Syringe design for circulating particulate suspensions

Abstract

The present invention relates to a syringe comprising: a syringe barrel having an open proximal end leading into an interior, the interior having a cylindrical wall and an angled distal surface terminating in an outlet; a plunger rod; and a plunger seal, a proximal end of the plunger seal configured to be attached to a distal end of the plunger rod, and a distal end of the plunger seal configured to be inserted through the open proximal end into the interior of the syringe barrel, the plunger seal forms a seal with the cylindrical wall of the interior of the syringe barrel, and the distal end of the plunger seal terminates at an angled distal surface, wherein the angled distal surface of the syringe barrel is sharper than the angled distal surface of the plunger seal. The invention also relates to a kit comprising such a syringe.

Description

Cross - Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 410,164, filed on September 26, 2022, the disclosure of which is incorporated herein by reference. Field of the Invention

[0002] The present invention generally relates to syringes, and particularly to syringes that are specifically configured for circulating particulate suspensions. Background Art

[0003] In known systems, fluid is circulated back and forth between two syringes, where the two syringes are connected together by a connector that fluidly couples the two syringes. For example, the fluid can be circulated back and forth to thoroughly mix the fluid.

[0004] The inventors have observed that when a particulate suspension is circulated back and forth between typical off-the-shelf syringes, the particulate suspension can migrate between the plunger seal and the syringe barrel, where the particulate suspension ends up on the plunger rod or inside the barrel.

[0005] Given these considerations, improvements to the present invention may be useful. Summary of the Invention

[0006] A summary of the present invention is given to aid understanding, and those skilled in the art will understand that aspects and features of the present invention can in some cases be advantageously used alone or in other cases in combination with other aspects and features of the present invention. Inclusion or exclusion of elements, components, etc. in this summary is not intended to limit the scope of the claimed subject matter. Thus, while the present invention is presented in terms of aspects or embodiments, it should be understood that individual aspects can be claimed separately or in combination with aspects and features of that embodiment or any other embodiment.

[0007] In various aspects, the present invention relates to a syringe that includes: (a) a syringe barrel having an open proximal end and a distal end including an outlet, the open proximal end of the syringe barrel leading to an interior that includes a cylindrical wall and an angled distal surface that terminates at the outlet, where the syringe barrel has an inner diameter; (b) a plunger rod having a proximal end and a distal end; and (c) a plunger seal having a proximal end and a distal end, the proximal end of the plunger seal being configured to attach to the distal end of the plunger rod, and the distal end of the plunger seal being configured to be inserted through the open proximal end into the interior of the syringe barrel, the plunger seal forming a seal with the cylindrical wall of the interior of the syringe barrel, the distal end of the plunger seal terminating at an angled distal surface, where the angled distal surface of the syringe barrel is sharper than the angled distal surface of the plunger seal.

[0008] In some embodiments, the distal surface of the plunger seal is in the form of a right circular cone having a first angle, and the angled distal surface of the syringe barrel is in the form of a frustum of a right circular cone having a second angle, wherein the first angle is less than the second angle. In some of these embodiments, the difference between the first angle and the second angle can range from 2° to 8°. In some of these embodiments, the first angle can range from 120° to 160°. In some of these embodiments, the second angle can range from 122° to 168°.

[0009] In some embodiments that can be used in combination with the above aspects and embodiments, the plunger seal includes a proximal rib having a first outer diameter and a distal rib having a second outer diameter, wherein the first outer diameter is greater than the second outer diameter. In some of these embodiments, the ratio of the first outer diameter to the second outer diameter ranges between 1.02:1 and 1.07:1. In some of these embodiments, the ratio of the first outer diameter to the inner diameter of the syringe barrel ranges between 1.10:1 and 1.05:1. In some of these embodiments, the proximal rib includes a proximally facing surface having a first slope and a distally facing surface having a second slope, wherein the first slope is greater than the second slope. In some of these embodiments, the plunger seal further includes one or more additional ribs between the proximal rib and the ribs.

[0010] In some embodiments that can be used in combination with the above aspects and embodiments, the proximal end of the plunger seal is provided with a threaded hole, and the distal end of the plunger rod is provided with a matching thread.

[0011] In some embodiments that can be used in combination with the above aspects and embodiments, a plunger flange is provided at the proximal end of the plunger rod, and a barrel flange is provided at the proximal end of the syringe barrel.

[0012] In some embodiments that can be used in combination with the above aspects and embodiments, the plunger seal is formed of an elastomer selected from elastomeric bromobutyl rubber, chlorobutyl rubber, elastomeric fluoropolymer, ethylene propylene diene monomer (EPDM), and ethylene propylene rubber (EPR).

[0013] In some embodiments that can be used in combination with the above aspects and embodiments, the plunger seal includes a low friction surface layer, such as a fluoropolymer surface layer.

[0014] Other aspects of the present invention relate to kits that include (a) a first syringe and a second syringe according to any one of the above aspects and embodiments, and (b) a connector that fluidly connects the outlet of the first syringe to the outlet of the second syringe.

[0015] In some embodiments, the first syringe is pre-filled with a particulate suspension. In some of these embodiments, the particulate suspension includes metal or polymer particles. In some of these embodiments, the particulate suspension includes a liquid embolic composition.

[0016] These and other features and advantages of the invention will become apparent from the following detailed description, and the scope of the claimed invention is set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and, together with the description, serve to explain the principles of the invention.

[0018] Figure 1A is a schematic view of a syringe design according to the invention.

[0019] Figure 1B is in contrast to Figure 1A a schematic view of a syringe design that is in contrast to the syringe design of

[0020] Figure 2A is a schematic longitudinal cross-sectional view of a syringe barrel according to an embodiment of the invention. Figure 2B is Figure 2A an enlarged view of region B in

[0021] Figure 3 is a schematic view of a plunger according to an embodiment of the invention.

[0022] Figure 4A is a schematic longitudinal cross-sectional view of a plunger seal according to an embodiment of the invention.

[0023] Figure 4B is a schematic longitudinal cross-sectional view of a plunger seal according to another embodiment of the invention.

[0024] Figure 5A is a schematic view of a right circular cone.

[0025] Figure 5B is a schematic view of a frustum of a right circular cone.

[0026] Figure 6 is a schematic view of two syringes employing a coupling arrangement according to the prior art.

[0027] While the invention is susceptible to various modifications and alternative forms, specific details thereof have been shown by way of example in the drawings and will be described in more detail. It should be understood, however, that the invention is not intended to limit the various aspects of the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION

[0028] The present invention will now be described with reference to an exemplary medical system that can be used in endovascular and endoscopic medical procedures. However, it should be noted that the reference to this particular procedure is provided for convenience only and is not intended to limit the present invention. Those of ordinary skill in the art will recognize that the concepts upon which the disclosed devices and associated methods of use are based can be used in any suitable procedure, medical or otherwise. The present invention can be understood with reference to the following description and drawings, in which like or similar reference numerals will be used to refer to like or similar parts.

[0029] The term "distal" refers to the part that is furthest from the user when the device is introduced into the patient's body. Conversely, the term "proximal" refers to the part that is closest to the user when the device is placed in the patient's body. As used herein, the terms "comprising," "including," or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not necessarily include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term "exemplary" is used in the sense of "an example" rather than "a model." Additionally, as used herein, the terms "about," "substantially," and "essentially" denote a numerical range within + / - 10% of the stated value or the implied value. Additionally, terms indicating component / surface geometry refer to both the exact shape and approximate shape.

[0030] It should be noted that references to "one embodiment," "some embodiments," "other embodiments," etc., indicate that the described embodiments may include certain features, structures, or characteristics, but each embodiment may not necessarily include that particular feature, structure, or characteristic. Moreover, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described, unless explicitly stated to the contrary. That is, the various individual elements described below, even if not explicitly shown in a particular combination, can still be considered combinable or arranged with each other to form other additional embodiments, or to supplement and / or enrich the described embodiments, as will be understood by those of ordinary skill in the art.

[0031] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in the sense including "and / or" unless the context clearly dictates otherwise.

[0032] In various aspects, the present invention relates to a syringe design that exhibits improved handling of particulate suspensions.

[0033] Now turning to Figure 1A , according to one embodiment of the present invention, syringe 100 is shown as being composed of a syringe barrel 110, a plunger 120, and a plunger seal 130. The syringe barrel 110 has an open proximal end 110o and a distal end including an outlet 110e. The open proximal end 110o of the syringe barrel 110 leads to an interior 110i having a cylindrical wall 110w and an angled distal surface 110d. The plunger 120 includes a plunger rod 120r having a proximal end and a distal end. A plunger flange 120f is located at the proximal end of the plunger rod 120r. The plunger seal 130 is located at the distal end of the plunger rod 120r. The plunger seal 130 has a proximal end and a distal end. The proximal end 130p of the plunger seal 130 is attached to the distal end of the plunger rod 120r. The plunger seal 130 is inserted into the interior 110i of the syringe barrel 110 through the open distal end 110o of the syringe barrel. The plunger seal 130 forms a seal with the cylindrical wall 110w of the syringe barrel 110. The distal end of the plunger seal 130 terminates in an angled distal surface 130d.

[0034] Now will be described in conjunction with Figure 2A , Figure 2B , Figure 3 , Figure 4A and Figure 4B a more detailed embodiment of a syringe composed of a syringe barrel 210, a plunger 220, and a plunger seal 230. Figure 2A is a schematic longitudinal cross-sectional view of a syringe barrel 210 according to one embodiment of the present invention. Figure 2B is Figure 2A an enlarged view of region B in Figure 2B . The illustrated syringe barrel 210 has an open proximal end 210o and a distal end including an outlet 210e having a threaded outlet port 210t. The open proximal end 210o of the syringe barrel 210 leads to an interior 210i having a cylindrical wall 210w and an angled distal surface 210d. As Figure 2B shown Figure 5B , the angled distal surface 210d takes the form of a partial conical surface, particularly the surface of a frustum of a right circular cone. The distal surface 210d terminates at the outlet 210e. When viewed in a longitudinal cross-section taken along the axis A - A' of the syringe barrel 210, the angled distal surface 210d has an angle α1. As can be seen by comparing Figure 2B and Figure 5B , the first cross-sectional angle α1 is twice the half-angle α of the frustum of the right circular cone of the angled distal surface 210d.

[0035] The total length L1 of the syringe barrel 210 and the length L2 of the interior 210i of the syringe barrel 210 can vary widely. In some embodiments, the total length L1 can range, for example, from 1.5 inches (3.81 cm) to 6 inches (15.2 cm), and the length L2 can range, for example, from 1.1 inches (2.79 cm) to 5.6 inches (14.2 cm). Similarly, the inner diameter D1 of the interior 210i of the syringe barrel 210 and the inner diameter D3 of the outlet 210e can vary widely. In some embodiments, the diameter D1 can range, for example, from 0.25 inches (0.64 cm) to 1.5 inches (3.81 cm). The outer diameter D2 of the syringe barrel 210 will be slightly larger than D1 and will vary based on material properties and the ability to form deep-drawn thin-walled parts.

[0036] Figure 3 FIG. 4 is a schematic view of an embodiment of a plunger 220 according to an embodiment of the present invention. The plunger 220 includes a plunger rod 220r having a proximal end and a distal end. A plunger flange 220f is located at the proximal end 220p of the plunger rod 220r. A distal portion 220t of the plunger that engages the plunger seal 230 is located at the distal end 220d of the plunger rod 220r. Although not explicitly shown, the distal portion 220t can be threaded to engage complementary threads in a hole in the plunger seal 230, as described below.

[0037] Figure 4A FIG. 8 is a schematic longitudinal cross-sectional view of a plunger seal 230 according to an embodiment of the present invention. The plunger seal 230 has a proximal end 230p and a distal end that terminates in an angled distal surface 230d. The proximal end 230p of the plunger seal 230 is configured to attach to the distal end 220d of the plunger rod 220r. In the embodiment shown, the proximal end 230p of the plunger seal 230 is provided with a threaded hole 230t. Although not specifically shown in Figure 3 FIG. 10, the distal end 220d of the plunger rod 220 can be provided with threads 220t to match the threads of the threaded hole 230t.

[0038] Figure 4A The plunger seal 230 of FIG. 14 is configured to be inserted through the open proximal end 210o of the syringe barrel 210 Figure 2A and Figure 2B into the interior 210i of the syringe barrel 210 shown in FIG. 18. The plunger seal 230 forms a seal with the cylindrical wall 210w of the syringe barrel 210. The distal end of the plunger seal 230 terminates in an angled distal surface 230d. As shown in Figure 4AAs shown, the angled distal surface 230d takes the form of a conical surface, specifically the surface of a right circular cone. When viewed in a longitudinal cross-section taken along the axis A-A' of the plunger seal 230, the angled distal surface 230d has an angle α2. As can be seen by comparing Figure 4A and Figure 5A the first cross-sectional angle α2 is twice the half-angle α of the right circular cone of the angled distal surface 230d.

[0039] Figure 4A The plunger seal 230 in the embodiment of

[0040] also includes three plunger seal ribs: a distal plunger seal rib 230r1, a middle plunger seal rib 230r2, and a proximal plunger seal rib 230r3. Although one central plunger seal rib 230r2 is shown, there may also be zero, two, three, or more central plunger seals.

[0040] The syringe shown above is particularly suitable for ejecting a particulate suspension from a syringe barrel. Numerous particulate suspensions are known in a wide variety of fields in which the syringe of the present invention can be used. However, a specific application will now be described that involves an injectable composition comprising a suspension containing, for example, metal radiopaque particles (e.g., tantalum, palladium, or gold) or polymer radiopaque particles (e.g., polymer particles containing covalently bound iodine atoms). A specific example is a liquid embolization composition in the form of a particulate suspension containing tantalum particles in a pre-filled syringe. The particles of such a particulate suspension tend to settle when at rest. One way to homogenize the particulate suspension is to use a connector to connect an empty syringe to a pre-filled syringe, the connector having a cavity extending therethrough, which connects the outlets of the two syringes together in an arrangement similar to that shown in FIG. 6. Once connected, the particulate suspension can be circulated or "reciprocated" between the two syringes. This arrangement can significantly improve the convenience of homogenization.

[0041] The inventors have found that typical off-the-shelf plungers and syringe barrels are effective in containing particulate suspensions and preventing leakage during autoclaving and storage. However, when the particulate suspension is circulated between syringes, it has been observed that the particulate suspension migrates proximally between the plunger seal and the syringe barrel and ultimately ends up on the plunger rod or inside the barrel. The present invention provides a number of innovations to address this deficiency.

[0042] One innovation that has been found to reduce the migration of particulate suspensions past the plunger seal 230 is to ensure that the angle α1 of the angled distal surface 210d of the syringe barrel 210 is less than the angle α2 of the angled distal surface 230d of the plunger seal 230. When the plunger seal 230 bottoms out in the syringe barrel 210, this will force the particulate suspension to the top of the syringe rather than simply compressing it or forcing it to move towards the plunger seal 230.

[0043] This can be seen again by referring to Figure 1A and Figure 1B In Figure 1A , the angle of the angled distal surface 110d of the syringe barrel 110 is less than the angle of the angled distal surface 130d of the plunger seal 130. As shown by the arrows in Figure 1A , this difference in angles is used to push distally towards the outlet 110e of the syringe barrel 110 all of the contents present in the syringe barrel 110.

[0044] Except that the angle of the angled distal surface 110d of the syringe barrel 110 is greater than the angle of the angled distal surface 130d of the plunger seal, Figure 1B it is Figure 1A the same as. When pushing distally towards the outlet 110e of the syringe barrel 110 most of the contents present in the syringe barrel 110, as shown by the arrows in Figure 1B , a portion of the fluid (or fluid suspension) present in the syringe 100 is pushed proximally towards the open proximal end 110o of the syringe barrel 110.

[0045] Referring again to Figure 2A , Figure 2B , Figure 3 , Figure 4A and Figure 4B , and specifically to Figure 2A , Figure 2B and Figure 4A , the angle α1 of the angled distal surface 210d of the syringe barrel 210 generally ranges from 120° to 160, advantageously from 132° to 152°. The angle α2 of the angled distal surface a230d of the plunger seal 230d generally ranges from 122° to 168°, advantageously from 136° to 156°. The difference between the angle α1 and the angle α2 generally ranges from about 2° to 8°, advantageously from 3° to 5°. It should be noted that the angles α1 and α2 can vary to a greater extent for other reasons such as molding convenience and aesthetics.

[0046] Another innovation that has been found to reduce the movement of particulate suspensions past the plunger seal is the outer diameter of the most proximal rib (e.g., Figure 4AThe diameter D4 of the proximal plunger seal rib 230r3 is increased relative to the diameters of the remaining ribs (e.g., the diameters D5 of both the distal plunger seal rib 230r1 and the central plunger seal rib 230r2). This is used to increase the compression of the proximal plunger seal rib 230r3 within the syringe barrel 210, thereby giving a tighter seal. In some embodiments, the ratio of D4 to D5 can range, for example, from 1.02:1 to 1.07:1.

[0047] Relative to the inner diameter D1 of the syringe barrel 210, the ratio of D4 to D1 can range, for example, from 1.10:1 to 1.05:1, and the ratio of D5 to D1 can range, for example, from 1.08:1 to 1.03:1. These ratios are also referred to as compression ratios. The higher the compression ratio, the greater the friction (making it difficult to move the plunger seal), and the greater the tendency to deform the ribs, which can cause particles to leak outside the ribs. In various embodiments, the ribs have an outer surface curvature that includes a radius ranging from 0.012 inches (0.030 cm) to 0.025 inches (0.063 cm), more typically ranging from 0.015 inches (0.038 cm) to 0.02 inches (0.51 cm).

[0048] In a particular embodiment, the diameter D4 of the proximal plunger seal rib 230r3 can be 0.274 inches (0.696 cm), the diameters D5 of the distal plunger seal rib 230r1 and the intermediate plunger seal rib 230r2 can be approximately 0.266 inches (0.676 cm), and the diameter D1 of the syringe barrel 210 can be approximately 0.253 inches (0.643 cm).

[0049] Another innovation is the use of a so-called "swept-forward design" for the proximal plunger seal rib 230r3, which helps to push any material escaping from the distal plunger seal rib 230r1 (and any central plunger seal rib 230r2) towards the front of the syringe. In Figure 4BThis design can be seen in [Figure 0], where the plunger seal rib 230rB is asymmetric because the distal surface 230r3d of the proximal plunger seal rib 230r3 is provided with a first slope, and the proximal surface 230r3p of the proximal plunger seal rib 230r3 is provided with a second slope greater than the first slope. For example, relative to the proximal surface 230r3p of the proximal plunger seal rib 230r3, the distal surface 230r3d of the proximal plunger seal rib 230r3 may have increased concavity and / or increased undercut. In some embodiments, the proximal surface 230r3p of the proximal plunger seal rib 230r3 may have a linear taper. By providing a smaller slope or undercut for the proximal surface 230r3p of the proximal plunger seal rib 230r3, the tendency of the proximal plunger seal rib 230r3 to buckle can be minimized.

[0050] A variety of materials can be used to construct the plunger seal described herein. For example, the plunger seal can be formed using a suitable elastomer such as bromobutyl rubber, chlorobutyl rubber, elastomeric fluoropolymer, ethylene propylene diene monomer (EPDM), and ethylene propylene rubber (EPR). The plunger seal can be formed using methods known in the art. As an example, in a first step, the elastomer can be formulated in a rolling mill and the resulting sheet can be calendered. Then, a sheet is placed in a mold (e.g., a metal mold) and the plunger seal is made by compression molding, during which the elastomer is forced into the cavity of the mold and, if reactive, the elastomer undergoes a complete curing reaction. After the plunger seal is formed, the part can be post-processed, e.g., by removing flash and gate residues, and the part can optionally be cleaned and the part can undergo surface treatment, e.g., by optionally coating or surface treating the plunger seal with a fluoropolymer to reduce friction.

[0051] A variety of materials can be used to construct the syringe barrel described herein. Typical materials for constructing the syringe barrel described herein include plastics such as polycarbonate, polypropylene, polyethylene, nylon copolymers, copolyesters, polyurethanes, cyclic olefins, polymethylpentene; glass; metals such as stainless steel, and other materials known in the art. A variety of materials can be used to construct the plunger described herein. Typical materials for constructing the plunger described herein include rigid plastics (unfilled or reinforced with glass fibers or fillers, glass, metal, and other materials known in the art).

[0052] Other aspects of the present invention relate to kits comprising a syringe according to the present invention. For example, the kit may include an empty syringe according to the present invention and a syringe according to the present invention pre-filled with a particulate suspension. Examples of particulate suspensions vary widely as discussed previously. In one particular embodiment, the particulate suspension may be a suspension of radiopaque metal or polymer particles in an injectable composition, such as a liquid embolization composition. The kit may also include a connector for fluidly coupling the two syringes together. For example, the connector may include a first port configured to provide fluid connection to the outlet port of the empty syringe, a second port configured to provide fluid connection to the outlet port of the pre-filled syringe, and a cavity fluidly connecting the first and second ports. For example, the first and second ports may include coupling mechanisms, such as multiple threads, for coupling to the threaded outlet ports of the syringe barrels described herein.

[0053] The foregoing discussion has been presented for purposes of illustration and description and is not intended to limit the invention to the form disclosed herein. It should be understood that various additions, modifications, and substitutions may be made to the embodiments disclosed herein without departing from the concept, spirit, and scope of the invention. In particular, for those skilled in the art, the principles of the invention may be embodied in other forms, structures, arrangements, proportions, and with other elements, materials, and components without departing from its concept, spirit, or scope or characteristics.

[0054] The following claims are hereby incorporated by this reference into the detailed description, where each claim stands on its own as a separate embodiment of the present invention. In the claims, the term "comprising / including" does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these features may be advantageously combined, and the inclusion in different claims does not mean that the combination of features is not feasible and / or advantageous. Additionally, singular references do not exclude plural. The terms "a", "an", "first", "second", etc. do not exclude a plurality. Any reference signs in the claims are provided only as examples for clarification and should not be construed as limiting the scope of the claims in any way.

Claims

1. A syringe, comprising: a syringe barrel having an open proximal end and a distal end including an outlet, the open proximal end of the syringe barrel leading to an interior which includes a cylindrical wall and an angled distal surface terminating at the outlet, wherein the syringe barrel has an inner diameter; a plunger rod having a proximal end and a distal end; a plunger seal having a proximal end and a distal end, the proximal end of the plunger seal being configured to be attached to the distal end of the plunger rod, and the distal end of the plunger seal being configured to be inserted through the open proximal end into the interior of the syringe barrel, the plunger seal forming a seal with the cylindrical wall of the interior of the syringe barrel, the distal end of the plunger seal terminating at the angled distal surface; wherein the angled distal surface of the syringe barrel is sharper than the angled distal surface of the plunger seal.

2. The syringe according to claim 1, wherein the distal surface of the plunger seal is in the form of a right circular cone having a first angle, and wherein the angled distal surface of the syringe barrel is in the form of a frustum of a right circular cone having a second angle, wherein the first angle is less than the second angle.

3. The syringe according to claim 2, wherein the difference between the first angle and the second angle ranges from 2° to 8°.

4. The syringe according to any one of claims 1 to 3, wherein the plunger seal includes a proximal rib having a first outer diameter and a distal rib having a second outer diameter, wherein the first outer diameter is greater than the second outer diameter.

5. The syringe according to claim 4, wherein the ratio of the first outer diameter to the second outer diameter ranges from 1.02:1 to 1.07:

1.

6. The syringe according to claim 4 or claim 5, wherein the ratio of the first outer diameter of the syringe barrel to the inner diameter ranges from 1.10:1 to 1.05:

1.

7. The syringe according to any one of claims 4 to 6, wherein the proximal rib includes a proximally facing surface having a first slope and a distally facing surface having a second slope, wherein the first slope is greater than the second slope.

8. The syringe according to any one of claims 4 to 7, wherein the plunger seal further includes one or more additional ribs between the proximal rib and the distal rib.

9. The syringe according to any one of claims 1 to 8, wherein the proximal end of the plunger seal is provided with a threaded hole, and the distal end of the plunger rod is provided with a matching thread.

10. The syringe according to any one of claims 1 to 9, wherein a plunger flange is provided at the proximal end of the plunger rod, and a barrel flange is provided at the proximal end of the syringe barrel.

11. The syringe according to any one of claims 1 to 10, wherein the plunger seal includes a low friction surface layer.

12. A kit, comprising a first syringe and a second syringe according to any one of claims 1 to 11, and a connector fluidly connecting the outlet of the first syringe to the outlet of the second syringe.

13. The kit according to claim 12, wherein the first syringe is pre-filled with a particulate suspension.

14. The kit according to claim 12, wherein the particulate suspension comprises metal or polymer particles.

15. The kit according to claim 13 or 14, wherein the particulate suspension is a liquid embolization composition.

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