Electromagnetic induction drives electron–hole separation in an optoelectronic nerve conduit to accelerate nerve repair†

As a photoelectric material, bismuth sulfide (Bi₂S₃) can convert light signals into electrical signals and thus hold tremendous promise in constructing wireless electrical stimulation to accelerate nerve regeneration. However, the easy recombination of electrons and holes weakens the electrical stimulation effect. Herein, core–shell Bi₂S₃@PPy nanorods were prepared via the in situ hydrothermal polymerization of conductive polypyrrole (PPy) on Bi₂S₃ and were then blended into poly-L-lactic acid powder to fabricate a nerve conduit via laser additive manufacturing. Under a rotating magnetic field, conductive Bi₂S₃@PPy in the conduit could cut the magnetic inductance line to generate induced electromotive force that could drive the electrons and holes of Bi₂S₃ in opposite directions, thereby achieving efficient separation. Results indicate that the enhanced electron–hole separation boosted photocurrent generation, with an output current of 7.5 μA, which was significantly higher than the photocurrent under light irradiation (5.0 μA) and the induced current under magnetic field (2.5 μA). Immunofluorescent staining demonstrated that the enhanced photocurrent could up-regulate the expression of neuronal markers Nestin and GFAP. Moreover, the intracellular influx of Ca²⁺ was improved, which indicated that the differentiation of BMSCs into neurons was promoted. Overall, this work provides a potential wireless electrical stimulation strategy for accelerating nerve repair.