Abstract: BACKGROUND: Based on the concept of the combination of medicine and industry and the advantages of traditional Chinese medicine treatment, the construction of a new composite material loaded with the effective active ingredient of traditional Chinese medicine is a hot research spot in the repair of spinal cord injury, and is expected to become an effective means to solve this problem.
OBJECTIVE: To observe the effect of supramolecular conducting hydrogel carrying ligustrazine in repairing spinal cord injury in rats.
METHODS: The supramolecular conducting hydrogel carrying ligustrazine was prepared and its microstructure, conductivity, rheology, swelling rate and in vitro release performance were characterized. 45 SD rats were divided into 3 groups by random number table method, with 15 rats in each group: no spinal cord injury in the sham operation group; spinal cord injury model was established in the model group; and supramolecular conducting hydrogel carrying ligustrazine was injected into the spinal cord injury area after model establishment in hydrogel group. BBB score was used to evaluate the recovery of hind limb motor function of each group before and 1, 7, 14, 21 and 28 days after modeling, respectively. 28 days after the model establishment, the spinal cord tissues were collected and analyzed by hematoxylin-eosin staining, immunohistochemical staining and western blot assay.
RESULTS AND CONCLUSION: (1) Under scanning electron microscopy, the supramolecular conducting hydrogel with ligustrazine displayed a three-dimensional micrometer-scale porous network structure with high porosity and a pore size of approximately 100 µm. The conductivity of the hydrogel was 7.66 S/m; the swelling rate was 3 764.42%, and it had certain mechanical stability and injection property. In vitro sustained release experiments demonstrated that the supramolecular conducting hydrogel with ligustrazine sustainably released ligustrazine for more than 800 hours. With the extension of time, the cumulative release of ligustrazine exhibited an increasing trend. (2) With the extension of modeling time, the hind limb motor function gradually recovered in the model group and the hydrogel group, and the hind limb motor function of the hydrogel group was better than that of the model group on 14, 21, and 28 days after modeling (P < 0.05). Hematoxylin-eosin staining demonstrated that the spinal cord tissue of the model group had cavities and a large number of inflammatory cells could be seen at the stump. In the hydrogel group, some inflammatory cells were infiltrated in the injured area of the spinal cord; the void area of the injured area was reduced; neuron cells appeared in the junction area, and the tissue arrangement was relatively neat. Immunohistochemical staining and western blot assay exhibited that the expression of tumor necrosis factor α and interleukin-6 protein in the rat spinal cord of the hydrogel group was lower than that in the model group (P < 0.05), and the expression of neuronal nuclear antigen protein was higher than that in the model group (P < 0.05). (3) These findings confirm that the supramolecular conducting hydrogel carrying ligustrazine can promote the repair of spinal cord injury.

Key words: spinal cord injury, ligustrazine, injectable conducting hydrogel, inflammation, tissue engineering scaffold