Dog alpha-fetoprotein immunochromatographic quantitative detection card

Abstract

The utility model relates to a kind of canine alpha-fetoprotein immunochromatographic quantitative detection card, belong to immunochromatographic detection device technical field.For the problem that sample leakage, chromatography uneven or detection window position deviation may exist in prior art, leading to inaccurate quantification.The detection card includes openable card shell and encapsulated chromatographic assembly in it;Chromatographic assembly includes the sample pad, the pad, the nitrocellulose membrane with detection line and quality control line and the absorbent pad sequentially stacked on the bottom plate, and the upper cover is provided with through sample inlet and detection port;Sample inlet is conical notch direct access sample pad surface, and detection port corresponds detection line and quality control line;Upper shell is provided with the scanning detection window corresponding to the detection port;Absorbent pad end extends 3~12mm beyond nitrocellulose membrane and abuts the inner wall of lower shell.The detection card is mainly used for the rapid, accurate quantitative detection of alpha-fetoprotein content in canine serum or plasma.

Description

Technical Field

[0001] This utility model relates to the technical field of immunochromatographic detection devices, and in particular to a quantitative immunochromatographic detection card for canine alpha-fetoprotein. Background Technology

[0002] In canine disease diagnosis, serum alpha-fetoprotein (AFP) serves as an important biomarker for liver tumors, and its quantitative detection is of great value for the early detection of malignant liver lesions. Currently, canine AFP detection mainly relies on laboratory enzyme-linked immunosorbent assay (ELISA). Although this method has high accuracy, it suffers from drawbacks such as complex operation procedures and long detection time, making it difficult to meet the needs of rapid screening in clinical settings.

[0003] For rapid testing scenarios, immunochromatographic test strips have emerged as a potential alternative due to their ease of use. However, in practical applications, these test strips still suffer from the following structural issues that affect quantitative accuracy: 1. Traditional test cards often have gaps or lack flow guiding structures between the sample application well and the sample pad. When adding the sample, the liquid is prone to stagnation on the well wall or seep into the gaps around the sample application well, which prevents the sample from quickly and fully wetting the beginning of the sample pad, causing delay in chromatography start-up or sample loss, and affecting the reproducibility of the test.

[0004] 2. The absorbent pad, as the driving force for the chromatographic liquid, directly affects the stability of the chromatography speed due to its effective absorbent length. In traditional immunochromatographic assay cards, the overlap between the absorbent pad and the nitrocellulose membrane is usually flush or only slightly extended. If the absorbent pad is not sufficiently extended, its absorbent capacity and capillary force are prone to decay in the later stages of chromatography, leading to a decrease or even stagnation of the chromatography front speed, especially for high-viscosity samples (such as whole blood), which can easily cause chromatography interruption. Lengthening can enhance the driving force, but if its end is not sufficiently fixed, it is prone to curling upwards due to water absorption and expansion or mechanical vibration. Curling reduces the effective contact area between the absorbent pad and the nitrocellulose membrane, further weakening the capillary force transmission efficiency, causing fluctuations in the detection line signal intensity, and affecting the quantitative repeatability of low-concentration target substances (such as canine AFP).

[0005] Improving the above-mentioned problems faces the following difficulties: First, the miniaturized design of the sample dispensing well needs to balance leakage prevention and rapid flow, posing a challenge to the flow channel structure; second, the absorbent pad has low rigidity, and achieving long-term anti-curling fixation of its end within a limited shell requires a special structural design. Although existing canine immunochromatographic assay cards involve chromatographic structures, no optimized solutions for the above key problems have been disclosed, especially lacking the precise chromatographic control required for quantifying canine AFP, a low-concentration tumor marker. Utility Model Content

[0006] The purpose of this invention is to solve the following problems: Existing immunochromatographic assay cards have the following defects: the sample wells lack a flow guide design, causing sample droplets to remain on the well walls or seep into the surrounding gaps, resulting in delayed chromatography start-up; when the end of the absorbent pad is not fixed in place, it tends to absorb water and swell, curling upwards, reducing the contact area with the nitrocellulose membrane, weakening the capillary driving force, and the traditional flush structure has insufficient water storage capacity, resulting in a decrease in driving force in the later stages of chromatography, affecting the stability of low-concentration target analytes detection.

[0007] Conventional sample loading wells may have insufficient depth or be misaligned, failing to concentrate and guide droplets to the center of the sample pad, resulting in uneven diffusion of the chromatography bands.

[0008] Improper spacing between the detection window and the nitrocellulose membrane (too large a distance exacerbates signal attenuation, too small a distance compresses the membrane surface) affects the accuracy of optical readings and the chromatography flow rate.

[0009] If the height of the limiting structure of the chromatography module is insufficient or lacks a guiding design, assembly is prone to jamming, and the fixing stress is uneven when the spacing is unreasonable.

[0010] Even if the end of the absorbent pad only touches the shell wall, it may still warp slightly; adhesive fixation can clog the fiber pores and reduce water absorption efficiency.

[0011] During the sample addition process, excess sample overflows from the inlet, contaminating the surface of the test card and the optical window.

[0012] Single-density absorbent pads cannot simultaneously ensure the continuity of chromatography driving force and water storage capacity, and are prone to backflow or premature saturation.

[0013] To achieve the above objectives, this utility model provides a canine alpha-fetoprotein immunochromatographic quantitative detection card, comprising: A closable housing and a chromatography assembly installed within the housing; the housing consists of an upper shell and a lower shell; the chromatography assembly includes a sample pad, a binding pad, a nitrocellulose membrane with detection lines and control lines, and an absorbent pad, which are sequentially stacked and fixed on a base plate along the chromatography direction; a cover plate is provided above the chromatography assembly, the cover plate having a through-type sample inlet and a detection port, the sample inlet being a conical groove extending to and directly through the surface of the sample pad below, and the detection port being aligned with the detection lines and control lines on the nitrocellulose membrane; the upper shell has a scanning detection window aligned with the detection port, the position of which corresponds to the detection lines and control lines on the nitrocellulose membrane; the chromatography assembly is installed in the lower shell, and the inner side of the lower shell has a protruding limiting member for locking and fixing the chromatography assembly; the absorbent pad extends towards the end of the chromatography process, its extension beyond the nitrocellulose membrane being 3~12mm, more preferably 8~12mm, most preferably 8mm, and the extended end abuts against the inner wall of the lower shell.

[0014] Preferably, the conical groove of this invention is a conical groove structure with a depth of 0.5~1mm, and the central axis of the conical hole formed at the bottom of the groove points vertically to the central area of ​​the sample pad.

[0015] Preferably, the scanning detection window of this invention is embedded with a transparent acrylic plate, and the vertical distance between the lower surface of the acrylic plate and the upper surface of the nitrocellulose membrane is 0.2~2mm.

[0016] Preferably, the protrusion limiting member of this utility model includes at least one set of symmetrically arranged protrusions, which are respectively fixed to the inner bottom surface of the lower shell and distributed at intervals. A limiting groove for accommodating the chromatography assembly is formed between adjacent protrusions. The top of the protrusion is provided with a guide slope facing the direction of loading the chromatography assembly. The side of the bottom plate is fitted with the inner sidewall of the protrusion to clamp and fix the chromatography assembly in the limiting groove.

[0017] Preferably, the inner sidewall of the lower shell of this invention has a downward slot at the position of the extended end of the absorbent pad; the width of the slot is larger than the width of the absorbent pad, and the extended end of the absorbent pad is embedded in the slot; an insert is provided that is interference-fitted with the slot, and when the insert is pressed into the slot along the vertical chromatography direction, the absorbent pad is pressed tightly to the bottom surface of the slot, forming a flat and fixed structure without curling.

[0018] Preferably, the cover plate of this utility model is provided with an annular anti-overflow groove, which is arranged around the sample inlet.

[0019] Preferably, the absorbent pad of this invention is composed of a first absorbent layer and a second absorbent layer stacked on top of each other; the first absorbent layer is located on top and is in contact with the nitrocellulose membrane, and its density is 20~30 mg / cm³. 3 The first layer has a thickness of 0.8~1.2mm; the second absorbent layer is located in the lower layer and is closely attached to the bottom surface of the lower shell, with a density of 35~45 mg / cm³. 3 The thickness is 0.6 to 0.8 times the thickness of the first absorbent layer; the first absorbent layer and the second absorbent layer are pressed together to form an integrated structure.

[0020] This utility model has at least the following beneficial effects: 1. The conical groove of this invention, with its direct-access sample pad, eliminates sample loading delays and ensures rapid start-up of chromatography; the scanning detection window is precisely aligned with the detection line / control line, ensuring optical positioning accuracy; the absorption pad extends 3~12mm, more preferably 8~12mm, and most preferably 8mm, and abuts against the shell wall to provide sufficient water storage capacity through its extra length, maintaining capillary stability in the later stages of chromatography; the end-abutting design inhibits water absorption curling, ensuring uniform pressure at the contact surface with the nitrocellulose membrane and improving the reproducibility of low-concentration target analytes detection.

[0021] 2. The depth and vertical orientation of the conical groove in this invention concentrate the droplet flow towards the center of the sample pad, reducing diffusion of the chromatography band. The 0.2~0.5mm spacing balances signal acquisition requirements with chromatography flowability, avoiding interference from ambient light or pressure on the membrane surface. The height of the protrusion and the guide slope enable smooth assembly, and the clearance fit releases stress and prevents component displacement.

[0022] 3. The interference fit of the insert vertically pressed into the slot in this utility model forces the end of the absorption pad to be flat and fixed, completely eliminating curling and without damaging the pore structure. The annular anti-overflow groove accommodates overflowing samples and prevents contamination of the optical interface. The dual-layer density gradient structure is synergistically optimized, with the upper layer rapidly draining and the lower layer storing water at high density, avoiding backflow or premature saturation.

[0023] Other advantages, objectives and features of this invention will be partly apparent from the following description, and partly understood by those skilled in the art through study and practice of this invention. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a canine alpha-fetoprotein immunochromatographic quantitative detection card according to the present invention; Figure 2 This is a three-dimensional structural diagram of the chromatography component of this utility model; Figure 3 This is a three-dimensional structural diagram of the cartridge of this utility model, with the chromatography components not yet assembled. Figure 4 This is a schematic diagram of the assembly structure of the chromatography component of this utility model.

[0025] The components include: a cassette 10, an upper shell 101, a lower shell 102, a scanning detection window 103, a transparent acrylic plate 104, a raised limiting component 105, a guide slope 106, a slot 107, an insert 108, a limiting groove 109, a chromatography assembly 20, a base plate 201, a sample pad 202, a binding pad 203, a nitrocellulose membrane 204, a detection line 2041, a quality control line 2042, an absorbent pad 205, a first absorbent layer 2051, a second absorbent layer 2052, a cover plate 206, a sample inlet 2061, an overflow prevention groove 2062, and a detection port 2063. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments, so that those skilled in the art can implement it based on the description.

[0027] As shown in Figures 1-4, this utility model discloses a canine alpha-fetoprotein immunochromatographic quantitative detection card, comprising an openable card housing 10 and a chromatography assembly 20 installed within the card housing 10. The card housing 10 is injection molded from an upper shell 101 and a lower shell 102, which can be made of ABS engineering plastic with a thickness of 1.5 mm. The upper shell 101 and the lower shell 102 are hinged on one side and have a snap-fit ​​on the other side to achieve opening and closing. The chromatography assembly 20 includes a PVC base plate 201 with dimensions of 60 mm × 15 mm × 0.5 mm. The following components are sequentially stacked and fixed on the base plate 201 along the chromatography direction: a glass fiber sample pad 202 (15 mm long), a conjugate pad 203 (approximately 10 mm long, coated with fluorescently labeled antibodies, such as anti-rabbit IgG antibodies or anti-alpha-fetoprotein antibodies sprayed with fluorescein-labeled antibodies), a nitrocellulose membrane 204 (approximately 25 mm long, with a detection line 2041 and a control line 2042; the control line 2042 is coated with rabbit IgG antibodies, and the detection line 2041 is coated with anti-alpha-fetoprotein antibodies), and an absorbent paper pad 205 (approximately 30 mm long, which can be set according to actual needs). The absorbent pad 205 extends towards the end of the chromatography column, extending beyond the nitrocellulose membrane 204 by 8 mm (example value; the extension length can be set as needed, such as 3, 8, 12 mm, etc.), with its end abutting against the inner wall of the lower shell 102. The cover plate 206 has a through-hole sample inlet 2061 and a detection port 2063. The sample inlet 2061 is a conical groove with a depth of 0.8 mm (example value) and a cone angle of 60°. The central axis of the groove bottom points vertically to the center of the sample pad 202. The detection port 2063 can be set to 4 mm × 3 mm, aligned with the center of the detection line 2041 and the quality control line 2042 of the nitrocellulose membrane 204. The scanning detection window 103 of the upper shell 101 is a rectangular opening (6 mm × 2 mm), with a 1 mm thick transparent acrylic plate 104 embedded inside. The scanning detection window 103 corresponds to the detection port 2063 on the cover plate 206. The inner side of the lower shell 102 has two sets of symmetrical ABS protrusions 105, with a height of 0.6 mm (example value) and a spacing of 58 mm, forming a limiting groove 109.

[0028] During assembly, the sample pad 202, binding pad 203, nitrocellulose membrane 204, and absorbent pad 205 are first sequentially bonded to the base plate 201. Then, the cover plate 206 is bonded and fixed to the base plate 201 to complete the encapsulation, thus assembling the chromatography module 20. At this time, the detection port 2063 of the cover plate 206 corresponds to the detection line 2041 and the quality control line 2042. The chromatography module 20 is inserted into the limiting groove 109 along the guide slope 106 of the lower shell 102, and the side of the base plate 201 or the cover plate 206 is fitted with the inner sidewall of the protrusion to form a clamping fixation. The extended end of the absorbent pad 205 abuts against the inner wall of the lower shell 102. The conical groove of the sample inlet 2061 is directly opposite the starting end of the sample pad 202. The upper shell 101 is closed for easy carrying. During testing, the upper shell 101 is opened, and 50 μL of collected serum sample is dropped into the injection port 2061. The sample converges along the conical surface of the conical groove and falls to the center of the sample pad 202. The upper shell 101 is then closed, and the chromatography process is allowed to proceed for approximately 15 minutes. During this time, the scanning detection window 103 completely covers the detection line 2041 and the control line 2042. During chromatography, the sample liquid, carrying fluorescent antibodies through the binding pad 203 via capillary action, flows through the nitrocellulose membrane 204 and binds to the AFP antibody on the detection line 2041. The remaining liquid is continuously absorbed by the absorption pad 205. The absorption pad 205, extending 3–12 mm, provides additional water storage space, and its end abuts against the shell wall to constrain its expansion and deformation, maintaining a constant chromatography speed. After 15 minutes, the test card is placed in a fluorescence immunoassay analyzer, and the fluorescence signal is read by scanning the detection window 103. Alternatively, the upper shell 101 can be opened before scanning.

[0029] In existing technologies, the absorbent pad is flush with the end of the nitrocellulose membrane and does not abut against the shell wall, leading to a decrease in driving force in the later stages of chromatography, and the absorbent pad is prone to curling and detachment. This embodiment solves three technical problems by extending the absorbent pad 205 by 10 mm and abutting against the inner wall of the lower shell 102, combined with the flow guidance of the conical groove and the precise positioning of the protruding limiting member 105: the 0.8 mm depth and directional design of the conical groove eliminate sample retention and shorten the chromatography start-up time; the gap fit of the limiting groove 109 prevents displacement of the chromatography component 20, ensuring that the detection line 2041 is always aligned with the scanning window 103; the extended section of the absorbent pad 205 effectively increases the water absorption capacity, and the end abutting inhibits curling, reducing chromatography speed fluctuations. Overall, stable quantitative detection of AFP in canine serum is achieved.

[0030] Two canine AFP samples with different concentrations were tested using test cards with extension lengths of 0, 3, 8, and 12 mm, respectively. S1 was a blank sample (0 ng / mL), and S2 was a sample with 70 ng / mL. Signal-to-noise ratio was compared, and the results are as follows: Table 1 Signal-to-noise ratio detection data As can be seen, the signal-to-noise ratio (SNR) is 11.143 when the elongation is 3 mm, which is a significant improvement compared to the elongation of 0 mm. The improvement is even more significant when the elongation is ≥8 mm, reaching 29.1, which is about 4 times higher than 0 mm. The performance of 8 mm and 12 mm is similar, with 8 mm being the optimal SNR value.

[0031] In addition, 10 samples with low AFP values ​​(concentrations below 70 ng / mL) were tested using test cards with extension lengths of 0, 3, 8, and 12 mm, respectively. Repeatability was evaluated using the coefficient of variation (CV), with an industry standard CV < 10%. Results from other manufacturers' ELISA kits were used as references. Each sample was tested three times. Detailed results are as follows: Table 2. Detailed data on coefficient of variation (CV) (unit: %) As can be seen, the CV (CV) of the 0 mm extension test card for low concentration samples (<30 ng / mL) was generally >10%, reaching a maximum of 18.17%, and only met the standard for medium-to-high concentration samples (>37 ng / mL). The 3 mm extension length improved the detection performance of the test card, meeting the CV standard for low concentration samples (>15 ng / mL). The 8 mm and 12 mm extension length test cards had a CV <8% for all samples, fully complying with the industry standard (CV <10%), and the CV for low concentration samples (6.5 ng / mL) was reduced to 3.6~4.55%.

[0032] Furthermore, in another embodiment, the injection port 2061 adopts a conical groove structure, which can be integrally injection molded with the cover plate 206 using ABS engineering plastic. The groove depth is set to 0.8 mm (example value), which can be adjusted within the range of 0.5 mm, 0.7 mm, or 1.0 mm. The bottom opening diameter of the conical groove is 1.5 mm, and the groove wall inclination angle is 30°. The central axis of the conical hole is strictly perpendicular to the central area of ​​the sample pad 202. The central area of ​​the sample pad 202 is defined as a rectangular area (total size 3 mm × 2 mm) 5 mm from its front edge and ±1 mm from its width axis. Preferably, the surface roughness Ra of the inner wall of the conical groove is ≤0.4 μm, which can be achieved by ultrasonic polishing. The center point of the bottom of the conical groove structure coincides with the vertical projection of the center of the sample pad 202. During operation, when a 50 μL serum sample is dripped into the injection port 2061, the droplet converges downward along the conical groove wall, and constrained by the groove depth and vertical orientation, forms a liquid column with a diameter of approximately 1.8 mm that falls precisely. The offset between the center of the liquid column and the center region of sample pad 202 is small.

[0033] Existing technologies use a straight cylindrical sample dispensing port, and the lack of a conical groove design results in droplets randomly wetting the sample pad. This embodiment solves the droplet diffusion problem by using a 0.8 mm deep conical groove and vertical orientation. The conical surface guides the liquid flow to concentrate, effectively shortening the initial wetting time of the sample pad; the vertical drop point positioning accuracy is improved, and the detection consistency is enhanced. This structure ensures the accuracy of quantitative detection of AFP in dogs.

[0034] Furthermore, in another embodiment, the transparent acrylic plate 104 embedded in the scanning detection window 103 can be made of optical-grade PMMA material, with a thickness of 1.0 mm and a light transmittance ≥92%. The transparent acrylic plate 104 is fixed to the window frame groove of the upper shell 101 by adhesive bonding, and the vertical distance between its lower surface and the upper surface of the nitrocellulose membrane 204 is set to 0.3 mm (example value), which can be adjusted within the range of 0.2 mm, 0.4 mm, or 1 mm. Preferably, the flatness of the lower surface of the transparent acrylic plate 104 is ≤0.01 mm. During detection, the optical probe of the fluorescence immunoassay analyzer is aligned with the scanning detection window 103 and emits excitation light. After passing through the transparent acrylic plate 104, the excitation light reaches the surface of the nitrocellulose membrane 204 and excites the fluorescent marker. The fluorescence signal penetrates the air layer and the transparent acrylic plate 104 and is captured by the probe. In this embodiment, the transparent acrylic plate 104 blocks external dust while facilitating observation and testing. During the carrying or chromatography waiting process, after the upper shell 101 and lower shell 102 are closed, a closed space is formed inside the casing 10, effectively preventing external influences.

[0035] Furthermore, in another embodiment, the protruding limiting member 105 includes two sets of symmetrically arranged ABS protrusions fixed to the inner bottom surface of the lower shell 102. Each set of protrusions consists of a pair of spaced-apart protrusions (such as bosses or protrusions), with a length of approximately 5 mm and a width of 2 mm. The distance between a pair of adjacent protrusions is approximately 18 mm, forming a limiting groove 109. The height of the protrusion is 1 mm (example value), which can be adjusted within the range of 0.5 mm, 4 mm, or 8 mm. A 45° guide slope 106 is provided at the top of the protrusion, and the height of the slope accounts for 1 / 3 of the total height of the protrusion. The side of the base plate 201 is in contact with the inner sidewall of the protrusion. The limiting groove 109 has a total width of 14.8 mm, forming an interference fit of 0.2 mm with the 15 mm width of the base plate 201.

[0036] During assembly, the chromatography module 20 is slid into the limiting groove 109 along the guide slope 106, and the guide slope 106 guides the base plate 201 to press down and pre-tighten. When the base plate 201 is fully in place, its side edge is interference-fitted with the inner wall of the protrusion, and the clamping is achieved by the deformation of the material itself to prevent the chromatography module 20 from shifting.

[0037] In this embodiment, the convex part and the chromatography component 20 are interlocked to clamp the chromatography component 20, which effectively prevents the chromatography component 20 from shifting, meets the requirements of optical scanning positioning accuracy, and makes tissue disassembly and disassembly convenient and quick. The guide slope 106 reduces the insertion resistance and improves efficiency.

[0038] Furthermore, in another embodiment, an ABS material slot 107 is formed on the inner sidewall of the lower shell 102 at the position corresponding to the extended end of the absorbent pad 205. The slot 107 has a width of 15.08 mm (example value), which is approximately 0.08 mm larger than the width of the absorbent pad 205 (15.0 mm) or greater. The extended end of the absorbent pad 205 is embedded in the slot 107. The insert 108 can be a thin plastic sheet with a thickness of 0.5-4 mm and a width of 15.03 mm, forming an interference fit with the slot 107 with an interference amount of approximately 0.05 mm. Preferably, the surface of the insert 108 has an anti-slip texture to facilitate manual pressing.

[0039] During assembly, first insert the end of the absorbent pad 205 into the slot 107. Then, press the insert 108 into the slot 107 perpendicular to the chromatography direction (perpendicular to the plane of the base plate 201). The vertical pressure during the pressing process causes the insert 108 to press the absorbent pad 205 tightly against the bottom surface of the slot 107. To verify the anti-curling property, 200 μL of water can be added to the fixed absorbent pad 205 to simulate the chromatography saturation state. After standing for 24 hours, the end warping height is observed to be optimal.

[0040] Compared to simply using adhesive to fix the end of the absorbent pad, this embodiment uses the width allowance of the slot 107 and the interference fit of the insert 108 to flatten and fix the absorbent pad, effectively eliminating curling and deformation. The downward pressure of the insert 108 forces flattening and fixing, and the absorbent pad 205 maintains contact with the nitrocellulose membrane 204 during the chromatography process to exert its effect.

[0041] Furthermore, in another embodiment, the cover plate 206 is provided with an annular anti-overflow groove 2062 surrounding the sample inlet 2061, integrally injection molded with the cover plate 206, and can be made of ABS engineering plastic. The anti-overflow groove 2062 has an inner diameter of 8.0 mm (2.0 mm larger than the diameter of the sample inlet 2061, which is 6.0 mm), an outer diameter of 12.0 mm, and a depth of 2.5 mm (example value), which can be adjusted within the range of 2.0 mm, 2.3 mm, or 3.0 mm. Preferably, the groove wall inclination angle is 70°, and the surface roughness Ra ≤ 0.8 μm. The central axis of the anti-overflow groove 2062 coincides with the central axis of the sample inlet 2061. The upper edge of the anti-overflow groove 2062 is 0.5 mm lower than the plane of the sample inlet 2061. During sample addition, if an excessive amount of sample (e.g., 70 μL) is added due to improper operation, the liquid exceeding the capacity of the sample inlet 2061 will flow into the annular anti-overflow groove 2062 along the groove wall. Preferably, the tank can accommodate a maximum overflow of 20 μL. The overflow liquid is constrained by the tank depth of 2.5 mm and surface tension, and remains in the tank without spreading, effectively solving the problem of sample contamination caused by operational errors and preventing liquid from contacting the detection window 103; at the same time, it maintains the cleanliness of the optical interface and prevents the overflow liquid from flowing out of the tank; the tank depth of 2.5 mm does not affect the positioning of the sample dispensing needle.

[0042] Furthermore, in another embodiment, the absorbent pad 205 is composed of a first absorbent layer 2051 and a second absorbent layer 2052 stacked together. The first absorbent layer 2051 can be made of glass fiber filter paper with a density of 25 mg / cm³. 3 (Example value), 1.0 mm thick, located in direct contact with the upper nitrocellulose membrane 204. The second absorbent layer 2052 can be made of absorbent paper with a density of 40 mg / cm³. 3 (Example value), the thickness can be set to 0.7 mm (0.7 times that of the first layer), located in the lower layer and closely attached to the bottom surface of the lower shell 102. The two layers of materials are bonded together by a hot-pressing composite process, for example, hot-pressing temperature 110℃, pressure 0.8 MPa, hot-pressing duration 10 seconds, to form an integrated structure with a total thickness of 1.65 mm after composite.

[0043] The low-density structure of the first absorbent layer 2051 enables rapid flow diversion, shortening the chromatography start-up time. The high-density structure of the second absorbent layer 2052 provides a larger water storage capacity. Compared to using a single-density absorbent pad, this embodiment prevents backflow through a density gradient design, and the high-density second layer 2052 inhibits liquid backflow; at the same time, it avoids premature saturation, with the low-density first layer 2051 rapidly diverting the flow, combined with the high-density layer storing water, extending the saturation time; and it maintains linear driving force, keeping the chromatography speed consistent, making it particularly suitable for high-concentration sample detection.

[0044] Although the embodiments of this utility model have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be applied to various fields suitable for this utility model. Other modifications can be easily made by those skilled in the art.

Claims

1. A quantitative immunochromatographic assay card for canine alpha-fetoprotein, characterized in that, It includes an openable housing and a chromatography assembly installed inside the housing; the housing consists of an upper shell and a lower shell; The chromatography assembly includes a sample pad, a binding pad, a nitrocellulose membrane with detection lines and control lines, and an absorption pad, which are sequentially stacked and fixed on a base plate along the chromatography direction. A cover plate is provided on top of the chromatography assembly. The cover plate has a through-type sample inlet and detection port. The sample inlet is a conical groove that extends directly to the surface of the sample pad below. The detection port is aligned with the detection lines and control lines on the nitrocellulose membrane. The upper shell is provided with a scanning detection window aligned with the detection port. The position of the scanning detection window corresponds to the detection line and quality control line on the nitrocellulose membrane. The chromatography assembly is installed in the lower shell, and the inner side of the lower shell is provided with a protruding limiting member for locking and fixing the chromatography assembly. The absorption pad extends to the end of the chromatography process, and its extension exceeds the length of the nitrocellulose membrane by 3~12mm, and the extended end abuts against the inner wall of the lower shell.

2. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The inlet has a conical groove structure, and the central axis of the conical hole formed at the bottom of the groove points vertically to the central area of ​​the sample pad.

3. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The scanning detection window is embedded with a transparent acrylic plate, and the vertical distance between the lower surface of the acrylic plate and the upper surface of the nitrocellulose membrane is 0.2~2mm.

4. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The protruding limiting member includes at least one set of symmetrically arranged protrusions, which are respectively fixed to the inner bottom surface of the lower shell and spaced apart. A limiting groove for accommodating the chromatography assembly is formed between adjacent protrusions. The top of the protrusion is provided with a guide slope facing the loading direction of the chromatography assembly. The side of the bottom plate is fitted with the inner sidewall of the protrusion to clamp and fix the chromatography assembly in the limiting groove.

5. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The inner wall of the lower shell has a downward slot corresponding to the extension end of the absorbent pad. The width of the slot is larger than the width of the absorbent pad, and the extension end of the absorbent pad is embedded in the slot. There is an insert that is interference-fitted with the slot. When the insert is pressed into the slot along the vertical chromatography direction, it presses the absorbent pad tightly to the bottom surface of the slot, forming a flat and fixed structure without curling.

6. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The cover plate is equipped with an annular anti-overflow groove, which surrounds the sample inlet.

7. The canine alpha-fetoprotein immunochromatographic quantitative detection card according to claim 1, characterized in that, The absorbent pad consists of a first absorbent layer and a second absorbent layer that are stacked on top of each other; The first absorbent layer is located on top and is in contact with the nitrocellulose membrane; its density is 20–30 mg / cm³. 3 The thickness is 0.8~1.2mm; The second absorbent layer is located in the lower layer and is in close contact with the bottom surface of the lower shell; its density is 35~45 mg / cm³. 3 The thickness is 0.6 to 0.8 times the thickness of the first absorbent layer; the first absorbent layer and the second absorbent layer are pressed together to form an integrated structure.

Images