Sensory-motor coupling electrical stimulation driven by a bionic Z-structured triboelectric nanogenerator improves functional recovery from spinal cord injury

Spinal cord injury (SCI) disrupts the neuronal relay circuits and causes limb paralysis. Although epidural elec-trical stimulation is a therapeutic approach for SCI, electrical stimulation pattern and continuous self-power capability are critical aspects that affect its effectiveness and clinical translation. Based on the tribo-electrification principle, we developed a novel bionic Z-structured triboelectric nanogenerator (BZ-TENG) which can convert the kinetic energy of joint flexion and extension into electricity after implantation adjacent to posterior side of the rat elbow joint. The BZ-TENG had an excellent electrical potential of up to 15 V and stability after 14,000 repeated compressions and it stimulated axonal regeneration without interfering with dorsal root ganglion neuronal activity in vitro. Additionally, we designed an innovative electrical stimulation pattern by transferring BZ-TENG generated currents to both sciatic nerves and the lateral spinal cord, which we named sensory-motor coupling electrical stimulation (SMCS). In vivo, BZ-TENG-SMCS significantly improved the re-covery of motor and sensory functions in SCI rats compared to spinal epidural stimulation alone (BZ-TENG-ESA) by promoting motor and sensory tract regeneration, axonal neogenesis, myelination, synapse formation, and inhibition of glial scar formation. The proposed BZ-TENG strategy provides a smart bio-adaptive and sustainable power source in vivo and is in combination with an SMCS pattern a promising novel approach for SCI therapy.