Injectable Near-Infrared Photothermal Responsive Drug-Loaded Multiwalled Carbon Nanotube Hydrogels for Spinal Cord Injury Repair

Spinal cord injury (SCI) has a high disability rate and poor treatment efficacy and severely affects the health and daily life of patients. Improving the local microenvironment after SCI is crucial for restoring the normal physiological function of the spinal cord. In this study, the injectable near-infrared (NIR) photothermal responsive drug-loaded multiwalled carbon nanotubes (DMWCNTs) containing hydrogel microspheres were prepared by microfluidic technology for SCI treatment. Specifically, paclitaxel (PTX) and vascular endothelial growth factor (VEGF) were loaded into dopamine-modified DMWCNTs, which were then further compounded into gellan gum (GG) by using microfluidic technology to obtain [PTX/VEGF]@DMWCNTs/GG microspheres. The physicochemical properties of the microspheres were characterized using various methods, including transmission electron microscopy (TEM), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, optical microscopy, and scanning electron microscopy (SEM). Results showed that microspheres with good injectability and controllable drug release were successfully prepared by using microfluidic technology. The presence of MWCNTs endowed the microspheres with photothermal responsiveness, which led to more drug release under NIR irradiation. The cytotoxicity test results showed that the microspheres had no obvious cytotoxicity and the drug-loaded MWCNTs containing hydrogel microspheres could promote the differentiation of neural stem cells (NSCs). Immunofluorescence results in rats with hemisectioned SCI showed that the microspheres promoted the differentiation of NSCs and the growth of neurons and inhibited the formation of astrocytes and glial scars at the lesion site. In conclusion, the injectable near-infrared photothermal responsive drug-loaded multiwalled carbon nanotube hydrogel microspheres prepared in this study exhibit a promoting effect on SCI repair and provide a strategy for developing transplantation materials for SCI treatment.