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

Analysis of the cell-free layer in a circular microchannels: trajectories of labeled red bllod cells

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

Erythrocyte deformability in a hyperbolic microchannel

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 cells

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.The authors acknowledge the financial support provided by: Student Mobility Placements with the program Lifelong Learning (Erasmus Program), 2007 Global COE Program “Global Nano-Biomedical Engineering Education and Research Network”, Japan. Grant-in-Aid for Science and Technology (PTDC/SAU-BEB/105650/2008, PTDC/EME-MFE/099109/2008 and PTDC/SAU-ENB/116929/2010) from the Science and Technology Foundation (FCT) and COMPETE, Portugal. The authors are also very grateful to Professor Mónica S.N. Oliveira (Strathclyde University), Professor Geyong M. Kim (University of Navarra) and Professor Sergio Arana (University of Navarra) for their discussion and suggestions to this research work

Visualization and measurement of red blood cells flowing in microfluidic devices

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.The authors acknowledge the financial support provided by 2007 Global COE Program “Global Nano-Biomedical Engineering Education and Research Network”, Japan and grant-in-Aid for Science and Technology, PTDC/SAU-BEB/105650/2008, PTDC/EME-MFE/099109/2008, PTDC/SAUENB/116929/2010, EXPL/EMS-SIS/2215/2013, scholarship SFRH/BD/91192/2012 and scholarship SFRH/BD/89077/2012 from FCT (Science and Technology Foundation), COMPETE, QREN and European Union (FEDER). The authors are also very grateful to Dr. Mónica Oliveira (Strathclyde University), Professor Takuji Ishikawa and Professor Takami Yamaguchi (Tohoku University) for their suggestions and support to this research work

Human red blood cell behaviour under homogeneous extensional flow in a hyperbolic-shaped microchannel

It 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 center line 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

The Japanese model in retrospective : industrial strategies, corporate Japan and the 'hollowing out' of Japanese industry

This article provides a retrospective look at the Japanese model of industrial development. This model combined an institutional approach to production based around the Japanese Firm (Aoki's, J-mode) and strategic state intervention in industry by the Japanese Ministry of International Trade and Industry (MITI). For a long period, the alignment of state and corporate interests appeared to match the wider public interest as the Japanese economy prospered. However, since the early 1990s, the global ambitions of the corporate sector have contributed to a significant 'hollowing out' of Japan's industrial base. As the world today looks for a new direction in economic management, we suggest the Japanese model provides policy-makers with a salutary lesson in tying the wider public interest with those of the corporate sector

Flow of red blood cells suspensions through hyperbolic microcontractions

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

Visualization of the cell-free layer (CFL) in a PDMS microchannel with a micro-stenosis

Red blood cells (RBCs) have a tendency to undergo axial migration due to the parabolic velocity profile which results in a high shear stress around wall that forces the RBC to move towards the center induced by the tank treading motion of the RBC membrane. As a result there is a formation of cell-free layer (CFL) with extremely low concentration of cells. Based on this phenomenon several works have proposed microfluidic designs to separate the suspending physiological fluid from whole in vitro blood. However, most of these studies have the aim of the complete extraction of cells from plasma which is not the case of the present study. The biomedical device that is present in this work aims to obtain a CFL with a low enough RBC propose a combination of image analysis techniques able to measure automatically the CFL thickness before and after micro-stenosis is used

Adenosine Triphosphate (ATP) as a Metric of Microbial Biomass in Aquatic Systems: New Simplified Protocols, Laboratory Validation, and a Reflection on Data From the Literature

The use of adenosine triphosphate (ATP) as a universal biomass indicator is built on the premise that ATP concentration tracks biomass rather than the physiological condition of cells. However, reportedly high variability in ATP in response to environmental conditions is the main reason the method has not found widespread application. To test possible sources of this variability, we used the diatom Thalassiosira weissflogii as a model and manipulated its growth rate through nutrient limitation and through exposure to three different temperatures (15°C, 20°C, and 25°C). We simplified the ATP protocol with hot‐water or chemical extraction methods, modified a commercially available luciferin‐luciferase assay, and employed single‐photon counting in a scintillation counter, all of which increased sensitivity and throughput. Per‐cell ATP levels remained relatively constant despite changes in growth rates by approximately 10‐fold in the batch culture (i.e., nutrient limitation) experiments, and approximately 2‐fold in response to temperature. The re‐examination of related literature values revealed that average cellular ATP levels differed little among taxonomic groups of aquatic microbes, even at the domain level, and correlated well with bulk properties such as elemental carbon or nitrogen. Fulfilling multiple cellular functions in addition to being the universal energy currency requires ATP to be maintained in a millimolar concentration range. Consequently, ATP relates directly to live cytoplasm volume, while elemental carbon and nitrogen are constrained by an indeterminate pool of detrital material and intracellular storage compounds. The ATP‐biomass indicator is sensitive, economical, and can be readily standardized among laboratories and across environments