Molecular Bioelectronics for Neural Interfacing and Repair

Mario I. Romero-Ortega

Bioengineering, University of Texas in Arlington and U.T. Southwestern Medical Center

UTARI March 20, 2014

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Peripheral Nerve Injury

Neurapaxia Axonotmesis Neurotmesis

Amputation

Aba and Cavalli, 2008

The Grow/No Grow Dilemma in PNI

Transection Nerve Injury:- Paralysis- Anesthesia- Allodynia- Can be permanent

Neuroma- Excruciating pain- Responsive to thermal,

barometric, and other stimuli.

- Can lead to phantom limb perception

GROW NO-GROW

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Boc

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DIRECTED GROWTH

Peripheral Neural Interfaces- Control growth to MEAs- Modality specificity- Avoid pain or aesthesias- Prevent neuromas

Peripheral Nerve Gap Injury

• Autografts remains the gold standard for bridging gap defects

• Limitations:– Available quantity of donor nerve– Scarring– Painful neuroma at donor site

– Graft thickness limited by revascularization

– Only 10% of axons after a nerve transection and ‘‘best’’ surgical apposition reach target organs (Witzel et al., 2005).

Peripheral nerve injuries that induce gaps larger than 2 cm require bridging strategies for repair

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FDA Approved Biosynthetic Nerve Conduits

Schlosshauer et al., 2006.

NeuraGen. Integra Neuroscience (collagen).

Neurolac.

(PL-caprolactone)

Neurotube.Synovis Micro (polyglocolide)

• Limited to the repair of short digital sensory nerve gaps (≤3cm) in humans.

• No luminar fillers or growth factors

Biomimetic Nerve Implant: BNI

Biodegradable conduit

Agarose

Collagen +

Agarose

Collagen + growth factors

7Tansey et al., 2011

BNI Short Nerve Gap Repair (10 mm)

Tansey et al., 2011

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BNI: EM Morphometry and Behavioral Recovery

Tansey et al., 2011Tansey et al., 2011

Long Gap Nerve Repair ( >30 mm)

Luminar saline Luminar ECM Muliluminal ECM Multiluminar ECM with growth facors

Complexity/Efficacy

CTR

GDNF

BSA GDNF_MP

PLGA Microparticle Growth Factor Release

Synergetic effects of pleiotrophic and neurotrophic factors on axonal growth in vitro.

Control

Combination A

Combination B

12Romero et al., Unpublished

Biodegradable conduit

Agarose

Collagen +

Agarose

Collagen

Growth Factor MP

Combination A

Control

GF-MP BNI: 30 mm Rabbit Peroneal Nerve

Romero et al., In preparation

Normalside

Injured side: No regeneration

Normalside

Injured side: Regeneration

4 weeks 6 weeks

GF-MP BNI: 30 mm Motor Recovery

Romero et al., In preparation

14Romero et al., Unpublished

Biodegradable conduit

Agarose

Collagen +

Agarose

Collagen

Growth Factor MP

GF-MP BNI: 30 mm Rabbit Peroneal Nerve

Alsmadi et al., submitted

Deployment of GF Coiled Microfibers in Microchannels

Alsmadi et al., Submitted

Deployment of GF Coiled Microfibers in Microchannels

Alsmadi et al., Submitted

Cheng-Jen Choung

Deployment of GF Coiled Microfibers in Microchannels

Alsmadi et al., Submitted

Bidirectional Molecular Guidance

Alsmadi et al., Submitted

More than 1.6 million Americans are amputees, and 185,000 more are expected to loss their limbs each year.

Ziegler-Graham et al., 2008

Modular Prosthetic Limb: JHAPL

Neural Control of Robotic Prosthesis

Kuiken et al., 2007

http://armdynamics.com/pages/tmr

Cortical Neuro-Electrode Interfaces

BMI- 3D Neural Control of Robotic ProsthesisCollinger, Andrew Schwartz, Univ Pittsburgh 2013

Current Challenges in PNS Neurointerfacing

- Tissue damage/Inflammation– limited functionality (weeks to months)

due to continued signal deterioration

- Current injection– Tissue damage due to metal dissolution

or water electrolysis.

- Motor decoding/Sensory encoding capability. – Sensitive neural recording from low

voltage (µV) signals.

– Accurate and efficient stimulation of specific neuron subtypes Luke Skywalker's Bionic Arm, "The Empire

Strikes Back (1980)

TMR(Targeted Muscle Reinnervation)-Prothese. Foto: Otto Bock/Michael Appelt

SynTouch BioTacG. Loeb, USC

Kinea Tactor: Johns Hopkins APL

Advanced Limb Prosthetics: Sensory Feedback

Selective Function and Neural Encoding

Motor Axon

20 distinct sensory modalities

Flat ElectrodeD. Durand, D. Tyler; CWRU

TIME ElectrodeS Micera; EPFL

Four weeks recording and efficacy of sensory stimulation decayed after 10 days” Rossini et al., 2010

Pierpaolo Petruzziello, 2010

K. Horch, 2004

K. Warnick, 2004

Motor Decoding/Sensory encoding

15 d 30 d 60 d

Regenerative Multielectrode Interface: REMI

Garde et al., 2009

Recording/Stimulation Free-Moving Animals

Garde et al., 2009

Kinematic Analysis during Bipedal Locomotion

Gait

Cineplex

Rats are also video tracked using Cineplex software (Plexon Inc.) to track angle between the joints.

Rats are trained on a robot treadmill (Robomedica, Inc.) for gait analysis to monitor recovery after peripheral nerve injury.

Firing Pattern of Single Unit Spikes recorded from Tibial Nerve

• Robot assisted standing on hind limbs – No Rhythmic Walking

Single Unit on Ch 2

45 Days Post Implant

Tonic Unit seen only on Ch 2, while Ch1 and 3 did not have Single Unit activity

Ch 1

Ch 2

Ch 3

Ch 2

Raster Plot

50 sec interval

1400 μsec

148 μV

Tonic to Bursting during Walking

• Robot assisted Bipedal Locomotion – Rhythmic Walking

Bursting Units elicited while walking as seen on Ch1, 2, 3

Channel 1 Channel 2 Channel 3

Ch 1

Ch 2

Ch 3

50 sec interval

1400 μsec

184 μV

1400 μsec

828 μV

1400 μsec

296 μV

Sensory Specific Evoked Neural Activity

Perievent Histogram bin = 500ms

Freq

uenc

y (s

pike

s/se

c)

Ch

ann

el

AC

han

ne

l B

0- 55 CFr

eque

ncy

(spi

kes/

sec)

Ch

ann

el

AC

han

ne

l B

0-50 gr

REMI: Mix Modality Interfacing

The rat sciatic nerve consist of 3 fascicles containing about 8,100 motor axons and 17,000 unmylinated axons (Castro et al., 2008)

Motor and SensoryModalities

ChAT

Badia et al. 2009

Badia et al. 2009

Axon Composition in PNS

Targeting Sensory Type Regeneration In Vivo

Directed Axonal Growth by NGF and NT-3

Unmyelinated Fibers

Myelinated Fibers

Both DRGs and ventral motor neurons grow towards A/B targets

Surrogate Targets

Muscle

Skin

Nerve

Nerve

Single Growth Factors

Multiple Growth Factors

BDNF/GDNFNT-3

PTN

BSA

BSA

BSA

NGF

NT-3

BDNF/GDNF

BDNF/GDNF

NT-3/NGF

BDNF/GDNF

BDNF/GDNF

BDNF/GDNF

PTN/NGF/NT-3

PTN/NGF

BSA

PTN

Anand et al., In Preparation

Painful Neuromas Occur in up to 80% of limb amputations

Sehirlioglu et al., 2009Healthy Nerve Neuroma

Granja et al., In Preparation

BNI- Nerve Block: Discouraging Nerve Growth

BNI

BNI-NB

Granja et al., In Preparation

BNI-NBBNI

BNI- Nerve Block: Discouraging Nerve Growth

Granja et al., In Preparation

Healthy Nerve

Guided Inhibition

r= .175mmX3channelsA= 0.29 sq.mm

r= 4.5 mmA= 25.4 sq.mm

Healthy Nerve

Uncontrolled Regeneration

Hollow tube

r= 4.5 mmA= 25.4 sq.mm

r= 9 mmA= 254 sq.mm

Simple Tubularization vs BNI-Nerve Block

Granja et al., In Preparation

BNI-NB Prevents Mechanoceptive Pain

Granja et al., In Preparation

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Grow-No Grow Strategies

Increasing Gap Length • Contact guidance: Agarose microchannels filled with collagen

• Growth Factors: Linear GFR Promote neuronal and functional recovery in 3 cm gaps

• Longer Gaps might be repair with GF-Gradient Multi-luminal implants.

Growth: Long Gap Repair

No Growth: Neuroma

• Amputated nerves: Differential growth of modality-specific axons

• Axon growth can be GF-directed separate Y-shaped compartments

Conditional Growth: Interfaces

• Surgical placement: Bone, Muscle

• Capped Tubularization: Silicon tubes, epineurium cap.

• BNI-NB can be used to prevent neuroma

Interfacing Amputated Nerves

Block Growth

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Bioelectronic Medicines

Nano-scale devices connect to groups of individual nerve fibres and change patterns of electrical signals to restore health to organs and biological functions

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Soft, Conformal Electrodes for Small Nerves and Inoperable Plexi

Walter Voit

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UTARI Michrochannel Multielectrode Array

Muthu Wijesundara Young-tae Kim

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UTARI MMEA: Fabrication

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UTARI MMEA: Recording/Stimulation

AcknowledgmentsUTA Students

Sanjay Anand

Nesreen Alsmadi

Benjamin Johnston

Vidhi Desai

Rafael Granja, MD

Aswini Kanneganti

Parisa Lotfi

Lokesh Patil

Srikanth Vasudevan

UTA/UTSW facultyYoung-tae KimJonathan ChengCheng-Jen ChuongJennifer Seifert

Plexon Inc.Edward KeeferHarvey Wiggins

Grant Sources:NIH NINDS Scottish Rite Hospital for ChildrenTexas Higher Education Coordinating BoardCrowley-Carter FoundationTexas Star Plus FundTissue Gen CorporationDefense Advanced Research Projects Agency (DARPA)

Microsystems Technology Office (MTO), Naval Warfare Systems Command (SPAWAR) Systems Center (SSC) Pacific grants No. N66001-11-1-4408 and No. N66001-11-C-4168.

UoW AustraliaGordon Wallace

UTARIMuthu WijesundarCaleb NothnagleEileen ClementsRet. Gral. Rick Lynch