Browsing by Author "Arana, Sergio"
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- Cell-free layer (CFL) measurements in complex geometries: contractions and bifurcationsPublication . Novais, Susana; Pinho, Diana; Bento, David; Pinto, Elmano; Yaginuma, Tomoko; Fernandes, Carla S.; Garcia, Valdemar; Pereira, Ana I.; Lima, José; Mujika, Maite; Oliveira, Mónica S.N.; Dias, Ricardo P.; Arana, Sergio; Lima, Rui A.In this chapter we discuss the cell-free layer (CFL) developed adjacent to the wall of microgeometries containing complex features representative of the microcirculation, such as contractions, expansions, bifurcations and confluences. The microchannels with the different geometries were made of polydimethylsiloxane (PDMS) and we use optical techniques to evaluate the cell-free layer for red blood cells (RBC) suspensions with different hematocrit (Hct). The images are captured using a high-speed video microscopy system and the thickness of the cell free layer was measured using both manual and automatic image analysis techniques. The results show that in in vitro microcirculation, the hematocrit and the geometrical configuration have a major impact on the CFL thickness. In particular, the thickness of the cell-free layer increases as the fluid flows through a contraction-expansion sequence and that this increase is enhanced for lower hematocrit. In contrast, the flow rates tested in this studies did not show a clear influence on the CFL thickness.
- Desenvolvimento de um microdispositivo biomédico para a separação de células sanguíneasPublication . Novais, Susana; Pinho, Diana; Pereira, Ana I.; Mujika, Maite; Arana, Sergio; Lima, Rui A.Neste trabalho procedeu-se ao desenho e implantação de um dispositivo biomédico, com capacidade de realizar a separação das células sanguíneas da camada de plasma. Numa primeira fase do trabalho realizou-se o desenho e fabricação do dispositivo, através da técnica de litografia suave. A segunda fase consistiu no estudo do escoamento sanguíneo com o objetivo de analisar o efeito das constrições na variação da espessura camada de plasma. Concluímos que a constrição proporciona um aumento da espessura da camada de plasma e à medida que se aumenta o hematócrito a camada de plasma tende a diminuir.
- Desenvolvimento de um microdispositivo biomédico para a separação de células sanguíneasPublication . Novais, Susana; Pinho, Diana; Pereira, Ana I.; Mujika, Maite; Arana, Sergio; Lima, Rui A.Neste trabalho procedeu-se ao desenho e implantação de um dispositivo biomédico, com capacidade de realizar a separação das células sanguíneas da camada de plasma. Numa primeira fase do trabalho realizou-se o desenho e fabricação do dispositivo, através da técnica de litografia suave. A segunda fase consistiu no estudo do escoamento sanguíneo com o objetivo de analisar o efeito das constrições na variação da espessura camada de plasma. Concluímos que a constrição proporciona um aumento da espessura da camada de plasma e à medida que se aumenta o hematócrito a camada de plasma tende a diminuir.
- 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.
- 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].
- Flow of red blood cells suspensions through hyperbolic microcontractionsPublication . Faustino, Vera; Pinho, Diana; Yaginuma, Tomoko; Calhelha, Ricardo C.; Kim, Geyong; Arana, Sergio; Ferreira, Isabel C.F.R.; Oliveira, Mónica S.N.; Lima, Rui A.The present study uses a hyperbolic microchannel with a low aspect ratio (AR) to investigate how the red blood cells (RBCs) deform under conditions of both extensional and shear induced flows. The deformability is presented by the degree of the deformation index (DI) of the flowing RBCs throughout the microchannel at its centerline. A suitable image analysis technique is used for semi-automatic measurements of average DIs, velocity and strain rate of the RBCs travelling in the regions of interest. The results reveal a strong deformation of RBCs under both extensional and shear stress dominated flow conditions.
- A influência de um campo magnético estático no escoamento sanguíneo com nanopartículas magnéticasPublication . Pereira, Nuno; Mujika, Maite; Arana, Sergio; Correia, Teresa Montenegro; Silva, Adrián; Gomes, Helder; Rodrigues, Pedro João; Lima, Rui A.Neste trabalho foram produzidas nanopartículas de óxido de ferro por síntese solvotérmica, posteriormente colocadas em suspensão num fluido fisiológico constituído por eritrócitos de forma a realizar estudos de escoamentos em microcanais.
- A influência de um campo magnético estático no escoamento sanguíneo com nanopartículas magnéticasPublication . Pereira, Nuno; Mujika, Maite; Arana, Sergio; Correia, Teresa Montenegro; Silva, Adrián; Gomes, Helder; Rodrigues, Pedro João; Lima, Rui A.De forma a realizar estudos de escoamentos em microcanais e avaliar a influência das nanopartículas, sob a ação de um campo magnético estático, na espessura da camada de plasma, foram produzidas nanoparticulas de óxido de ferro por síntese solvotérmica, sendo posteriormente colocadas em suspensão num fluido fisiológico constituído por eritrócitos. Verificou-se que as nanopartículas com características magnéticas proporcionam a diminuição da espessura da camada de plasma, um comportamento contrário ao observado com nanopartículas sem características magnéticas.
- Measurement of red blood cells deformation index in a hyperbolic microchannelPublication . Faustino, Vera; Pinho, Diana; Yaginuma, Tomoko; Calhelha, Ricardo C.; Man-Kim, Gyeong; Arana, Sergio; Lima, Rui A.; Ferreira, Isabel C.F.R.; Oliveira, Mónica S.N.A hyperbolic microchannel was used for the purpose of observing the deformation index of the erythrocytes after contact with human tumour cell line (HCT-15 - colon carcinoma). Three cases were compared and the results showed that the deformation index decreases when erythrocytes are in contact with HCT-15.
- The effect of a static magnetic field on the flow of iron oxide magnetic nanoparticles through glass capillariesPublication . Pereira, Nélson; Mujika, Maite; Arana, Sergio; Correia, Teresa Montenegro; Silva, Adrián; Gomes, Helder; Rodrigues, Pedro João; Lima, Rui A.lron oxide nanoparticles were developed using Solvolherrnal synthesis and suspended in a physiological fluid consLiluted by erYlhrocytes in a rder to perfarm studies af flow behaviour in glass microchannels. The main purpose af this work was to study lhe influence af different iron oxide nanoparticles and magnetic fields in lhe plasma layer thickness and also the inftuence Df lhe magnelic field in lhe area composed of nanoparticles auracled to the waU af lhe microchannel. The results obtained show lhat nanoparticJes with magnetic characteristics promote the thinning of the plasma layer, in contrast to the behaviour observcd with mmoparticles without magnetic characteristics. It was also observed upon application of magnetic fields with differem intensities, the plasma layer tend to disappear in some areas depending on the type af particles. Moreover, lhe area of nanoparticles attracted to the microchannel wall increases wilh lhe increase of lhe magnetic field intensity.