Magnetoactive Composite Conduits Based on Poly(3-hydroxybutyrate) and Magnetite Nanoparticles for Repair of Peripheral Nerve Injury

Peripheral nerve injury poses a threat to the mobility and sensitivity of a nerve, thereby leading to permanent function loss due to the low regenerative capacity of mature neurons. To date, the most widely clinically applied approach to bridging nerve injuries is autologous nerve grafting, which faces challenges such as donor site morbidity, donor shortages, and the necessity of a second surgery. An effective therapeutic strategy is urgently needed worldwide to overcome the current limitations. Herein, a magnetic nerve guidance conduit (NGC) based on biocompatible biodegradable poly(3-hydroxybutyrate) (PHB) and 8 wt % of magnetite nanoparticles modified by citric acid (Fe₃O₄-CA) was fabricated by electrospinning. The crystalline structure of NGCs was studied by X-ray diffraction, which indicated an enlarged β-phase of PHB in the composite conduit compared to a pure PHB conduit. Tensile tests revealed greater ductility of PHB/Fe₃O₄-CA: the composite conduit has Young's modulus of 221 ± 52 MPa and an elongation at break of 28.6 ± 2.9%, comparable to clinical materials. Saturation magnetization (σ_s) of Fe₃O₄-CA and PHB/Fe₃O₄-CA is 61.88 ± 0.29 and 7.44 ± 0.07 emu/g, respectively. The water contact angle of the PHB/Fe₃O₄-CA conduit is lower as compared to pure PHB, while surface free energy (σ) is significantly higher, which was attributed to higher surface roughness and an amorphous phase as well as possible PHB/Fe₃O₄-CA interface interactions. In vitro, the conduits supported the proliferation of rat mesenchymal stem cells (rMSCs) and SH-SY5Y cells in a low-frequency magnetic field (0.67 Hz, 68 mT). In vivo, the conduits were used to bridge damaged sciatic nerves in rats; pure PHB and composite PHB/Fe₃O₄-CA conduits did not cause acute inflammation and performed a barrier function, which promotes nerve regeneration. Thus, these conduits are promising as implants for the regeneration of peripheral nerves.