Browsing by Author "Yaginuma, Tomoko"
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- Analysis of the cell-free layer in a circular microchannels: trajectories of labeled red bllod cellsPublication . Meireles, Catarina; Pereira, Ana I.; Yaginuma, Tomoko; Lima, Rui A.In this experimental work, we measure the trajectories of the cell-free layer (CFL) by tracking labeled red blood cells (RBCs) flowing around the boundary of the RBCs core. The circular glass microchannels studied are 100 um in diameter. The images are captured using confocal system and are post-processed using Image J and MATLAB. The results suggest that the trajectories follows a polynomial function.
- 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.
- Cell-free layer measurements in a bifurcation microchannel : comparison between a manual and automatic methodsPublication . Bento, David; Pinho, Diana; Pinto, Elmano; Yaginuma, Tomoko; Correia, Teresa Montenegro; Lima, José; Pereira, Ana I.; Lima, Rui A.In the present work, in vitro blood flowing through a bifurcation microchannel was studied. The aim was to measure the Trajectories of the cell-free layer (CFL) by using different methods, i. e., a manual and two automatic methods.
- Cell-free layer measurements in a bifurcation microchannel : comparison between a manual and automatic methodsPublication . Bento, David; Pinho, Diana; Pinto, Elmano; Yaginuma, Tomoko; Correia, Teresa Montenegro; Lima, José; Pereira, Ana I.; Fernandes, Carla S.; Dias, Ricardo P.; Lima, Rui A.In the present work, in vitro blood flowing through a bifurcation microchannel was studied. The aim was to measure the Trajectories of the cell-free layer (CFL) by using different methods, i. e., a manual and two automatic methods.
- Erythrocyte deformability in a hyperbolic microchannelPublication . Faustino, Vera; Yaginuma, Tomoko; Pinho, Diana; Calhelha, Ricardo C.; Ferreira, Isabel C.F.R.; Lima, Rui A.Serious diseases such as diabetes and malaria are deeply related to microcirculation disorders caused by abnormal erythrocytes deformability [1]. Therefore, various studies on red blood cells (RBCs) deformation have been carried out but those studies rather focus on shear ow or extensional ow [2-6]. In this study, a relatively low aspect ratio (AR) hyperbolic microchannel was used in order to create an extensional ow combined with a shear ow, where AR= h w , h means the depth and w means the width of the microchannel. The objective of the study is to investigate the degree of RBC deformation throughout the microchannel at the centerline (y = 0). The blood samples were RBCs diluted with the Hank's Balanced Salt Solution (HBSS) with the hematocrit (Hct) level set to be 2%. A polydimethylsiloxane (PDMS) microchannel, having a hyperbolic contraction region followed by an abrupt expansion shape, was fabricated by a soft-lithography technique. The dimensions of the microchannel: width of the inlet (w), length of contraction region (l), width of the exit of contraction (wc) and depth (h) were 400 m, 580 m, 20 m and 14 m, respectively. Hence, the AR was 0:035. The experimental equipment consisted of an inverted microscope (Diaphot 300, Nikon), a high-speed camera (FASTCAM SA3, Photron) connected to a computer and a 1mL syringe (TERUMO R SYRING) controlled by a syringe pump (PHD ULTRA). The manufactured PDMS microchannel was placed on the stage of the microscope where the ow rate Q of the working uids was kept constant at 0:5 L=min. The owing RBCs were recorded by a high speed camera at a frame rate of 7500 frames/s and analyzed. The DI was obtained by DI= a b a + b where a refers to the major axis and b refers to the minor axis of the ellipse best tted to RBCs. High DI values in the contraction region were observed. It is possible to say that the RBCs highly elongate with both extensional and shear dominated ows achieved by a hyperbolic microchannel with a relatively low aspect ratio AR.
- Extensional flow-based microfluidic device: deformability assessment of red blood cells in contact with tumor cellsPublication . Faustino, Vera; Pinho, Diana; Yaginuma, Tomoko; Calhelha, Ricardo C.; Ferreira, Isabel C.F.R.; Lima, Rui A.Red blood cell (RBC) deformability has become one of the important factors to assess blood and cardiovascular diseases. The interest on blood studies have promoted a development of various microfluidic devices that treat and analyse blood cells. Recent years, besides the RBC deformability assessment, these devices are often applied to cancer cell detection and isolation from the whole blood. The devices for cancer cell isolation rely mainly on size and deformability of the cells. However, the examination of deformability of the RBCs mixed with cancer cells is lacking. This study aims at determining the deformation index (DI) of the RBCs in contact with cancer cells using a hyperbolic microchannel which generates a strong extensional flow. The DIs of human healthy RBCs and human RBCs in contact with a tumor cell line (HCT-15, colon carcinoma) were compared by analyzing the flowing RBCs images captured by a high speed camera. The results reveal that the RBCs that were in contact with HCT-15 cells have lower deformability than the normal RBCs.
- 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.
- Flow of red blood cells through a microfluidic extensional device: an image analysis assessmentPublication . Yaginuma, Tomoko; Pereira, Ana I.; Rodrigues, Pedro João; Lima, Rui A.; Oliveira, Mónica S.N.; Ishikawa, Takuji; Yamaguchi, TakamiThe present study aims to assess the deformability of red blood cells (RBCs) under extensionally dominated microfluidic flows using an image based technique. For this purpose, a microchannel having a hyperbolic shaped-contraction was used and the images were captured by a standard high-speed microscopy system. The images acquired display RBCs with various light intensity levels and image analysis was used to quantify the deformation index (DI) of the RBCs considering these light intensity differences. Additionally, the velocities of different intensity-level RBCs flowing along the centerline of the channel were measured using particle tracking velocimetry. The preliminary results at two different flow rates reveal a highly deformable nature of RBCs when submitted to strong extensional flows. It was also observed that the low intensity cells exhibit a slightly higher velocity than intermediate intensity cells, which we attribute to the cells being located in different planes
- Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannelPublication . Yaginuma, Tomoko; Oliveira, Mónica S.N.; Lima, Rui A.; Ishikawa, Takuji; Yamaguchi, TakamiIt is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field. We measured the deformation index (DI) as well as the velocity of the RBCs travelling along the centerline of the channel for four different flow rates and analyze the impact of the particle Reynolds number. The results show that human RBC deformation tends to reach a plateau value in the region of constant extensional rate, the value of which depends on the extension rate. Additionally, we observe that the presence of a sudden expansion downstream of the hyperbolic contraction modifies the spatial distribution of cells and substantially increases the cell free layer (CFL downstream of the expansion plane similarly to what is seen in other expansion flows. Beyond a certain value of flow rate, there is only a weak effect of inlet flow rates on the enhancement of the downstream CFL. These in vitro experiments show the potential of using microfluidic systems with hyperbolic-shaped microchannels both for the separation of the RBCs from plasma and to assess changes in RBC deformability in physiological and pathological situations for clinical purposes. However, the selection of the geometry and the identification of the most suitable region to evaluate the changes on the RBC deformability under extensional flows are crucial if microfluidics is to be used as an in vitro clinical methodology to detect circulatory diseases.
- 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.