A biodegradable piezoelectric vertebral implant for programmable electro-neuromodulation in spinal cord injury

Spinal cord stimulation has emerged as a promising therapeutic strategy for spinal cord injury (SCI), yet conventional electronic implants remain limited by surgical risk and long-term safety concerns. We introduce a biodegradable piezoelectric cryogel (Piezo Gel) that enables programmable electro-neuromodulation without implanted electronics. Engineered to replicate spinal column mechanics, Piezo Gel converts physiological motion into localized bioelectrical signals; externally applied ultrasound (US) further amplifies this output, enabling non-invasive, on-demand neuromodulation. In acute severe SCI rats, US-activated Piezo Gel markedly improved locomotor recovery, elevated Basso–Beattie–Bresnahan (BBB) scores, and promoted bladder functional remodeling. In mild contusion rats, a phase-adaptive neuromodulation strategy shifted from US-triggered stimulation during the acute immobilization phase to motion-driven stimulation during subacute rehabilitation, dynamically matching the evolving pathological microenvironment after SCI. This sequential electrostimulation paradigm produced marked restoration of coordinated gait. Together, these findings establish an electronic-free platform for programmable electro-neuromodulation that integrates US and physiological motion, offering a clinically translatable strategy for SCI repair.