Distal thrombus removal device

Abstract

A distal thrombus removal device, comprising a wall apposition protective umbrella (1) and a built-in removal device (2). The wall apposition protective umbrella (1) comprises a pushing unit (11) and a basket (12). A first end of the basket (12) is connected to the pushing unit (11), and a second end is provided with an opening (121). The pushing unit (11) is tubular. The wall apposition protective umbrella (1) is configured to be located at a distal end of an aspiration catheter (3). The basket (12) is arranged on the side of the pushing unit (11) facing away from the aspiration catheter (3), and the basket (12) is configured to capture a thrombus. The built-in removal device (2) is configured to penetrate through the wall apposition protective umbrella (1) and extend out of the opening (121). The built-in removal device (2) is configured to cut and remove the thrombus, so as to clear the obstructions at the distal end of the aspiration catheter (3) and an adjacent area of the aspiration catheter (3).

Description

Distal thrombus remover

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on January 9, 2024, with application number 202410028529.8. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of medical device technology, for example, to a distal thrombus remover. Background Art

[0003] Thrombus aspiration is used in the clinical treatment of peripheral vascular embolism. After the peripheral aspiration catheter is delivered to its proper position, the aspiration catheter will, under the action of negative pressure, draw the blocked thrombus into the catheter lumen and expel it from the body, achieving thrombus removal. However, during the use of the aspiration catheter, when a thrombus blocks the distal end of the aspiration catheter (away from the operator) or a thrombus blocks the adjacent blood vessels, aspiration will not proceed. The operator needs to withdraw the aspiration catheter first, then deliver auxiliary equipment or use other methods to restore the normal aspiration procedure. This process consumes a certain amount of time and energy of the operator, increasing the difficulty of treatment.

[0004] Summary of the Invention

[0005] The present application provides a distal thrombus remover, which can clear the distal end of the suction catheter and the adjacent blood vessel area when the suction catheter is kept in a predetermined position, and can prevent the thrombus from escaping, avoid the suction catheter from being unable to suction, so that the operation can be carried out smoothly and the difficulty of treatment is reduced.

[0006] The present application provides a distal thrombus remover, comprising:

[0007] The wall-adhering protective umbrella comprises a pushing unit and a basket, wherein the first end of the basket is connected to the pushing unit and the second end is provided with an opening. The pushing unit is tubular, the wall-adhering protective umbrella is configured to be located at the distal end of the aspiration catheter, and the basket is located on a side of the pushing unit away from the aspiration catheter, and the basket is configured to capture thrombi;

[0008] The built-in remover is configured to penetrate the wall-adhering protective umbrella and extend out of the opening. The built-in remover is configured to cut and remove thrombus to clear the distal end of the suction catheter and the adjacent area of ​​the suction catheter.

[0009] In some possible implementations, the pushing unit includes a first guide wire and a catheter, the catheter is connected between the first guide wire and the basket, and an end of the catheter facing away from the basket is provided with an oblique cut.

[0010] In some possible implementations, the catheter includes a first tube portion and a second tube portion connected to each other, the first tube portion is elastic, and the second tube portion is provided with the oblique cut.

[0011] In some possible implementations, the first tube portion is a coiled spring structure, and the second tube portion is a polymer material structure.

[0012] In some possible implementations, the catheter is configured to be in at least one of the following situations:

[0013] The inner side of the catheter is provided with an intimal layer;

[0014] An outer tube layer is provided on the outside of the catheter.

[0015] In some possible implementations, the basket is made of a memory alloy, the basket can be radially contracted and expanded, and the opening is a closed opening.

[0016] In some possible embodiments, the built-in remover includes a delivery guide wire assembly, a filter, and a distal spring connected in sequence, the distal spring is configured to serve as a dredging guide, and the filter is configured to cut and remove the thrombus.

[0017] In some possible embodiments, the delivery guidewire assembly includes a second guidewire and a proximal spring, the proximal spring connecting the second guidewire and the filter, the proximal spring supported on the pushing unit, the length of the proximal spring greater than the length of the distal spring, and the outer diameter of the proximal spring greater than the outer diameter of the distal spring.

[0018] In some possible embodiments, the filter is made of a memory alloy material, the first end of the filter is fixed to the delivery guide wire assembly, and the second end can slide along the center line of the delivery guide wire assembly. The filter can converge inward toward the center line and expand outward away from the center line.

[0019] In some possible implementations, the end of the distal spring facing away from the filter screen is a smooth surface.

[0020] In some possible embodiments, a developing ring is provided in the filter toward the first end of the conveying guide wire assembly, and the outer diameter of the developing ring is larger than the inner diameter of the first end of the filter, so that the first end of the filter is clamped between the developing ring and the conveying guide wire assembly.

[0021] In some possible implementations, the basket is provided with at least four development points, and a development ring is provided between the basket and the conduit.

[0022] In some possible implementations, the distal spring is made of a developing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of a distal thrombus remover provided in an embodiment of the present application in use;

[0024] FIG2 is a schematic diagram of a Y-shaped valve provided in an embodiment of the present application in a state of pushing a protective umbrella against a wall;

[0025] FIG3 is a schematic diagram of a wall-adhering protective umbrella provided in an embodiment of the present application;

[0026] FIG4 is a schematic diagram of the distal end face of a catheter provided in an embodiment of the present application;

[0027] FIG5 is a schematic end view of a basket provided in an embodiment of the present application;

[0028] FIG6 is a schematic cross-sectional view of a filter screen provided in an embodiment of the present application;

[0029] FIG7 is a schematic diagram of a filter screen provided in an embodiment of the present application;

[0030] FIG8 is a partial schematic diagram of a wall-adhering protective umbrella provided in an embodiment of the present application.

[0031] In the picture:

[0032] 1. Wall-adhering umbrella; 11. Pushing unit; 111. First guidewire; 112. Catheter; 1121. Oblique incision; 1122. First tube section; 1123. Second tube section; 12. Basket; 121. Opening;

[0033] 2. Internal remover; 21. Delivery guidewire assembly; 211. Second guidewire; 212. Proximal spring; 22. Filter; 221. Mesh; 222. Proximal portion; 223. Distal portion; 224. Connection; 225. Inner tube; 23. Distal spring; 24. Development ring;

[0034] 100, Y-shaped valve;

[0035] 3. Suction catheter. DETAILED DESCRIPTION

[0036] The following is a further description of the technical solutions of the embodiments of the present application in conjunction with the accompanying drawings. The embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of this application.

[0037] In the description of this application, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0038] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first feature being in direct contact with the second feature, or may include the first feature being in contact with the second feature through another feature between them instead of being in direct contact. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0039] As shown in Figures 1, 2 and 8, this embodiment provides a distal thrombus remover, which is used in conjunction with the suction catheter 3. The distal thrombus remover includes a wall-adherent protective umbrella 1 and a built-in remover 2. The wall-adherent protective umbrella 1 includes a pushing unit 11 and a basket 12. The first end of the basket 12 is connected to the pushing unit 11, and the second end is provided with an opening 121. The pushing unit 11 is tubular. The wall-adherent protective umbrella 1 can be located at the distal end of the suction catheter 3, and the basket 12 is provided on the side of the pushing unit 11 away from the suction catheter 3. The basket 12 is configured to capture thrombi. The built-in remover 2 can penetrate the wall-adherent protective umbrella 1 and can extend out of the opening 121. The built-in remover 2 is configured to cut and remove thrombi to clear the distal end of the suction catheter 3 and its adjacent areas.

[0040] The meaning of proximal or distal is a concept of relative position with respect to the operator. Relatively speaking, the position closer to the operator is the proximal end, and the position farther from the operator is the distal end.

[0041] During use, the wall-adhering protective umbrella 1 is located at the distal end of the suction catheter. Due to the setting of the tubular pushing unit 11, the suction catheter always remains in a conductive state. When the suction catheter is working, since the basket 12 at the distal end of the wall-adhering protective umbrella 1 is unfolded at the distal end, when the distal end of the suction catheter and the adjacent blood vessel area are blocked, the built-in remover 2 can be pushed toward the distal end of the suction catheter to the opening 121 extending from the wall-adhering protective umbrella 1 to cut and remove the blocked thrombus. At this time, if the thrombus escapes, the escaped thrombus can be captured and intercepted by the basket 12, thereby restoring the access to the distal blood vessel. After the operation is completed, the surgeon can withdraw and remove the wall-adhering protective umbrella 1 and the built-in remover 2 together. The thrombus can be cleared and intercepted while the suction catheter remains in a predetermined position without being withdrawn from the body, avoiding the situation where suction cannot be performed, allowing the operation to proceed smoothly and reducing the difficulty of treatment.

[0042] As shown in Figures 1 and 3, in one embodiment, the pushing unit 11 includes a first guide wire 111 and a catheter 112, both of which are attached to the inner wall of the blood vessel, wherein the first guide wire 111 plays a pushing role, and the catheter 112 is connected between the first guide wire 111 and the basket 12. When used in conjunction with the suction catheter 3, as shown in Figure 2, the first guide wire 111 of the wall-adhering protective umbrella 1 is pushed, and the wall-adhering protective umbrella 1 enters the suction catheter 3 from the Y-shaped valve 100. At this time, the outer side of the pushing unit 11 is attached to the inner wall of the suction catheter 3 and can run inside the suction catheter 3. Continue to push the first guide wire 111, pre-place the wall-adhering protective umbrella 1 into the distal end of the suction catheter 3, and the basket 12 is extended from the distal end of the suction catheter 3 and released to expand, and the suction catheter 3 performs suction work. An oblique cut 1121 is provided at one end of the catheter 112 away from the basket 12. Since the wall protection umbrella 1 is provided with the oblique cut 1121, the wall protection umbrella 1 will not cause blood flow obstruction when passing through the Y-shaped valve 100, thereby reducing surgical risks.

[0043] As shown in Figures 1 and 7, the internal remover 2 includes a sequentially connected delivery guidewire assembly 21, a filter 22, and a distal spring 23. The distal spring 23 is configured as a dredging guide. The distal spring 23 can pass through the thrombus and play a guiding role, facilitating the subsequent removal of the thrombus. The delivery guidewire assembly 21 includes a second guidewire 211 and a proximal spring 212. The proximal spring 212 connects the second guidewire 211 and the filter 22. The proximal spring 212 is supported by the pushing unit 11. The proximal spring 212 is supported by the inner wall of the catheter 112. The proximal spring 212 plays a supporting role to ensure the stable cooperation between the internal remover 2 and the wall-adhering protective umbrella 1.

[0044] When the distal end of the suction catheter 3 is blocked, the operator pushes the second guide wire 211 from the proximal end and sends the built-in remover 2 into the blocked distal end of the suction catheter 3. At this time, the distal spring 23 passes through the blockage and continues to push the built-in remover 2 to the distal end. The filter 22 reaches the blockage and cuts by pushing and pulling the second guide wire 211 to restore negative pressure suction or cover and remove the thrombus. During this process, thrombus escape may occur. Since a basket 12 is set at the distal end of the suction catheter 3, the broken thrombus will be captured by the basket 12 of the wall-adhering protective umbrella 1. By retracting the second guide wire 211, the built-in remover 2 covering the thrombus can be withdrawn outside the body; by retracting the first guide wire 111, the basket 12 closes centripetally, pushing the captured broken thrombus toward the tube mouth of the suction catheter 3 and withdrawing it out of the body through negative pressure, ensuring smooth suction during the operation and no thrombus escape. After the suction is completed, the basket 12 is withdrawn to the proximal end of the suction catheter 3, and the Y-shaped valve 100 is grasped and withdrawn. The wall-adhering protective umbrella 1 can be withdrawn out of the body together with the suction catheter 3.

[0045] When performing interventional treatment for peripheral vascular embolism, the wall-adherent protective umbrella 1 and the built-in remover 2 are compressed and placed in the introduction sheath, as shown in Figure 1: the introduction sheath is pushed to the distal position of the thrombus, the introduction sheath and the second guide wire 211 are retracted, and at the same time, the first guide wire 111 is kept stationary, the basket 12 of the wall-adherent protective umbrella 1 is decompressed and expanded, and then the introduction sheath and the second guide wire 211 are retracted to the thrombus, the second guide wire 211 is kept stationary, and the introduction sheath is continued to be retracted, and the built-in remover 2 is decompressed and released to wrap the thrombus; after completing the interventional treatment, the second guide wire 211 is first retracted to retract the built-in remover 2 into the introduction sheath, and then the first guide wire 111 is retracted to retract the wall-adherent protective umbrella 1 into the introduction sheath, and finally the sheath is withdrawn from the body, and the operation is completed. The wall-adherent protective umbrella 1 and the built-in remover 2 of the present application are assembled in the manner shown in FIG1 , so that the built-in remover 2 is accommodated in the pushing unit 11 of the wall-adherent protective umbrella 1. When the instrument is pushed to the thrombus lesion, the built-in remover 2 and the wall-adherent protective umbrella 1 can reach the thrombus at the same time, and then be released by controlling the corresponding guide wire, which greatly shortens the operation time and makes the operator's operation easier.

[0046] The first guide wire 111 and the catheter 112 are an integral structure or a split structure. When the structures are split, the first guide wire 111 can be plugged into the inner wall of the catheter 112. The outer diameter of the catheter 112 is slightly smaller than the inner diameter of the suction catheter 3, which is convenient for pushing. Among them, the commonly used materials for the first guide wire 111 are nickel titanium, stainless steel, platinum tungsten, platinum iridium, platinum nickel, platinum, gold, tantalum, tungsten, polyether ether ketone (Poly Ether-Ether-Ketone, PEEK), polyamide (Polyamides, PA), polyethylene (Polyethylene, PE), polytetrafluoroethylene (Polytetrafluoroethylene, PTFE), etc., which can provide sufficient support, pushing properties, and good flexibility. The commonly used materials for the catheter 112 can be stainless steel and nickel titanium, etc.

[0047] As shown in Figures 1, 3, and 4, catheter 112 includes a first tube portion 1122 and a second tube portion 1123 connected to each other. First tube portion 1122 is elastic, and second tube portion 1123 is provided with an oblique cutout 1121. For example, first tube portion 1122 is a spring-wound structure braided from stainless steel wire to ensure good flexibility at the distal end. Second tube portion 1123 is made of a polymer material, which provides good support and facilitates the creation of oblique cutout 1121 during manufacture.

[0048] The inner side of catheter 112 is provided with an inner membrane layer (not shown) to enhance lubricity and permeability. The inner membrane layer is made of polytetrafluoroethylene (PTFE). The outer side of catheter 112 is provided with an outer tube layer (not shown). The outer tube layer is coated with a polymer to enhance smoothness and facilitate instrument delivery.

[0049] As shown in Figures 1, 3, and 5, the basket 12 is made of a memory alloy, including but not limited to nickel-titanium alloy. The basket 12 is connected to the spring structure of the catheter 112 and can radially contract and expand. When located within the suction catheter 3, it is constrained by the suction catheter 3 and in a radially contracted state. When located at the distal end of the suction catheter 3, the basket 12 expands, conforming to the inner wall of the blood vessel. The opening 121 is closed, facilitating the capture of thrombi. Optionally, the basket 12 can be shaped like a petal, as shown in Figure 8, with the largest outer diameter in the middle. This allows the basket 12 to deform according to the size of the blood vessel inner wall, ensuring that the outer side of the basket 12 conforms to the inner wall of the blood vessel, further preventing thrombus escape. Furthermore, the opening 121 at the distal end of the basket 12 is a closed structure. Combined with the woven mesh of the basket 12, the basket 12 can be retracted and closed, pushing the captured thrombus toward the center for suction.

[0050] The filter 22 is configured to cut and remove blood clots. The filter 22 cuts the blood clots and assists with suction. The filter 22 is provided with mesh holes 221, through which blood clots enter the filter 22. The filter 22 collects the blood clots and removes them to the body, thereby restoring access to the blood vessels. The mesh holes 221 are quadrilateral holes.

[0051] The proximal spring 212 is longer than the distal spring 23, and its outer diameter is larger than that of the distal spring 23. This provides better support for the proximal spring 212, allowing the instrument to be delivered into the distal passageway. The distal spring 23 is highly flexible, adapting to tortuous blood vessels and ensuring effective dredging. Both ends of the proximal spring 212 are secured to the second guidewire 211. Materials for the proximal spring 212 include, but are not limited to, materials with good plasticity, such as stainless steel. Materials for the distal spring 23 include, but are not limited to, materials with imaging properties, such as platinum tungsten and platinum iridium, enabling full-length imaging.

[0052] The second guide wire 211 includes but is not limited to nickel titanium, stainless steel, platinum tungsten, platinum iridium, platinum nickel, platinum, gold, tantalum, tungsten, PEEK, PA, PE, PTFE and other materials that can provide sufficient support, pushability and good flexibility. There is a hydrophilic coating on the proximal outer surface of the second guide wire 211.

[0053] The end of the distal spring 23 away from the filter 22 is a smooth surface to ensure that the distal spring 23 does not damage the blood vessel. Optionally, the end surface of the distal spring 23 is a semi-sphere, or can be other relatively smooth shapes without sharp corners, without limitation.

[0054] As shown in Figures 1 and 6, the filter 22 is made of a shape memory alloy, including but not limited to nickel-titanium, iron alloy, and other alloy materials with shape memory properties and sufficient strength. The filter 22 can be radially contracted and expanded. When the internal remover 2 is pushed, the filter 22 is in a contracted state. When the internal remover 2 is in place, the filter 22 is expanded. The internal remover 2 is introduced through an introduction sheath. The filter 22 is in a contracted state when it is in the introduction sheath. When it is pushed to the wall-adhering protective umbrella 1, the introduction sheath is withdrawn, at which point the filter 22 is released and expands. The filter 22 is laser cut and heat-set and surface-treated.

[0055] Optionally, the first end of the filter 22 is fixed to the delivery guidewire assembly 21, and the second end is capable of sliding along the centerline of the delivery guidewire assembly 21. The filter 22 can converge inward toward the centerline and expand outward away from the centerline. The filter 22, distal spring 23, and proximal spring 212 are co-centered. The filter 22 is fixed to the proximal spring 212, and the distal end of the filter 22 can move along the centerline, resulting in a more compact structure.

[0056] As shown in FIG7 , in one embodiment, the filter 22 includes a proximal portion 222 and a distal portion 223. The proximal portion 222 is a curved surface, while the distal portion 223 is a conical surface. The proximal and distal portions 222 and 223 are smoothly connected, and the outer diameter of the connection 224 between the proximal and distal portions 222 and 223 is larger than the outer diameters at either end of the filter 22. The distal end of the filter 22, or the distal portion 223, is configured to absorb thrombi and has a small outer diameter for ease of movement. The middle portion, or the connection 224, has a larger outer diameter, which facilitates the collection of thrombi into the proximal portion 222 of the filter 22. In another embodiment, the filter 22 has an ellipsoidal shape when deployed. By employing the filter 22 structure with a small outer diameter at both ends and a large outer diameter in the middle, thrombi are more easily captured.

[0057] Optionally, an inner tube 225 is provided within the filter 22. The inner tube 225 and the filter 22 are co-centered and can be extended or shortened. The proximal end of the inner tube 225 is fixed to the proximal end of the filter 22, while the distal end of the inner tube 225 is movable relative to the distal spring 23. This allows the filter 22 to have different cross-sectional widths when deployed, allowing it to accommodate wall-adhering umbrellas 1 of different specifications.

[0058] A developing ring 24 is provided in the filter 22 at the proximal end (first end) facing the conveying guide wire assembly 21. The outer diameter of the developing ring 24 is larger than the inner diameter of the proximal end (first end) of the filter 22, so that the first end of the filter 22 is clamped between the developing ring 24 and the conveying guide wire assembly 21, which can prevent the proximal end of the filter 22 from falling off and displacing, thereby improving the connection reliability. The developing ring 24 is sleeved and fixed on the inner tube 225.

[0059] The basket 12 is provided with at least four developing points, and a developing ring 24 is provided between the basket 12 and the catheter 112. The developing points and the developing ring 24 are positioning and developing structures to ensure that the instrument reaches the target point.

Claims

1. A distal thrombus removal device, comprising: An adherent protection umbrella (1), comprising a pushing unit (11) and a wire basket (12). The first end of the wire basket (12) is connected to the pushing unit (11), and the second end is provided with an opening (121). The pushing unit (11) is tubular. The adherent protection umbrella (1) is arranged to be able to be located at the distal end of the aspiration catheter (3), and the wire basket (12) is arranged on the side of the pushing unit (11) facing away from the aspiration catheter (3). The wire basket (12) is arranged to capture thrombus; An internal removal device (2), arranged to be able to penetrate through the adherent protection umbrella (1) until it extends out of the opening (121). The internal removal device (2) is arranged to cut and remove thrombus to dredge the second end of the aspiration catheter (3) and the adjacent area of the aspiration catheter (3).

2. The distal thrombus removal device according to claim 1, wherein The pushing unit (11) comprises a first guide wire (111) and a catheter (112). The catheter (112) is connected between the first guide wire (111) and the wire basket (12). One end of the catheter (112) facing away from the wire basket (12) is provided with an inclined cut (1121).

3. The distal thrombus removal device according to claim 2, wherein, The catheter (112) comprises a first pipe portion (1122) and a second pipe portion (1123) which are connected to each other. The first pipe portion (1122) has elasticity, and the second pipe portion (1123) is provided with the inclined cut (1121).

4. The distal thrombus removal device according to claim 3, wherein, The first pipe portion (1122) is a coil spring structure, and the second pipe portion (1123) is a polymer material structure.

5. The distal thrombus removal device according to claim 2, wherein, The catheter (112) is arranged in at least one of the following situations; The inner side of the catheter (112) is provided with an inner membrane layer; The outer side of the catheter (112) is provided with an outer pipe layer.

6. The distal thrombus removal device according to claim 1, wherein, The wire basket (12) is made of a shape memory alloy material. The wire basket (12) can be radially constricted and expanded, and the opening (121) is a closed end.

7. The distal thrombus removal device according to any one of claims 1-6, wherein, The internal removal device (2) comprises a delivery guide wire assembly (21), a filter screen (22) and a distal spring (23) which are connected in sequence. The distal spring (23) is arranged for dredging and guiding, and the filter screen (22) is arranged to cut and remove thrombus.

8. The distal thrombus removal device according to claim 7, wherein, The delivery guide wire assembly (21) comprises a second guide wire (211) and a proximal spring (212). The proximal spring (212) connects the second guide wire (211) and the filter screen (22). The proximal spring (212) is supported on the pushing unit (11). The length of the proximal spring (212) is greater than the length of the distal spring (23), and the outer diameter of the proximal spring (212) is greater than the outer diameter of the distal spring (23).

9. The distal thrombus removal device according to claim 7, wherein, The filter screen (22) is made of a shape memory alloy material. The first end of the filter screen (22) is fixed to the delivery guide wire assembly (21), and the second end can slide along the center line of the delivery guide wire assembly (21). The filter screen (22) can constrict inward towards the center line and expand around the center line away from the center line.

10. The distal thrombus removal device according to claim 7, wherein, One end of the distal spring (23) facing away from the filter screen (22) is a smooth surface.

11. The distal thrombus removal device according to claim 7, wherein, A developing ring (24) is provided at a first end of the filter screen (22) facing the wire delivery assembly (21). The outer diameter of the developing ring (24) is greater than the inner diameter of the first end of the filter screen (22), so that the first end of the filter screen (22) is clamped between the developing ring (24) and the wire delivery assembly (21).

12. The distal thrombus removal device according to claim 7, wherein, The wire basket (12) is provided with at least four developing points, and a developing ring (24) is provided between the wire basket (12) and the catheter (112).

13. The distal thrombus removal device according to claim 7, wherein, The material of the distal spring (23) is a developing material.

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