Method of manufacturing expansile filamentous embolization devices
An embolization device for occluding a body cavity includes one or more elongated, expansible, hydrophilic embolizing elements non-releasably carried along the length of an elongated filamentous carrier that is preferably made of a very thin, highly flexible filament or microcoil of nickel/titanium alloy. At least one expansile embolizing element is non-releasably attached to the carrier. A first embodiment includes a plurality of embolizing elements fixed to the carrier at spaced-apart intervals along its length. In second, third and fourth embodiments, an elongate, continuous, coaxial embolizing element is non-releasably fixed to the exterior surface of the carrier, extending along a substantial portion of the length of the carrier proximally from a distal tip, and optionally includes a lumenal reservoir for delivery of therapeutic agents. Exemplary methods for making these devices include skewering and molding the embolizing elements. In any of the embodiments, the embolizing elements may be made of a hydrophilic, macroporous, polymeric, hydrogel foam material. In the second, third and fourth embodiments, the elongate embolizing element is preferably made of a porous, environmentally-sensitive, expansile hydrogel, which can optionally be made biodegradable and/or bioresorbable, having a rate of expansion that changes in response to a change in an environmental parameter, such as the pH or temperature of the environment.
1. A method for making an embolization device, the method comprising:
providing an elongated, flexible, filamentous carrier having a looped portion; and
coaxially encapsulating at least a portion of the looped portion of the carrier in an expansile hydrophilic polymer.
2. The method of claim 1 , wherein encapsulating at least a portion of the looped portion of the carrier comprises:
providing an elongated member of the polymer in a softened state; and
skewering the member coaxially with the carrier.
3. The method of claim 2 wherein providing the elongated member comprises inserting the member into a tubular holder such that the member is radially confined and axially restrained therein.
4. The method of claim 1 wherein encapsulating at least a portion of the looped portion of the carrier comprises:
providing a mold having an elongated cavity therein;
disposing the carrier coaxially within the cavity of the mold; and
transferring the polymer into the cavity such that the polymer is thereby molded into a member coaxially encapsulating at least a portion of the length of the carrier.
5. The method of claim 1 wherein the carrier includes an axial lumen, and wherein encapsulating at least a portion of the looped portion of the carrier comprises substantially filling the lumen of the encapsulated portion of the carrier with the polymer.
6. The method of claim 1 wherein the carrier includes an axial lumen, and further comprising forming an axial reservoir in the lumen.
7. The method of claim 6 wherein forming the axial reservoir comprises:
inserting an elongated mandrel into the lumen of the carrier before the encapsulation thereof; and
removing the mandrel from the lumen of the carrier after the encapsulation thereof.
8. A method for delivering a therapeutic agent to a patient, the method comprising:
making an embolization device in accordance with the method of claim 6 ;
disposing the therapeutic agent in the axial reservoir of the device; and
embolizing a body cavity of the patient with the device.
9. The method of claim 1 further comprising dehydrating the polymer to shrink it.
10. The method of claim 9 wherein dehydrating the polymer comprises immersing the device in a hygroscopic medium.
11. The method of claim 9 wherein dehydrating the polymer comprises heating the device.
12. The method of claim 1 wherein the polymer has a rate of hydration in an aqueous medium that is a function of a physical parameter of the medium, and further comprising setting the rate of hydration of the polymer in response to the parameter.
13. The method of claim 12 wherein adjusting the rate of hydration comprises treating the polymer with an acid.
14. The method of claim 12 further comprising immersing the device for a period of time in an aqueous medium having the physical parameter, wherein the period of time and the physical parameter of the medium are selected to as to soften the polymer and render it lubricious without substantially expanding it.