Wire Electrodes Embedded in Artificial Conduit for Long-term Monitoring of the Peripheral Nerve Signal

Massive efforts to develop neural interfaces have been made for controlling prosthetic limbs according to the will of the patient, with the ultimate goal being long-term implantation. One of the major struggles is that the electrode’s performance degrades over time due to scar formation. Herein, we have developed peripheral nerve electrodes with a cone-shaped flexible artificial conduit capable of protecting wire electrodes from scar formation. The wire electrodes, which are composed of biocompatible alloy materials, were embedded in the conduit where the inside was filled with collagen to allow the damaged nerves to regenerate into the conduit and interface with the wire electrodes. After implanting the wire electrodes into the sciatic nerve of a rat, we successfully recorded the peripheral neural signals while providing mechanical stimulation. Remarkably, we observed the external stimuli-induced nerve signals at 19 weeks after implantation. This is possibly due to axon regeneration inside our platform. To verify the tissue response of our electrodes to the sciatic nerve, we performed immunohistochemistry (IHC) and observed axon regeneration without scar tissue forming inside the conduit. Thus, our strategy has proven that our neural interface can play a significant role in the long-term monitoring of the peripheral nerve signal.

Use of an Intra-Arterial Catheter as a Provisional Conduit for Regulated Outflow Management in the Setting of Artery-Only Digital Replantation

Successful replantation of distal digital segments necessitates the establishment of sufficient outflow to minimize congestion and progressive tissue necrosis. In cases where only arterial anastomosis is feasible, an artificial outlet must be provided to maintain physiological requirements until microvenous circulation regenerates. This can be accomplished using any number of "exsanguination techniques" designed to facilitate egress through ongoing passive blood loss. Although reportedly effective, these measures are imprecise and carry a substantial risk of infection, scarring, and/or uncontrolled hemorrhage. Herein, we describe a preemptive alternative for provisional venous drainage, whereby direct catheterization of a distal arterial branch is used to enhance the precision of outflow management following artery-only digital replantation. The establishment of intravascular access, using the technique described, permits remote manipulation of the microcirculatory environment through timed administration of heparinized saline and regulated removal of controlled volumes of blood.

Nanofibrous nerve conduits for repair of 30-mm-long sciatic nerve defects

It has been confirmed that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nerve conduit can promote peripheral nerve regeneration in rats. However, its efficiency in repair of over 30-mm-long sciatic nerve defects needs to be assessed. In this study, we used a nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nerve conduit to bridge a 30-mm-long gap in the rat sciatic nerve. At 4 months after nerve conduit implantation, regenerated nerves were cally observed and histologically assessed. In the nanofibrous graft, the rat sciatic nerve trunk had been reconstructed by restoration of nerve continuity and formation of myelinated nerve fiber. There were Schwann cells and glial cells in the regenerated nerves. Masson's trichrome staining showed that there were no pathological changes in the size and structure of gastrocnemius muscle cells on the operated side of rats. These findings suggest that nanofibrous poly(3-hydroxybutyrate-co-3-hydroxyvalerate) nerve conduit is suitable for repair of long-segment sciatic nerve defects.