WO2005095954A1

WO2005095954A1 - A filter for separating blood-corpuscles and plasma from blood, and blood analysis system using this filter

Info

Publication number: WO2005095954A1
Application number: PCT/KR2005/000934
Authority: WO
Inventors: Jee-Hoon Seo; Jae-Seon Lee; Seung-Joo Kang
Original assignee: All Medicus Co., Ltd.
Priority date: 2004-03-31
Filing date: 2005-03-31
Publication date: 2005-10-13
Also published as: KR20050096489A

Abstract

Disclosed herein is a construction for separating blood by structures with a given angle placed in a microchannel formed on a planar substrate. The invention provides a filter for separating a blood corpuscle component and a plasma component from blood, which is used in a microsystem for the analysis of blood, the filter comprising: a substrate having a microchannel formed thereon, the microchannel having one input section and at least two output sections with a given angle to each other; and a plurality of rectangular structures formed in the microchannel at a givel angle to the input section of the microchannel. The rectangular structures allow blood in the microchannel to be separated into the flow of a blood corpuscle component and the flow of a plasma component by the interval between and arrangement of the rectangular structures.

Description

A FILTER FOR SEPARATING BLOOD-CORPUSCLES AND PLASMA FROM BLOOD, AND BLOOD ANALYSIS SYSTEM USING THIS FILTER

Technical Field The present invention relates to a filter for separating a blood corpuscle component and a plasma component from blood, and a blood analysis system including this filter, and more particularly, to a filter which can simply separate blood corpuscles from a very small amount of blood on a planar substrate within a short period of time by non-power sources, such as the capillary phenomenon, and other devices for applying pressure from the outside.

Background Art As the standard of living becomes higher, persons who simply check the individual health status in the house gradually increase. Having a medical examination in a large hospital to .check individual health status is a lot of loss in terms of cost and time. Thus, to simply check the individual health status in the house, devices which can be used by the end-users in a simple, fast and precise manner are required. In the case of checking the health status from blood tests, a large amount of blood is taken and medically examined in a hospital. However, with the recent development in the technology of high-sensitivity sensors or other devices, the person himself can examine items selected for a medical examination, and thus, many measurements become possible even with a very small amount of blood. Disclosure of Invention It is an object of the present invention to separate a blood corpuscle component and a plasma component from blood on a planar substrate by a simple- to-manufacture filter using microfluidics . Another object of the present invention is to effectively separate and extract blood corpuscles by a filter having rectangular structures with a given angle placed in a microchannel on an integrated chip, without a need to use filter membranes or other devices to treat a biological sample and blood on the chip in a collective process. In still another object of the present invention is to provide a blood filter which can be manufactured in a very simple process and thus applied in a microsystem or a biosensor system, and to separate very small amounts of various blood components by this blood filter alone and to analyze the separated blood components in an optical or electrochemical analysis device within a short period of time. With respect to the above-described objects, disclosed is a construction for separating blood components by structures with a given angle placed in microchannels formed on a planar substrate. In one aspect, the present invention provides a filter for separating a blood corpuscle component and a plasma component from blood, which is used in a microsystem for analysis of blood, the filter comprising: a substrate having a microchannel formed thereon, the microchannel having one inlet and at least two outlets with a given angle to each other; and a plurality of rectangular structures formed in the microchannel at a given angle to the inlet of the microchannel, the rectangular structures allowing blood in the microchannel to be separated into the flow of a blood corpuscle component and the flow of a plasma component by the interval between and arrangement of the rectangular structures. In another aspect, the present invention provides a microsystem for the analysis of blood, comprising: a substrate having a microchannel formed thereon, the microchannel having one inlet and at least two outlet with a given angle to each other; a plurality of rectangular structures formed in the microchannel at a given angle to the inlet of the microchannel, the rectangular structures allowing blood in the microchannel to be separated into the flow of a blood corpuscle component and the flow of a plasma component by the interval between and arrangement of the rectangular structures; and biosensors for blood analysis integrated at the end of the microchannel. According to the present invention, it is possible to separate a blood corpuscle component and a plasma component by the filter, which is manufactured in a simple process, can be driven with no power using the capillary phenomenon caused by a design, and uses icrofluidics using a difference in fluid resistance between the mechanical structures. Also, it is possible to effectively separate and extract blood corpuscles by the filter having the rectangular structures with a given angle placed in the microchannel on the chip in an array configuration, without a need to use filter membranes or other devices to treat samples on the chip in a collective process. In addition, the filter can be manufactured in a very simple process, and thus, applied in a microsystem or a biosensor system. When a plurality of the filters according to the present invention, which have been are connected in series, are used, high-purity plasma can be separated. The use of the separated plasma allows operations, including the diagnosis of a marker showing the expression of important cancer, the detection of various important proteins in the human body, and the measurement of various viruses in the human body. Thus, the present invention can be used as an important element technology of a system for examining the health status of the human body with a very small amount of blood without the addition of buffer or other solutions. This filter system can be used to separate a very small amount of a sample in performing blood analysis in hospitals or other bio-related laboratories, and will become one of very important and useful technologies necessary in a biosensor system of collecting and analyzing less than a few μl of blood.

Brief Description of Drawings Embodiments of the present invention will be described in detail with reference to the accompanying drawings wherein: FIG. 1 is a conceptual view of a filter according to a first embodiment of the present invention, which comprises microstructures in a microchannel on a substrate; FIG. 2 is a perspective view of the filter of FIG. 1; FIG. 3 is a graphic view showing the performance of a filter as a function of the angle of an output channel in the filter; FIG. 4 is a conceptual view of a filter according to a second embodiment of the present invention, in which microstructures in a microchannel on a substrate are arranged in a staggered configuration; FIG. 5 is a conceptual view of a filter according to a third embodiment of the present invention, in which microstructures in a microchannel on a substrate are randomly omitted; FIG. 6 shows the interpretation of the movement of blood in a filter according to the present invention; and FIG. 7 is a photograph showing the appearance of separation of blood in the filter of FIG. 4.

Best Mode for Carrying Out the Invention FIG. 1 is a conceptual view of a filter comprising microstructures in a microchannel on a substrate, and

FIG. 2 is a perspective view of the filter of FIG. 1.

If there is a need to separate blood on a planar substrate, blood is then injected into the inlet of a microsystem or biosensor system by a capillary phenomenon or an external power source and flows along a given pathway (microchannel) by the capillary phenomenon or the external power source. As shown in FIGS. 1 and 2, blood injected into the inlet 102 passes through a filter comprising the rectangular array-type structures 106 with a given angle in the microchannel 103. The array-type structures 106 have a given angle to the inlet 102, and are arranged in a parallel or staggered configuration. And between these structures 106, there are intervals through which a blood corpuscle component and a plasma component will flow. The rectangular structures are arranged with a given interval in the microchannel 103, and come in contact with the upper and lower portions of the microchannel 103. Also, these rectangular structures are determined at the optimum conditions by appropriate hydromechanic equations and simulations in order to prevent blood corpuscles from being blocked. The rectangular structures are located at a position at which the main microchannel (or inlet channel) 102 into which a biosa ple or blood sample flows meets the microchannels (or outlet channels) 108 and 110 which are diverged from each other. By these rectangular structures thus formed, the original blood flow is separated into two flows due to the fluid resistance of the structures, in which the blood flows in a longitudinal direction to the microchannel 108 or flows in a transverse direction to the microchannel 110. The blood whose flow has been separated passes through the structures by continuously advancing blood, in which the blood flows through the structures to the downward channel 108 and flows through the intervals between the structures to the longitudinal channel 110. In this respect, the separation ratio between the blood corpuscle component and the plasma component is determined by the following several variables: i) the number, arrangement configuration and location of the array structures 106 in the microchannel; ii) the longitudinal and transverse intervals between the rectangular array structures 106; iii) the angle of the rectangular array structures 106 to the inlet channel 102, and the angle of the downward outlet 108 to the inlet channel 102; and iv) the ratio of width between the outlet channels 108 and 110. Each of the variables has the following effects. First, although an increase in the number of the rectangular structures in the microchannel can provide an increase in the separation efficiency for blood, it can result in clogging by blood corpuscles. Since the content of the blood corpuscle component in blood is about 45-50% by volume, this clogging phenomenon is a very important factor in manufacturing blood separation systems, such as a filter. Thus, according to the present invention, the number and location of the rectangular structures in the microchannel are so adjusted that the blood corpuscle and plasma components of blood are separated in the optimum conditions. The longitudinal and transverse intervals between the rectangular structures have a close connection with the factor set forth in the variable i) . If the intervals are too narrow, a clogging phenomenon can also be caused by blood corpuscles. The intervals between the rectangular structures are preferably designed in view of the size of blood corpuscles so that the clogging phenomenon caused by blood corpuscles is eliminated to the maximum possible extent. The effect of the angle of the rectangular structures to the inlet of the microchannel will now be described. The flow of blood injected into the inlet of the microchannel is suddenly retarded by the rectangular structures. For this reason, in order to the clogging of blood corpuscles and a reduction in efficiency from occurring due to the retardation of blood flow, it is preferable that the rectangular structures and the microchannel should have more than a given angle to each other. The ratio of width between the channels along which the separated blood fluids flow has a connection with the pressure in the channels. Namely, as the channel width becomes wider or narrower, the flow rate of blood through the structures vary, and this is also one important factor in blood separation. The blood corpuscle component and the plasma component, which have been separated from each other as described above, move to a measurement or component analysis location in a microsystem or a biosensor system. Namely, the end of each of the output channels 108 and 110 has a configuration capable of either directly analyzing blood with various integrated sensors or transferring the separated blood sample effluent from the channel end to a second analysis and measurement system by a device such as a syringe, a pipette or a spoid. The planar substrate is generally made of an easy- to-process and easy-to-handle material, such as plastic, glass or silicon wafer. The most important elements in the present invention are the rectangular structures in the microchannel. By these rectangular structures, the blood corpuscle component and the plasma component are separated from each other, in which the separation efficiency of only about 89-90% rather than 100% can provide sufficiently meaningful values. Namely, even when the inventive blood filter has an efficiency of only about 80-90%, the use of at least two filters connected in series can achieve the separation of almost 100% of blood corpuscles and plasma from blood. Hereinafter, one example of a method for manufacturing the blood filter according to the present invention will be described. A bare silicon wafer is placed in a furnace wherein a thermal oxide film is grown on the silicon wafer to a thickness of about 0.4 μm. Then, photoresist is spin-coated on the thermal oxide film and irradiated with UV light through a mask in a photolithographic process so as to pattern a filter. The filter patterned in this process is subjected to a dry etching (DRIE) process to form a microchannel and rectangular structures. In this respect, the depths of the microchannel and the rectangular structures can vary depending on the amount of use of a biosample or blood, but must be at least 10 μm in order for the blood corpuscle component to pass without clogging. After performing the dry etching process as described above, the silicon wafer is covered with a lid so as to seal the microchannel and the rectangular structures before experiments. In the present invention, the lid is made of polydimethylsiloxane (PDMS). More than a given amount of PMDS is placed and hardened on the silicon wafer and punched at portions corresponding to the inlet and outlets of the microchannel so as to make the entrance and exit of blood easy. After injecting actual blood into the device thus manufactured, the separated blood components are extracted from the respective channels and quantitatively measured. The measurement results are shown in FIG. 3. FIG. 4 is a conceptual view of a filter in which microstructures are arranged in the microchannel in a staggered configuration, and FIG. 5 is a conceptual view of a filter having a structure in which microstructures are randomly omitted. FIG. 7 is a photograph showing the appearance of separation of blood in the filter of FIG. 4. The rectangular structures in the microchannel can be manufactured in various configurations, have a given angle to the microchannel, and arranged in an array configuration. This arrangement has the optimum conditions to separate the blood corpuscle and plasma components of blood, which were determined by the results of various related experiments and simulations. The rectangular structures are arranged either in an inline configuration as shown in FIG. 1 or in a staggered configuration as shown in FIG. 4. These two configurations have a slight difference in separation efficiency, and it is expected that the staggered configuration will be slight higher in separation efficiency than the inline configuration. The interval between the rectangular structures is a variable capable of adjusting the fluid resistance in the microchannel and also determined by experiments and simulations. Generally, the interval between the rectangular structures is smaller than the general size of red blood cells (8-10 μm) for a transverse direction and greater than the size of red blood cells for a longitudinal direction, so that the blood corpuscle components are difficult to pass in the transverse direction but easy to pass in the longitudinal direction. Also, the angle of the rectangular structures to the microchannel acts as a factor as the interval between the structures, and the efficiency of blood separation varies depending on the angle of the microchannel along which a biosample and blood flow, to the microchannel from which the separated blood components flow out. FIG. 6 shows the movement of blood in the inventive filter, which was interpreted by computer simulation tools. In FIG. 6, "Inline Type" represents the case where the rectangular structures are arranged in an inline configuration, and "Staggered Type" represents the case where the rectangular structures are arranged in a staggered configuration. The interpretation of the movement of blood for the two arrangements of the rectangular structures were performed while recording the physical property values of the blood corpuscle component and the plasma component and adjusting the size of the microchannel, the arrangement and configuration of the rectangular structures, the angle of the structures to the microchannel, and the like. As a result, how the separation efficiency differs between the rectangular structures arranged in the inline configuration and the rectangular structures arranged in the staggered configuration could be confirmed. The white lines in the enlarged portions of FIG. 6 represent the flow of the blood corpuscle component, and the others represent the flow of plasma. As can be seen in FIG. 6, in the rectangular structures arranged in an inline configuration, the flow of blood corpuscles is larger in the transverse direction than in the longitudinal direction, indicating that the efficiency of separation of the blood corpuscle component and the plasma component is lower than that of the rectangular structures arranged in the staggered configuration. In the rectangular structures arranged in the staggered configuration, the flow of blood corpuscles is larger in the longitudinal direction than in the transverse direction, indicating that the blood corpuscles are concentrated on the longitudinal microchannel 108, and the efficiency of separation of the blood corpuscle component and the plasma component is higher than that of the structures arranged in the staggered configuration. The embodiments described herein are provided for a better understanding of the present invention only so as to allow persons skilled in the art to easily understood and practice the present invention, and are not construed to limit the scope of the present invention. It will be evident to persons skilled in the art that various modifications and variations to these embodiments are possible.

Industrial Applicability According to the present invention as described above, it is possible to manufacture the filter in a simple process and to separate the blood corpuscle and plasma components with the filter using microfluidics .

Also, it is possible to effectively separate and extract blood corpuscles by the filter having the rectangular structures with a given angle arranged in the microchannel on the chip in an array configuration, without a need to use membranes or other devices to treat a sample on the chip in a collective process. In addition, the filter can be manufactured in a very simple process, and thus, applied in a microsystem or a biosensor system.

Claims

What Is Claimed Is :

1. A blood filter for separating a blood corpuscle component and a plasma component from blood, which is used in a microsystem for the analysis of blood, the filter comprising: a substrate having a microchannel formed thereon, the microchannel having one inlet and two outlets with a given angle to each other; and a plurality of rectangular structures formed in the microchannel at a given angle to the inlet of the microchannel, the rectangular structures allowing blood in the microchannel to be separated into the flow of a blood corpuscle component and the flow of a plasma component by the interval between and arrangement of the rectangular structures.

2. The blood filter of Claim 1, wherein the substrate is any one selected from the group consisting of silicon, PDMS, PMMA and electroplated substrates.

3. The blood filter of Claim 1, wherein the rectangular structures are arranged either in an inline configuration or in a staggered configuration.

4. The blood filter of Claim 1, wherein pluralities of the filters are connected in series.

5. The blood filter of Claim 1, wherein the interval between and arrangement of the rectangular structures are determined by the size of a sample to be separated and the equation of hydromechanics in the microchannel .

6. A microsystem for the analysis of blood, comprising: a substrate having a microchannel formed thereon, the microchannel having one inlet and two outlets with a given angle to each other; a plurality of rectangular structures formed in the microchannel at a given angle to the inlet of the microchannel, the rectangular structures allowing blood in the microchannel to be separated into the flow of a blood corpuscle component and the flow of a plasma component by the interval between and arrangement of the rectangular structures; and biosensors for blood analysis integrated at the end of the microchannel.