em três repetições de cada tratamento, com base em quatro plantas por repetição. A produtividade da cultura hidropónica de tomate da cv. Durinta (16,7 kg m-2) aumentou e a matéria seca (6,3 g 100 g-1) diminuiu comparativamente com a produção convencional no solo (12,7 kg m-2 e 6,7 g 100 g-1, respetivamente), enquanto para a cv. Romana a produtividade e teor de matéria seca foram semelhantes em ambos os sistemas de produção (média de 9,7 kg m-2 e 7,3 g 100 g-1, respetivamente). As características de qualidade, como o calibre dos frutos, a cor e a firmeza, não foram influenciados pelo sistema de produção e revelaram-se dependentes da cultivar. Os frutos da cv. Durinta produzidos em hidroponia foram menos doces e, para ambas as cultivares, possuíam menor acidez. A concentração dos frutos em N, Mg e Fe foram semelhantes para ambas as cultivares, independentemente do sistema de produção. O teor em P e Ca do tomate hidropónico para ambas as cultivares, bem como o conteúdo de K da cv. Romana, foram superiores aos frutos produzidos no solo. A qualidade dos frutos e as diferenças de produtividade entre os dois sistemas de produção podem não ser preponderantes para a tomada de decisão dos produtores, embora a produção hidropónica, considerando os referidos problemas de solo e a melhor gestão das estratégias de marketing, com a antecipação da colheita na estação da primavera/verão e com a possibilidade de produção de tomate na época de outono/inverno, possa ser uma opção rentável.
- Blood flow in a bifurcation and confluence microchannel: effect of the cell-free layer in velocity profilesPublication . Pinho, Diana; Bento, David; Rodrigues, Raquel Oliveira; Fernandes, Carla S.; Garcia, Valdemar; Lima, Rui A.A few detailed studies have been performed in complex in vitro microvascular networks composed by bifurcations and confluences. The main purpose of the present work is to numerically simulate the flow of two distinct fluids through bifurcation and confluence geometries, i. e red blood cells (RBCs)suspended in Dextran40 with about 14% of heamatocrit and pure water. The simulations of pure water and RBCs flows were performed resorting to the commercial finite volume software package FLUENT. A well known hemodynamic phenomenon, known as Fahraeus-Lindqvist effect, observed in both in vivo and in vitro studies, results in the formation of a marginal cell-free layer (CFL) at regions adjacent to the wall. Recently, studies have shown that the formation of the CFL is affected by the geometry of the microchannel and for the case of the confluences a CFL tend to appear in the middle of the microchannel after the apex of the confluence. By using the CFL experimental data, the main objective of this work is to implement a CFL in the numerical simulations in order to obtain a better understanding of the effect of this layer on the velocity profiles.
- Blood flow in a bifurcation and confluence microchannel: the effect of the cell-free layer in the velocity profilesPublication . Pinho, Diana; Bento, David; Rodrigues, Raquel Oliveira; Fernandes, Carla S.; Garcia, Valdemar; Lima, Rui A.A few detailed studies have been performed in complex in vitro microvascular networks composed by bifurcations and confluences. The main purpose of the present work is to numerically simulate the flow of two distinct fluids through bifurcation and confluence geometries, i. e red blood cells (RBCs) suspended in Dextran40 with about 14% of heamatocrit and pure water. The simulations of pure water and RBCs flows were performed resorting to the commercial finite volume software package FLUENT. A well known hemodynamic phenomenon, known as Fahraeus-Lindqvist effect [1, 2], observed in both in vivo and in vitro studies, results in the formation of a marginal cell-free layer (CFL) at regions adjacent to the wall [3]. Recently, studies have shown that the formation of the CFL is affected by the geometry of the microchannel and for the case of the confluences a CFL tend to appear in the middle of the microchannel after the apex of the confluence [4, 5]. By using the CFL experimental data, the main objective of this work is to implement a CFL in the numerical simulations in order to obtain a better understanding of the effect of this layer on the velocity profiles.
- Blood flow in microchannels manufactured by a low cost technique: xurographyPublication . Pinto, Elmano; Taboada, Bruna Rafaela Pereira; Faustino, Vera; Cidre, Diana; Rodrigues, Raquel Oliveira; Miranda, João Mário; Garcia, Valdemar; Dias, Ricardo P.; Lima, Rui A.The xurography is a technique that has been used to make molds to produce microchannels. In contrast to soft lithography [1, 2], xurography uses equipments and materials commonly used in the printing industry, such as cutting plotters, vinyl and other materials. The main advantage of this technique is to fabricate microchannels at a reduced cost [3, 4]. The Fahraeus-Lindqvist effect is a well know phenomenon that happens in microcirculation, where red blood cells (RBCs) have tendency to migrate toward the centre of the microtube resulting in a marginal cell-free layer (CFL) at regions adjacent to the wall [5]. Recently several studies showed strong evidence that the formation of the CFL is affected by the geometry of the microchannel [1, 6, 7] and the physiological conditions of the working fluid, such as the hematocrit (Hct) [2, 8]. The main objective of the present work is to fabricate polydimethysiloxane (PDMS) microchannels by using a soft xurography technique in order perform blood flow studies. Additionally, a high-speed video microscopy system is used to measure the CFL thickness in two different geometries, i. e., bifurcations and confluences.
- Carbon-based magnetic nanocarrier for controlled drug release: a green synthesis approachPublication . Oliveira, Jéssica; Rodrigues, Raquel Oliveira; Barros, Lillian; Ferreira, Isabel C.F.R.; Marchesi, Luís; Koneracka, Martina; Jurikova, Alena; Zavisova, Vlasta; Gomes, Helder; Oliveira, JessícaIn this study, hydrophilic magnetic nanoparticles were synthesized by green routes using a methanolic extract of Rubus ulmifolius Schott flowers. The prepared magnetic nanoparticles were coated with carbon-based shell for drug delivery application. The nanocomposites were further chemically functionalized with nitric acid and, sequentially, with Pluronic® F68 (CMNPs-plur) to enhance their colloidal stability. The resulting material was dispersed in phosphate buffer solution at pH 7.4 to study the Doxorubicin loading. After shaking for 48 h, 99.13% of the drug was loaded by the nanocomposites. Subsequently, the drug release was studied in different working phosphate buffer solutions (i.e., PB pH 4.5, pH 6.0 and pH 7.4) to determine the efficiency of the synthesized material for drug delivery as pH-dependent drug nanocarrier. The results have shown a drug release quantity 18% higher in mimicking tumor environment than in the physiological one. Therefore, this study demonstrates the ability of CMNPs-plur to release a drug with pH dependence, which could be used in the future for the treatment of cancer "in situ" by means of controlled drug release.
- Cell-free layer analysis in a polydimethysiloxane microchannel: A global approachPublication . Pinto, Elmano; Faustino, Vera; Pinho, Diana; Rodrigues, Raquel Oliveira; Lima, Rui A.; Pereira, Ana I.The cell-free layer (CFL) is a hemodynamic phenomenon that has an important contribution to the rheological properti es of blood flowing in microvessels. The present work aims to find the closest function describing RBCs flowing around the cell depleted layer in a polydimethysiloxane (PDMS) microchannel with a diverging and a converging bifurcation. The flow behaviour of the CFL was investigated by using a high-speed video microscopy system where special attention was devoted to its behaviour before the bifurcation and after the confluence of the microchannel. The numerical data was first obtained by using a manual tracking plugin and then analysed using the genetic algorithm approach. The results show that for the majority of the cases the function that more closely resembles the CFL boundary is the sum of trigonometric functions.
- Deformation of red blood cells, air bubbles and droplets in microfluidic devices: flow visualizations and measurementsPublication . Bento, David; Rodrigues, Raquel Oliveira; Faustino, Vera; Pinho, Diana; Fernandes, Carla S.; Pereira, Ana I.; Garcia, Valdemar; Miranda, João Mário; Lima, Rui A.Techniques, such as micropipette aspiration and optical tweezers, are widely used to measure cell mechanical properties, but are generally labor-intensive and time-consuming, typically involving a difficult process of manipulation. In the past two decades, a large number of microfluidic devices have been developed due to the advantages they offer over other techniques, including transparency for direct optical access,lower cost, reduced space and labor, precise control, and easy manipulation of a small volume of blood samples. This review presents recent advances in the development of microfluidic devices to evaluate the mechanical response of individual red blood cells (RBCs) and microbubbles flowing in constriction microchannels.Visualizations and measurements of the deformation of RBCs flowing through hyperbolic,smooth,and sudden-contraction microchannels were evaluated and compared. In particular, we show the potential of using hyperbolic-shaped microchannels to precisely control and assess small changes in RBC deformability in both physiological and pathological situations. Moreover, deformations of air microbubbles and droplets flowing through a microfluidic constriction were also compared with RBCs deformability.
- Development and characterization of magnetic nanoparticles for theranostic applicationsPublication . Rodrigues, Raquel Oliveira; Bañobre-López, Manuel; Gallo, Juan; Tavares, Pedro B.; Lima, Rui A.; Silva, Adrián; Gomes, HelderMagnetic nanoparticles (MNPs), especially iron oxide nanoparticles, have attracted much attention in the last decades due to their remarkable physicochemical and magnetic properties. These properties coupled with their low toxicological effects, make MNPs ideal for biomedical applications1. In addition, chemical functionalization with specific biocompatible targeting molecules provides them with the ability to selectively attach to cells or tissues.
- Development and optimization of a biological protocol for DNA detection of escherichia coli O157:H7 by quartz crystal microbalance (QCM)Publication . Rodrigues, Raquel Oliveira; Pérez-Lorenzo, Eva; Arana, Sergio; Amaral, Joana S.; Rodrigues, Pedro S.; Mujika, MaiteEscherichia coli 0157:H7 is a foodborne pathogen classified as an Enterohemorrhagic E. coli being associated to foodborne outbreaks with high mortality. Since the traditional methods for its detection are often time-consuming, there is a need to develop new techniques that allow rapid, simple, reliable, specific and sensitive detection for a quick and effective medical intervention, as well as to ensure food safety. In the last years different approaches have bee suggested for this purpose including the use of biosensors based on different bioreceptors such enzymes, antibodies and DNA. Recently, there has been a growing interest regarding DNA biosensors due to advantages such as DNA high specificity and stability and the possibility developing devices that can be reusable after thermal melting of the DNA duplex [1].
- Development and optimization of a biological protocol for DNA detection of escherichia coli O157:H7 by quartz crystal microbalance (QCM)Publication . Rodrigues, Raquel Oliveira; Pérez-Lorenzo, Eva; Arana, Sergio; Amaral, Joana S.; Rodrigues, Pedro S.; Mujika, MaiteEscherichia coli O157:H7 is a foodborne pathogen associated to outbreaks with high mortality. Since the traditional methods for its detection are often time-consuming, there is a need to develop new techniques that allow a rapid, simple, reliable, specific and sensitive detection. The present study aimed to develop a biological protocol for DNA detection of E. coli O157:H7 using a Quartz Crystal Microbalance with Dissipation (QCM-D), to be applied as a genosensor based on the evaluation of the immobilization/hybridization mass phenomena. Since genosensors use immobilized DNA single strands to detect the complementary sequence by hybridization, it is very important to optimize the conditions used during probe immobilization and target hybridization. In this study, several parameters (concentration, incubation time and temperature) were studied and optimized, on the steps of DNA thiol Probes immobilization, 6-Mercapto-1-hexanol (MCH) blocking agent deposition and DNA Target hybridization. Additionally, both the DNA probe and target oligonucleotides were linked to fluorochromes allowing the use of Epifluorescence microscopy, to verify the mass deposition results obtained by the QCM-D device, in the gold electrode.