A microfluidic device for partial cell separation and deformability assessment

Blood flow in microcirculation shows several interesting phenomena that can be used to develop microfluidic devices for blood separation and analysis in continuous flow. In this study we present a novel continuous microfluidic device for partial extraction of red blood cells (RBCs) and subsequent measurement of RBC deformability. For this purpose, we use polydimethylsiloxane (PDMS) microchannels having different constrictions (25%, 50% and 75%) to investigate their effect on the cell-free layer (CFL) thickness and separation efficiency. By using a combination of image analysis techniques we are able to automatically measure the CFL width before and after an artificial constriction. The results suggest that the CFL width increases with enhancement of the constriction and contributes to partial cell separation. The subsequent measurements of RBCs deformation index reveal that the degree of deformation depends on the constriction geometries and hematocrit after the cell separation module. The proposed microfluidic device can be easily transformed into a simple, inexpensive and convenient clinical tool able to perform both RBC separation and deformability analysis in one single device. This would eliminate the need for external sample handling and thus reducing associated labor costs and potential human errors

Red blood cells motion in a glass microchannel

The motion of the red blood cells (RBCs) flowing in microvessels and microchannels depend on several effects, such as hematocrit (Hct), geometry, and temperature. According to our knowledge, the effect of the temperature on RBC motion was never investigated at a microscale level. Hence, the aim of the present work is to determine the effect of the temperature on the RBC’s trajectories and to investigate the best approximation of the trajectories through a nonlinear optimization. In vitro human blood was pumped through a 100 mm circular microchannel and by using a confocal micro- PTV system the RBC’s trajectories were measured at different temperatures, i.e., 25◦C and 37◦C. In this study we measured the motion of forty cells flowing in the middle of the microchannel and applied different functions to approximate its behavior.This study was supported in part by the following grants: Grant-in-Aid for Science and Technology (PTDC/SAU-BEB/108728/2008, PTDC/SAU-BEB/105650/2008 and PTDC/EME-MFE/099109/2008) from the Science and Technology Foundation (FCT) and COMPETE, Portugal

Motion of red blood cells in a glass microchannel: a global optimization approach

Este artigo também deve ser anexado ao Departamento Tecnologia Mecânica, docente Rui Alberto Madeira Macedo Lima.In this work we characterized the behavior of red blood cell motion through a glass microchannel. In this study we consider the radial displacement of forty red blood cells and use different functions to approximate the radial displacement of each of them, by means of global optimization using stretched simulated annealing method. Some numerical results are shown

Técnicas de separação biomimética em microfluídica

A separação e a identificação de células são essenciais em várias aplicações biomédicas, incluindo a biologia celular e os métodos de diagnóstico e terapêuticos. O sangue é um fluido não-Newtoniano contendo inúmeras informações preciosas sobre o estado fisiológico e patológico do corpo humano. No entanto, devido à sua complexidade, existem actualmente poucos métodos de análise precisos. A maioria das técnicas convencionais usadas na separação e contagem de células são dispendiosas e normalmente é necessário usar agentes externos adicionais para identificar as células. As técnicas biomiméticas de separação em microfluídica usam fenómenos microfluídicos, que ocorrem à microescala, para realizar a separação de determinadas células sanguíneas. Estes fenómenos incluem a separação do plasma, a camada livre de células (CLC), a migração dos glóbulos brancos (GBs), também designados por leucócitos, e a lei da bifurcação. Recentemente, vários investigadores têm replicado estes efeitos, que acontecem em ambientes in vivo, em sistemas microfluídicos, ou seja, em ambientes in vitro. Nos microcanais, os glóbulos vermelhos (GVs), devido à sua deformabilidade e ao gradiente de velocidades (às forças de sustentação), tendem a concentrar-se na zona central dos microcanais, enquanto os GBs e os GVs rígidos (tal como, os GVs infectados com malária) tendem a migrar para a CLC que se forma nas zonas próximas das paredes. A lei da bifurcação estabelece, relativamente ao comportamento dos GVs, que em microcanais com bifurcações eles tendem a escolher o microcanal de secção maior.Os autores agradecem à FCT, COMPETE, QREN e União Europeia (FEDER) pelo financiamento através dos seguintes projetos: PTDC/SAU-BEB/105650/2008, PTDC/SAU-BEB/108728/2008, PTDC/EME-MFE/099109/2008 ePTDC/SAU-ENB/116929/2010

Cell-free layer (CFL) analysis in a glass capillary: comparison between a manual and automatic method

In this study, in vitro blood flowing through a 100 m glass capillary was studied. The images were captured using a confocal system and post-processed using Image J and MatLab. The aim of the present work, was to measure the trajectories of the cell-free layer (CFL) by using two different methods, i. e., a manual method (MM) and an automatic method (AM). For theMM we have used amanual tracking plugin (MTrackJ) from Image J to track labeled red blood cells (RBCs) flowing around the boundary of the RBCs core. For the AM we have used a MatLab scripts to measure automatically the CFL trajectories. The preliminary numerical results suggest that the CFL trajectories follow a polynomial function for both methods.The authors acknowledge the financial support provided by: PTDC/SAU-BEB/108728/2008, PTDC/SAU-BEB/105650/2008, PTDC/EME-MFE/099109/2008 and PTDC/SAU-ENB/116929/2010 from the FCT (Science and Technology Foundation) and COMPETE, Portugal

A comparison between a manual and automatic method to characterize red blood cell trajectories

The current study proposes an automatic method for the segmentation and tracking of red blood cells (RBCs) flowing through a 100 u m glass capillary. The measurements obtained with the proposed automatic method are compared with a manual tracking method using nonlinear optimization techniques.The authors acknowledge the financial support provided by: PTDC/SAUBEB/108728/2008, PTDC/SAU-BEB/105650/2008 and PTDC/EME-MFE/ 099109/2008 from the FCT (Science and Technology Foundation) and COMPETE, Portugal

Nanopartículas de óxido de ferro: relação entre parâmetros morfológicos/químicos e a sua citotoxicidade

Desde a sua descoberta as nanopartículas têm sido aplicadas nas mais diversas áreas da ciência. De facto, atualmente, é comum observar o uso de nanopartículas em áreas como a eletrónica, ótica e ambiente. À medida que o número de aplicações foi crescendo, particularmente na área do ambiente e da tecnologia biomédica, tornou-se necessário avaliar a possível citotoxicidade das nanopartículas

Generation of micro-sized PDMS particles by a flow focusing technique for biomicrofluidics applications

Polydimethylsiloxane (PDMS), due to its remarkable properties, is one of the most widely used polymers in many industrial and medical applications. In this work, a technique based on a flow focusing technique is used to produce PDMS spherical particles with sizes of a few microns. PDMS precursor is injected through a hypodermic needle to form a film/reservoir over the needle's outer surface. This film flows towards the needle tip until a liquid ligament is steadily ejected thanks to the action of a coflowing viscous liquid stream. The outcome is a capillary jet which breaks up into PDMS precursor droplets due to the growth of capillary waves producing a micrometer emulsion. The PDMS liquid droplets in the solution are thermally cured into solid microparticles. The size distribution of the particles is analyzed before and after curing, showing an acceptable degree of monodispersity. The PDMS liquid droplets suffer shrinkage while curing. These microparticles can be used in very varied technological fields, such as biomedicine, biotechnology, pharmacy, and industrial engineering.The authors acknowledge the financial support provided by Fundação para a Ciência e a Tecnologia (FCT), COMPETE and FEDER through the Projects PTDC/SAU-ENB/116929/2010, EXPL/EMS-SIS/2215/2013, PTDC/QEQ-FTT/4287/2014 and fellowship SFRH/BD/89077/2012. Partial support from the spanish Ministry of Science and Education (Grant No. DPI2013-46485), Junta de Extremadura (Grant No. GR10047), and “la Caixa” Foundation (predoctoral grant) is gratefully acknowledged too. Finally, we thank Jos e M. Montanero for his helpful suggestions and discussion on the results.info:eu-repo/semantics/publishedVersio

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

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.This study was supported in part by the following grants: Grant-in-Aid for Scientific Research (S) from the Japan Society for the Promotion of Science (JSPS; no 19100008), Grant-in-Aid for Science and Technology (PTDC/SAL-BEB/108728/2008, PTDC/SAU-BEB/105650/2008 and PTDC/EME-MFE/099109/2008) from the Science and Technology Foundation (FCT) and COMPETE, Portugal. We also acknowledge the support from the 2007 Global COE Program “Global NanoBiomedical Engineering Education and Research Network’

Cell-free layer measurements in bifurcating microchannels: a global approach

In the present work, in vitro blood flowing through bifurcating microchannels was studied, with the aim of characterizing the cell-free layer (CFL). The original images were obtained by means of a high-speed video microscopy system and then processed in MatLab using the Image Processing Toolbox. The numerical data was obtained automatically and analyzed by optimization techniques using the genetic algorithm approach. The results suggest that the CFL were formed in a similar way at the upper and lower regions in all bifurcations, and the measurements can be approximated through a sum of trigonometric functions