Preparation of Upconversion Nanoparticles (UCNPs)-Polyethylene Glycol (PEG)/Merocyanine540 (M540) Photosensitizer by Core–Shell Structure and Its Application in the Treatment of Spinal Cord Injury

Abstract

The objective of this study is to investigate the adjuvant effect of UCNP-PEG-M540 based on a core–shell structure in spinal cord injury (SCI) treatment. 90 female healthy adult SD rats were divided into a control (Ctrl) group, a UCNP, and a UCNP-PEG-M540 group according to different transplantation materials to observe the recovery of behavioral function and axonal regeneration in rats to evaluate the application effect. The diameter of the UCNP was approximately 24 nm, and the distribution was uniform, which conformed to nanoscale particles. The diffraction pattern of UCNP based on the core–shell structure was basically the same as that of the UCNP naked core. At 4–12 weeks of treatment, the BBB score of the UCNP-PEG-M540 group was higher based on that of the Ctrl and UCNP groups; the IOD value of NF200-positive staining in the UCNP-PEG-M540 group was much higher to that in the Ctrl group and UCNP group; the IOD value of GFAP-positive staining and the gray value of CFAP were lower to those of the Ctrl group and UCNP group. UCNP-PEG-M540 based on a core–shell structure can further promote the absorption of 980 nm near-infrared light in injured tissues of SCI rats and inhibit glial cell aggregation, thereby reducing the formation of glial cells and promoting the repair of SCI and the recovery of behavioral function.