Untitled

Funder

Organizational Unit

Publications

Microscale flow dynamics of red blood cells in microchannels: an experimental and numerical analysis

Publication . Lima, Rui A.; Fernandes, Carla S.; Dias, Ricardo P.; Ishikawa, Takuji; Imai, Yohsuke; Yamaguchi, Takami

The blood flow dynamics in microcirculation depends strongly on the microvascular networks composed with short irregular vessel segments which are linked by numerous bifurcations. This paper presents the application of a confocal micro-PTV system to track RBCs through a rectangular polydimethysiloxane (PDMS) microchannel with a bifurcation. By using a confocal micro-PTV system, we have measured the effect of bifurcation on the flow behaviour of both fluorescent particles diluted in pure water and RBCs in concentrated suspensions. After performing simulations with the commercial finite element software package POLYFLOW, some experimental results were compared with the numerical results and the limitations of these simulations were outlined.

2011Conference object

Open access

Visualization and measurement of red blood cells flowing in microfluidic devices

Publication . Rodrigues, Raquel Oliveira; Pinho, Diana; Faustino, Vera; Yaginuma, Tomoko; Bento, David; Fernandes, Carla S.; Garcia, Valdemar; Lima, Rui A.

Several experimental techniques were performed in the past years using in vitro environments, in an attempt to not only understand the blood flow behaviour in microcirculation but also develop microfluidic devices as an alternative clinical methodology to detect blood diseases. Hence, the visualization and measurement of red blood cells (RBCs) flowing in a microfluidic device are important to provide not only essential information about hydrodynamic characteristics of the blood but also vital information to diagnose the initial symptoms of diseases during clinical investigations. For instance, RBC rigidity has been correlated with myocardial infarction, diabetes mellitus, hypertension, and also other haematological disorders and diseases that affect RBC deformation more directly, such as, hereditary spherocytosis, sickle cell anaemia and malaria. Regarding a better understanding of the RBCs deformation and motion, we present in this paper a compilation of studies made in our research group, using several microfluidic devices with different microchannel geometries and fabrication techniques (i.e., soft-lithography, xurography and hybrids) that focus in the shear and extensional flow behaviour, either in healthy or chemically stiffed RBCs.

2014Conference object

Open access

Red blood cell dispersion in 100 μm glass capillaries: the temperature effect

Publication . Pinho, Diana; Pereira, Ana I.; Lima, Rui A.; Ishikawa, Takuji; Imai, Yohsuke; Yamaguchi, Takami

The rheological behaviour of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature. Previous in vitro studies have measured the Hct effect on the radial dispersion (Dyy) at both diluted and concentrated suspensions of RBCs. However, according to our knowledge the effect of the temperature on RBC Dyy was never studied. Hence, the main purpose of the present work is to investigate the effect of the temperature on the RBC Dyy. In vitro human blood was pumped through a 100 μm glass capillary and by using a confocal micro-PTV system the RBC Dyy was calculated at two different temperatures, i.e., 25ºC and 37ºC.

2010Conference object

Open access

Conceção de um dispositivo de micro-cromatografia hidrodinâmica para separação de células sanguíneas e visualização do mecanismo de separação

Publication . Pires, Bianca Catarina de Sousa; Dias, Ricardo P.; Ribeiro, António E.

As células que compõem o sangue apresentam tamanhos diferentes. Estudos anteriores revelam que esta diferença de tamanhos leva a diferentes velocidades de migração das diferentes células em canais com diâmetros próximos das arteríolas. Este trabalho teve como intuito o estudo das velocidades de migração de glóbulos vermelhos (GVs) numa rede de canais formados por empacotamentos de esferas de vidro, este método é conhecido por cromatografia hidrodinâmica. Para tal procedeu-se ao empacotamento de várias colunas tubulares com esferas de vidro de diferentes diâmetros. Foram feitos 5 empacotamentos nos quais os diâmetros médios das esferas eram 115, 150, 337,5, 875 e 2000µm. Para cada coluna empacotada fez-se passar no seu interior uma suspensão de GVs de ovelha em soro fisiológico (1% em volume de GVs), do qual se retirou o tempo de residência dos GVs para diferentes caudais: 0,25mL/min a 3 mL/min. Repetiu-se este procedimento para uma solução de sacarose a uma concentração de 1 g/L, também para os mesmos caudais, de forma a permitir o cálculo dos RRTs (a razão entre o tempo de residência dos GVs e o tempo de residência da sacarose), sendo estes valores menores que um na esmagadora maioria dos casos. Os valores obtidos para os RRTs sugerem que alguns dos empacotamentos desenvolvidos podem ser utilizados para separar GVs de moléculas dissolvidas no sangue (como as proteínas), com dimensões da ordem de grandeza da sacarose, dado que os GVs se movem mais rapidamente no interior das colunas empacotadas do que moléculas dissolvidas de menor dimensão que os GVs. Determinou-se por microscopia que o diâmetro dos GVs de ovelha era cerca de 4,6µm. Por fim, para haver uma maior perceção do fluxo sanguíneo no interior das colunas empacotadas produziram-se alguns microcanais em polidimetilsiloxano com características aproximadas às colunas empacotadas, onde se observou a formação de camadas livres de células e zonas de estagnação (em diferentes regiões dos microcanais). O primeiro fenómeno conduz a um aumento da velocidade de migração dos GVs enquanto o segundo conduz à retardação dos GVs. The cells that comprise the blood have different sizes. Previous studies have shown that this size difference can lead to different rates of migration of the cells in channels with diameters of the arterioles. This work aimed to study the migration velocities of red blood cells (GVs) through channels formed by the packing of glass beads, this method is known by hydrodynamic chromatography. For this, different chromatographic columns were packed with glass beads of different diameters. Five packings were made for which the mean diameters of the spheres were 115, 150, 337,5, 875 and 2000µm. A suspension of GVs from sheep in physiological saline (with 1% Hct) was passed inside each packed column and the residence time of the GVs was calculated for different flow rates: 0,25mL/min to 3 mL/min. This procedure was repeated for a sucrose solution at a concentration of 1g/l to allow the calculation of RRTs (the ratio between the residence time of the GVs and residence time of sucrose), this values being inferior to one in the majority of the experiments. With the values obtained for the RRTs it was concluded that some of the developed packed columns can be used to separate the GVs from small molecules dissolved in the blood plasma (such as proteins), with dimensions of the order of magnitude of sucrose, since the GVs migrate faster through the packed columns than molecules smaller than them. Using a microscope it was possible to calculate the diameter of the GVs (around 4,6µm). Finally, to have a greater perception of blood flow within the packed columns, it were produced microchannels constituted by polydimethylsiloxane with characteristics approximating the packed columns and it was possible to observe the formation of cell-free layers and zones of stagnation (at different regions of the microchannels). The former effect leads to the in-crease of the GVs velocities while the second one has an opposite influence in the GVs velocities.

2012Master thesis

Open access

Extensional flow-based microfluidic device: deformability assessment of red blood cells in contact with tumor cells

Publication . 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.

2014Journal article

Open access