CN111733074A

CN111733074A - Micro-fluidic chip and system for high-flux magnetic sorting of circulating tumor cells

Info

Publication number: CN111733074A
Application number: CN202010750322.3A
Authority: CN
Inventors: 朱志军; 王学斌; 孙丽莹
Original assignee: Beijing Friendship Hospital
Current assignee: Beijing Friendship Hospital
Priority date: 2020-07-30
Filing date: 2020-07-30
Publication date: 2020-10-02
Anticipated expiration: 2040-07-30
Also published as: CN111733074B

Abstract

The invention discloses a micro-fluidic chip for high-flux magnetic sorting of circulating tumor cells, which comprises a sample introduction part, a micro-fluidic sorting area and a sample outlet part. The micro-fluidic separation area is of a closed cavity structure, and the sample inlet part and the sample outlet part are respectively connected with two ends of the micro-fluidic separation area; the sample injection part comprises a blood sample injection port and a buffer liquid inlet; the sample outlet part comprises a magnetic bead cell collecting port and a non-magnetic bead cell collecting port; the microfluidic sorting area comprises three structural areas, namely a purification structural area, a cell focusing structural area and a magnetic bead sorting structural area. The microfluidic chip has the advantages of high background cell clearance rate, high tumor cell capture rate, high tumor cell survival rate and capability of realizing high-flux capture.

Description

Micro-fluidic chip and system for high-flux magnetic sorting of circulating tumor cells

Technical Field

The invention relates to a micro-fluidic chip, in particular to a micro-fluidic chip for high-flux magnetic separation of circulating tumor cells and a micro-fluidic chip system formed by the micro-fluidic chip.

Background

Tumor is the main disease endangering human health in the present society, the most effective method for treating tumor is surgical resection at present, but even if the patient receives surgical resection treatment, the patient still has the risk of tumor recurrence and metastasis, and one of the reasons of poor prognosis is that cancer cells can easily enter and spread through blood. Such free tumor cells may already be present in the blood of these patients prior to surgical resection.

In 1896, Ashworth found tumor cell-like cells in the peripheral blood of 1 patient who died from cancer, and thus proposed the concept of Circulating Tumor Cells (CTCs). CTC refers to a portion of the cancer cells that have detached from a primary tumor and entered the lymphatic system, blood circulation, of a patient. This fraction of cells may already be present in the blood circulation before the patient is subjected to surgery, which may encourage more CTCs to enter the blood circulation and thus accelerate tumor metastasis. With the progress of research in recent years, the application of CTC gradually becomes a hotspot of anticancer therapy, and is called as 'liquid biopsy', a plurality of researches find that CTC not only can be used as a novel marker for early diagnosis of tumors, but also can be used as one of sensitive indexes for detecting recurrence and metastasis of tumors after operation, and by extracting and researching CTC in blood of a patient, a personalized treatment scheme is hopefully provided for the patient, a metastasis and recurrence path of the tumors is thoroughly blocked, and the CTC application is also a basis for realizing in vitro culture and drug sensitivity experiments of CTC. The capture of CTC has certain difficulty, and the main difficulties are that the cell has special properties, the content of CTC is extremely low, the activity of the cell is poor, and the efficient extraction and the maintenance of enough activity for the next-stage experiment are difficult.

There are currently a number of methods for isolating CTCs in a patient's blood that can be broadly divided into two broad categories based on principles, namely positive enrichment methods, generally based on antigen-antibody principles, that specifically capture target CTCs, such as the american CellSearch system, which is one of the few american FDA approved systems for CTC extraction, based on the use of an antibody molecule targeting epithelial cell adhesion (EpCAM) to specifically recognize CTCs. However, the CellSearch system has some defects, for example, the CellSearch system cannot realize full-automatic sorting and intelligent capture of EpCAM positive cells, because CTCs are changed in a human body at any time, when epithelial-mesenchymal sample change occurs, the EpCAM antigen on the surface of the CTCs disappears, so that the CTC extraction system based on the antibody recognition is ineffective, and the cells extracted by the method are generally poor in activity, so that later experiments are greatly limited. The principle of the negative enrichment method is opposite to that of the positive enrichment method, and the residual cells in the whole blood are collected to be the CTC by adopting various means to remove the background cells in the whole blood, for example, the CTC is separated by using a density gradient centrifugation method widely used at present, and the CTC is obtained by removing the background cells such as red blood cells, platelets, white blood cells and the like in the whole blood based on the density difference between the blood cells.

In the initial stage of experimental research, the inventor designs and manufactures a microfluidic chip for sorting circulating tumor cells by using a microfluidic chip technology and adopting a deterministic lateral displacement principle, and the authorization publication number is CN 208604119U. The capture rate of the microfluidic chip is 85.1 +/-3.2%, the microfluidic chip has the advantages of rapidness, high efficiency, no need of centrifugation in the whole process, less cell damage and the like, and in subsequent clinical experiments, the corresponding capture system is proved to be capable of successfully capturing CTC in peripheral circulating blood of a patient. However, the inventors have found that the sorting apparatus and method have many problems in the course of experimental research. Firstly, the micro-fluidic chip mainly has the function of removing background cells, and samples passing through the micro-fluidic chip still need to rely on the existing commercialized magnetic separation equipment to carry out separation of CTC, so that the whole system has large volume, high experimental cost and complicated switching pipelines; secondly, most of the existing mature magnetic bead cell sorting equipment are magnetic column-like structures, in an experiment, the sorting of the structures is limited by flow, a large amount of liquid cannot pass through the structures in a short time, and in the sorting process, a part of cells can remain in a magnetic column, so that the loss of CTC is caused; finally, although the average clearance rates of the microfluidic chip on white blood cells, red blood cells and platelets are respectively as follows: 99.3 + -1.6%, 99.6 + -0.8%, 99.9 + -1.2%, but the remaining background cells are still too large relative to the number of CTCs and there is still a need to improve the extraction purity.

In summary, how to capture CTCs of various subtypes efficiently and efficiently with high activity and in a comprehensive manner has become a bottleneck in the development of this field, and a novel microfluidic chip for CTC sorting is in urgent need.

Disclosure of Invention

The invention aims to provide a micro-fluidic chip for high-flux magnetic sorting of circulating tumor cells.

Another technical problem to be solved by the present invention is to provide a microfluidic chip system composed of the microfluidic chip.

In order to achieve the purpose, the invention adopts the following technical scheme:

according to a first aspect of the embodiments of the present invention, a microfluidic chip for high-throughput magnetic sorting of circulating tumor cells is provided, which includes a sample introduction part, a microfluidic sorting area and a sample discharge part, wherein the microfluidic sorting area is a closed cavity structure, and the sample introduction part and the sample discharge part are respectively connected to two ends of the microfluidic sorting area; the sample introduction part comprises a blood sample introduction port and a buffer liquid inlet; the sample outlet part comprises a magnetic bead cell collecting port and a non-magnetic bead cell collecting port; wherein:

the microfluidic sorting area comprises three structural areas, namely a purification structural area, a cell focusing structural area and a magnetic bead sorting structural area; the sample introduction part is connected with the head end of the purification structure area, the head end of the cell focusing structure area is communicated with the tail end of the purification structure area, the tail end of the cell focusing structure area is communicated with the head end of the magnetic bead sorting structure area, and the tail end of the magnetic bead sorting structure area is communicated with the sample discharge part;

the purification structure area is provided with a primary filter structure for removing red blood cells and platelets in the whole blood sample, and the purification structure area is also provided with a waste liquid outlet;

the cell focusing structure area is composed of two focusing branch passages which are arranged side by side and are mutually independent; the two focusing branch passages are arranged in mirror symmetry with each other by taking the axis of the cell focusing structural region as a symmetry axis, the outer wall of the top surface of each focusing branch passage is a horizontal top wall, the inner wall of the top surface is provided with a plurality of linear convex edges, and each convex edge is arranged in parallel and is obliquely arranged at a set angle with the symmetry axis;

and magnets capable of attracting magnetic beads are symmetrically arranged on two sides of the magnetic bead sorting structural area.

Preferably, each rib is inclined to the symmetry axis to form an acute angle, wherein the acute angle is towards the bead sorting structure region.

Wherein preferably, the acute angle is 60-70 deg.

Preferably, the condition parameters of the convex edge are as follows: hg is more than d and less than or equal to 2d, Ht is more than Hg, Dob is more than 2d and more than or equal to Lob; d is the diameter of the focused cell, Hg is the vertical distance between the ribs and the bottom surface, Ht is the height of the ribs, Dob is the horizontal distance between the ribs, and Lob is the horizontal width of the ribs.

Wherein preferably, the width of the focusing branch passage is greater than or equal to 400 μm; the length is more than or equal to 1.5 cm.

Preferably, the central region of the cell focusing structure region corresponds to the non-magnetic bead cell collecting port, the two side regions of the central region correspond to the magnetic bead cell collecting port, and the central region is 1/2 region extending from the two sides of the symmetry axis to the total width.

Wherein preferably, the bottom surface of the focusing branch passage is a flat wall; the two side walls of the focusing branch passage are perpendicular to the flat wall of the bottom surface.

Preferably, the head end of the focusing branch passage is provided with a second grid structure.

Preferably, the purification structure area is composed of two purification branch passages which are arranged side by side and are mutually independent; the two purification branch passages are arranged in mirror symmetry with the axis of the purification structure area as a symmetry axis;

a micro-column array is arranged in the purification branch passage, a gap is formed between the micro-column array and the inner side wall of the purification branch passage, and the gap forms a target cell passage; the micro-column array is formed by arranging a plurality of micro-column rows in parallel, and the micro-column rows are formed by arranging a plurality of micro-columns; the head end of the micro-column row is far away from the axis of the purification structure area, and the tail end of the micro-column row is close to the axis of the purification structure area and is obliquely arranged according to a set angle; the radial section of the microcolumn is oval, the diameter of the oval is 28-33 mu m, and the symmetrical diameter of the oval is 20-25 mu m; in the same microcolumn row, the distance between the centers of eggs of two adjacent microcolumns is 40-45 μm, and the minimum distance between the centers of eggs of two adjacent microcolumn rows is 60-65 μm.

Wherein preferably, the inclination set angle of the micro-column row is 1.5-2.5 °.

Preferably, the width of the purification branch channel is 1-2 mm, the length of the micro-column array is 3-4 cm, and the height is 20-30 μm.

Preferably, the blood sample injection port and the buffer solution inlet are simultaneously connected with the head ends of the two purification branch passages; and a grid-shaped structure area is also arranged in the head end of the purification branch passage.

Preferably, the tail ends of the micro-column arrays of the two purification branch passages are connected with a waste liquid outlet, and a grid-shaped structure area is arranged between the micro-column array and the waste liquid outlet; the tail end of the target cell channel is communicated with the cell focusing structure area.

Preferably, the blood sample inlet is communicated with the head end of the micro-column array in the purification structure area through a shunt sample inlet tube, and is used for shunting the blood sample to the micro-column array on two sides of the purification structure area through the shunt sample inlet tube.

Preferably, the shunt sample inlet pipe is internally provided with a first grid-shaped structure.

Preferably, the magnetic bead sorting structure region is a conical structure, and the width of the conical structure gradually increases from the head end to the tail end.

Preferably, the length of the magnetic bead sorting structure area is more than or equal to 4 cm; the width of the tail end of the magnetic bead separation area is 3 times of that of the head end of the magnetic bead separation area.

Preferably, the N pole of the magnet on both sides of the magnetic bead sorting structural region is close to the magnetic bead sorting structural region, and the S pole is far away from the magnetic bead sorting structural region.

Preferably, the non-magnetic bead cell collecting port of the sample outlet part is communicated with the center of the magnetic bead sorting structure region through a non-magnetic bead cell collecting pipe; the magnetic bead cell collecting port is communicated with two sides of the magnetic bead sorting structure area through a magnetic bead cell shunt pipe.

According to a second aspect of the embodiments of the present invention, a microfluidic chip system for high throughput magnetic sorting of circulating tumor cells is provided, which is formed by connecting the above microfluidic chips in parallel.

Wherein, the blood sample inlet and the buffer solution sample inlet are of a double-channel structure which is stacked up and down; the waste liquid outlet and the outlet channel of the purification structure area are of a two-channel structure stacked up and down, and the non-magnetic bead labeled cell outlet and the magnetic bead labeled cell outlet are of a two-channel structure stacked up and down.

The invention has the advantages and beneficial effects that:

(1) the microfluidic chip provided by the invention can be used for various CTC sorting modes, namely the CTC capturing mode can be changed by only adjusting the types of the magnetic beads, and the structure of the chip is not required to be changed. And if the magnetic beads coated with the leukocyte-specific antibodies are used, the micro-fluidic chip captures CTCs for a negative enrichment method, and the CTCs are obtained from a non-magnetic-bead cell collecting port.

(2) The micro-fluidic chip provided by the invention can effectively remove background cells by the design of three structural regions. When the sample introduction speed of the blood sample is 100 mul/min, the liquid inlet speed of the corresponding PBS buffer solution is 100 mul/min, the average capture rate of the negative enrichment mode is 85.2 +/-1.2 percent, and the capture rate of the positive enrichment mode is 85.0 +/-1.0 percent.

(3) In the invention, the negative enrichment mode and the positive enrichment mode have no obvious difference, and the average clearance Rr of the platform to white blood cells, red blood cells and platelets is more than 99 percent.

(4) The tumor cell line cells captured by the microfluidic chip provided by the invention are observed by using a cell counter to show that the cell form is complete and the cell membrane is not damaged, and the captured cells are cultured again, so that the survival rate is more than 90%. Effectively solves the problems of low capture rate and poor activity of captured circulating tumor cells in the prior art, and provides powerful support for subsequent experiments.

(5) The micro-fluidic chip provided by the invention can realize high-flux separation, the capture efficiency is optimal when the liquid flux is 100ul/min, and the maximum available sample injection speed is 500 ul/min.

(6) The microfluidic chip provided by the invention can be used as an independent functional unit to perform parallel expansion of a plurality of chips according to requirements.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a microfluidic chip according to the present invention;

FIG. 2 is a schematic diagram of a structure of a purification structure region of a microfluidic chip according to the present invention;

FIG. 3 is a schematic diagram of a sample injection part of the microfluidic chip according to the present invention;

FIG. 4 is an enlarged view of portion A of FIG. 2;

FIG. 5 is a schematic diagram of a micro-column structure of the microfluidic chip according to the present invention;

FIG. 6 is an enlarged view of portion B of FIG. 2;

FIG. 7 is a schematic diagram of a cell focusing structure region of a microfluidic chip according to the present invention;

FIG. 8 is an enlarged view of portion C of FIG. 7;

FIG. 9 is a schematic diagram of the structure of the horizontal flat-top wall concave-convex of the cell focusing structure region of the microfluidic chip according to the present invention;

FIGS. 10A to 10E are schematic diagrams illustrating experimental designs of a cell focusing structure region and a magnetic bead sorting structure region of a microfluidic chip according to the present invention;

FIGS. 11A to 11D are schematic structural diagrams of experimental design schemes of a cell focusing structure region of a microfluidic chip according to the present invention;

FIG. 12 is a diagram of the focusing effect of the microfluidic chip under the fluorescence microscope in the present invention;

FIG. 13 is a schematic diagram of a magnetic bead sorting structure region of a microfluidic chip according to the present invention;

FIG. 14 is a schematic diagram of a sample outlet portion of a microfluidic chip according to the present invention;

FIG. 15 is a schematic diagram of a rib structure of a cell focusing structure region of a microfluidic chip according to the present invention;

FIG. 16 is a schematic structural diagram of a microfluidic chip system for high-throughput magnetic sorting of circulating tumor cells using a microfluidic chip according to the present invention;

FIG. 17 is a diagram of tumor cell lines captured by a microfluidic chip observed using a cell counter;

fig. 18 is a schematic diagram of the sorting of circulating tumor cells using the microfluidic chip of the present invention.

Description of reference numerals:

the device comprises a sample introduction part 1, a blood sample introduction port 11, a buffer solution inlet 12, a shunt sample introduction pipe 13 and a first grid-shaped structure 131;

a microfluidic sorting region 2;

a purification structure region 21, a purification branch passage 211, a micro-column array 212, an inner side wall 213, a target cell passage 214, a micro-column row 215, a micro-column 216, a grid-shaped structure region 217 and a waste liquid outlet 218;

cell focusing structure region 22, focusing branch passage 221, horizontal top wall 222, rib 223, second grid structure 224;

a magnetic bead sorting structure region 23, a magnet 231;

a sample outlet 3, a magnetic bead cell collection port 31, a magnetic bead cell shunt 311, a non-magnetic bead cell collection port 32, and a non-magnetic bead cell collection tube 321.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The terms "inner" and "outer" as used herein are relative, with "inner" generally referring to the side closer to the central axis of the chip and "outer" being the opposite, side further from the axis.

Example 1

As shown in FIG. 1, the present invention provides a microfluidic chip for high throughput magnetic sorting of circulating tumor cells. The micro-fluidic chip comprises a sample introduction part 1, a micro-fluidic separation area 2 and a sample outlet part 3. The microfluidic separation area 2 is a closed cavity type structure, and the blood sample is filtered and separated after flowing through the cavity type structure. Therefore, the sample inlet 1 is used as a sample inlet channel for a blood sample, and the sample outlet 3 is used as a target cell outlet channel, which are respectively connected with two ends of the microfluidic separation region 2. The buffer solution is injected to assist the flow of the blood sample at the same time of the sample introduction of the blood sample, and therefore, the sample introduction part 1 includes a blood sample introduction port 11 and a buffer solution inlet 12. The outlet 3 is used for shunting different harvested cells, and therefore the outlet 3 includes a magnetic bead cell collecting port 31 and a non-magnetic bead cell collecting port 32. After being incubated by magnetic beads, the whole blood sample of the patient enters the microfluidic separation area 2 of the chip from the sample introduction part 1, and after being filtered and separated by the microfluidic separation area 2, magnetic bead cells and non-magnetic bead cells respectively flow out from the magnetic bead cell collection port 31 and the non-magnetic bead cell collection port 32 of the sample discharge part 3 for collection.

The microfluidic sorting section 2, one of the main points of the present invention, will be described in detail below.

The microfluidic separation region 2 is composed of three structural regions, namely a purification structural region 21, a cell focusing structural region 22 and a magnetic bead separation structural region 23, which are respectively arranged in the direction from the sample inlet part 1 to the sample outlet part 3, and the direction is also the fluid direction of the sample. Sample introduction part 1 is connected with purification structure district 21 head end, and cell focusing structure district 22 head end and purification structure district 21 tail end intercommunication, and the tail end and the 23 head ends of magnetic bead sorting structure district intercommunication in cell focusing

structure district

22, 23 tail ends of magnetic bead sorting structure district and 3 intercommunications of appearance portion of appearing. The whole blood sample incubated by the magnetic beads is firstly purified by the purification structural area 21, the purpose of purification is to remove small-diameter cells such as red blood cells and platelets in the whole blood sample, the purified sample enters the cell focusing structural area 22, the cells larger than the sorting critical radius are focused to the central position of the chip in the cell focusing structural area 22 according to the sorting critical radius of the passage, the cells flow into the magnetic bead sorting structural area 23 at the central position according to a linear path, the cells flowing in the magnetic bead sorting structural area 23 according to the linear position continue to flow into the non-magnetic bead cell collecting pipe 321 at the linear position, and the magnetic bead combined cells flow out from the magnetic bead cell collecting pipes at both sides under the attraction of a flow channel magnetic field.

The structure of the purification structure region 21 is further illustrated below, as shown in FIGS. 2 to 6:

the purification structure area 21 is provided with a primary filter structure for removing red blood cells and platelets in the whole blood sample, and the purification structure area 21 is composed of two purification branch passages 211 which are arranged side by side and are mutually independent; the two purification branch passages 211 are arranged in mirror symmetry with the axis of the purification structure area 21 as a symmetry axis;

as shown in fig. 2 and 4, the purification branch passage 211 has a bottom surface and a top surface, and two side walls perpendicular to the bottom surface and the top surface, the adjacent side wall of the two purification branch passages 211 is an inner side wall 213, and the other side wall opposite to the inner side wall 213 is an outer side wall, the purification branch passage 211 is internally provided with a micro-column array 212, a gap is formed between the micro-column array 212 and the inner side wall 213 of the purification branch passage 211, and the gap forms a target cell passage 214; the micro-column array 212 is formed by arranging a plurality of micro-column rows 215 in parallel, and the micro-column rows 215 are formed by arranging a plurality of micro-columns 216; the microcolumn 216 is fixedly connected to the top and bottom surfaces of the purification branch passage 211. The microcolumn row 215 is obliquely disposed, specifically, the oblique manner is that the head end of the microcolumn row 215 is far away from the axis of the purification structure region 21, and the tail end of the microcolumn row 215 is close to the axis of the purification structure region 21 and is obliquely disposed according to a set angle, and the oblique angle is an angle between the microcolumn row 215 and the axis of the purification structure region 21, and can also be understood as an included angle between the microcolumn row 215 and the target cell channel 214.

As shown in FIG. 5, the radial cross-section of the microcolumn 216 is oval, the diameter B of the oval is 28 to 33 μm, and the symmetric diameter A of the oval is 20 to 25 μm; the egg-heart distance C between two adjacent microcolumns 216 in the same microcolumn row 215 is preferably 40-45 μm, and the minimum egg-heart distance D between two adjacent microcolumn rows 215 is 60-65 μm. The above numerical ranges are possible and preferred, and in the embodiment of the present invention, the specific data used are: the diameter B of the oval is recommended to be in the range of 31 μm, and the symmetrical diameter A of the oval is recommended to be 23 μm; the distance C between two adjacent microcolumns 216 in the same microcolumn row 215 is 41 μm, and the minimum distance D between two adjacent microcolumn rows 215 is 62 μm.

The inclination angle of the microcolumn row 215 is set to 1.5 to 2.5 °. In the embodiment of the present invention, the inclination setting angle E of the microcolumn row 215 is 1.7 °. In the embodiment of the present invention, the width of the purification branch passage 211 is preferably 1mm, and the length of the micro-column array 212 is 3cm and the height is 20 μm. Depending on the actual requirements, adjustments within the parameters described in the present invention are also possible.

The structure and size of the micro pillars 216, the distance between the micro pillars 216, and the distance between the micro pillar rows 215 determine the critical deflection radius of the micro pillar array 212 to be 4 to 5 μm. I.e., cells larger than 5 μm will be deflected along the array towards the target cell pathway 214, and cells smaller than 5 μm will flow in the original direction without changing the flow direction.

The blood sample inlet 11 and the buffer liquid inlet 12 are connected to the head ends of the two purification branch passages 211 at the same time, specifically, the blood sample inlet 11 is connected to a shunt sample inlet tube 13, the shunt sample inlet tube 13 is of a branch structure, and the two outer sides of the head end of the purification structure area 21 are connected to the two ends of the branch structure, so as to shunt the blood sample to the micro-column arrays 212 on the two sides of the purification structure area 21. The buffer solution inlet 12 is connected with the center of the purification structure area 21, the buffer solution can flow into the two purification branch passages 211 through the inlet, and the head ends of the purification branch passages 211 are also provided with a grid structure area 217. The purpose of the grid-like structure 217 is to ensure that the fluid enters the chip in a certain direction and to prevent foreign matter from entering the chip, so that the grid-like structure is formed by a plurality of fences, which are arranged parallel to the axis of the purification structure 21, thereby allowing the fluid to flow into the purification structure 21 in a direction parallel to the axis.

As shown in fig. 6, the tail ends of the micro-column arrays 212 of the two purification branch passages 211 are connected to a waste liquid outlet 218, and a grid-shaped structure area 217 is further provided between the micro-column array 212 and the waste liquid outlet 218; the tail end of the target cell pathway 214 communicates with the cell focusing structure region 22.

As shown in fig. 3, a first grid structure 131 is disposed in the flow splitting sample inlet tube 13, the design purpose of the first grid structure 131 is the same as that of the grid structure area 217, and the first grid structure 131 is disposed in the flow splitting sample inlet tube 13, mainly ensuring that the inflow direction of the fluid cells flows in a set direction during the inflow of the sample, and preventing foreign matters from entering the chip.

The structure of the cell focusing structure region 22 is further described below, as shown in FIGS. 7 to 9:

in the present invention, three structural regions are closely related. The second structure region, the cell focusing structure region 22, mainly depends on the principle that the path of the spheroids passing through the flow channel with a specific shape is deviated and finally stabilized at a certain position, and aims to focus the disordered white blood cells and CTC cells passing through the flow channel of the front structure region at the center of the flow channel of the chip and stably flow into the next structure region along a straight line, so as to achieve the focusing effect. This part of structural design and third structural region-magnetic bead sorting structure district 23 design should, specifically should be: the central region of the cell focusing structure region 22 corresponds to the non-magnetic bead cell collecting port 32, the two side regions of the central region correspond to the magnetic bead cell collecting port 31, and the central region is a 1/2 region extending from the two sides of the symmetry axis to the total width. If the second structure is cancelled, cells sorted by the first structure area, namely the purification structure area 21, enter the third structure area disorderly and flow out from the final cell collecting port, and each collecting port obtains mixed cells, so that the magnetic sorting cannot be completed. Secondly, the focusing effect of the structure directly influences the length and the width of the third structure area. The better the focusing effect, the more obvious the separation effect of the non-magnetic bead attached cells and the magnetic bead attached cells is, the shorter the length of the flow channel required by the third structure area is, and the narrower the width of the flow channel required is. And thirdly, in a negative enrichment mode, the structure also has the function of secondarily removing trace red blood cells and blood platelets remained in the purification structure area 21, and the small diameter of the structure area cannot be focused by the structure area, so that the small diameter of the structure area finally flows out of the magnetic bead cell collection port 31, and the purity of CTC flowing out of the non-magnetic bead cell collection port 32 cannot be influenced.

The cell focusing structure region 22 is composed of two mutually independent focusing branch passages 221 arranged side by side; the two focusing branch channels 221 are arranged in mirror symmetry with respect to each other with the axis of the cell focusing structure region 22 as a symmetry axis. As shown in fig. 9, the outer wall of the top surface of the focusing branch channel 221 is a horizontal top wall 222, the inner wall of the top surface is provided with a plurality of convex ribs 223 towards the bottom surface, the ribs are rectangular sheet-shaped ribs, the ribs are arranged in parallel, an acute angle α is formed between the ribs and the symmetry axis of the cell focusing structure region 22, and the acute angle α faces the magnetic bead sorting structure region 23. The angle alpha is preferably 60 deg. -70 deg., and in an embodiment of the invention the acute angle alpha is 70 deg.. The parameters of the above structure directly influence the cell focusing effect. As shown in fig. 15, in the embodiment of the present invention, the parameters of the ribs are: hg is more than d and less than or equal to 2d, Ht is more than Hg, Dob is more than 2d and more than or equal to Lob; d is the diameter of the focused cell, Hg is the vertical distance between the ribs and the bottom surface, Ht is the height of the ribs, Dob is the horizontal distance between the ribs, and Lob is the horizontal width of the ribs. Here, the horizontal distance is a horizontal line distance.

In the examples of the present invention, d is 10 μm, Hg is 20 μm, Ht is 25 μm, Lob is 20 μm, and Dob is 50 μm. As shown in FIG. 8, the width of the focusing branch channel 221 should be equal to or greater than 400 μm theoretically, i.e., the whole width of the cell focusing structure region 22 is equal to or greater than 800 μm, and in the embodiment of the present invention, the width of the focusing branch channel 221 is 600 μm and W is 1200. The longer the length, the better theoretically. To reduce the volume, embodiments of the present invention preferably use a length of 1.5 cm.

The structure and parameters of the focusing branch channel 221 can be focused and divided according to the size of the cell, the critical diameter of the cell of the focusing branch channel 221 is 10 μm, the cell larger than 10 μm will be focused on the inner side of the focusing branch channel 221, the inner side is the adjacent side of the two focusing branch channels 221, other cells, namely the cell smaller than 10 μm, still run according to the original path, and finally the target cell is stabilized at a fixed position according to the difference of the cell diameter and flows out of the structure region. The bottom surface of the focusing branch passage 221 is a flat wall, and both side walls are perpendicular to the bottom surface.

The two focusing branch channels 221 are symmetrically arranged, so that the cells can be focused and shunted, and simultaneously, the high-flux flowing of the sample can be satisfied. In the early development, the second structural region was designed as a cell focusing region in order to align or collect large-diameter cells as much as possible in a line or in one region according to the cell diameter of the cells passing through the purification structural region 21.

As shown in fig. 10A to 10E, the flow cytometer is designed to simulate a flow cytometer, and a narrow channel is provided to allow cells to pass through a narrow channel and then to be ejected, so that the cells form a regular flow stream. The initial scheme is set to be 15 mu m and the height is 30 mu m, but experiments show that the structure can play a good role at low flow, but with the continuous increase of the sample injection speed, when the sample injection speed is about 80 mu L/min, the pressure born by the narrow pipeline is obviously higher than other parts, so that the chip structure bursts, and the requirement of high flux of the sorted CTC can not be met. After the structural scheme provided by the invention is adopted, the fastest flow rate can reach 1ml/min without bursting only for the structure, and the sample injection speed is about 12.5 times faster than that of the prior design.

As shown in fig. 11A to 11D, the inventor further designs the focusing structure, in which the outer wall of the top surface is a horizontal top wall, the inner wall of the top surface is provided with a plurality of protruding ribs towards the bottom surface, the ribs are rectangular sheet-shaped ribs, and the ribs are arranged in parallel. The suspended cells move under the influence of the pressure field induced by the microstructure, and a transverse pressure gradient perpendicular to the flow direction of the fluid is generated by utilizing inclined barriers in the micro-channel, so that the particles can be deflected and arranged along the transverse flow caused by the gradient. Fig. 11A shows the ribs arranged obliquely, and they are inclined to form an acute angle toward the magnetic bead sorting structure region 23. Fig. 11B and 11C show a fishbone structure, in which two top walls with ribs are symmetrically connected and form an included angle. The angle of fig. 11B is towards the bead sorting structure region 23. The angle of FIG. 11C is toward the primary filter passage. Fig. 11D is the final protection structure provided by the present invention. The assessment requirements on each structure are as follows: when the cells flow through the structure, the cells are gathered towards the center of the chip and finally stably flow out of the structure at a fixed position of the chip according to the diameter of the cells, so that the cell focusing effect is realized, the focusing effect is irrelevant to the flow rate of a sample, the high-throughput requirement of equipment can be realized, and the secondary removal of red blood cells and platelets can be indirectly realized.

Fig. 11A is the most basic structure for satisfying the function, but in order to increase the flux and improve the efficiency, the structure needs to be expanded into a mirror image dual channel, so that two schemes of fig. 11B and 11C are designed. However, experiments show that when the two structures are used for sample injection, the liquid flow mode in the center of the chip is different from that of the single structure, and cells tend to gather towards two sides of the chip, so that the purpose of gathering the cells in the center of the chip cannot be achieved. Therefore, the inventor divides the fluid entering the chip into two separate parts without mutual interference on each other on the basis of fig. 11B, as shown in fig. 12, 15um red microspheres and 5um green microspheres are used for sample injection under a fluorescence microscope, a track picture is shown in fig. 12, visible red microspheres (shown as R in the figure) are focused at the central position of the passage and stably flow out of the structural region, and green microspheres (shown as G in the figure) flow out according to the original path. The excellent focusing effect also plays a role in secondarily removing trace red blood cells and platelets remained in the purification structure area 21 in the negative enrichment mode, and the CTC which flows out of the non-magnetic bead cell collection port 32 cannot be influenced in purity because the diameter of the CTC is small and the CTC cannot be focused by the structure area and finally flows out of the magnetic bead cell collection port 31.

The first end of the cell focusing structure region 22 is provided with a second grid-shaped structure 224, the second grid-shaped structure 224 is a grid column, the radial cross section of the grid column is rectangular or racetrack-shaped, in the embodiment of the present invention, the racetrack-shaped structure is racetrack-shaped, that is, two ends of the long axis of the rectangle are arc ends, the long axis is arranged in parallel with the long axis of the cell focusing structure region 22, and the purpose of the structure is to ensure that the inflow direction of the fluid cells flows along the set direction of the grid column during the inflow process of the sample.

The structure of the magnetic bead sorting structure region 23 of the present invention is further described below, as shown in FIG. 13:

the third structural region, the magnetic bead sorting structural region 23, should satisfy two main requirements: the first is to slow down the flow rate of the cells as much as possible and provide enough time for the cells to deflect, so that the flow channel width in the area needs to be widened as much as possible; secondly, the cells enter different sample outlets respectively to achieve the purpose of sorting, and the area is designed to ensure that the cells flowing out of the second stage continue to move along the original path along a straight line, so that the original flow channel cannot be changed.

The third structural region, the magnetic bead sorting structural region 23, is intended to apply a magnetic force to the focused cells flowing out of the front region, and to change the flow direction of the cells attached by the magnetic beads, thereby completing the separation of target cells. This partial flow channel structure requires that the passing cells cannot change the flow path due to the flow channel, i.e. maintain a linear motion, and slow the cell flow speed as much as possible to obtain a sufficient deflection time without applying a magnetic field. The specific structure is shown in fig. 10A to fig. 10E, the inventor designs a plurality of flow channel structures to verify the effect of each flow channel, and the difficulty is that the flow channel width is increased, the direction of the flow beam in the flow channel is changed, and how to select a design scheme for changing from a narrow flow channel to a wider flow channel becomes difficult. For this reason, the inventors tried various design schemes, that is, fig. 10A, 10C and 10E are single-side widening type channels, and the difference is that fig. 10A is slow widening and fig. 10C and 10E are rapid widening, and experiments show that cells entering the channel through the two ways change the deviation of the channel to the widening side, and are disorderly arranged in the vertical direction of the channel, which cannot meet the requirement, and the design scheme fails. Fig. 10B and 10D show a double-sided widening flow channel, in which fig. 10B shows a slow widening and fig. 10D shows a rapid increase. However, the experimental inventor finds that the design method can only ensure that the cells flowing in from the middle of the original flow channel move forward along a straight line in a decelerating manner, but the cells at the edges still change the flow direction to two sides respectively to finally form three flow beams, so the experimental method cannot meet the design requirement.

On the basis of observing the above experimental data, the inventors found that: the magnitude of the channel width variation can severely affect the cell flow path. Therefore, the inventor adopts a horn-shaped flow channel design, the flow channel is gradually widened, the width of the outlet is approximately 3 times of that of the inlet, and experiments show that the design can ensure that the cells flow into the flow channel and move approximately along a straight line and has an obvious speed reduction effect. This scheme is the best scheme.

In a specific embodiment, as shown in fig. 13, the magnetic bead sorting structure region 23 is a conical structure, and the top view is similar to a trumpet shape, and the width gradually increases from the head end to the tail end. The length of the magnetic bead sorting structure region 23 is theoretically as large as possible, but in order to reduce the volume as much as possible without affecting the effect, the embodiment of the present invention is designed to be 4 cm. The width of the tail end of the magnetic bead separation area is 3 times of that of the head end.

In the embodiment of the present invention, magnets 231 capable of attracting magnetic beads are symmetrically disposed on both sides of the magnetic bead sorting structure region 23. In the preferred embodiment of the present invention, the magnet 231 is made of neodymium magnet, which has the advantages of strong magnetic force, low cost, mature processing technology and easy availability. The magnet 231 is located outside the magnetic bead sorting structure region 23, and both the magnets 231 have N-poles close to the magnetic bead sorting structure region 23 and S-poles far from the magnetic bead sorting structure region 23. The magnet 231 is a hollow rectangular magnet frame.

The advantages of the above scheme are: (1) the cells were kept in linear motion without the application of a magnetic field. (2) The flow channel has a sufficient length to allow the cells to be magnetically attracted to a sufficient distance to migrate from the center of the chip to the outside of the chip.

The sample outlet 3 of the present invention is explained below, as shown in fig. 14:

the sample outlet 3 includes a magnetic bead cell collecting port 31 and a non-magnetic bead cell collecting port 32, and the magnetic bead cell collecting port 31 is communicated with two outer sides of the magnetic bead sorting structure region 23 through a magnetic bead cell shunt tube 311. Magnetic bead cell shunt tubes 311 is U type structure, and magnetic bead sorting structure district 23 is connected to both ends, and this structure can be collected by flowing out from magnetic bead cell collection mouth 31 behind the shunting of magnetic bead cell shunt tubes 311 with the magnetic bead combination cell that magnet 231 attracts. The non-magnetic bead cell collecting port 32 is centrally communicated with the magnetic bead sorting structure area 23 through a non-magnetic bead cell collecting pipe 321, and is used for collecting cells which are not combined with magnetic beads.

As shown in fig. 16, the microfluidic chip provided by the present invention can also be used as an independent functional unit for different sorting requirements, and multiple functional units are connected in parallel, so as to increase the sorting speed and the sorting throughput. In order to reduce the volume and realize high flux, the blood sample inlet and the buffer solution sample inlet can be designed into two channels which are stacked up and down in a parallel structure; the waste liquid outlet and the outlet channel of the purification structure region 21 may be designed as a dual channel structure stacked up and down, and the non-magnetic bead labeled cell outlet and the magnetic bead labeled cell outlet may be designed as a dual channel structure stacked up and down.

The structure of the microfluidic chip provided by the invention is described above. The microfluidic chip provided by the invention can realize high-throughput tumor cell sorting. The following methods are recommended by the inventors, and other methods suitable for the microfluidic chip provided by the present invention may be used. As shown in FIG. 18, s1, s2 and s3 represent the three steps of the method of the present invention, respectively. RBC are red blood cells, PLT are platelets, WBC are white blood cells, CTC are circulating tumor cells. In the figure, a is a buffer solution, b is a whole blood sample incubated with magnetic beads, c is a waste solution containing red blood cells and platelets, d is collected magnetic cells, and e is collected non-magnetic cells.

The sorting method mainly comprises the following steps:

(s 1) incubating the whole blood sample in admixture with magnetic beads for sorting, the magnetic beads being bound to the target cells; the whole blood sample incubated with the magnetic beads enters the chip through the blood sample inlet 11, is shunted into the micro-column array 212 of the two purification branch passages 211 through the shunt sample inlet tube 13, and simultaneously the buffer solution enters the purification branch passages 211 through the buffer solution inlet 12; when the sample flows through the micro-column array 212, the cells with the radius larger than the sorting critical radius collide with the micro-columns and laterally move to the side of the target cell passage 214 to be converged and flow into the cell focusing structure region 22; cells smaller than the sorting critical radius do not laterally displace after colliding with the microcolumns 216, and flow out of the chip through the waste liquid outlet 218 after flowing through the microcolumn array 212 according to the original path;

(s 2) the sample after passing through the purification structure region 21 continues to flow into the two focusing branch channels 221 of the cell focusing structure region 22, and the fluid pressure generated by the sample flowing through the ridge structure of the horizontal top wall 222 drives the cells with the radius larger than the sorting critical radius to focus on the center of the chip and keep flowing into the magnetic bead sorting structure region 23 linearly; cells smaller than the sorting critical radius remain routed into the magnetic bead sorting structure region 23;

(s 3) the sample passing through the cell focusing structure region 22 continuously flows into the magnetic bead sorting structure region 23, the magnetic bead binding cells are attracted by the channel magnetic field constructed by the magnets 231 at the two sides of the magnetic bead sorting structure region 23 and are shunted to the magnetic bead cell collecting port 31 by the magnetic bead cell shunting pipe 311 for collection, the non-magnetic bead binding cells still flow into the non-magnetic bead cell collecting pipe 321 in a linear shape and flow out from the non-magnetic bead cell collecting port 32 for collection, and therefore sorting of the circulating tumor cells is completed.

The target cells are circulating tumor blood cells or leukocytes.

The micro-fluidic chip provided by the invention can be suitable for various CTC sorting modes, namely the CTC capturing mode can be changed by only adjusting the types of the magnetic beads, and the structure of the chip is not required to be changed. For example, using magnetic beads coated with CTC-specific antibodies, the microfluidic chip specifically captures CTCs for a positive enrichment process, and CTCs are obtained from the magnetic bead cell collection port 31; if the magnetic beads coated with the leukocyte-specific antibodies are used, the microfluidic chip captures CTC for a negative enrichment method, and the CTC is obtained from a non-magnetic bead magnetic storm collecting port.

In order to realize the magnetic sorting of the third structural region, namely the magnetic bead sorting structural region 23, it is also important to select a suitable magnetic bead, and various brands in the market can select the magnetic beads with different diameters, so that too small magnetic beads cannot provide enough force to deflect cells in a magnetic field, and too large magnetic beads can be stressed too strongly to break the attached cells or block the flow channel. The inventor tests magnetic beads with the diameters of 1 mu m, 2 mu m, 5 mu m and 10 mu m, and the final experimental result shows that the magnetic beads with the diameters of more than or equal to 5 mu m and less than or equal to 10 mu m can better achieve the experimental aim.

The specific experimental data of the invention are as follows:

1. the experimental method comprises the following steps:

the performance verification of the microfluidic chip comprises the capture efficiency, the optimal sample injection speed experiment and the background cell clearance experiment. And finally, observing the cell morphology by using a cell counter, culturing the captured cells again and calculating the survival rate, wherein the cell membrane is not damaged.

In the research, a liver cancer cell line HepG2 is selected and added into peripheral blood of a healthy human body to simulate CTC, and the cells are transfected by lentiviruses to express Green Fluorescent Protein (GFP) for the convenience of counting. The peripheral blood of the human body in need is from healthy volunteers. All volunteers signed written informed consent and were approved by the ethics committee to comply with the declaration of helsinki.

(1) Capture efficiency and optimum sample introduction speed experiment:

whole blood was diluted 10-fold with PBS to prevent channel blockage. Then, tumor cell line cells are mixed into the diluted blood sample, the concentration is adjusted to be 1 × 102/ml, and 5um diameter magnetic beads are added for incubation as the instruction (CD 45 magnetic beads and CD16 magnetic beads can be selected for a negative enrichment mode, and EpCAM magnetic beads can be selected for a positive enrichment mode), the sample and buffer are respectively injected into the sample and buffer inlets at different flow rates, the tumor cell line cells at the sample outlet are counted by using a fluorescence microscope to select an optimal flow rate, and then the inventor calculates the optimal recovery efficiency R by using an equation (in the negative enrichment mode, R ═ C1V 1/(C1V 1 + C2V2+ C3V 3), R ═ C2V 2/(C1V 1 + C2V2+ C3V 3) where C1 and V1 denote the concentration of the non-labeled cell sample channel and the volume of the solution, C2 and V2 denote the concentration of the labeled cell sample channel of the magnetic beads and the volume of the solution, c3 and V3 indicate the concentration of the waste liquid flowing out of the channel and the volume of the solution. This was repeated several times.

(2) Background cell clearance:

to test the performance of the platform in removing blood cells (mainly red blood cells, platelets, white blood cells), the inventors added tumor cell line cells to 10 fold diluted whole blood, adjusted its concentration to 1 × 102 cells/ml, and processed at the optimal flow rate. After the device was stably operated, the inventors calculated each background cell clearance Rr separately using the formula (in a negative enrichment mode: Rr ═ C4V4-C1V 1)/C4V 4; in a positive enrichment mode: Rr ═ C4V4-C2V 2)/C4V 4, where C1 and V1 represent the cell concentration and the solution volume of the non-magnetic bead labeled cell exit channel, respectively, C2 and V2 represent the concentration and the solution volume of the magnetic bead labeled cell exit channel, and C4 and V4 represent the concentration and the solution volume of the starting sample). This was repeated several times.

2. The statistical method comprises the following steps:

in this study, all statistical analyses were performed using SPSS (version 22.0; IBM Corp., Armonk, NY, USA), with the capture rate at different sample rates using analysis of variance, with different feed rates as the X-axis, and the average capture rate as the Y-axis, and using GraphPad Prism 6.0 (GraphPad Software, La Jolla, Calif., USA) to plot the statistical plots; under the condition of the optimal liquid inlet speed, different concentration capture efficiency groups are doped, and complete random analysis of variance is used up in comparison; simple linear regression analysis was performed on the number of cells initially incorporated into different tumor cell lines and the average number of captured cells on the platform, and a simple linear equation was plotted using a graph of GraphPad Prism 6.0 (GraphPad Software, La Jolla, Calif., USA) with the number of cells initially incorporated into the tumor cell line on the X axis and the average number of captured cells on the Y axis. Background cell clearance experiments, clearance of leukocytes, platelets, and erythrocytes were described using mean ± standard deviation. P <0.05 was considered statistically significant.

3. As a result:

(1) capture efficiency and optimum sample introduction speed experiment:

according to multiple researches, the CTC enrichment and recovery efficiency is influenced by the sample injection speed when the microfluidic chip is used for sorting cells, so that the optimal sample injection speed is found, and the highest recovery rate is calculated to be the most important parameter of the platform.

The inventor firstly specifies the sample injection speed of different blood samples, which is 20 mul/min, 60 mul/min, 100 mul/min, 200 mul/min, 300 mul/min,/500 mul/min, 800 mul/min and 1200 mul/min from slow to fast, and the sample injection speed of the corresponding buffer solution measured by the inventor in the experiment is the same as that of the sample solution according to the principle that the plane of the blood sample solution and the plane of the buffer solution are positioned at the center of the chip.

In experiments, the inventors found that: with the increase of the sample injection speed, the capture rate of the platform to HepG2-GFP cells is gradually reduced, in order to balance the relationship between the capture rate of the HepG2-GFP cells and the time required by the experiment, the optimal sample injection speed of a blood sample is finally selected to be 100 mu l/min, the liquid inlet speed of the corresponding PBS buffer solution is 100 mu l/min, the average capture rate of the negative enrichment mode is 85.2 +/-1.2 percent at the moment, and the capture rate of the positive enrichment mode is 85.0 +/-1.0 percent, so that the optimal capture efficiency of the platform is obtained.

(2) Background cell clearance:

according to the method, a blood sample of a healthy volunteer is diluted and then mixed with 1 × 102 HepG-2 as a test sample, the optimal sample introduction speed of the blood sample is 100 μ l/min, the corresponding liquid inlet speed of PBS buffer solution is 100 μ l/min, the volumes of a sample inlet and a final sample collection outlet and the blood cell concentration in the sample inlet and the final sample collection outlet are calculated under the normal working state that the platform is filled with the blood sample, the detection platform has a blood cell removal effect, the negative enrichment mode and the positive enrichment mode have no significant difference through calculation, and the average clearance rate Rr of the platform to white blood cells, red blood cells and platelets is greater than 99%.

(3) Cell viability rate: as shown in fig. 17, the tumor cell line cells captured by the microfluidic chip have complete cell morphology and no damage to cell membranes when observed by using a cell counter, and the captured cells are cultured again, so that the survival rate is more than 90%.

Claims

1. A micro-fluidic chip for high-flux magnetic separation of circulating tumor cells comprises a sample introduction part (1), a micro-fluidic separation area (2) and a sample outlet part (3), wherein the micro-fluidic separation area (2) is of a closed cavity type structure, and the sample introduction part (1) and the sample outlet part (3) are respectively connected with two ends of the micro-fluidic separation area (2); the sample introduction part (1) comprises a blood sample introduction port (11) and a buffer liquid inlet (12); the sample outlet part (3) comprises a magnetic bead cell collecting port (31) and a non-magnetic bead cell collecting port (32); the method is characterized in that:

the microfluidic sorting region (2) comprises three structural regions, namely a purification structural region (21), a cell focusing structural region (22) and a magnetic bead sorting structural region (23); the sample introduction part (1) is connected with the head end of the purification structure area (21), the head end of the cell focusing structure area (22) is communicated with the tail end of the purification structure area (21), the tail end of the cell focusing structure area (22) is communicated with the head end of the magnetic bead sorting structure area (23), and the tail end of the magnetic bead sorting structure area (23) is communicated with the sample discharge part (3);

the purification structure area (21) is provided with a primary filter structure for removing red blood cells and platelets in the whole blood sample, and the purification structure area (21) is also provided with a waste liquid outlet (218);

the cell focusing structure area (22) is composed of two mutually independent focusing branch passages (221) which are arranged side by side; the two focusing branch passages (221) are arranged in mirror symmetry with the axis of the cell focusing structural region (22) as a symmetry axis, the outer wall of the top surface of each focusing branch passage (221) is a horizontal top wall (222), the inner wall of the top surface is provided with a plurality of linear convex edges (223), and each convex edge (223) is arranged in parallel and is obliquely arranged at a set angle with the symmetry axis;

and magnets (231) capable of attracting magnetic beads are symmetrically arranged on two sides of the magnetic bead sorting structural region (23).

2. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 1, wherein:

each rib (223) and the symmetry axis are obliquely arranged to form an acute angle, wherein the acute angle faces to the magnetic bead sorting structure area (23).

3. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 2, wherein:

the acute angle is 60-70 degrees.

4. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 3, wherein:

the condition parameters of the convex rib (223) are as follows: hg is more than d and less than or equal to 2d, Ht is more than Hg, Dob is more than 2d and more than or equal to Lob; d is the diameter of the focused cell, Hg is the vertical distance between the ribs (223) and the bottom surface, Ht is the height of the ribs (223), Dob is the horizontal distance between the ribs (223), and Lob is the horizontal width of the ribs (223).

5. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 4, wherein:

the width of the focusing branch path (221) is greater than or equal to 400 μm; the length is more than or equal to 1.5 cm.

6. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 5, wherein:

the central area of the cell focusing structure area (22) corresponds to the non-magnetic bead cell collecting port (32), the two side areas of the central area correspond to the magnetic bead cell collecting port (31), and the central area is 1/2 area which extends to the total width from the two sides of the symmetrical shaft.

7. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 1, wherein:

the bottom surface of the focusing branch passage (221) is a flat wall; two side walls of the focusing branch passage (221) are perpendicular to the flat wall of the bottom surface.

8. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 1, wherein:

the head end of the focusing branch passage (221) is provided with a second grid-shaped structure (224).

9. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 1, wherein:

the purification structure area (21) is composed of two purification branch passages (211) which are arranged side by side and are mutually independent; the two purification branch passages (211) are arranged in mirror symmetry with the axis of the purification structure region (21) as a symmetry axis;

a micro-column array (212) is arranged in the purification branch passage (211), a gap is formed between the micro-column array (212) and the inner side wall (213) of the purification branch passage (211), and the gap forms a target cell passage (214); the micro-column array (212) is formed by arranging a plurality of micro-column rows (215) in parallel, and the micro-column rows (215) are formed by arranging a plurality of micro-columns (216); the head end of the micro-column row (215) is far away from the axis of the purification structure area (21), and the tail end of the micro-column row is close to the axis of the purification structure area (21) and is obliquely arranged according to a set angle; the radial section of the microcolumn (216) is oval, the diameter of the oval is 28-33 mu m, and the symmetrical diameter of the oval is 20-25 mu m; in the same micro-column row (215), the distance between the centers of eggs of two adjacent micro-columns (216) is 40-45 μm, and the minimum distance between the centers of eggs of two adjacent micro-column rows (215) is 60-65 μm.

10. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 9, wherein:

the inclination set angle of the micro-column row (215) is 1.5-2.5 degrees.

11. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 9, wherein:

the width of the purification branch passage (211) is 1-2 mm, the length of the micro-column array (212) is 3-4 cm, and the height is 20-30 μm.

12. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 9, wherein:

the blood sample injection port (11) and the buffer solution inlet (12) are simultaneously connected with the head ends of the two purification branch passages (211); and a grid-shaped structure area (217) is also arranged in the head end of the purification branch passage (211).

13. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 12, wherein:

the tail ends of the micro-column arrays (212) of the two purification branch passages (211) are connected with a waste liquid outlet (218), and a grid-shaped structure area (217) is arranged between the micro-column arrays (212) and the waste liquid outlet (218); the tail end of the target cell channel (214) is communicated with the cell focusing structure area (22).

14. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 9, wherein:

the blood sample injection port (11) is communicated with the head end of the micro-column array (212) of the purification structure area (21) through a shunt sample inlet pipe (13) and is used for shunting a blood sample to the micro-column array (212) on two sides of the purification structure area (21) through the shunt sample inlet pipe (13).

15. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 14, wherein:

a first grid-shaped structure (131) is arranged in the shunt sample inlet pipe (13).

16. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 1, wherein:

the magnetic bead sorting structure area (23) is a conical structure, and the width of the conical structure gradually increases from the head end to the tail end.

17. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 16, wherein:

the length of the magnetic bead sorting structure area (23) is more than or equal to 4 cm; the width of the tail end of the magnetic bead separation area is 3 times of that of the head end of the magnetic bead separation area.

18. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 17, wherein:

the N pole of the magnet (231) on two sides of the magnetic bead sorting structural area (23) is close to the magnetic bead sorting structural area (23), and the S pole is far away from the magnetic bead sorting structural area (23).

19. The microfluidic chip for high throughput magnetic sorting of circulating tumor cells of claim 18, wherein:

the non-magnetic bead cell collecting port (32) of the sample outlet part (3) is communicated with the center of the magnetic bead sorting structure area (23) through a non-magnetic bead cell collecting pipe (321); the magnetic bead cell collecting port (31) is communicated with the two sides of the magnetic bead sorting structural region (23) through a magnetic bead cell shunt tube (311).

20. A microfluidic chip system for high throughput magnetic sorting of circulating tumor cells, characterized in that the microfluidic chip system of any one of claims 1 to 19 is formed by connecting the microfluidic chips in parallel.

21. The microfluidic chip system for high throughput magnetic sorting of circulating tumor cells of claim 20, wherein:

the blood sample inlet and the buffer solution sample inlet are of a two-channel structure which is stacked up and down; the waste liquid outlet and the outlet channel of the purification structure area (21) are of a two-channel structure which is stacked up and down, and the non-magnetic bead labeled cell outlet and the magnetic bead labeled cell outlet are of a two-channel structure which is stacked up and down.