Combined filter and device for separating plasma from whole blood, method for separating plasma from whole blood

Abstract

The application discloses a combined filter for separating plasma from whole blood, comprising a whole blood sample adding chamber, a first combined filter membrane, an intermediate chamber, a second combined filter membrane and a plasma collecting chamber arranged in sequence along a filtering direction of a whole blood sample flow; and the whole blood sample is filtered multiple times through the first combined filter membrane and the second combined filter membrane to obtain a plasma sample. The application further provides a combined filter device and a method for separating plasma from whole blood. The combined filter provided by the application can further improve the recovery rate, recovery quality and recovery efficiency of the whole blood separation plasma, and meets the demand of in-vitro diagnosis on the pretreatment of the whole blood sample.

Description

Technical Field

[0001] This invention belongs to the field of medical testing technology, and in particular relates to a combined filter and device for separating plasma from whole blood, and a method for separating plasma from whole blood. Background Technology

[0002] In in vitro diagnostics (IVD) using blood samples to obtain clinical diagnostic information, plasma / serum is typically separated from whole blood samples through pretreatment before testing. Direct use of whole blood samples for testing can interfere with the analysis process due to the presence of blood cells, affecting the accuracy of the results. Currently, the most mature whole blood separation method uses centrifugation to separate plasma / serum, with a relative centrifugal force (RCF) of 1000–1200 g and a centrifugation time of 5–10 minutes. The problems with centrifugation are: 1. It requires specialized centrifugation equipment and professional operators; 2. The centrifugation equipment is large and complex to operate, making it difficult to integrate with small and medium-sized testing equipment and achieve automation; 3. During the transfer of the upper plasma / serum obtained after centrifugation, a portion of plasma / serum must be retained to avoid remixing with blood cells; 4. The centrifugation time is relatively long, making it difficult to meet the growing clinical demand for rapid testing. For example, for molecular markers with short half-lives, rapid plasma separation for testing can accurately determine the content of the analyte. Similarly, in the treatment of myocardial infarction patients, rapid plasma separation for testing can gain valuable time.

[0003] The filtration separation method uses filter membranes, microcolumns, microspheres, etc. to capture or retain blood cells and separate plasma / serum. It has advantages such as high separation efficiency, small equipment size, high degree of automation integration, and simple operation, and is particularly suitable for point-of-care testing (POCT) applications.

[0004] Patent document CN109925884A discloses a method for whole blood filtration and a filter membrane structure for whole blood filtration. This filter membrane structure consists of two filter membranes stacked sequentially from top to bottom; the filter membranes have a porous structure; the pore size of the stacked filter membranes gradually decreases from top to bottom, while the area gradually increases from top to bottom. This filter membrane structure is prone to clogging due to residual whole blood samples, resulting in a low plasma recovery rate and failing to meet the blood volume requirements for multi-item testing.

[0005] Patent document CN110857904A discloses a method for obtaining plasma from whole blood samples, a blood filter, and a microfluidic chip. The blood filter includes a coarse filtration module and a purification module. The coarse filtration module includes a first filter cup and a filter element, preferably a cellulose acetate column. The purification module includes a second filter cup, a ring-shaped pressure plate, and a filter membrane, preferably a Pall Vivid GR plasma separation membrane. This method has a relatively slow filtration speed, and excessive filter membrane layers or overload clogging can lead to difficulty in plasma filtration and low plasma recovery efficiency. Summary of the Invention

[0006] The main objective of this invention is to provide a combined filter and apparatus for whole blood plasma separation, and a method for whole blood plasma separation, thereby further improving the recovery rate, recovery quality, and recovery efficiency of whole blood plasma, and meeting the requirements of in vitro diagnostics for whole blood sample pretreatment.

[0007] To achieve the first objective of the present invention, a combined filter for separating plasma from whole blood is provided, comprising a whole blood sample loading chamber, a first combined filter membrane, an intermediate chamber, a second combined filter membrane, and a plasma collection chamber arranged sequentially along the flow filtration direction of the whole blood sample;

[0008] The whole blood sampling chamber is equipped with a sampling port for adding whole blood samples;

[0009] The first combined filter membrane includes a first support member, and a first coarse filter membrane and a first fine filter membrane stacked sequentially on the first support member for filtering whole blood samples to obtain intermediate filtrate. The first coarse filter membrane is a filter membrane that can capture blood cells and divide the filtrate into longitudinal and lateral flows. The filtration area of ​​the first coarse filter membrane is larger than that of the first fine filter membrane. The surface of the first support member is provided with a perforated structure to facilitate the passage of intermediate filtrate into the intermediate chamber.

[0010] The intermediate chamber is used to temporarily store the intermediate filtrate obtained by filtration through the first combined filter membrane.

[0011] The second combined filter membrane includes a second support member, and a second coarse filter membrane and a second fine filter membrane stacked sequentially on the second support member for filtering intermediate filtrate to obtain plasma samples. The second coarse filter membrane is capable of capturing blood cells and separating the filtrate into longitudinal and lateral flows. The filtration area of ​​the second coarse filter membrane is equal to the filtration area of ​​the second fine filter membrane. The surface of the second support member is provided with a perforated structure to facilitate the passage of plasma samples into the plasma collection chamber.

[0012] The plasma collection chamber is equipped with a sample outlet for exporting plasma samples.

[0013] The combined filter provided by this invention filters out some blood cells by configuring the filtration area of ​​the first coarse filter membrane to be larger than that of the first fine filter membrane. This effectively prevents trapped blood cells from depositing on the surface of the first fine filter membrane, reduces the flow resistance of plasma through the first fine filter membrane, and increases the permeation flux of plasma through the first fine filter membrane. At the same time, the filter area of ​​the second coarse filter membrane is set to be equal to that of the second fine filter membrane to filter out the remaining blood cells, thereby delaying the occurrence of filter membrane clogging to the maximum extent and effectively improving the filter membrane's capacity. Furthermore, filter membranes that can capture blood cells and can divide the filtrate into longitudinal and lateral flows are selected as the first and second coarse filter membranes, thereby inducing cross-flow shear force during the filtration process, effectively preventing the deposition of trapped blood cells.

[0014] Specifically, the first and second coarse filter membranes are glass fiber filter membranes that can capture blood cells and separate the filtrate into longitudinal and lateral flows.

[0015] Specifically, the first and second fine filtration membranes are polysulfone or polyethersulfone membranes with asymmetric structures.

[0016] Specifically, during assembly, the first and second filter membranes need to be pretreated, including anti-hemolysis treatment and blocking treatment. The anti-hemolysis treatment is used to suppress hemolysis to the greatest extent, and the blocking treatment is used to avoid protein adsorption to the greatest extent.

[0017] Specifically, the whole blood sample loading chamber is also provided with multiple vent holes, which are arranged around the sample loading port to expel air bubbles from the whole blood sample.

[0018] Specifically, the plasma collection chamber is equipped with a funnel structure around the sample outlet to guide the flow of plasma samples, thereby reducing the dead volume of plasma retained in the combined filter.

[0019] Specifically, the sample outlet adopts a beveled structure. The beveled structure guides the collected plasma sample to quickly gather at the tip of the bevel, reducing the surface tension of the plasma droplets and accelerating the drop speed of the plasma sample, thereby effectively improving the plasma sample recovery efficiency.

[0020] Specifically, the sample outlet adopts a guide needle structure, which utilizes the guiding effect of the guide needle to quickly gather the collected plasma sample to the tip of the guide needle, thereby effectively improving the plasma sample recovery efficiency.

[0021] To achieve the second objective of the present invention, a combined filter device is provided, comprising the above-described combined filter for separating plasma from whole blood, a receiving cup for collecting plasma samples, a vacuum container, and a vacuum generating device. The vacuum container includes a sealed cavity, the sealed cavity having a filter interface that is sealed and connected to the combined filter, and a vacuum interface that connects the interior of the sealed cavity to the vacuum generator. The filter interface has a central mounting groove that is fixed to the receiving cup, and a sealing cavity through hole disposed around the opening of the mounting groove.

[0022] When a whole blood sample enters the first combined filter membrane, the pressure in the vacuum container is adjusted to the first set pressure by a vacuum generator until the intermediate filtrate passes through the first combined filter membrane and enters the intermediate chamber.

[0023] When the intermediate filtrate enters the second combined filter membrane, the pressure in the vacuum container is adjusted to the second set pressure by the vacuum generator until the intermediate filtrate passes through the second combined filter membrane and enters the plasma collection chamber, thereby realizing the separation of whole blood samples through the combined filter to obtain the corresponding plasma samples, which then flow into the receiving cup to complete the plasma sample collection.

[0024] The first set pressure is greater than the second set pressure.

[0025] The combined filter device provided by the present invention adjusts the pressure inside the vacuum container according to the filtrate when it enters different combined filter membranes. When it enters the first combined filter membrane, a higher first set pressure is used to ensure that the whole blood sample can fully contact the first coarse filter membrane and the first fine filter membrane, thereby improving the capture effect of blood cells. At the same time, when the intermediate filtrate enters the second combined filter membrane, a lower second set pressure is used to ensure that the intermediate filtrate can pass through the second coarse filter membrane and the second fine filter membrane more quickly, thereby delaying the occurrence of filter membrane blockage to the greatest extent and avoiding hemolysis of red blood cells to the greatest extent.

[0026] Specifically, the range of the first set pressure is -10kPa to -20kPa, and the range of the second set pressure is -30kPa to -40kPa.

[0027] Specifically, the vacuum generating device includes a vacuum pump, a negative pressure sensor, pipelines, a three-way connector, a three-way control valve, and a controller. The inlet of the vacuum pump is connected to the first outlet of the three-way control valve, while the outlet of the vacuum pump is connected to the atmosphere.

[0028] The second outlet of the three-way control valve is connected to the atmosphere, while the inlet of the three-way control valve is connected to the first port of the three-way connector.

[0029] The negative pressure sensor is connected to the second port of the tee connector;

[0030] The vacuum interface of the vacuum container is connected to the third port of the tee connector;

[0031] The controller is used to monitor the negative pressure sensor readings, switch the three-way control valve passage, adjust the vacuum pump speed, and use relevant control strategies to monitor the pressure difference acting on the combined filter to ensure the smooth completion of the whole blood filtration process.

[0032] To achieve the third objective of this invention, a method for separating plasma from whole blood is provided, which is implemented using the above-described combined filter device, and includes the following steps:

[0033] Step 1: Place the receiving cup in the mounting slot of the vacuum container, connect the combined filter to the filter interface of the vacuum container and seal it. At the same time, preset the first set pressure and the second set pressure for the vacuum pump through the controller. The first set pressure is greater than the second set pressure.

[0034] Step 2: Add the whole blood sample into the whole blood sample chamber through the sample dispensing port of the combined filter, ensuring that the whole blood sample is fully diffused on the surface of the first coarse filter membrane of the first combined filter membrane;

[0035] Step 3: Switch the three-way control valve to connect the sealed cavity of the vacuum container with the vacuum pump. When the vacuum pump is started, the controller automatically adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the first set pressure and lasts for 10-20 seconds. Under the action of pressure difference, the whole blood sample passes through the first combined filter membrane, and the filtered intermediate filtrate enters the intermediate chamber and diffuses fully on the surface of the second coarse filter membrane of the second combined filter membrane.

[0036] Step 4: The controller adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the second set pressure. Under the action of pressure difference, the intermediate filtrate passes through the second combined filter membrane, and the filtered plasma sample enters the plasma collection chamber and is collected at the sample outlet. The collected plasma sample drips from the sample outlet into the receiving cup below.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. For the two-stage filtration mode of whole blood samples, the first stage uses a specially configured combination filter membrane to filter out some blood cells, which can effectively prevent the trapped blood cells from depositing on the surface of the first fine filter membrane, reduce the flow resistance of plasma through the first fine filter membrane, and increase the permeation flux of plasma through the first fine filter membrane. The second stage uses a combination filter membrane configured by stacking coarse and fine filter membranes to filter out the remaining blood cells, which can delay the occurrence of filter membrane blockage to the maximum extent and effectively improve the filter membrane load.

[0039] 2. A vacuum generator is used to generate and control the pressure difference acting on the combined filter. Different negative pressure values ​​are set according to the filtration process of whole blood samples, and the negative pressure inside the vacuum container is controlled through closed-loop feedback. The appropriate pressure difference control strategy not only delays the occurrence of filter membrane blockage to the maximum extent, but also avoids hemolysis of red blood cells to the greatest extent. Attached Figure Description

[0040] Figure 1 This is an exploded view of the combined filter provided in this embodiment;

[0041] Figure 2 This is a cross-sectional view of the combined filter provided in this embodiment;

[0042] Figure 3 This is a flow path diagram of a whole blood sample passing through the first combined filter membrane provided in this embodiment;

[0043] Figure 4 This is a schematic diagram of the combined filter device provided in this embodiment;

[0044] Figure 5 This is a cross-sectional view of the vacuum container provided in this embodiment;

[0045] Figure 6 This is a flowchart of the whole blood plasma separation method provided in this embodiment;

[0046] In the diagram, 1. Combined filter, 2. Vacuum container, 3. Receiving cup, 4. Vacuum generator, 5. First combined filter membrane, 51. First coarse filter membrane, 52. First fine filter membrane, 53. First support member, 6. Second combined filter membrane, 61. Second coarse filter membrane, 62. Second fine filter membrane, 63. Second support member, 7. Sample dispensing port, 71. Exhaust port, 8. Whole blood sample dispensing chamber, 9. Intermediate chamber, 10. Plasma collection chamber, 11. Sample outlet, 12. Filter interface, 13. Mounting slot; 14. Vacuum interface. Detailed Implementation

[0047] like Figure 1 and Figure 2 As shown, the combined filter 1 includes a sample inlet 7, an exhaust port 71, a whole blood sample inlet chamber 8, a first combined filter membrane 5, an intermediate chamber 9, a second combined filter membrane 6, a plasma collection chamber 10, and a sample outlet 11.

[0048] The sample loading port 7 is located at the top of the whole blood loading chamber 8 and is used for adding whole blood samples. The whole blood loading chamber 8 is used for temporary storage of whole blood samples. The whole blood loading chamber 8 is also provided with multiple exhaust holes 71, which are arranged around the sample loading port 7.

[0049] The first combined filter membrane 5 is arranged between the whole blood sample loading chamber 8 and the intermediate chamber 9, and includes a first coarse filter membrane 51, a first fine filter membrane 52 and a first support member 53.

[0050] More specifically, the first coarse filter membrane 51 and the first fine filter membrane 52 of the first combined filter membrane 5 are stacked, with the first coarse filter membrane 51 positioned above the first fine filter membrane 52. The effective area of ​​the first coarse filter membrane 51 is slightly larger than that of the first fine filter membrane 52. The first coarse filter membrane 51 is preferably made of glass fiber filter membrane with blood cell capture function and longitudinal and lateral flow functions. The first fine filter membrane 52 is preferably made of polysulfone or polyethersulfone membrane with an asymmetric structure. The first support member 53 has a hollow structure design in the middle to support the first coarse filter membrane 51 and the first fine filter membrane 52 and ensure the smooth passage of intermediate filtrate. The area of ​​the hollow part of the first support member 53 is equal to the effective filtration area of ​​the first coarse filter membrane 51 and slightly larger than the area of ​​the first fine filter membrane 52. The hollow part of the first support member 53 is slightly lower than the surrounding part to form a shallow groove to accommodate the first fine filter membrane 52. The depth of the groove is equivalent to the thickness of the first fine filter membrane 52.

[0051] like Figure 3 As shown, a whole blood sample is added to the surface of the first coarse filter membrane 51 of the first combined filter membrane 5. The whole blood sample enters the glass fiber filter membrane and forms longitudinal and lateral flows. Some blood cells are captured by the glass fiber filter membrane. At the same time, based on the filter membrane combination method of the first coarse filter membrane 51 being stacked on top of the first fine filter membrane 52 and the effective area of ​​the first coarse filter membrane 51 being slightly larger than the area of ​​the first fine filter membrane 52, part of the filtrate of the first coarse filter membrane 51 vertically permeates into the interior of the first fine filter membrane 52, and the other part flows parallel across the surface of the first fine filter membrane 52, causing cross-flow shear force on the surface of the first fine filter membrane 52, effectively increasing the permeation flux of plasma through the first fine filter membrane 52.

[0052] The volume of the intermediate chamber 9 is greater than the volume corresponding to the amount of intermediate filtrate filtered by the first combined filter membrane 5. The filtration rate of the first combined filter membrane 5 is greater than the filtration rate of the second combined filter membrane 6. The intermediate filtrate passing through the first combined filter membrane 5 is buffered and temporarily stored in the intermediate chamber 9 before entering the second combined filter membrane 6 for a second stage of filtration.

[0053] The second combined filter membrane 6 is arranged between the intermediate chamber 9 and the plasma collection chamber 10, and includes a second coarse filter membrane 61, a second fine filter membrane 62 and a second support member 63.

[0054] In this design, the second coarse filter membrane 61 and the second fine filter membrane 62 of the second combined filter membrane 6 are stacked, with the second coarse filter membrane 61 positioned above the second fine filter membrane 62. The areas of the second coarse filter membrane 61 and the second fine filter membrane 62 are equal. The first coarse filter membrane 61 is preferably made of glass fiber, which has blood cell capture function and longitudinal and lateral flow capabilities. The first fine filter membrane 62 is preferably made of asymmetric polysulfone or polyethersulfone membrane. The second support member 63 has a concave-convex structure in its middle section to support the second coarse filter membrane 61 and the second fine filter membrane 62 and ensure the smooth passage of plasma samples. The area of ​​the concave-convex portion of the second support member 63 is equal to the effective filtration area of ​​the second coarse filter membrane 61 and the second fine filter membrane 62. The concave-convex portion of the second support member 63 is slightly lower than the surrounding portion to prevent the second fine filter membrane 62 from completely adhering to the support surface and affecting its effective utilization.

[0055] The plasma collection chamber 10 is used for collecting plasma samples. The sample outlet 11 is located at the bottom of the plasma collection chamber 10 for discharging plasma samples.

[0056] The volume of the plasma collection chamber 10 should be as small as possible to reduce the dead volume of plasma retained in the combined filter. In this embodiment, the plasma collection chamber 10 has a guiding effect to guide the collected plasma sample to the sample outlet 11 at the bottom. The guiding effect of the oblique cut makes the collected plasma sample quickly gather to the tip of the oblique cut, reducing the surface tension of the formed plasma droplets and accelerating the drop speed of the plasma sample, thereby effectively improving the plasma sample recovery efficiency.

[0057] The diameter of the outlet 11 is smaller than that of the receiving cup 3, ensuring that the plasma sample can fall into the receiving cup 3.

[0058] In addition, the first combined filter membrane 5 and the second combined filter membrane 6 are treated with anti-hemolysis technology to minimize the occurrence of hemolysis. The first combined filter membrane 5 and the second combined filter membrane 6 are also sealed to minimize protein adsorption.

[0059] The periphery of the first combined filter membrane 5 and the second combined filter membrane 6 is sealed by a sealing element or by processes such as hot pressing or adhesive bonding to prevent blood cells from leaking from the periphery of the filter membrane. In this example, a sealing element is used to facilitate quick assembly during use.

[0060] like Figure 4 and Figure 5In addition, this embodiment also provides a combined filter device for whole blood filtration using the combined filter 1 proposed in the above embodiment. It also includes a vacuum container 2, a receiving cup 3, and a vacuum generator 4. The vacuum container 2 includes a sealed cavity. The sealed cavity is provided with a filter interface 12 that is sealed and connected to the combined filter 1, and a vacuum interface 14 that connects the inside of the sealed cavity to the vacuum generator 4. The filter interface 12 is provided with a mounting groove 13 in the center that is fixed to the receiving cup 3, and a sealing cavity through hole provided around the opening of the mounting groove 13.

[0061] The filter interface 12 is adapted to the combined filter 1. Pre-pressure forces the seal to deform, achieving a sealing effect, so that the disposable combined filter 1 and the vacuum container 2 combine to form a sealed cavity. Preferably, the filter interface 12 and its seal are designed separately so that the seal, as a consumable part, can be disassembled and replaced at any time.

[0062] The mounting groove 13 is adapted to the receiving cup 3, serving to support and fix the receiving cup 3, and structurally ensuring that the receiving cup 3 is easy to put on and take off. Preferably, the diameter of the hole in the receiving cup holder 13 is slightly larger than the diameter of the receiving cup 3, so that the receiving cup 3 is confined in the mounting groove 13 and supported by the flange of the mounting groove 3.

[0063] The vacuum interface 14 is compatible with the pipeline of the vacuum generating device 4. The connection between the vacuum interface 14 and the pipeline must be sealed. The receiving cup 3 can be a sample cup or a microcentrifuge tube.

[0064] The vacuum generating device 4 includes a vacuum pump, a negative pressure sensor, piping, a three-way connector, a three-way control valve, and a controller. The inlet of the vacuum pump is connected to the first outlet of the three-way control valve, and the outlet of the vacuum pump is connected to the atmosphere; the second outlet of the three-way control valve is connected to the atmosphere, and the inlet of the three-way control valve is connected to the first port of the three-way connector; the negative pressure sensor is connected to the second port of the three-way connector; and the vacuum interface 14 of the vacuum container 2 is connected to the third port of the three-way connector. The controller is used to monitor the negative pressure sensor reading, switch the three-way control valve path, adjust the vacuum pump speed, and employ relevant control strategies to monitor the pressure differential acting on the combined filter, ensuring the smooth completion of the whole blood filtration process.

[0065] A vacuum pump is used to establish negative pressure inside the vacuum container 2, and a miniature diaphragm pump is preferred.

[0066] The negative pressure sensor is used to provide feedback on the negative pressure inside the vacuum container 2, and the pressure sensor is preferably mounted on a circuit board.

[0067] The three-way control valve is used to switch the external gas path of vacuum container 2. By controlling the three-way control valve, vacuum container 2 can be connected to the vacuum pump or to the atmosphere. An electromagnetic control valve is preferred. When vacuum container 2 is connected to the vacuum pump, the vacuum pump can evacuate air to establish an internal negative pressure environment; when vacuum container 2 is connected to the atmosphere, atmospheric pressure can be restored.

[0068] The controller uses closed-loop control to read the negative pressure sensor readings in real time and adjust the vacuum pump speed accordingly, ensuring stable negative pressure inside the vacuum container 2. Preferably, the closed-loop control is implemented using a PID control algorithm.

[0069] The combined filter device for whole blood plasma separation in this embodiment has a filter membrane area of ​​2 cm². 2 It can process 600μL of whole blood sample at one time, with hematocrit (HCT) of 40%-50%, and can stably recover 200-220μL of plasma within 50-70 seconds without hemolysis.

[0070] This embodiment also provides a method for separating plasma from whole blood, implemented using the combined filter device provided in the above embodiments, such as... Figure 1 As shown, it includes the following steps:

[0071] Step 1: Place the receiving cup in the mounting slot of the vacuum container, connect the combined filter to the filter interface of the vacuum container and seal it. At the same time, preset the first set pressure and the second set pressure for the vacuum pump through the controller. The first set pressure is greater than the second set pressure.

[0072] Step 2: Add the whole blood sample into the whole blood sample chamber through the sample dispensing port of the combined filter, ensuring that the whole blood sample is fully diffused on the surface of the first coarse filter membrane of the first combined filter membrane;

[0073] Step 3: Switch the three-way control valve to connect the cavity structure of the receiving cup holder with the vacuum pump. When the vacuum pump is started, the controller automatically adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the first set pressure. In this embodiment, the first set pressure is -20kPa and lasts for 10-20 seconds. Under the action of pressure difference, the whole blood sample passes through the first combined filter membrane, and the filtered intermediate filtrate enters the intermediate chamber and diffuses fully on the surface of the second coarse filter membrane of the second combined filter membrane.

[0074] Step 4: The controller adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the second set pressure. In this embodiment, the second set pressure is -40kPa. Under the action of pressure difference, the intermediate filtrate passes through the second combined filter membrane, and the filtered plasma sample enters the plasma collection chamber and is collected at the sample outlet. The collected plasma sample drips through the sample outlet into the receiving cup below.

[0075] After the plasma samples have been collected, stop the vacuum pump, switch the three-way control valve to connect the vacuum container to the atmosphere, then remove the combined filter and take out the receiving cup containing the plasma samples.

[0076] To further illustrate the special configuration of the disposable combined filter of the present invention, combined with the corresponding separation pressure setting method and the oblique cut structure of the plasma outlet, and the beneficial effects on improving the recovery rate, recovery quality and recovery efficiency of whole blood separated plasma, relevant comparative experiments were conducted.

[0077] As mentioned above, the plasma recovery volume and filtration time vary depending on the hematocrit of the whole blood sample. The following are experimental data for whole blood samples with smaller hematocrits. The whole blood samples used in the comparative experiments are the same. The specific results are as follows:

[0078] The conventional filter is configured with a coarse filter membrane and a fine filter membrane stacked on top of each other, with the coarse filter membrane placed on top of the fine filter membrane. The areas of the coarse filter membrane and the fine filter membrane are equal, as shown in Table 1, which compares the combined filter with the conventional filter.

[0079] Table 1

[0080]

[0081] Under the same coarse / fine filtration membrane combination conditions, the disposable combined filter with a special membrane configuration can delay membrane clogging and increase membrane load, which not only reduces the number of filtration operations, but also effectively increases the recovery volume of plasma samples and reduces the filtration time of whole blood samples.

[0082] The results of comparing different negative pressure settings and constant negative pressure settings during the filtration process are shown in Table 2.

[0083] Table 2

[0084]

[0085] When a whole blood sample passes through the first combined filter membrane under a small pressure difference, the intermediate filtrate diffuses on the surface of the second combined filter membrane. When the negative pressure is increased, the pressure difference disperses and acts on the first and second combined filter membranes. However, when a larger pressure difference acts directly on the first coarse filter membrane, more blood cells captured by the glass fiber filter membrane will enter the second combined filter membrane, causing the second fine filter membrane to become clogged, resulting in a decrease in plasma recovery and an increase in filtration time.

[0086] Table 3 shows a comparison between the oblique and flat incision structures of the plasma sampling port.

[0087] Table 3

[0088]

[0089] The oblique cut structure of the sample outlet can quickly gather plasma samples, effectively reducing the filtration time of whole blood samples; the oblique cut structure of the sample outlet reduces the dead space volume of the filter, which helps to increase the plasma recovery volume.

Claims

1. A combined filter for separating plasma from whole blood, characterized in that, The whole blood sample is provided in sequence along the flow and filtration direction of the whole blood sample: a whole blood sample dispensing chamber, a first combined filter membrane, an intermediate chamber, a second combined filter membrane, and a plasma collection chamber. The whole blood sampling chamber is equipped with a sampling port for adding whole blood samples; The first composite filter membrane includes a first support member, and a first coarse filter membrane and a first fine filter membrane stacked sequentially on the first support member for filtering whole blood samples to obtain intermediate filtrate. The first coarse filter membrane is capable of capturing blood cells and dividing the filtrate into longitudinal and lateral flows. The filtration area of ​​the first coarse filter membrane is larger than that of the first fine filter membrane, so that part of the filtrate from the first coarse filter membrane vertically penetrates into the interior of the first fine filter membrane, and the other part flows parallel across the surface of the first fine filter membrane, causing cross-flow shear force on the surface of the first fine filter membrane. The surface of the first support member is provided with a perforated structure to facilitate the passage of intermediate filtrate into the intermediate chamber. The intermediate chamber is used to temporarily store the intermediate filtrate obtained by filtration through the first combined filter membrane. The second combined filter membrane includes a second support member, and a second coarse filter membrane and a second fine filter membrane stacked sequentially on the second support member for filtering intermediate filtrate to obtain plasma samples. The second coarse filter membrane is capable of capturing blood cells and separating the filtrate into longitudinal and lateral flows. The filtration area of ​​the second coarse filter membrane is equal to the filtration area of ​​the second fine filter membrane. The surface of the second support member is provided with a perforated structure to facilitate the passage of plasma samples into the plasma collection chamber. The plasma collection chamber is equipped with a sample outlet for exporting plasma samples; When the whole blood sample enters the first combined filter membrane, the first set pressure is adjusted to -10kPa to -20kPa until the intermediate filtrate passes through the first combined filter membrane and enters the intermediate chamber. When the intermediate filtrate enters the second combined filter membrane, the pressure is adjusted to the second set pressure of -30kPa to -40kPa until the intermediate filtrate passes through the second combined filter membrane and enters the plasma collection chamber.

2. The combined filter for separating plasma from whole blood according to claim 1, characterized in that, The first and second coarse filter membranes are glass fiber filter membranes that can capture blood cells and separate the filtrate into longitudinal and lateral flows.

3. The combined filter for separating plasma from whole blood according to claim 1, characterized in that, The first and second fine filtration membranes are polysulfone or polyethersulfone membranes with asymmetric structures.

4. The combined filter for separating plasma from whole blood according to claim 1, characterized in that, The whole blood sample loading chamber is also provided with multiple vents, which are arranged around the sample loading port.

5. The combined filter for whole blood plasma separation according to claim 1, characterized in that, The plasma collection chamber is equipped with a funnel structure around the sample outlet to guide the flow of plasma samples.

6. The combined filter for separating plasma from whole blood according to claim 1, characterized in that, The sample outlet adopts a slanted cut structure.

7. A combined filter device, characterized in that, The invention includes a combined filter for separating plasma from whole blood as described in any one of claims 1 to 6, a receiving cup for collecting plasma samples, a vacuum container, and a vacuum generating device. The vacuum container includes a sealed cavity, the sealed cavity having a filter interface that is sealed and connected to the combined filter, and a vacuum interface that connects the interior of the sealed cavity to the vacuum generator. The filter interface has a central mounting groove that is fixed to the receiving cup, and a sealing cavity through hole around the opening of the mounting groove. When a whole blood sample enters the first combined filter membrane, the vacuum generator is used to adjust the pressure in the vacuum container to a first set pressure until the intermediate filtrate passes through the first combined filter membrane and enters the intermediate chamber. When the intermediate filtrate enters the second combined filter membrane, the vacuum generating device is used to adjust the pressure in the vacuum container to the second set pressure until the intermediate filtrate passes through the second combined filter membrane and enters the plasma collection chamber, thereby realizing the separation of whole blood samples through the combined filter to obtain the corresponding plasma samples, which then flow into the receiving cup to complete the plasma sample collection.

8. The combined filter device according to claim 7, characterized in that, The vacuum generating device includes a vacuum pump, a negative pressure sensor, pipelines, a three-way connector, a three-way control valve, and a controller. The inlet of the vacuum pump is connected to the first outlet of the three-way control valve, and the outlet of the vacuum pump is connected to the atmosphere. The second outlet of the three-way control valve is connected to the atmosphere, while the inlet of the three-way control valve is connected to the first port of the three-way connector. The negative pressure sensor is connected to the second port of the tee connector; The vacuum interface of the vacuum container is connected to the third port of the tee connector; The controller is used to monitor the negative pressure sensor readings, switch the three-way control valve passage, adjust the vacuum pump speed, and use relevant control strategies to monitor the differential pressure acting on the combined filter.

9. A method for separating plasma from whole blood, characterized in that, This is achieved by the combined filter device according to any one of claims 7-8, comprising the following steps: Step 1: Place the receiving cup in the mounting slot of the vacuum container, connect the combined filter to the filter interface of the vacuum container and seal it. At the same time, preset the first set pressure and the second set pressure for the vacuum pump through the controller. The first set pressure is greater than the second set pressure. Step 2: Add the whole blood sample into the whole blood sample chamber through the sample dispensing port of the combined filter, ensuring that the whole blood sample is fully diffused on the surface of the first coarse filter membrane of the first combined filter membrane; Step 3: Switch the three-way control valve to connect the sealed cavity of the vacuum container with the vacuum pump. When the vacuum pump is started, the controller automatically adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the first set pressure and lasts for 10-20 seconds. Under the action of pressure difference, the whole blood sample passes through the first combined filter membrane, and the filtered intermediate filtrate enters the intermediate chamber and diffuses fully on the surface of the second coarse filter membrane of the second combined filter membrane. Step 4: The controller adjusts the speed of the vacuum pump according to the reading of the negative pressure sensor, so that the negative pressure inside the sealed cavity reaches and stabilizes at the second set pressure. Under the action of pressure difference, the intermediate filtrate passes through the second combined filter membrane, and the filtered plasma sample enters the plasma collection chamber and is collected at the sample outlet. The collected plasma sample drips from the sample outlet into the receiving cup below.

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