U.S. patent application number 12/432343 was filed with the patent office on 2009-11-26 for hybrid bioelectrical interface device.
Invention is credited to Mohammad Reza Abidian, Paul S. Cederna, Brent M. Egeland, Daryl A. Kipke, David C. Martin, Antonio Peramo, Sarah Richardson-Burns, Melanie G. Urbancheck.
Application Number | 20090292325 12/432343 |
Document ID | / |
Family ID | 41342652 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090292325 |
Kind Code |
A1 |
Cederna; Paul S. ; et
al. |
November 26, 2009 |
HYBRID BIOELECTRICAL INTERFACE DEVICE
Abstract
A hybrid bioelectrical interface (HBI) device can be an
implantable device comprising an abiotic component operable to
transmit charge via electrons or ions; a biological component
interfacing with the neural tissue, the biological component being
sourced from biologic, biologically-derived, or bio-functionalized
material; and a conjugated polymer component that together provide
a means to chronically interface living neural tissue with
electronic devices for extended durations (e.g. greater than 10
years). In some embodiments, conjugated polymers provide a
functional electrical interface for charge transfer and signal
transduction between the nervous system and an electronic device
(e.g. robotic prosthetic limb, retinal implant, microchip).
Inventors: |
Cederna; Paul S.; (Milan,
MI) ; Egeland; Brent M.; (Ann Arbor, MI) ;
Abidian; Mohammad Reza; (Ann Arbor, MI) ; Peramo;
Antonio; (Ann Arbor, MI) ; Urbancheck; Melanie
G.; (Ann Arbor, MI) ; Kipke; Daryl A.;
(Pinckney, MI) ; Richardson-Burns; Sarah; (Ann
Arbor, MI) ; Martin; David C.; (Ann Arbor,
MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
41342652 |
Appl. No.: |
12/432343 |
Filed: |
April 29, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61049988 |
May 2, 2008 |
|
|
|
Current U.S.
Class: |
607/2 |
Current CPC
Class: |
A61L 27/34 20130101;
A61N 1/36125 20130101; A61N 1/0551 20130101; A61N 1/0543 20130101;
A61F 2250/0001 20130101; A61L 27/3675 20130101; A61F 2/72 20130101;
A61N 1/05 20130101 |
Class at
Publication: |
607/2 |
International
Class: |
A61N 1/00 20060101
A61N001/00 |
Goverment Interests
GOVERNMENT INTEREST
[0002] This invention was made with government support under Grant
No. W911NF0610218 awarded by the Army Research Office. The
government has certain rights in the invention.
Claims
1. A hybrid bioelectrical interface device for interfacing living
neural tissue with electronic devices comprising: an abiotic
component operable to transmit charge via electrons or ions; a
biological component interfacing with the neural tissue, said
biological component being sourced from biologic,
biologically-derived, or bio-functionalized material; and a
conjugated polymer component interfacing said abiotic component and
said biological component, said conjugated polymer component
promoting electronic to ionic charge transfer between said abiotic
and biological components.
2. The hybrid bioelectrical interface device according to claim 1,
wherein said device further comprises a housing encapsulating at
least a portion of said biological component, said conjugated
polymer component and said abiotic component.
3. The hybrid bioelectrical interface device according to claim 2,
wherein said housing comprises a rigid framework, a hydrogel, a
permeable membrane, an impermeable membrane or a polymeric
material.
4. The hybrid bioelectrical interface device according to claim 1,
wherein said device further comprises one or more of an
electrolyte, a biologically active agent and cells.
5. The hybrid bioelectrical interface device according to claim 1,
wherein said abiotic component is selected from the group
consisting of a wire, an electrode, an electrode array, a
microelectrode array or a microelectromechanical system.
6. The hybrid bioelectrical interface device according to claim 1,
wherein said conjugated polymer component comprises
poly(3,4-ethylenedioxythiophene) (PEDOT), poly(pyrrole),
polyanilines, polyacetylenes, poly-3-hexylthiophene, melanins, poly
(diallyldimethylammonium chloride, poly-4-vinylpyridine,
poly(vinylalcohol), polythiophenes, conjugated derivatives thereof,
functionalized polymers thereof or polymer blends thereof.
7. The hybrid bioelectrical interface device according to claim 6,
wherein said conjugated polymer component comprises
poly(3,4-ethylenedioxythiophene) (PEDOT).
8. The hybrid bioelectrical interface device according to claim 1,
wherein said biological component comprises skeletal myocytes,
cardiomyocytes, smooth muscle cells, acellularized tissue,
extracellular matrix material (ECM) or combinations thereof.
9. An implantable hybrid bioelectrical interface device for
interfacing living neural tissue with electronic devices
comprising: an abiotic component operable to transmit charge via
electrons or ions; a biological component interfacing with the
neural tissue, said biological component being biologic,
biologically-derived, or bio-functionalized; a conjugated polymer
scaffold interfacing said abiotic component and said biological
component, said conjugated polymer scaffold promoting electronic to
ionic charge transfer between said abiotic and biotic components;
and a housing having an electrolyte, said housing substantially
surrounding at least a portion of said biological component, said
conjugated polymer scaffold and said abiotic component.
10. The implantable hybrid bioelectrical interface device according
to claim 9, wherein said housing comprises at least one of a stent,
a hydrogel, a permeable membrane, an impermeable membrane or a
polymeric material.
11. The implantable hybrid bioelectrical interface device according
to claim 9, wherein said abiotic component is selected from the
group consisting of a wire, an electrode, an electrode array, a
microelectrode array or a microelectromechanical system.
12. The implantable hybrid bioelectrical interface device according
to claim 9, wherein said conjugated polymer component comprises
poly(3,4-ethylenedioxythiophene) (PEDOT), poly(pyrrole),
polyanilines, polyacetylenes, poly (diallyldimethylammonium
chloride, poly-4-vinylpyridine, poly(vinylalcohol), polythiophenes
or polymer blends thereof.
13. The implantable hybrid bioelectrical interface device according
to claim 12, wherein said conjugated polymer is FeCl.sub.4.sup.-
doped poly(3,4-ethylenedioxythiophene) (PEDOT), and said
FeCl.sub.4.sup.- doped poly(3,4-ethylenedioxythiophene) (PEDOT) is
disposed within or around at least a portion of said biological
component.
14. The implantable hybrid bioelectrical interface device according
to claim 9, wherein said biological component comprises skeletal
myocytes, cardiomyocytes, smooth muscle cells, acellularized
tissue, extracellular matrix material (ECM) or combinations
thereof.
15. A hybrid bioelectrical interface (HBI) device comprising: an
abiotic component operable to transmit charge via electrons or
ions; a acellularized tissue disposed at least partially on said
abiotic component; a conjugated polymer scaffold disposed at least
partially within said biological component or at least partially
covering said biological component; and a housing comprising a
polymer or a hydrogel material, said housing having a proximal end
and a distal end, said housing covering at least a portion of at
least one of said abiotic component, said acellularized tissue and
said conjugated polymer scaffold.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/049,988 filed on May 2, 2008. The disclosure of
the above referenced application is incorporated herein by
reference.
FIELD
[0003] The present technology relates to implantable hybrid
bioelectrical interface devices that interface living neural tissue
with artificial electronic components, in particular,
neural-robotic bioelectrical coupling.
BACKGROUND SUMMARY
[0004] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0005] Engineered limb prosthetics hold great potential for
millions of spinal cord injury, neuromuscular disease, and
amputation victims. Although sophisticated microelectronics and
robotics facilitate ever closer approximations of human movement,
interfacing the mechanical to the biological has proved
challenging. Furthermore, providing graded sensory feedback from
the prosthetic to the individual is critically important.
Fundamentally, interface technologies must transduce neuron-based
bioelectric action potentials saltatory conduction along myelinated
axons mediated by mass transfer (ion currents) directly or
indirectly to an electrical current through a metallic conductor.
Multiple studies have dramatically demonstrated volitional
prosthetic control using implanted cortical electrodes in primate
models. With these successful demonstrations, the practical aspects
of using central neural electrodes for human deployment including
their surgical invasiveness, biofouling, encapsulation, foreign
body response, and reliance on capacitive and high impedance
electronics--all which lead to time-related signal
degradation--become foremost challenges.
[0006] To avoid some of these obstacles, natural functional and
anatomic separation of axons into fascicles in the peripheral
nervous system may provide a more attractive interface site.
Indeed, neurotization, or targeted muscle reinnervation procedures
exploit peripheral nerve sorting, biologic plasticity, and
ultimately, neuromuscular junction stability. Expanding this
concept to human volitional prosthetic control, some in the field
have recently demonstrated that Targeted Muscle Reinnervation
(TMR), or independent reinnervation of several individual muscle
partitions by isolated nerves (from the brachial plexus), could
indirectly drive a robotic prosthetic through surface EMG
(electromyography) recordings. These exciting clinical results are
already being deployed in select patients, but donor muscle
limitations and reliance on non-integrated surface EMG may preclude
achieving individual axonal fidelity (i.e. proximal interphalangeal
joint flexion of the index finger), and sensory feedback has only
been partially addressed.
SUMMARY
[0007] In one aspect of the present technology, hybrid
bioelectrical interface (HBI) devices for interfacing living neural
tissue with electronic devices comprises: an abiotic component
operable to transmit charge via electrons or ions; a biological
component interfacing with the neural tissue, the biological
component being sourced from biologic, biologically-derived, or
bio-functionalized material; and a conjugated polymer component
interfacing the abiotic component and the biological component,
such that the conjugated polymer component promotes electronic to
ionic charge transfer between the abiotic and biotic
components.
[0008] In a further aspect, the hybrid bioelectrical interface
(HBI) devices comprise a housing providing for coordinated and
structural direction for nerves to be interfaced with synthetic
neural devices and artificial prostheses. The hybrid bioelectrical
interface (HBI) devices can include a housing made from a polymer
material such as polydimethylsiloxane (PDMS) or a hydrogel
material, for example, agarose. The housing can contain a
structural framework to provide rigidity, support and improved
handling characteristics for the housing and the components
contained therein. The housing surrounds a biological component
that is interfaced with conjugated polymer. The conjugated polymer
in turn, interfaces with an abiotic component and a biological
component. The conjugated polymer component and biological
components can be covered or surrounded by the housing.
[0009] Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
[0010] The drawings described herein are for illustration purposes
only and are not intended to limit the scope of the present
disclosure in any way.
[0011] FIG. 1A depicts a graphical representation of an
illustrative embodiment of the implantable hybrid bioelectrical
interface device showing in partial exploded view the various
components of the hybrid bioelectrical interface device in
accordance with the present technology.
[0012] FIG. 1B depicts a graphical representation of an
illustrative embodiment of the implantable hybrid bioelectrical
interface device showing in cross-sectional view the distal portion
of the hybrid bioelectrical interface device illustrating a
plurality of abiotic electrodes held by a surrounding framework in
proximate contact with the biological component (myocytes) for
recording and/or stimulating action potentials through a conducting
polymer within the length of the device in accordance with the
present technology.
[0013] FIG. 2 depicts the manufacture of two hybrid bioelectrical
interface devices having in which the abiotic component is a
cluster of microwires connected to an EED (FIG. 2, A), the biotic
component is either an acellularized tissue scaffold or a naturally
based hydrogel scaffold both of which can be seeded with
dissociated skeletal muscle cells (FIG. 2, B), the conjugated
polymer component is either a PEDOT-coated acellularized tissue
scaffold or in situ polymerized PEDOT that is polymerized directly
within the either acellularized tissue scaffold or naturally based
hydrogel scaffold seeded with living muscle cells (FIG. 2,
D&H), the container is a tubular polymer membrane that is
filled with a hydrogel matrix which serves as an electrolytes as
well as a structural and nutritive support for the muscle cells and
implanted nerve (FIG. 2, G&J). The proximal end of a single
motor nerve fascicle is inserted into the open end of the hybrid
bioelectrical interface device so that it contacts the muscle cells
and the conjugated polymer component of the device
[0014] FIG. 3A depicts a hybrid bioelectrical interface device for
in vitro studies. The abiotic component is interfaced with
acellularized muscle tissue having PEDOT conjugated polymer
disposed within. Neural structures have formed neuromuscular
junctions with the myocytes to form myotubes in the acellular
muscle tissue.
[0015] FIG. 3B depicts a schematic representation of a hybrid
bioelectrical interface device having myocytes growing on the
abiotic component and enveloped in PEDOT conjugated polymer. The
myocytes and PEDOT are placed within a hydrogel scaffold providing
a nutritive environment for the myocytes/myotubes.
[0016] FIG. 4 depicts a graphical representation of the process
steps in fabricating an embodiment of the hybrid bioelectrical
interface device using a housing consisting of agarose in
accordance with the present technology.
[0017] FIG. 5A is a optical microphotograph of a hydrogel housing
surrounding a poly(3,4-ethylenedioxythiophene) (PEDOT) conjugated
polymer cylinder as graphically represented in FIG. 4. The inset
represents the distal end of the hybrid bioelectrical interface
device. As shown in FIG. 6A-6C, the insets are reproduced in
magnified form as marked by the dotted lines.
[0018] FIG. 5B is a magnified optical micrograph of the inset shown
in FIG. 5A depicting the distal end of the hybrid bioelectrical
interface device. The inset represents a magnified portion of the
distal end of the hybrid bioelectrical interface device in
accordance with the present technology.
[0019] FIG. 5C is a magnified optical micrograph of the inset shown
in FIG. 5B depicting the distal end of the hybrid bioelectrical
interface device. The inset represents a portion of the
poly(3,4-ethylenedioxythiophene) (PEDOT) conjugated polymer
cylinder in accordance with the present technology.
[0020] FIG. 5D is a magnified optical micrograph of the inset shown
in FIG. 5C a portion of the poly(3,4-ethylenedioxythiophene)
(PEDOT) conjugated polymer cylinder in accordance with the present
technology.
[0021] FIG. 6A depicts a graphical representation of an embodiment
of the hybrid bioelectrical interface device. The housing made from
agarose covers a framework (stainless steel stent) partially
disposed from the distal and proximal ends towards the center of
the device. A cylindrical tube made up entirely of
poly(3,4-ethylenedioxythiophene) (PEDOT) is formed in the middle of
the HBI device housing within the stainless steel stent.
[0022] FIG. 6B depicts a graphical representation of an embodiment
of the hybrid bioelectrical interface device. The housing and
center portion of the device is made from agarose. A stainless
steel stent is inserted into the agarose partially disposed from
the distal and proximal ends towards the center of the device,
[0023] FIG. 6C depicts a graphical representation of an embodiment
of the hybrid bioelectrical interface device. The housing made from
agarose covers a stainless steel stent partially disposed from the
distal and proximal ends towards the center of the device. A spiral
cylindrical tube made up of poly(3,4-ethylenedioxythiophene)
(PEDOT) is formed in the middle of the device within the stainless
steel stent.
[0024] FIG. 6D depicts a graphical representation of an embodiment
of the hybrid bioelectrical interface device. The housing made from
agarose covers a polydimethylsiloxane (PDMS) cylindrical tube.
[0025] FIG. 7A depicts a schematic representation demonstrating
mid-peroneal nerve interposition using the hybrid bioelectrical
device in vivo for purposes of bridging a critical efferent motor
conduction gap. Other neural pathways are divided to isolate the
efferent pathway.
[0026] FIG. 7B is a photograph of the peroneal nerve interposed
with the hybrid bioelectrical device and prepared for efferent
recording of stimulation applied proximally to the sciatic nerve
and distally recording transmitted action potentials.
[0027] FIG. 7C depicts a schematic representation demonstrating
mid-sural nerve interposition using the hybrid bioelectrical device
in vivo for purposes of bridging a critical afferent sensory
conduction gap. For afferent experiments, the sural nerve from a
rat model was isolated by dividing the tibial and peroneal nerves,
followed by antidromic sensory electrodiagnostic studies.
[0028] FIG. 7D depicts a electromyography trace of an intact nerve
signaling efferent (motor) nerve action potentials.
[0029] FIG. 7E depicts a electromyography trace of proximal nerve
conduction of efferent (motor) nerve action potentials following
nerve division preceding interposition of the hybrid bioelectrical
interface device.
[0030] FIG. 7F depicts a maintained electromyography trace of
distal nerve conduction of efferent (motor) nerve action potentials
following nerve division preceding interposition of the hybrid
bioelectrical interface device.
[0031] FIG. 7G. depicts a electromyography trace of nerve
conduction of efferent (motor) nerve action potentials applied
across the hybrid bioelectrical interface device made with
acellular muscle framework having poly(3,4-ethylenedioxythiophene)
(PEDOT) dispersed throughout the acellular muscle. This represents
successful electrical signal delivery across a critical conduction
gap in vivo.
[0032] FIG. 7H depicts a electromyography trace of nerve conduction
of efferent (motor) nerve action potentials wherein the stimulation
is applied directly to the hybrid bioelectrical interface device
made with acellular muscle having poly(3,4-ethylenedioxythiophene)
(PEDOT).
[0033] FIG. 7I depicts a electromyography trace of an intact nerve
signaling efferent (motor) nerve action potentials stimulated and
recorded at a distal position to the hybrid bioelectrical interface
device made with acellular muscle having
poly(3,4-ethylenedioxythiophene) (PEDOT) dispersed throughout the
acellular muscle.
[0034] FIG. 8A depicts a bar graph depicting efferent nerve
conduction across the peroneal nerve. The bar graphs depict the
results of measured current (mA) delivered directly to: 1) intact
peroneal nerve, 2) nerve interposited with an autograft of rat
nerve measuring 20 mm and nerve interposited with the hybrid
bioelectrical device measuring 20 mm.
[0035] FIG. 8B depicts a bar graph depicting efferent nerve
conduction across the peroneal nerve. The bar graphs depicts the
results of measured compound muscle action potential amplitude
(millivolts) recorded at a point of musculature distal to point of
stimulation in three nerve constructs, 1) intact peroneal nerve, 2)
nerve interposited with an autograft of rat nerve measuring 20 mm
and nerve interposited with the hybrid bioelectrical device
measuring 20 mm.
[0036] FIG. 8C depicts a bar graph depicting efferent nerve
conduction across the peroneal nerve. The bar graphs depicts the
results of measured nerve conduction latency (milliseconds)
recorded at a point of musculature distal to point of stimulation
in three nerve constructs, 1) intact peroneal nerve, 2) nerve
interposited with an autograft of rat nerve measuring 20 mm and
nerve interposited with the hybrid bioelectrical device measuring
20 mm.
[0037] FIG. 8D depicts a bar graph depicting efferent nerve
conduction across the peroneal nerve. The bar graphs depicts the
results of measured nerve conduction velocity (meters per second)
recorded at a point of musculature distal to point of stimulation
in three nerve constructs, 1) intact peroneal nerve, 2) nerve
interposited with an autograft of rat nerve measuring 20 mm and
nerve interposited with the hybrid bioelectrical device measuring
20 mm.
[0038] FIG. 9A depicts a bar graph depicting afferent sensory nerve
action potentials (SNAPs) for signal propagation across the sural
nerve. The bar graphs depict the results of current (mA) delivered
directly to, the sural nerve proximal to the point of recording
(antidromic schema) in three constructs, 1) intact sural nerve, 2)
nerve interposited with an auto aft of rat nerve measuring 20 mm
and nerve interposited with the hybrid bioelectrical device
measuring 20 mm.
[0039] FIG. 9B depicts a bar graph depicting antidromic afferent
sensory nerve action potentials (SNAPs) for signal propagation
across the sural nerve. The bar graphs depicts the results of
measured sensory nerve action potential amplitude (millivolts)
recorded at a nerve site distal to the point of stimulation in
three nerve constructs, 1) intact sural nerve, 2) nerve
interposited with an autograft of rat nerve measuring 20 mm and 3)
nerve interposited with the hybrid bioelectrical device measuring
20 mm.
[0040] FIG. 9C depicts a bar graph depicting antidromic afferent
sensory nerve action potentials (SNAPs) for signal propagation
across the sural nerve. The bar graphs depicts the results of
measured sensory nerve conduction latency (milliseconds) recorded
at a nerve site distal to the point of stimulation in three nerve
constructs, 1) intact sural nerve, 2) nerve interposited with an
autograft of rat nerve measuring 20 mm and 3) nerve interposited
with the hybrid bioelectrical device measuring 20 mm.
[0041] FIG. 9D depicts a bar graph depicting antidromic afferent
sensory nerve action potentials (SNAPs) for signal propagation
across the sural nerve. The bar graphs depicts the results of
measured sensory nerve conduction velocity (meters per second)
recorded at a nerve site distal to the point of stimulation in
three nerve constructs, 1) intact sural nerve, 2) nerve
interposited with an autograft of rat nerve measuring 20 mm and 3)
nerve interposited with the hybrid bioelectrical device measuring
20 mm.
DETAILED DESCRIPTION
[0042] The following description is merely exemplary in nature and
is not intended to limit the present disclosure, application, or
uses.
[0043] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a", "an" and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0044] When an element or layer is referred to as being "on",
"engaged to", "connected to" or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to", "directly connected to" or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0045] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0046] Spatially relative terms, such as "inner," "outer,"
"beneath", "below", "lower", "above", "upper" and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0047] According to the principles of the present technology, the
hybrid bioelectrical interface device (HBI) device can be an
implantable device comprising interacting synthetic/natural
materials, biological components, and abiotic devices that together
provide a means to chronically interface living neural tissue with
electronic devices for extended durations (e.g. 1-100 years). In
some embodiments, conjugated polymers provide a functional
electrical interface for charge transfer and signal transduction
between the nervous system and an electronic device (e.g. an
electrode, robotic prosthetic limb, retinal implant and microchip).
In addition, the conjugated polymers can be disposed in and around
a biological component. The biological component can be coupled to
electrically active biological components such as nerve
constituents, nerve fascicles, neurons, myocytes, cardiomyocytes,
and other biological cells and structures that can conduct an
afferent and/or efferent electrical signal. The conjugated polymer
component can also undergo a change in bias upon electrical or
electronic stimulation that can result in actuation, effectively a
reversible volume change in the polymer matrix and/or ion flux with
the surrounding electrolyte medium. This behavior of the conjugated
polymer can be exploited to provide controlled release of the
materials, molecules, or devices incorporated into the conjugated
polymer matrix or into the conjugated polymer substrate as a form
of drug or biologically active agent, for example, adhesion
molecules, chemotactic agent growth factor delivery.
A. HYBRID BIOELECTRICAL INTERFACE (HBI) DEVICE
[0048] The technology described herein relates to a bio-artificial
neuromuscular interface herein termed a hybrid bioelectrical
interface device (HBI) that is illustratively shown in FIG. 1. The
HBI device is an implantable device that provides a functional,
electrical interface between an external electronic device (EED)
and an electrically-active tissue such as the sensory nerves, motor
nerves or cardiac tissue. In some embodiments, the present
technology described herein provides an HBI device having an
abiotic component intended for long-term implantation in the body,
however in some embodiments the HBI device can be deployed outside
the body as long as it is still connected to the electronic
prosthetic device. A chronic interface with the peripheral nervous
system that allows for recording as well as stimulation, opens the
door to a number of new devices and treatments. The HBI device
performs electronic and/or ionic charge transfer and bi-directional
signal transduction between neural tissue and an abiotic component
through a conjugated polymer such as poly
(3,4-ethylenedioxythiophene) PEDOT. The central component of the
HBI is a conjugated polymer coating, network, or scaffold that can
have functional contact on one end with an abiotic component, for
example, an electrode which connects to an EED and on the other end
with cells, tissue, a biological material, or a biomimetic or
bio-functionalized material that has a functional interface with
the neural tissue. The HBI device can be used to perform one or
both of the following functions; 1) send signals and information
(e.g. electrical stimulation, deliver bioactive agents) and 2)
receive information (e.g. monitoring/sensing, recording, or
transduction of signal to EED).
[0049] Various embodiments of the HBI device are illustratively
shown in the present disclosure in FIGS. 1-3B, however, the HBI
device is not limited to these embodiments, and one of ordinary
skill in the art can readily ascertain different embodiments
containing the same major components. However, many have similar
functions and major components. These components include 1) An
abiotic component such as a wire, microelectrode array, electrode,
a microelectromechanical system, or any other artificial, synthetic
electronic component that transmits charge via electrons or ions.
In some embodiments an electrode can be directly connected to the
EED. 2) A biological or biologically derived or bio-functionalized
component which interfaces the electrically active tissue. 3) A
conjugated polymer component that interfaces both the abiotic
component and the biological component facilitating and/or
enhancing electronic to ionic charge transfer between the abiotic
and biological components of the device. 4) Optionally, a housing,
for example, a membrane, polymer or hydrogel microtube within which
the biological component and conjugated polymer and other
components of the HBI device are housed, making the HBI device a
self-contained device that can be implanted in a body, for
coordinated neural growth and innervation within the device and for
connectivity with electronic devices and prosthetic limbs. The HBI
may have multiple abiotic, biological and conjugated polymer
components but must contain at least one of each. It should be
appreciated, however, that variations can exist between the
disclosed embodiments and their specific components and alternative
embodiments that are intended to be within the scope of the present
application.
I) Abiotic Conductor Component
[0050] The abiotic conductor can include metallic, ceramic, organic
and silicon containing materials and devices that are capable of
conducting stimulatory and sensory electrical, ionic, electronic,
mechanical, physical, magnetic e.g. pulsed electromagnetic,
acoustic and optical signals in vivo and in vitro. These components
can include a host of electrical sensing and recording components,
including metal wires, plain metal electrodes, ceramic and/or
polymer patterned electrodes, microelectrode arrays, electrode
arrays and microelectrodes. Electrodes can incorporate substrates
having any conducting material or combination of conducting and
non-conducting materials. A number of exemplary electrically
conductive substrate configurations are described and can be
understood that other configurations can be used. In non-limiting
embodiments, electrically conductive substrates can be manufactured
from metals including, but not limited to: Gold (Au), Platinum
(Pt), Iridium (Ir), Palladium (Pd), Tungsten (W), Nickel (Ni),
Copper (Cu) Aluminum (Al), Stainless Steel (SS), Indium-Tin-Oxide
(ITO), Zinc (Zn), Titanium (Ti), Tungsten (W) and their alloys and
oxides. Other electrically conductive substrates can include:
carbon, carbon fiber, glassy carbon, carbon composites, carbon
paste, conductive ceramics, for example, doped silicon (Si),
conductive monomers and polymers, e.g.
poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(pyrrole).
[0051] Abiotic components comprising one or more electrode arrays
can include any suitable support material upon which a plurality of
conducting material channels, dots, spots are formed. In general,
if the support material of the electrode is to come into contact
with biological fluid, the support should be essentially
biocompatible. The microelectrode arrays of the present technology
need not be in any specific shape, that is, the electrodes need not
be in a square matrix shape. Contemplated electrode array
geometries can include: squares; rectangles; rectilinear and
hexagonal grid arrays various polygon boundaries; concentric circle
grid geometries wherein the electrodes form concentric circles
about a common center, and which may be bounded by an arbitrary
polygon; and fractal grid array geometries having electrodes with
the same or different diameters. Interlaced electrodes can also be
used in accordance with the present technology. In some
embodiments, the array of electrodes can comprise about 9 to about
16 electrodes in a 4.times.4 matrix, 16 to about 25 electrodes in
about a 5.times.5 matrix, 10 to 100 electrodes in a 10.times.10
matrix. Other sized arrays, for example polymer based Michigan and
Utah electrodes known in the art may be used in accordance with the
present technology.
[0052] Production of patterned array of microelectrodes can be
achieved by a variety of microprinting methodologies commonly known
in the production of micro-arrays, including, without limitation,
by ejecting a plurality of electro-conducting polymers via a
multi-line head nozzle, via ink-jetting techniques and the like.
They can be patterned using photolithographic and etching methods
known for computer chip manufacture. The micromechanical components
may be fabricated using compatible "micromachining" processes that
selectively etch away parts of the silicon wafer, or comparable
substrate, or add new structural layers to form the mechanical
and/or electromechanical components.
[0053] Micro-electro-mechanical systems (MEMS) based electrodes
formed on polymeric supports such as those contemplated in
Micro-electro-mechanical systems (MEMS) manufacture can include
depositing thin films of conducting material on a support material,
applying a patterned mask on top of the films by photolithographic
imaging or other known lithographic methods, and selectively
etching the films. A thin film may have a thickness in the range of
a few nanometers to 100 micrometers. Deposition of
electroconducting materials for use as micro or nano electrodes
contemplated in the present technology can also include chemical
procedures such as chemical vapor deposition (CVD),
electrodeposition, epitaxy and thermal oxidation and physical
procedures like physical vapor deposition (PVD) and casting.
II) Biological Component
[0054] As used herein, the biological component of the present
technology can in non-limiting examples, include autologous,
allogous or allogeneic or xenogeneic tissue, preferably, tissue
capable of supporting the growth of neural tissue, including
neurons and substructures thereof, skeletal muscle, cardiac muscle,
smooth muscle, and cells thereof. In some embodiments, the
biological component can contain a plurality of cells derived from
autologous, allogous or allogeneic or xenogeneic tissue sources,
for example, skeletal myocytes, cardiac myocytes or smooth muscle
cells derived from line tissue, e.g. biopsy samples or from
cultured cells. Alternatively, the biological component can include
acellular tissue. Acellular tissue can be made illustratively by
obtaining tissue sample harvested from a suitable donor, and then
submersed in a balanced salt solution, such as Dulbecco's phosphate
buffered saline. The disrupting of cell membranes then includes
submersing the biological tissue sample in a solution including
glycerol, whereas denaturing and removing intracellular proteins
includes submersing the biological tissue in at least one detergent
solution. The one or more detergent solutions can comprise ionic
detergent solutions and nonionic detergent solutions. In some
embodiments, the tissue sample can be submersed in a succession of
ionic and nonionic solutions, where the ionic detergent solutions
can include sodium deoxycholate or sodium dodecyl sulfate, and the
nonionic detergent solutions can include TRITON.RTM. X-100. In
addition, the acellular tissue sample is preferably rinsed with
distilled water between each solution change. The resulting
acellularized tissue constrict can then be stored in a physiologic
saline solution. Methods useful for the production and use of
biological component comprising acellular tissue is described in
Dennis, R. G., et al. U.S. Pat. No. 6,448,076, Ser. No. 09/896,651
issued Sep. 10, 2002 and is hereby incorporated herein in its
entirety.
[0055] In some embodiments, the biological component can also
include a matrix material that is prepared by forming a hydrogel
scaffold and the like. The hydrogel scaffold can be made of any
commonly known biocompatible hydrogel material, including hydrogels
that are made from organic sources, including polysaccharides,
polypeptide and proteins, and combinations thereof. In some
embodiments, the hydrogel scaffold is then embedded with or mixed
with a population of autologous, allogous or allogeneic or
xenogeneic tissue constituents, for example, skeletal myocytes,
cardiac myocytes or smooth muscle cells derived from live tissue,
e.g. biopsy samples or from cultured cells. In addition to the
hydrogel and cells, the biological component can also include one
or more biologically active agents including: but not limited to,
neural cell adhesion molecule (N-CAM), neuroglial CAM or NgCAM,
TAG-1, contactin-2, myelin-associated glycoprotein (MAG), and
deleted in colorecteal cancer protein (DCC); extra cellular matrix
adhesion molecules: e.g. laminin, fibronectin, tenascin and
perlecan; muscle and/or cell surface markers, e.g. cluster of
differentiation markers (CD) molecules and combinations thereof,
extra cellular matrix components, vitamins, minerals, drugs,
medicaments, pharmaceutical compositions, amino acids, peptides,
proteins, e.g. enzymes, antibodies, receptors, ion-ligand channels,
glycoproteins, glycolipids, lipids, sterols, fatty acids,
glycerides, nucleic acids including DNA, cDNA, RNA, mRNA, siRNA,
shRNA, miRNA, polynucleotides, oligonucleotides, coding-gene
sequences, non-coding genetic sequences and combinations
thereof.
III) Conjugated Polymers
[0056] The conjugated polymer is a conducting (electrons or ions)
coating (also known as conductive polymers), inter-connected
network, or matrix that can be formed by electrochemical
polymerization, chemical (oxidative or vapor deposition)
polymerization, and in situ polymerization in a tissue or around
cells or in a gel or scaffold or any combination thereof. The
conjugated polymer can be deposited on a substrate using a variety
of methods including but not limited to electrochemical deposition,
evaporation, spin-coating, solvent-casting, chemical vapor
deposition (CVD), layer-by-layer electrostatic interaction,
electrostatic processing (electrospray/jetting/spinning),
compressed air-spray, and atomization.
[0057] The term "conjugated polymer(s)" is used interchangeably
with "conducting polymer(s)". Conjugated polymers are formed from
their monomeric form via electrochemical polymerization, oxidative
polymerization and other methods commonly used in the art. The
conjugated polymer polymerized around an electrically conjugated
substrate can also be referred to as a conducting polymer network
due to its three dimensional, fuzzy, soft fibrils that extend out
from the electrically conjugated substrate. In some embodiments,
the conducting polymer network contains embedded biological
components including cells, cellular constituents, bioactive
molecules or substances and combinations thereof. In certain
embodiments of the present technology, the conjugated polymers can
be polymerized in the presence of dopants, tissue, cells, cell
parts, cellular constituents, other bioactive molecules, viral,
plasmid, yeast, dendromer, quantum dot, or micro-nano particle gene
delivery vectors, and/or biodegradable micro-nano particles or
fibers that are comprised of naturally-derived or synthetic
polymers that may be decorated with surface functional groups or
molecules intended for interaction with specific cells or molecules
in the target effector tissue or may be employed for
controlled-release delivery of one or more bioactive molecules,
including, but not limited to, neural cell adhesion molecule
(N-CAM), neuroglial CAM or NgCAM, TAG-1, contactin-2,
myelin-associated glycoprotein (MAG), and deleted in colorecteal
cancer protein (DCC); extra cellular matrix adhesion molecules:
e.g. laminin, fibronectin, tenascin and perlecan; muscle and/or
cell surface markers (CD) molecules and the like and combinations
thereof contained within.
[0058] In some embodiments, the conducting polymers can include,
but are not limited to: polythiophenes,
poly(3,4-ethylenedioxythiophene) (PEDOT), poly(pyrrole),
polyanilines, polyacetylenes, poly-3-hexylthiophene, melanins both
natural and synthetic, poly (diallyldimethylammonium chloride,
poly-4-vinylpyridine, poly(vinylalcohol), conjugated derivatives
thereof, functionalized polymers thereof, polymer blends thereof
and composites with the ability to conduct electronic charge or
ions, and hybrid polymer-metal materials that are electrically or
ionically conductive. Other conjugated polymers useful in the
present technology can include functionalized copolymers made from
EDOT and other conducting polymer derivatives, functional groups
such as RGD, IKVAV, YIGSR peptides, and other functional groups
that can be covalently attached to the conducting monomer, or they
can be linked to spacers having bifunctional moieties that can be
attach to the conjugated monomer used in making the conjugated
polymer. A covalent attachment can be effected using any covalent
chemistry known in the art, for example carboxylic functional
attachment. Examples of preferred covalent attachment chemistries
include amine, amide, ester, ether, and their heteroatom cognates,
e.g., sulfonamide, thioether, and so forth. Typically, each pair of
entities to be joined can jointly comprise a pair of reactive
groups, such as a nucleophile and an electrophile, one respectively
on each member of the pair. Where the biological entity
(biomolecule, cell, cell fragment, organelle, or other biologically
active molecule) is to be directly attached to the monomer or
polymer, each will contain one reactive group of a pair. Where
attachment is to take place through a linker, the linker will
contain two reactive groups, one of which is capable of covalently
reacting with a reactive group of the monomer and the other of
which is capable of covalently reacting with a reactive group of
the biological entity. The reactive group(s) can be already present
as part of the monomer, linker, or biological entity, or it can be
added thereto by reaction prior to performing the attachment
reaction. Where attachment is to take place through a linker, the
linker can be attached first to the polymer, first to the
biological entity, or concurrently to both. Typically, the entities
to be covalently attached can be suspended or dissolved in an
appropriate solvent, e.g., aqueous methanol, aqueous ethanol,
acetonitrile, dimethyl formamide, acetone, dimethyl sulfoxide, or a
combination thereof, at an appropriate pH, commonly about pH 7 to
about pH 10, and at a temperature from about 10.degree. C. to about
40.degree. C. A neutral-to-basic pH is typically used and this is
in most cases provided by addition of a base to the reaction
medium. Examples of preferred bases for this purpose include
inorganic bases and organic nitrogenous bases. Among inorganic
bases, metal hydroxides, carbonates, and bicarbonates are
preferred, preferably alkali metal hydroxides, carbonates, and
bicarbonates, and combinations thereof.
[0059] In some embodiments, conjugated polymers can also include
non-conductive monomer or polymer that can be made conductive in
the presence of an appropriate doping system. In some embodiments,
conjugated polymers useful herein can also be chemically
synthesized to contain functional side groups that can allow for
binding of proteins, lipids and nucleic acids before or after
polymerization. In addition to functionalization of the conducting
polymers, bioactive molecules, including proteins, lipids and
nucleic acids can be also attached to the conjugated polymers
through hydrogen bonding, electrostatic and non-polar interactions.
In some embodiments, the conjugated polymer is biodegradable and
will dissolve in the presence of biological fluid, for example,
when the device is implanted in situ e.g. implantable brain
prostheses, neural stimulators, transient heart devices and the
like. The biodegradable conjugated polymer can include, but are not
limited to, polypyrrole, poly(3,4-ethylenedioxythiophene) (PEDOT)
block PEG, and poly(3,4-ethylenedioxythiophene), tetramethacrylate
and others which are commercially available from TDA Research Inc.,
Wheat Ridge Colo., USA.
[0060] Conjugated polymers contemplated by the present technology
typically require counter ions for polymerization and
electroconductivity across the electrode-tissue interface. The
conjugated polymers are reached with a polyelectrolyte at the
molecular level. Electron delocalization is a consequence of the
presence of conjugated double bonds in the conducting polymer
backbone. To make the conducting polymers electrically conductive,
it is necessary to introduce mobile carriers into the double bonds,
this is achieved by oxidation or reduction reactions (called
"doping"). The concept of doping distinguishes conducting polymers
from all other kinds of polymers. This process can be assigned as
p-doping or n-doping in relation to the positive or negative sign
of the injected charge in the polymer chain by analogy to doping in
inorganic semiconductors. These charges remain delocalized being
neutralized by the incorporation of counter-ions (anions or
cations) denominated dopants. In certain embodiments, ionic
electrolytes or dopants used to polymerize conducting polymers
include but are not limited to: poly(styrene sulfonate) (PSS; Sigma
Aldrich, St. Louis, Mo., USA), LiCIO.sub.4, Phosphate-buffered
saline (PBS; HyClone, Logan, Utah), Hank's Balanced Salt Solution
(HBSS, HyClone), Collagen, Poly-D-Lysine (PDL), Poly-L-Lysine,
poly-omithine, and bioactive molecules of interest having the
appropriate ionic charge for the type of doping system used and can
include, but is not limited to: dexamethasone or other
anti-inflammatory agents, antibiotics, anti-mitotics, growth
factors, scar-reducing, poly acrylic acid, dodecylbenzene sulfonic
acid (DBSA), p-toluenesulfonic acid (p-TSA) and combinations
thereof. Methods for attaching linkers and other functional groups
to the conjugated polymer useful in the methods of the present
technology are disclosed in patent application Ser. No. 12/038,138
titled: "Carboxylic Acid-Modified EDOT For Bioconjugation" filed on
Feb. 27, 2008, and methods for making and polymerizing conjugated
polymers are disclosed in Martin et al., U.S. Patent Application
Publication 2007/0060815 (Ser. No. 11/512,479) which are both
incorporated herein in their entireties.
IV) Optional Housing Structures
[0061] An electrolyte composition can be included with the
conjugated polymer and/or biological components to provide support
and growth for growing neural cells and/or myocyte cells. In some
embodiments, physiological and/or nutritive electrolytes (e.g.
vitamins, minerals, carbon food sources, amino acids and the like)
can be incorporated within the polymer, membrane, or hydrogel
housing and/or the conjugated polymer component. Alternatively, the
physiological electrolytes can be added separately to any one of
the conjugated polymer component, the biological component and
combinations of the two. Further the electrolyte fluid may be
comprised of autologous serum-derived or naturally present
electrolyte solution. In some embodiments, the physiological
electrolytes can include any commonly known electrolyte
compositions in dry or fluid form that is used for rehydration
purposes.
B. METHODS OF PREPARING AND USING THE HYBRID BIOELECTRICAL
INTERFACE DEVICE
[0062] In some embodiments of the present technology, the HBI
device can include an abiotic construct operably connected
electrically and/or ionically with conjugated polymer. The
conjugated polymer can be prepared around the biological component
and the abiotic component in several ways. In some embodiments, a
substrate, for example, a polydimethylsiloxane (PDMS) film, sheet
or strip can be sputtered on at least one surface with gold,
forming a thin film. Upon the gold covered surface
poly(3,4-ethylenedioxythiophene) (PEDOT) can be formed from
monomers of EDOT. Methods for forming PEDOT covered surfaces are
known in the art. Methods useful for forming PEDOT covered surfaces
are described in Martin et al., U.S. Patent Application Publication
2007/0060815 (Ser. No. 11/512,479) which is incorporated herein in
its entirety. However, other conjugated polymers described above
can also be formed on the surface of the substrate. The PDMS sheet
can be rolled up having the PEDOT facing the interior lumen of the
rolled tube thereby forming a microtube housing. The microtube
housing when implanted in vivo can have a first proximal end and a
second distal end. As used herein, the proximal end is the end
closest to the central nervous system and the distal end is the end
closest the effector tissue, for example, the arm, hand, leg or
foot musculature. The microtube housing can be filled with a
biological component and the biological component can be linked to
an abiotic component within one of the proximal or distal ends of
the housing. An Illustrative method for forming the conjugated
polymer component in the housing is shown in FIG. 4.
[0063] The HBI device can be used to provide a suitable target
effector site for nerve structures that have been severed to form
neuromuscular junctions as a treatment for neuropathy. In still
other embodiments, the HBI device can be used to transmit
physiologic motor action potentials in vivo and form a
bioelectrical coupler for providing appropriate efferent prosthetic
limb control and afferent prosthetic feedback. In order to provide
such prosthetic limb control, the coupling of the nerve structures
with the prosthetic limb requires that a closed loop sensory path
be formed.
[0064] In some embodiments, the HBI device of the present
technology electrically and ionically couples action potentials
travelling via the nerves to an external electronic device capable
of coordinating such action potential signals and converts these to
limb motion. To construct a bidirectional hybrid bioelectrical
interface, a peripheral nerve fascicle can be isolated from a
nerve, and inserted into the proximal end of the HBI device
housing, for example a microtube. The nervous tissue can be sutured
or glued to the housing to anchor the fascicle within the housing.
In some embodiments, the biologic component, for example,
dissociated muscle cells (myocytes) can be housed inside the lumen
of the housing. These cells release chemical signals which
encourage peripheral nerve growth toward them. Inside the housing,
axons will extend away from the fascicle and make contact with the
myocytes. When an axon reaches a myocyte, it forms a neuromuscular
junction and the myocyte begins to differentiate from a muscle
precursor cell into a myotube. Eventually, many individual myotubes
combine to form muscle tissue, which is then supported by the body.
This muscle tissue will respond electrically to action potentials
that come from the peripheral nerve fascicles as is propagated
through the HBI device. The biological component upon which the
muscle is created has been permeated with conductive polymer and
should maintain its electrical connection to the electrode after
the muscle forms. The electrode should record an average of the
electrical activity from the tube lumen and muscle. Additionally,
if current is passed through the electrode, it should stimulate the
tube lumen and muscle, which will in turn stimulate any axon, which
innervates the HBI device.
[0065] In some embodiments, the HBI device shown illustratively in
FIG. 2, can be formed by providing an abiotic component consisting
of a cluster of microwires connected to an external electronic
device (EED) The biological component can be either an
acellularized tissue scaffold or a naturally based hydrogel
scaffold that is seeded with dissociated skeletal muscle cells,
myocytes, or cardiac myocytes present in the biological component.
The conjugated polymer component can include a PEDOT-coated
acellularized tissue scaffold or in situ polymerized PEDOT that is
polymerized directly within the either acellularized tissue
scaffold or naturally based hydrogel scaffold seeded with living
muscle cells. In some embodiments, the conjugated polymer can be
polymerized randomly within and/or on the exterior surface of the
biological component, arranged in a pattern within and/or on the
exterior of the biological component, (for example a spiral
pattern) or can be completely polymerized as a complete coating,
substantially covering the biological component. The housing can
include a hydrogel polymer, for example agarose, a tubular polymer
membrane, which may be permeable to nutrients, or impermeable. (See
FIGS. 4 and 5). The housing can also be filled with a hydrogel
matrix which provides a source of electrolytes as well as a
structural and nutritive support for the growth of muscle cells and
the implanted nerve. In some embodiments, the housing can also have
a rigid framework, for example, a stent or two or more stents
disposed within the housing to provide the housing with support,
especially if the housing is made from a hydrogel as shown in FIG.
6. Various orientations of the conjugated polymer within the
housing are illustrated in non-limiting examples, as shown in FIGS.
6A-6D. In some embodiments, the proximal end of a single motor
nerve fascicle can be inserted into the proximal end of the HBI
container so that it contacts the biological component for example,
muscle cells, and the conjugated polymer component of the device.
The nerve can regenerate in a coordinated fashion within the HBI
container and form synapses with the muscle cells (the natural
target of the nerve) as well as possibly form synapse-like
junctions (capacitive interface) with the PEDOT electrode
component. The stability, viability and functional activities of
the living cells (e.g. to form neuro-muscular junctions between the
nerve tissue and myocytes) within the HBI device can also be
facilitated by the presence of soluble biologically active agents
(e.g. soluble drugs, nerve cell chemotactic agents, growth factors,
cell adhesion molecules, e.g. neural cell adhesion molecule
(N-CAM), neuroglial CAM or NgCAM, TAG-1, contactin-2,
myelin-associated glycoprotein (MAG), and deleted in colorecteal
cancer protein (DCC); extra cellular matrix adhesion molecules:
e.g. laminin, fibronectin, tenascin and perlecan; muscle and/or
cell surface markers (CD molecules) and the like) in the hydrogel.
The interfaced wire-conjugated polymer electrode component of the
HBI can serve as the electrical connection between the EED and the
nerve allowing for "recording" of action potentials from the muscle
cells and/or the nerve itself as well as making possible electrical
stimulation of the muscle cells and nerve via the HBI.
[0066] In some embodiments, an in vivo construct can be used to
determine conductive properties of a HBI device utilizing
chemically polymerized PEDOT on a chemically acellularized biologic
muscle scaffold. These in vitro constructs are illustratively shown
in FIGS. 3A and 3B. In some embodiments, a HBI device can include a
durable, high-fidelity, biologically integrated neural prosthetic
interface that uses PEDOT-coated chemically acellularized muscle
scaffolds (ACM) to detect the cortical synthesis of motor signals
in the peripheral nervous system (PNS) in order to control robotic
prosthetics. These materials do not possess cellular machinery
necessary for action potential propagation and presumably conduct
via electron mass transport. In this embodiment, composite
abiotic-biotic constructs can be designed to match the 2-3 mm
caliber of an adult rat peroneal nerve. There is no housing
component in this in vitro embodiment. Biological component
including animal derived acellular muscle scaffold and subsequent
construct lengths can be manufactured to vary from about 2 mm to
about 50 mm, within the predicted length range needed within an
electronic interface device.
[0067] These composite constructs can be directly coapted both
proximally and distally to viable rat hindlimb peroneal nerves
immediately after nerve transaction, creating an interposition. The
interface between the viable nerve and the composite construct is
created through direct epineural coaptation of the nerve to the
composite material. This technique allows the individual axons to
come in direct contact with the polymer deposited on the composite
construct. Charge transfer between the abiotic component in contact
at least partially with a conjugated polymer, e.g. PEDOT and nerve
is thus possible. There is a notable lack of directionality to this
interface. The HBI device embodied in this version, through varied
stimulation locations, can thus be used for both efferent neural
signal detection and signal delivery. The proximal biotic component
can be stimulated with recording signals within the construct,
whereby the construct is "sensing" the biologic depolarizing
current and acting as a probe, or recording wire. Furthermore, the
recording can be performed distal to the construct altogether. The
construct interposition will sense, propagate, and deliver biologic
currents. Although this is not a proposed in vivo use (the distal
nerve will eventually undergo Wallerian degeneration), it does
allow in vivo construct conduction quantification. In some
embodiments, stimulating the HBI device directly and measuring
nerve conduction in the distal nerve, or using the HBI device as a
stimulating wire can therefore be achieved. This embodiment creates
a model necessary for in vivo stimulation parameter testing and
optimization prior to construct use as a true afferent neural
stimulator.
[0068] In some embodiments, the in vitro HBI device can be
assembled in a cell culture dish in a liquid cell media.
Furthermore, for in vitro studies, rather than the proximal end of
a living nerve, the neural interface would be a nerve explant,
dissociated neural cells, an organotypic slice culture, or some
other form of explanted tissue or tissue-derived substance. Use of
an in vitro model allows for more extensive testing and
verification of success metrics, specifically verification of motor
unit formation. These metrics include but are not limited to 1)
electrophysiology: EMG recordings from muscle cells, 2) Histology:
immunocytochemistry for acetylcholine receptor clustering
(post-synaptic), change in agrin localization (pre-synaptic),
phalloidin for actin cytoskeleton, 3) Chemical sensing:
acetylcholine release detection (using PEDOT or AIROX sensing
electrodes).
[0069] Example embodiments are provided so that this disclosure
will be thorough, and will fully convey the scope to those who are
skilled in the art. Numerous specific details are set forth such as
examples of specific components, devices, and methods, to provide a
thorough understanding of embodiments of the present disclosure. It
will be apparent to those skilled in the art that specific details
need not be employed, that example embodiments may be embodied in
many different forms and that neither should be construed to limit
the scope of the disclosure. In some example embodiments,
well-known processes, well-known device structures, and well-known
technologies are not described in detail.
C. EXAMPLES
Example 1
In Vivo Use of an Hybrid Bioelectrical Interface Device
[0070] Methods and Materials
[0071] Animal Model: Experiments were performed using two month
old, male, specific pathogen free F344 rats (Charles River
Laboratory, Kingston, N.Y.). Biosynthetic Construct Preparation:
ACM neural interface constructs were prepared from acellularization
of whole F344 rat lower limb (Charles River, Wilmington, Mass.)
vastus lateralis muscles. The acellular muscles were then dissected
into bundles of several myofibrils under microscopic magnification
using a Nikon SMZ-10A stereomicroscope (Nikon Instruments,
Melville, N.Y., USA). These bundles had a maximum fiber length of
20 mm and a diameter of 2.0-3.0 mm (approximate dimensions of an
intact rat peroneal nerve). These fibers subsequently underwent a
single-cycle chemical PEDOT polymerization process using iron
chloride (III) (Eq. 1).
##STR00001##
[0072] Experimental Groups: Electrophysiologic data was obtained in
multiple experimental and control groups. Efferent peroneal nerve
construct groups included 1) Acellular muscle (ACM)(n=10); 2)
Acellular muscle chemically polymerized with EDOT using FeCl3
(ACM-PEDOT) (n=20); or 3) Acellular muscle after FeCl.sub.3
treatment in absence of EDOT monomer (ACM-Fe)(n=10). Control groups
included: 1) Intact peroneal nerve (Intact) (n=70); 2) Intact
peroneal nerve treated with lidocaine (Intact-Lidocaine) (n=5); 3)
Divided and repaired peroneal nerve, with no nerve graft
(Epineural) (n=5); 4) Divided and repaired peroneal nerve gap using
a nerve autograft (Nerve Graft) (n=20); and 5) Divided and
unrepaired peroneal nerve (Nerve Gap) (n=20). Construct and gap
lengths included 5 mm, 10 mm, 15 mm and 20 mm. Afferent sural nerve
experimental groups included 1) 20 mm ACM-Fe (n=5); and 2) 20 mm
ACM-PEDOT (n=5). Control groups included: 1) Intact sural nerve
(Intact) (n=19); and 2) 20 mm nerve autograft (Nerve Graft)
(n=5).
[0073] Operative Technique: Aided by a Zeiss operating microscope,
105 individual peroneal or sural nerve segments were resected from
anesthetized live adult F344 rats (Charles River, Wilmington,
Mass.) and the resultant nerve gap was acutely bridged using
equivalent length biosynthetic constructs. The exposed proximal
nerve, construct, and distal nerve were sequentially coapted using
epineural 10-0 nylon monofilament sutures. The native nerve was
stimulated proximal to the construct interposition and NCV and EMG
measurements were obtained distally. To test conduction through the
construct, this preparation exploits in vivo distal nerve segment
excitability immediately after division, prior to Wallerian
degeneration.
[0074] Electrophysiology: Customized TECA Synergy EMG station
(Viasys Healthcare, Madison, Wis.) algorithms were used to deliver
current and measure resultant compound muscle action potentials
(CMAPs) in the EDL and antidromic Sensory Nerve Action Potentials
(SNAPs) in the sural nerve. Measurements included amplitude, nerve
conduction velocity (NCV) and latency in all groups.
[0075] Oxidative chemical PEDOT polymerization process employing
iron chloride (III)--a mild, naturally present oxidizer was used to
provide spontaneous, organized deposition on biologic substrates,
including acellular muscle (ACM) which may avoid rejection common
to all synthetic scaffolds. We used conventional clinical
electrophysiologic measurements including nerve conduction studies
(NCS) and electromyography (EMG) in a living rat to determine if
PEDOT coated ACM interposition constructs (ACM-PEDOT) were
bioelectrically relevant and could detect or deliver efferent
(motor) nerve action potentials (see electrophysiological results
shown in FIGS. 7A-9D). This single model, however, allows us to
determine whether a biologic, non-immunogenic scaffold (ACM) coated
with an electroconductive polymer (PEDOT), can enhance the
electrical and ionic transport characteristics, detect an efferent
action potential in a divided nerve, convert that action potential
to an electronic signal, and facilitate transport of that signal to
the remnant of a divided nerve to generate a physiologic action
potential. Initially, to validate the experimental design and
verify stimulator-originated nerve action potential generation in
the native neural tissue, sodium channels (necessary to develop
membrane potentials, and ultimately, nerve depolarization) were
pharmacologically blocked in the intact nerve using Lidocaine. When
0.1 ml 1% lidocaine hydrochloride was applied directly to a 10 mm
segment of intact peroneal nerve for 30 seconds, all
electrophysiological responses measured at the extensor digitorum
longus (EDL) muscle were eliminated. Absence of accessory or
aberrant conduction pathways through serum or adjacent tissues was
demonstrated by absence of any electrophysiological response in
nerve segments distal to empty nerve resection sites (gaps)
following proximal stimulation. ACM-PEDOT biosynthetic constructs
were prepared by acellularizing, shaping, and treating the ACM
fibers with a single-cycle chemical PEDOT polymerization process
using FeCl.sub.3.
[0076] Results and Discussion
[0077] The above described ACM-PEDOT containing HBI devices,
conducted physiologic currents across interpositions of up to 20
mm--the maximum length tested. Efferent NCS/EMG results (shown in
FIGS. 8A-8D) demonstrate ACM-PEDOT constructs conduct physiologic
0.53.+-.0.19 mA (mean.+-.SD) currents up to 20 mm with maximal
resultant compound muscle action potential (CMAP) amplitude of
16.60.+-.5.29 mV, (FIG. 8B) and latency of 1.09.+-.0.15 ms (FIG.
8C). ANOVA with post-hoc analysis and post-hoc power analysis
performed for each measured outcome demonstrated that ACM-PEDOT
electrophysiologic parameters are not different from NCV/EMG values
for intact nerve or from similar length nerve autografts
(p>0.05, .beta.<0.2). ACM-PEDOT constructs showed a
statistical increase in conductive velocity (40.2.+-.8.71 m/s)
compared with intact nerve (22.15.+-.3.68 m/s) (p<0.05). To
determine conductivity contribution of the polymerization reagent
iron chloride alone, we created constructs using the same chemical
PEDOT deposition process, minus EDOT monomer. These ACM-Fe
constructs were non-conductive. Likewise as an additional negative
control, constructs created from ACM-alone were non conductive
(data not shown). Unlike the millivolt electrical potentials
observed in the muscular end organ of the peroneal nerve above, the
sural nerve (purely sensory) relies upon microvolt sensory nerve
action potentials (SNAPS) for signal propagation. These small
signals pose a much greater challenge from a monitoring standpoint
as technical factors and signal to noise issues assume greater
importance. We tested whether ACM-PEDOT constructs were relevant in
this setting by dividing the much smaller sural nerve, and
repeating experiments described above, results shown in FIGS.
9A-9D. In this setting, 20 mm ACM-PEDOT constructs transmit
discrete antidromic microvolt SNAP's with a mean amplitude of
35.78.+-.27.56 .mu.V and latency of 2.68.+-.0.36 ms when stimulated
with a 1.22.+-.0.29 mA (FIG. 9B). ANOVA with post-hoc analysis
performed for each measured outcome demonstrated that ACM-PEDOT
performance does not differ from intact nerve (43.29.+-.18.28
.mu.V, 2.78.+-.0.23 ms, 0.84.+-.1.12 mA, respectively) (p>0.05,
.beta.<0.2), and outperforms 20 mm nerve autografts, which
required more stimulation (8.08.+-.3.22 mA) (p<0.05) leading to
lower signal to noise ratio. ACM-PEDOT shows increased NCV
(23.06.+-.4.67 m/s) compared with intact nerve (16.38.+-.1.35 m/s)
(p<0.05). As previously demonstrated in the efferent motor
action potential experiment, ACM, ACM-Fe, and nerve gaps were
non-conductive. Chemically polymerized PEDOT-coated acellular
muscle constructs can couple efferent motor action potentials and
afferent sensory nerve action potentials in the distal end of a
divided nerve to physiologic scale charge transport across an
ACM-PEDOT biosynthetic construct with electrophysiologic parameters
similar to intact peripheral nerve. It was also demonstrated that
the signal conduction across the ACM-PEDOT construct has a greater
velocity than intact nerve and is maintained over at least a 20 mm
distance. Since signal conduction is distance-dependent, and since
there is no conduction across longer constructs (10 mm, 15 mm, and
20 mm) in any of the control groups, including the acellular muscle
scaffold alone, acellular muscle scaffold with iron, and the
unreconstructed nerve gap, we speculate the ACM-PEDOT functions
through a mass-transfer (ion) effect. The ability to connect these
scaffolds to external monitoring equipment should make it possible
to monitor axonal sprouting and regeneration following clinical or
experimental nerve manipulations. The ability to apply an external
electrical field could also be used to direct and enhance the rate
and extent of neural regeneration.
CONCLUSION
[0078] Peripheral nerve efferent and afferent action potentials
were detected and propagated in vivo using a hybrid bioelectrical
interfacing device composed of PEDOT chemically deposited on
biologically derived acellular muscle. The production,
implantation, and in vivo electrophysiologic properties of these
hybrid neural constructs and their ability to detect efferent
(motor) action potentials proximally and deliver afferent (sensory)
action potentials distally with electrophysiologic characteristics
similar to intact peripheral nerve. It is possible that these
electrically active biosynthetic scaffolds will make possible high
resolution peripheral nerve interfaces necessary for next
generation bionic arms and legs.
[0079] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the invention. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the invention, and all such modifications are intended to be
included within the scope of the invention.
* * * * *