IN VIVO CROSSLINKING OF EMBOLIC HYDROGELS USING BIOORTHOGONAL CLICK CHEMISTRY

A crosslinked embolic hydrogel is disclosed, the crosslinked embolic hydrogel comprising a hydrophilic polymer functionalized with first reactive groups and a crosslinking agent functionalized with second reactive groups; wherein the first and second reacting groups comprise a biorthogonally reactive pair that react to form the crosslinked embolic hydrogel. Methods and systems are also disclosed.

FIELD OF THE INVENTION

The present disclosure relates generally to crosslinked embolic hydrogels, methods, and systems.

BACKGROUND

Numerous embolization products have been developed, both for interventional oncology, as well as treatment of aneurysms. These embolization products often include coils that can be delivered relatively easily into large blood vessels, but which often do not embolize large vessels efficiently or completely. Alternatively, embolic plugs have been created for large vessels, but can be difficult to deliver. Similarly, for smaller vessels or arterio-venous malformations (AVMs) it can be difficult to embolize using either coils or plugs due to the small and/or complex nature of the embolization target. Therefore, a need exists for embolization improvements, both for large and small blood vessels.

SUMMARY

This disclosure is directed, in a first aspect, to a crosslinked embolic hydrogel, the crosslinked embolic hydrogel is formed from a hydrophilic polymer functionalized with first reactive groups and a crosslinking agent functionalized with second reactive groups; wherein the first and second reactive groups comprise biorthogonally reactive pairs that react to form the crosslinked embolic hydrogel.

In a second aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the first or second reactive groups include a plurality of amine groups, acid groups, and combinations thereof.

In a third aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or second reactive groups include an azide group.

In a fourth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or second reactive groups include an alkyne, tetrazine, fluorosydnones, or combinations thereof.

In a fifth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or the second reactive groups include a strained alkyne.

In a sixth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the first reactive groups and second reactive groups form a covalent bond when brought in contact with each other.

In a seventh aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the first and second reactive groups form a tri-azole ring upon reacting.

In an eighth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the hydrophilic polymer or the crosslinking agent are retained on an embolization coil.

In a ninth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the hydrophilic polymer or crosslinking agent are retained on microbeads.

In a tenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the hydrophilic polymer, the crosslinking agent, or both include branched polymers.

In an eleventh aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the hydrophilic polymer, the crosslinking agent, or both include non-branched polymers.

In a twelfth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, each of the hydrophilic polymer and crosslinking agent include at least two reactive groups.

In a thirteenth aspect, a method for forming a crosslinked embolic hydrogel is disclosed, the method includes providing a hydrophilic polymer functionalized with first reactive groups; and providing a crosslinking agent functionalized with second reactive groups; combining the hydrophilic polymer with the crosslinking agent such that the first and second reactive groups bound form a crosslinked embolic hydrogel.

In a fourteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or second reactive groups include a plurality of amine groups, acid groups, and combinations thereof.

In a fifteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or second reactive groups include an azide group, an alkyne, tetrazine, fluorosydnones, or combinations thereof.

In a sixteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the first or the second reactive groups include a strained alkyne.

In a seventeenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, the first and second reactive groups form a tri-azole ring upon reacting.

In an eighteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the hydrophilic polymer or the crosslinking agent are retained on an embolization coil.

In a nineteenth aspect, in addition to one or more of the preceding or following aspects, or in the alternative to some aspects, either the hydrophilic polymer or crosslinking agent are retained on microbeads.

In a twentieth aspect, a system for forming a crosslinked embolic hydrogel, the system having a hydrophilic polymer functionalized with first reactive groups; and a crosslinking agent functionalized with second reactive groups; the first and second reactive groups include a biorthogonally reactive pair.

DETAILED DESCRIPTION

This disclosure is directed, in a first aspect, to a crosslinked embolic hydrogel. the crosslinked embolic hydrogel is formed from a hydrophilic polymer functionalized with first reactive groups and a crosslinking agent functionalized with second reactive groups; wherein the first and second reactive groups comprise biorthogonally reactive pairs that react to form the crosslinked embolic hydrogel. Thus, the biorthogonally reactive pairs selectively react with one another to form the hydrogel.

In certain embodiments a two-part injectable in vivo crosslinking hydrogel is formed. In an example embodiment, a hydrophilic polymer is functionalized with biorthogonally reactive end groups and is made into a dilute aqueous solution. A crosslinking agent with corresponding biorthogonally reactive groups is also made. When the two are sequentially injected into the arterial vasculature of a patient they combine in the smaller blood vessel to form a crosslinked hydrogel, blocking blood flow. The hydrophilic polymer and crosslinking agent react to form a gel only where the two components combine with each other in concentrations high enough to form a crosslinked network (the gel point). Due to the bioorthogonality of the reaction, neither component will typically substantially react with anything else in the body other than its counterpart, offering high levels of chemo selectivity.

The hydrophilic polymers and crosslinking agents may have, for example, a branched or linear architecture, including stars, dendrites, combs, etc. Generally the average reactive functionality between the components is 2 or greater. In some implementations the average reactive functionality is greater than 2, greater than 3, greater than 4, or greater than 5. Optionally the average reactive functionality is less than 10, less than 9, less than 8, less than 7, or less than 6. In certain implementations the average functionality is from 2 to 10, from 3 to 8, from 4 to 7, or from 5 to 6. It will be understood that in some implementations, especially for large reactive bodies, the average functionality can be greater than 10.

The reactive groups can be, for example, an azide, alkyne, tetrazine, fluorosydnones, or combinations thereof. An azide group is particularly appropriate because it is small, metabolically stable, and does not naturally exist in cells. Thus, azide groups do not have major competing biological side reactions. An alkyne group is not as small, but it still has significant stability and bioorthogonality. Specific biorthogonal click pairings include, for example, strain-promoted azide-alkyne (SPAAC) click reactions; inverse electron-demand Diels-Alder (iEDDA) conjugations using tetrazine and either transcyclooctene, norbornene, or cyclopropane; and nitrile oxides to strained alkenes.

In some implementations either a hydrophilic polymer with a first reactive group or a crosslinking agent with a first reactive group is bonded to an embolic coil. The coil can be delivered so that it anchors in the target vessel and partially blocks the vessel. Thereafter a liquid containing the counterpart reactive group (either a crosslinking agent or a hydrophilic polymer with a second reactive group) is added. The first and second reactive groups react until gelling and embolization occurs.

It is alternatively possible to coat microbeads with a first reactive group so as to reduce the “set-up” time for forming the embolization and/or reduce the amount of hydrogel that must be formed. The presence of the microbeads reduces the volume of space to be filled by the hydrogel, and as such less hydrogel is needed. In an example embodiment the microbeads containing one reactive group of a reactive pair are delivered to a target (such as a cancerous tumor) and then a material (such as a hydrogel or other crosslinking agent) comprising the other reactive group of the reactive pair is added to the same location to crosslink the microbeads. In this manner the microbeads can be incorporated into a hydrogel and/or crosslinked with one another. Microbeads can be administered by way of a catheter or other application device. In an example embodiment microbeads are administered into a target zone via a catheter, and thereafter a crosslinking agent is administered via the catheter to bind the beads to one another and form a hydrogel securing the beads in place, thereby embolizing a target location.

In some implementations the microbeads are all the same size, while in other implementations the microbeads vary in size. For example, relatively large microbeads can be administered along with relatively small microbeads that can occupy the space between the relatively large microbeads, reducing the amount of hydrogel necessary. Also, microbeads can be administered in conjunction with other biorthogonal oligomers. For example, for smaller vessels alternate injections of small microbeads containing a first reactive group on the surface followed with injections of a second reactive group including biorthogonal oligomers molecules to bind microbeads together until desired embolization is achieved.

Referring now to the figures,FIG. 1is a schematic representation of biorthogonally reactive pairs secured to polymers and/or crosslinking agent. The biorthogonally reactive pair100includes a first reactive composition102and a second reactive composition104. First reactive composition102includes a first reactive group106and is secured to a base material110, such as a polymer (for example a hydrophilic polymer) or a crosslinker agent. The second reactive composition104includes a second reactive group108that is secured to a different base112, such as a polymer or crosslinking agent. The first reactive compositions102and second reactive composition104are shown schematically, and it will be appreciated that the figure does not show the chemical structure or relative size of the molecules or reactive groups.

In actual practice the base materials110,112, such as a hydrophilic polymer or a crosslinker agent, are typically much larger than the reactive groups106,108. Examples of suitable base materials110,112include, as mentioned above, various polymer components or various crosslinker components. The base materials110,112can be joined, using the click chemistry described herein, to form an embolic material, such as an embolic material to cut off blood flow to cancerous tumors, or an embolic material to fill an aneurism. The base material, besides being a polymeric composition, can include a substrate such as microbeads, coils, tubes or similar substrates. The use of microbeads, for example, is beneficial because the microbeads themselves will partially fill an area to embolized, and as such less of other materials are needed. In use, the microbeads are delivered to a target (such as a cancerous tumor) and then a material forming a reactive pair is added to the same location to crosslink with the microbeads. In this manner the microbeads can be incorporated into a hydrogel and/or crosslinked with one another. Similarly, an embolization coil used to fill a volume (such as an aneurism) can be coated with one part of a reactive pair. A material, typically a polymer with two or more matching reactive pairs on each molecule, is then delivered to the location where the coil has been placed, thereby crosslinking and filling gaps in the embolization coil. In this manner the relatively precise deliverability of the embolization coil is combined with the precise, localize reaction with a crosslinking material to form a seal that is less porous than the embolization coil alone.

The reactive groups106,108are selected so as to be biorthogonally reactive such that they readily react only with one another. However, when they are brought in contact with one another they readily form a covalent bond, which then binds the polymer or crosslinking agents110,112to one another. In the representation shown inFIG. 1the base materials110,112are shown as each containing only one reactive group106,108. Generally each base material110,112will be secured to more than one reactive group106,108so as to promote crosslinking of materials, not just reaction of materials. The presence of multiple reactive groups106,108(as discussed below with regard toFIG. 2) provides for a more robust crosslinking and gelling result. Multiple reactive groups106,108are also beneficial because they compensate for some reactive groups that do not react, such as those that are sterically hindered, while still allowing crosslinking to occur with the remaining reactive groups. It will be appreciated, however, that in some situations only one reactive group106,108is present, such as when the reactive groups are secured to a larger substrate, such as a microbead, in which case a multitude of reactive groups secured to the microbead performs similar to a very large polymer by allowing crosslinking between microbeads to occur or by allowing microbeads to be secured by covalent bonds within a hydrogel.

FIG. 2is a schematic representation of a first branched polymeric material214showing first biorthogonally reactive groups206secured to a polymeric backbone216. This figure is shown for representative purposes, and it will be understood that the polymeric backbone216can have multiple configurations. It will be appreciated that the polymeric material214can have (for example) a branched or linear architecture, including stars, dendrites, combs, etc. The reactive groups206are not reactive with one another, but rather primarily reactive only with biorthogonally reactive counterparts on a separate molecule. The two pairs of a biorthogonally reactive pair are typically not located on the same polymer otherwise they would react with themselves. The location of the reactive groups206can vary depending upon the type and size of the polymeric backbone216, such as being located at the end of branches of the backbone216, along the backbone216itself between the end of branches, or at both the ends of the branches and along the backbone.

FIG. 3is a schematic representation of a second branched polymeric material318showing second orthogonally reactive groups308. As was the case with reactive groups206ofFIG. 2, reactive groups308are not reactive with one another, but rather primarily reactive only with biorthogonally reactive counterparts on a separate molecule. Thus, the polymeric material214ofFIG. 2can react with the polymeric material318ofFIG. 3, but reactive groups206and polymeric material214do not react with themselves, and polymeric material318and reactive groups308do not react with themselves.

In the constructions shown inFIG. 2andFIG. 3the two polymer backbones, despite being schematic representations, are shown as approximately the same size, and as having the same approximate number of reactive groups. In some embodiments the two polymeric materials forming the two biorthogonal polymeric back bones will be approximately the same size, the same shape, and have approximately the same number of reactive groups. However, in other implementations the two polymer backbones will have different sizes, different shapes, and different numbers of reactive groups. For example, in an embodiment, a first component having a first reactive group will be on a much larger polymer backbone than a second component having a second reactive group. This difference in size can be used, for example, when it is desirable to place the first component in a target zone (such as the blood supply of a tumor or an aneurism), and to then administer a second component on smaller polymeric backbone. The benefit of the smaller polymeric backbone can be to promote penetration of the second smaller component deeper into the target zone so as to reach (and react with) as much of the first component as possible.

The shape of the polymeric backbones can also be selected to obtain desirable results. In some implementations a branching backbone is desired (such as shown inFIG. 2), in other implementations a star shaped construction is desired (such as shown inFIG. 3). Although these two constructions show multiple reactive groups on complex branched polymers, in the alternative the polymer can be unbranched and have just two reactive groups in an example construction. Further, it will be understood that multiple polymeric constructions can be used at once, such as having a first reactive group on a variety of different polymeric constructions (straight, star, branched, etc.). The variety of polymeric constructions can be beneficial in applications where voids of a variety of shapes and sizes are desired, such as blocking the blood vessels serving a tumor, in which case the vessels can vary substantially in size.

In addition, in some constructions it is desirable to have a greater number of a first reactive group than of a second reactive group. This can be true, for example, when it is particularly desirable that all of the second reactive group be bonded. By having an excess of the first reactive group the chances of binding to a high proportion of the second reactive group is increased. Thus, in many implementations the first and second reactive groups will be generally or approximately equal to one another, but in some implementations one reactive group will be at least 25 percent more common, at least 50 percent more common, at least 75 percent more common, at least 100 percent more common, at least 200 percent more common, or at least 300 percent more common than a second reactive group.

FIG. 4Ais a schematic representation of first and second polymeric materials ofFIG. 2andFIG. 3reacted together to form a hydrogel420.FIG. 4Bis a closeup representation of a portion of the hydrogel ofFIG. 4A, showing reacted pairs422formed of first reactive group106and second reactive group108. It will be appreciated that in typical circumstances there will be some non-reacted groups, such as a non-reacted first reactive group106shown inFIG. 4B. As noted above, the relative ratio of first and second reactive groups106,108will often be close to 1:1, but in certain embodiments one of the reactive groups106,108will be more common than the other, such as when various application details and/or geometries mean that only a portion of one of the reactive groups is likely to react, or where full reaction of one of the groups is particularly desired (in which case higher numbers of the other reactive pair is desired).

FIG. 5is a schematic representation of a non-branched polymeric material514showing orthogonally reactive groups508secured to a polymeric backbone516. Typically the polymeric material514will have at least two reactive groups508so as to permit crosslinking. The reactive groups can account for a small or large portion of the overall polymeric material514. For example, the molecular weight of the reactive groups can account for, as an example, greater than one percent of the total polymeric material, greater than two percent of the total polymeric material, greater than five percent of the total polymeric material; or greater than ten percent of the total polymeric material.

FIG. 6is a schematic representation of a microbead630having orthogonally reactive groups606secured to the beads, such as by polymeric backbones616. This schematic representation is not intended to be drawn to scale, and is only a functional representation of the various components. It will be appreciated that the reactive groups606can be secured to the microbead630without a polymeric backbone, thus directly to microbead630. However, in such cases the crosslinking agent (not shown) must be long enough to bridge between microbeads630and ideally between multiple microbeads630.

The microbeads can have, for example, a diameter from about 10 microns to 1,000 microns (1 millimeter), optionally less than 900 microns, less than 800 microns, less than 700 microns, less than 600 microns, less than 500 microns, less than 400 microns, less than 300 microns, less than 200 microns or less than 100 microns. In some embodiments the microbeads are less than 90 microns, less than 80 microns, less than 70 microns, less than 60 microns, less than 50 microns, less than 40 microns, less than 30 microns, or less than 20 microns.

FIG. 7is a schematic representation of a kidney740with a tumor742being treated with microbeads730to create an embolic seal. Microbeads730can be administered by way of a catheter750that extends through the descending aorta752to the renal artery and then into smaller renal arteries. The microbeads730are administered into a target zone, and thereafter a crosslinking agent is administered to bind the beads to one another and form a hydrogel securing the beads in place and embolizing small target renal arteries. The microbeads flow into various narrowing blood vessels, but crosslinking of the microbeads or incorporating them into a hydrogel provides improved sealing and reduction of blood flow.

The microbeads can all be of the same size or be of different sizes. Also the microbeads can all be delivered at once or delivered over time, but typically the microbeads will be delivered in a first stage followed by delivery of a crosslinking agent that is generally not administered as part of a microbead. However, both materials can be administered by microbead in some embodiments, such as situations where a first microbead is administered followed by a much smaller second microbead that is able to penetrate deeper into the deposit of the first microbeads. Also, it is possible to use a combination of microbeads and non-microbeads to deliver reactive materials, such as by having a first reactive group on microbeads but also on polymeric materials not secured to a micro bead. In this manner the second reactive group binds the beads to one another and to the polymeric materials.

FIG. 8is a schematic representation of a cross section of blood vessel860with a peripheral occlusion device formed from a coil864, such as an embolization coil, coated with a crosslinkable hydrogel (not shown). Various constructions can be implemented, but in a typical embodiment the combination of the coil864itself along with a hydrogel that is formed by in vivo crosslinking forms a rapid and effective embolism. In an example embodiment the coil864comprises a flexible substrate, such as a non-reactive bio-compatible metal material coated with one of a pair of biorthogonal reactive groups. The biorthogonal reactive groups can be directly secured to the flexible substrate, bounded to a polymeric backbone that is in turn secured to the flexible substrate, or otherwise secured thereto. Upon placement within a target zone a crosslinking material is added having the other pair of the biorthogonal reactive group. The biorthogonal reactive pairs react to form a hydrogel surrounding the substrate, such as a coil. In this manner the coil is more readily stabilized, but also the open areas between the coil strands are filled with hydrogel, and gaps around the perimeter of the coil (adjacent to a blood vessel wall, for example) are filled in with hydrogel.

Similarly,FIG. 9is a schematic representation of an aneurysm966being treated with a coil964to create an embolism in a blood vessel960. As is the case with the occlusion device ofFIG. 9, in a typical embodiment the combination of the coil964itself along with a hydrogel that is formed by in vivo crosslinking forms a rapid and effective embolism. In an example embodiment the coil964comprises a flexible substrate, such as a non-reactive bio-compatible metal material coated with one of a pair of biorthogonal reactive groups. The biorthogonal reactive groups can be directly secured to the flexible substrate, bounded to a polymeric backbone that is in turn secured to the flexible substrate, or otherwise secured thereto. Upon placement within a target zone a crosslinking material is added having the other pair of the biorthogonal reactive group. The biorthogonal reactive pairs react to form a hydrogel surrounding the substrate, such as a coil. In this manner the coil is more readily stabilized, but also the open areas between the coil strands are filled with hydrogel, and gaps around the perimeter of the coil (adjacent to a blood vessel wall, for example) are filled in with hydrogel.

It should be noted that, as used in this specification and the appended claims, the phrase “configured” describes a system, apparatus, or other structure that is constructed to perform a particular task or adopt particular characteristics. The phrase “configured” can be used interchangeably with other similar phrases such as “arranged”, “arranged and configured”, “programmed” “constructed and arranged”, “constructed”, “manufactured and arranged”, and the like.

All publications and patent applications in this specification are indicative of the level of ordinary skill in the art to which the present technology pertains. All publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated by reference.

This application is intended to cover adaptations or variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive.