Characterization of a Temporary Peripheral Nerve Stimulation Electrode Utilizing a Bioabsorbable Suture Substrate

Abstract

Electrical stimulation after peripheral nerve injury (PNI) has the potential to promote more rapid and complete recovery of damaged fiber tracts. While permanently implanted devices are commonly used to treat chronic or persistent conditions, they are not ideal solutions for transient medical therapies due to high costs, increased risk of surgical injury, irritation, infection, and persistent inflammation at the site of the implant. Furthermore, removal of temporary leads placed on or around peripheral nerves may have unacceptable risk for nerve injury, which is counterproductive in developing therapies for PNI treatment. Transient devices which provide effective clinical stimulation while being capable of harmless bioabsorption may overcome key challenges in these areas. However, current bioabsorbable devices are limited in their robustness and require complex fabrication strategies and novel materials which may complicate their clinical translation pathway. In this study, we present a simple bioabsorbable / biodegradable electrode fabricated by modifying standard absorbable sutures, and we present data characterizing our prototype's stability in vitro and in vivo.

Figure 1:

Fabrication scheme for a coated bioabsorbable suture electrode

Figure 2:

Microcracked surface coating (gold) observed under digital and scanning electron microscopy.

Figure 3:

Bode plot (averaged, n=8), baseline EIS impedance (blue) and phase (red) behavior of suture electrode in 1x PBS.

Figure 4:

Cyclic Voltammogram (averaged, n=8), baseline I (current) - V (Potential vs. Ag/AgCl) characteristics of suture electrode in 1x PBS.

Figure 5:

Corresponding Cathodic Charge Storage Capacity of suture electrode in 20 mM H₂O₂ / PBS reactive aging solution over time (4 weeks)

Figure 6:

Swelling and delamination along the length of a suture electrode after 14 days in 20 mM H₂O₂ / PBS reactive aging solution.

Figure 7:

Impedance (n=6) EIS at 1kHz of suture electrode in 20 mM H₂O₂ / PBS reactive aging solution over time (4 weeks).

Figure 8:

Percent survival of subcutaneously implanted suture electrodes over 14 days (n=7)