Implantable device including a resorbable carrier

An implantable device for body tissue, including an electrical subsystem that flexes within and interfaces with body tissue and a carrier that operates in the following two modes: provides structural support for the electrical subsystem during implantation of the device in body tissue and allows flexing of the electrical subsystem after implantation of the device in body tissue. The implantable device is preferably designed to be implanted into the brain, spinal cord, peripheral nerve, muscle, or any other suitable anatomical location. The implantable device, however, may be alternatively used in any suitable environment and for any suitable reason.

TECHNICAL FIELD

This invention relates generally to the implantable device field, and more specifically to an implantable device including a resorbable carrier.

BACKGROUND

Conventional microfabricated electrode arrays by themselves are often not mechanically robust enough to be inserted into body tissue. Therefore, they must be coupled to a carrier that is strong enough to resist buckling while being inserted into the tissue. Conventional carriers typically remain implanted with the microfabricated electrode arrays, potentially reducing the ability of the microfabricated electrode arrays to move freely in the tissue. Thus, there is a need for an improved carrier that increases the ability of the microfabricated electrode arrays to move freely. This invention provides such an improved and useful carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of preferred embodiments of the invention is not intended to limit the invention to these embodiments, but rather to enable any person skilled in the art to make and use this invention.

As shown inFIGS. 1 and 2, the implantable device of the preferred embodiments includes a carrier10and an electrical subsystem12coupled to the carrier10. The carrier10functions to facilitate the insertion of the electrical subsystem12and is adapted to allow the electrical subsystem12to move freely in the tissue. The implantable device is preferably designed to be implanted into the brain, spinal cord, peripheral nerve, muscle, or any other suitable anatomical location. The implantable device, however, may be alternatively used in any suitable environment and for any suitable reason.

The carrier10functions to facilitate the insertion of the electrical subsystem12and is adapted to allow the electrical subsystem12to move freely in the tissue or other substances. The electrical subsystem12is preferably attached to the carrier10such that the carrier functions to provide structural support. The carrier may include a sharpened end adapted to penetrate the tissue and aid in the insertion of the carrier and electrical subsystems into the tissue. The carrier10may also include alignment and or fixation features to facilitate positioning and stabilizing the electrical subsystem12in the tissue.

The carrier10of the preferred embodiments is resorbable into tissue after a period of time. Upon resorption of the carrier10, the electrical subsystem12supported by the carrier will be left to float freely in the brain or other suitable tissue or material. The resorbable carrier is preferably made of a material that demonstrates at least one of the following characteristics: minimal foreign body reaction, biocompatibility, biodegradability, long-term mechanical and chemical stability, sterilizability, and sufficient porosity. The material is preferably adapted to undergo a controlled action and reaction to the surrounding tissue, a controlled chemical breakdown and resorption, replacement by regenerating tissue, stimulation of regeneration of living tissues, or any combination thereof. The resorbable carrier is preferably made from a bioresorbable polymer. The bioresorbable polymer is preferably polyglycolide or polylactide, but may alternatively be made from any suitable bioresorbable material such as a biodegradable magnesium alloy or a corrodible iron alloy. If the bioresorbable polymer is polyglycolide (or any other material that absorbs into the body after approximately one month), the carrier absorbs into the body at about the same time the body heals around the implanted device, which may be advantageous in some situations. If the bioresorbable polymer is polylactide (or any other material that absorbs into the body after approximately one year), the carrier absorbs into the body much after the body heals around the implanted device, which may be advantageous in other situations.

The carrier10may further extend the functionality of the device by providing fluidic channels through which therapeutic drugs, drugs to inhibit biologic response to the implant, or any other suitable fluid or substance may be transmitted. The fluidic channels are preferably channels defined by the geometry of the carrier10, but may alternatively be separate microtubes molded, inserted, woven, knitted, or otherwise disposed into the carrier10. The channels preferably provide for the precise delivery of specific pharmaceutical compounds to localized regions of the body, such as the nervous system, and could facilitate, for example, intraoperative mapping procedures or long-term therapeutic implant devices. The fluidic channels may also provide a location through which a stiffener (or even a shape-memory alloy such as Nitinol) may be inserted to aid with the implantation or to facilitate post-implantation navigation of the device. The shape of the carrier is preferably tubular with about a 1-mm diameter, but may alternatively be solid or any other suitable shape of any suitable diameter for the desired functions.

The carrier10is preferably made from a material that is woven or knitted, but may alternative be made from a material that is cast, molded, or machined. The carrier10is preferably flexible, but may alternatively be rigid or semi rigid. The material may be uniformly rigid, or rigid only in a particular direction (such as the axial direction). The resorbable carrier may also be impregnated with fluids and/or deliver the fluids such as drugs and/or neurotrophins, similar to the “Stent Device and Method” of U.S. Pat. No. 7,001,680, which is incorporated in its entirety by this reference. The carrier10may be further adapted to act as a template for tissue regeneration and/or as a matrix for autologous or analogous cells or stem cells.

The carrier10may be made from a combination of materials. The layers or portions of distinct materials may have distinct absorption, degradation, or incorporation times. The distinct materials may further include distinct particles, agents, and/or cells that they deliver or release into the tissue. The carrier10may further include scaffolding for structural support and/or for drug or cell delivery. The scaffolding is preferably bioresorbable, but may alternatively remain implanted with the device.

The carrier10may be manufactured in one of several variations. In a first variation, the carrier may be manufactured such that the weave of the material is large enough to accept “weaving” of the electrical subsystem12directly into the fabric. In this variation, the electrical subsystem can be adapted to be woven in and out of the resorbable carrier to secure the electrical subsystem12to the carrier10. A single electrical subsystem12could be woven into the fabric or multiple subsystems could be incorporated, resulting in a three-dimensional system of electrical subsystems. In a second variation, the electrical subsystem could be coupled directly to the surface of the carrier using a biocompatible adhesive such as epoxy or silicone. In this variation, the weave of the resorbable carrier may be tighter and/or the porosity of the carrier may be smaller as the electrical subsystem12is not woven into the material in this variation. In a third variation, the resorbable carrier may be manufactured as a concentric, multi-lumen structure. In this variation, the electrical subsystem12may be coupled to the carrier between the inner and outer lumens of the electrical subsystem.

Although the carrier10is preferably one of these several variations, of several various materials, manufactured in several variations, the carrier may be any suitable element, material, manufactured in any suitable fashion to facilitate the insertion of the electrical subsystem12and to allow the electrical subsystem12to move freely in the tissue or other substances.

The electrical subsystem12of the preferred embodiments functions to interface with the tissue, or any other suitable substance, within which it has been implanted. The electrical subsystem12may include multiple different electrical subsystems or a plurality of the same subsystems. The electrical subsystem12is preferably at least one of several versions or any combination thereof.

The electrical subsystem12is preferably a neural interface electrode array. The electrode array preferably has a plurality of electrode sites, and more preferably both stimulation sites20and recording sites22. The neural interface electrode array is adapted to provide dynamic tunable electrical stimulation ranging from stimulation with macroscale specificity to microscale directional, patterning. The electrode array is preferably adapted to optimally sample (record) and/or selectively activate (stimulate) neural populations. The plurality of electrode sites can be tuned for recording, stimulation, or any combination thereof. Additionally, at least two electrode sites may be grouped to form a larger composite site that enables tuning the neural interface region for recording and/or stimulation.

The neural interface electrode array is preferably made from a thin-film polymer substrate, such as parylene or some combination of parylene and inorganic dielectrics, but may alternatively be made out of any suitable material including, for example, silicon. The neural interface electrode array is preferably made such that there is high density of electrode sites at a first end of the array (the distal end) and bonding regions at a second end of the array (the proximal end). The distal end of the array is preferably coupled to the carrier10to provide structural support. The electrode array may further include fluidic channels providing the capability to deliver therapeutic drugs, drugs to inhibit biologic response to the implant, or any other suitable fluid.

The neural interface electrode array in this variation is preferably a composite assembly that includes the neural interface electrode array and the carrier10. The neural interface electrode array includes two pieces, a distal element and a proximal element. The distal element wraps or is woven around the circumference of the carrier10. Ascending from the distal element, are preferably interconnects that transition from the outer surface of the carrier10into a single connector14, such that the entire proximal element is imbedded in silicone. To facilitate adhesion between the carrier10and the neural interface electrode array, small non-homogeneous perforations are preferably micromachined in the neural interface electrode array to allow for the material of the carrier10to form a robust anchor with the electrode array.

In a second version of the preferred embodiments, as shown inFIG. 3, the neural interface electrode array preferably defines series of “cut-aways” or perforations18that axially extend in a discontinuous manner along the length of the neural interface electrode array. With the perforations, the neural interface electrode array preferably has adequate flexibility to allow bending and flowing of the device within body tissue after implantation of the device. The perforations18preferably extend in a radial direction completely through the neural interface electrode array, and preferably extend in a circumferential direction approximately 45-90 degrees. The neural interface electrode array preferably includes two perforation series, and thus the neural interface electrode array preferably extends 180-270 degrees in the areas with perforations. The perforation series is preferably discontinuous (i.e., the neural interface electrode array extends completely in the circumferential direction at particular points along the length of the neural interface electrode array). While the neural interface electrode array has been described as having perforations, it is also possible for the neural interface electrode array to be described as being one or more strips that are circumferentially connected by several “bridges”.

In a third version of the preferred embodiments, the neural interface electrode array omits the “bridges” and is merely one or more rectangular and generally planar (i.e., either flat or slightly curved) “strips”. The carrier provides structural support for these “strips” to be placed onto a stylet and implanted into body tissue. Although the electrical subsystem12is preferably one of these three versions, the electrical subsystem12may be any suitable element or combination of elements to perform the desired functions.

The device of the preferred embodiments may further include an additional electrical subsystem that functions to operate with the electrical subsystem12. The additional electrical subsystem may include multiple different electrical subsystems or a plurality of the same subsystems. The additional electrical subsystem is preferably at least one of several versions or any combination thereof. In a first version, the additional electrical subsystem is a suitable electronic subsystem to operate with an implantable neural interface. The additional electrical subsystem may be a printed circuit board with or without on-board integrated circuits and/or on-chip circuitry for signal conditioning and/or stimulus generation, an Application Specific Integrated Circuit (ASIC), a multiplexer chip, a buffer amplifier, an electronics interface, an implantable pulse generator, an implantable rechargeable battery, integrated electronics for either real-time signal processing of the input (recorded) or output (stimulation) signals, integrated electronics for control of the fluidic components, any other suitable electrical subsystem, or any combination thereof. Although the additional electrical subsystem is preferably one of these several subsystems, the additional electrical subsystem may be any suitable element or combination of elements to operate any suitable electrical subsystem12.

The device of the preferred embodiments may further include a connector14that functions to couple the electrical subsystem12to the additional electrical subsystem. The connector14is preferably one of several versions. As shown inFIGS. 1 and 2, the cable is preferably a flexible ribbon cable. The ribbon cable is preferably polymer ribbon cable, but may alternatively be any other suitable ribbon cable. The connector14may alternatively be any suitable element to couple the electrical subsystem12to the additional electrical subsystem, such as wires, conductive interconnects, etc. The ribbon cable may be encased in silicone or any other suitable material. In some versions, the electrical subsystem may have multiple ribbon cables. Preferably, multiple ribbon cables would be physically attached along their entire length, using a suitable adhesive such as medical grade adhesive or any other suitable connection mechanism. The cable is preferably connected to the electrical subsystems through ball bonds or any other suitable connection mechanisms. The connector14may alternatively be seamlessly manufactured with the first and or additional electrical subsystem. The connector14may further include fluidic channels adapted to deliver therapeutic drugs, drugs to inhibit biologic response to the implant, or any other suitable fluid.

As shown inFIG. 3, the device of the preferred embodiments may further include a stylet16. The stylet16of the preferred embodiments functions to penetrate the tissue or other material and/or functions to provide structural support to the device during implantation of the device. The stylet16is preferably inserted into a lumen of the carrier10, but may alternatively be located and inserted into any suitable component of the device in any suitable manner. The stylet16may include a sharpened end adapted to penetrate the tissue and aid in the insertion of the stylet, the carrier10, and/or the electrical subsystems into the tissue. The stylet16is preferably removed from the tissue following the placement of an electrical subsystem, but may alternatively be adapted to remain in the tissue while still allowing the implanted electrical subsystem12to float freely in the brain. This may be accomplished by the stylet being selectively flexible (through electrical stimulus or other suitable method) or by being resorbable into the tissue after a period of time. The stylet16is preferably made from a stiff material such as metal, but may alternatively be made from any suitable material. In one variation, the metal is an insulated metal wire. In this variation, the insulated metal wire may not have insulation covering a sharpened tip, and thus can be used as a conventional single-channel microelectrode.

As shown inFIG. 4, a method of implanting and using the implantable device and its corresponding electrical components preferably includes the following steps: (a) providing an electrical subsystem and a carrier that provides structural support for the electrical subsystem; (b) implanting the electrical subsystem and the carrier into the body tissue; and (c) dissolving the carrier into the body tissue and allowing the electrical subsystem to flex within and interface with the body tissue. Step (c) may include dissolving the carrier into the body tissue at a rate approximately equal to the healing process of the body tissue, or may include dissolving the carrier into the body tissue at a rate much slower than the healing process of the body tissue. The method may also include providing a stylet, placing the electrical subsystem and the carrier onto the stylet, and penetrating the body tissue with the stylet.

Although omitted for conciseness, the preferred embodiments include every combination and permutation of the various carriers10, the various electrical subsystems, the various connectors, the various stylets, and the various methods of use.