Advanced materials (Deerfield Beach, Fla.)

Wireless Device with Aligned Nanofibers to Help Nerve Repair

Updated

Abstract

An ultrasound-responsive nerve guidance conduit achieved nerve reinnervation comparable to autografts in an 8-mm sciatic nerve defect rat model.

  • is associated with severe motor and sensory dysfunction, leading to tissue atrophy.
  • An ultrasound-responsive, piezoelectric nanofiber nerve guidance conduit was developed to aid in peripheral nerve regeneration.
  • The conduit is made from poly-l-lactic acid nanofibers, providing both structural support and wireless electrical stimulation.
  • Incorporation of polyethylene glycol improved the conduit’s mechanical properties and enhanced its biocompatibility.
  • Ultrasound activation of the conduit generates an electric field that may facilitate directional axon elongation.

Simplified

Key numbers

627.8 ± 41.8
Nerve Reinnervation Rate
Total count in the group.
55.3 ± 15.7%
Ratio
Force of operated relative unoperated muscle in the group.
130.5 ± 3.1
Contracture Angle
Contracture angle at 12 weeks in the group.

Key figures

Figure 1
Design, fabrication, and structure of the ultrasound-driven for nerve regeneration
Highlights the APNF-NGC’s aligned structure and fabrication enabling wireless for nerve repair
ADMA-37-e03343-g004
  • Panel A
    Schematic of ultrasound-driven APNF-NGC bridging a sciatic nerve injury between proximal and distal stumps
  • Panel B
    Illustration of APNF roles in promoting nerve regeneration including structural support and electrical stimulation
  • Panel C
    Fabrication process showing of aligned fibers, mat formation, and rolling into a nerve conduit
  • Panel D
    Schematic of APNF-NGC design with a four-channel cylindrical structure and dimensions (10 mm length, 0.80 mm and 0.23 mm radii)
  • Panel E
    Photograph of the APNF-NGC next a ruler for size reference
  • Panel F
    SEM image showing the detailed surface morphology and cylindrical shape of the APNF-NGC (scale bar = 500 µm)
  • Panel G
    Molecular structures of the APNF materials: poly-l-lactic acid () and polyethylene glycol ()
Figure 2
Mechanical, structural, and surface properties of electrospun and PLLA/ nanofiber mats
Highlights how PEG blending improves mechanical stiffness, crystallinity, and surface hydrophilicity of nanofiber mats
ADMA-37-e03343-g002
  • Panel A
    SEM image of electrospun PLLA nanofibers showing aligned fiber structure; inset FFT image assesses fiber alignment
  • Panel B
    Stress-strain curves comparing PLLA film and electrospun mats with varying PEG content (PEG10, PEG20, PEG30)
  • Panel C
    Bar graph of showing mechanical stiffness of PLLA film and electrospun mats with increasing PEG content
  • Panel D
    Schematic illustrating PEG addition converting PLLA from amorphous crystalline phase with shear piezoelectric α-phase
  • Panel E
    thermograms showing heat flow versus temperature for PLLA/PEG electrospun mats with different PEG concentrations
  • Panel F
    Bar graph quantifying α-phase PLLA crystallinity percentage for PLLA and PLLA/PEG mats
  • Panel G
    Schematic illustrating differences in hydrophilicity and surface charge on PLLA versus PLLA/PEG affecting cell growth
  • Panel H
    Surface potential heatmaps and values for single nanofiber strands of PLLA and PEG20 showing surface charge differences
  • Panel I
    Bar graph of contact angles showing PLLA mat is visibly less hydrophilic (higher ) than PEG20 mat
Figure 3
Ultrasound-induced piezoelectric effects and enhancing axon growth in motor neurons
Highlights enhanced axon elongation under electrical stimulation and shows ultrasound-driven piezoelectric outputs in the conduit
ADMA-37-e03343-g005
  • Panel A
    (FEA) showing displacement distribution in the under ultrasound
  • Panel B
    FEA showing piezoelectric potential generated in the APNF-NGC under ultrasound
  • Panel C
    FEA illustrating the electric field distribution and direction within the APNF-NGC under ultrasound
  • Panel D
    Schematic of the electrical measurement setup for APNF exposed ultrasound from a probe
  • Panel E
    Voltage output of APNF under 40 kHz ultrasound showing oscillating voltage peaks around ±80 mV
  • Panel F
    Current output of APNF under 40 kHz ultrasound showing oscillating current peaks around ±30 nA
  • Panel G
    Schematic of in vitro setup using cultured on nanopatterned surface with electrical stimulation
  • Panel H
    Optical microscopy images of axon elongation over 3 days; electrical stimulation (100 mV AC) samples appear to have visibly longer axons than no stimulation
  • Panel I
    Quantification of axon length over 3 days showing increased elongation with 100 mV electrical stimulation compared to control
Figure 4
vs : limb function recovery after sciatic nerve injury in rats
Highlights comparable limb function recovery and ankle movement angles between APNF-NGC and autograft treatments after nerve injury
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  • Panel A
    Timeline of in vivo experiment showing surgery, ultrasound treatment, and evaluation points at weeks 4, 8, and 12
  • Panel B
    Diagram of sciatic nerve injury in SD rats and comparison of autograft and APNF-NGC nerve repair methods
  • Panel C
    Video-gait analysis images showing ankle position at toe-off phase during walking at 4, 8, and 12 weeks for autograft and APNF-NGC groups
  • Panel D
    Graph of toe-off phase ankle angles over 4, 8, and 12 weeks showing no significant difference (n.s.) between autograft and APNF-NGC groups
  • Panels E and F
    Photographs and graph of measured at 12 weeks by leg pulling, showing no significant difference between autograft and APNF-NGC groups
Figure 5
vs : nerve regeneration and muscle recovery after sciatic nerve injury
Highlights comparable nerve regeneration and muscle recovery between APNF-NGC and autograft treatments at 12 weeks
ADMA-37-e03343-g006
  • Panel A
    Schematic of measurement setup on sciatic nerve and
  • Panel B
    Isometric tetanic force values at 12 weeks post-surgery for Autograft and APNF-NGC groups showing no significant difference
  • Panel C
    Photographs of isolated TA muscles at Week 12 comparing operated (left) and normal (right) sides for Autograft and APNF-NGC groups
  • Panels D-I and D-II
    Toluidine blue stained semi-thin sciatic nerve sections for Autograft (D-I) and APNF-NGC (D-II) groups showing myelinated axons
  • Panel E
    Quantification of area from semi-thin sections showing no significant difference between Autograft and APNF-NGC
  • Panel F
    Quantification of myelinated axon count from semi-thin sections showing no significant difference between Autograft and APNF-NGC
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Full Text

What this is

  • () is a major clinical challenge, often resulting in serious dysfunction and tissue atrophy.
  • Traditional treatment with autografts has limitations, prompting the exploration of alternative methods.
  • This research introduces an innovative ultrasound-responsive conduit made from piezoelectric nanofibers to enhance nerve regeneration.

Essence

  • The study presents a novel nanofiber conduit (APNF-NGC) that promotes peripheral nerve regeneration through structural support and wireless electrical stimulation. In vivo tests show comparable nerve reinnervation to autografts, indicating potential for clinical application.

Key takeaways

  • The APNF-NGC achieved nerve reinnervation comparable to autografts in a rat model with an 8 mm sciatic nerve defect, validated by multiple assessment methods.
  • Ultrasound activation of the APNF-NGC generates an electric field that enhances axon elongation and Schwann cell activity, promoting nerve regeneration.
  • Mechanical properties of the APNF-NGC were optimized through the incorporation of polyethylene glycol (PEG), improving biocompatibility and piezoelectric response.

Caveats

  • The study was conducted in a rat model, which may limit the direct applicability of findings to human patients.
  • While the APNF-NGC demonstrated comparable outcomes to autografts, it did not fully restore muscle function, indicating further optimization may be necessary.

Definitions

  • Peripheral nerve injury (PNI): Damage to peripheral nerves that disrupts motor and sensory function, often requiring surgical intervention.
  • Acousto-piezoelectric: A material property where mechanical stress (from ultrasound) generates electrical charge, aiding in nerve regeneration.

Simplified

Funding

Competing interests

The authors declare no conflict of interest.
PubMed

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