Neutrophil Decoys with Anti‐Inflammatory and Anti‐Oxidative Properties Reduce Secondary Spinal Cord Injury and Improve Neurological Functional Recovery

Abstract Following spinal cord injury (SCI), immune cell infiltration creates an inflammatory and oxidative microenvironment (known as the secondary injury), which causes neuron death and spinal cord damage, and dramatically hinders neurological functional recovery. Strategies that inhibit the infiltration and/or function of neutrophils offer promises for SCI treatment because they can reduce the secondary injury; however, such strategies remain largely unexplored. Herein, a strategy using neutrophil membrane‐coated nanoparticles (NPs) as decoys (neutrophil decoy, ND) is presented to reduce local neutrophil infiltration and relieve oxidative stress in the injured spinal cord after SCI. Coated with membranes of activated neutrophils, the NDs inherit multiple receptors from the “parent” neutrophils, which can adsorb and neutralize the elevated neutrophil‐related cytokines. In addition, polydopamine NPs with multi‐antioxidative properties (selected as the core for ND) scavenge excessive reactive oxygen and nitrogen species. In a contusion model of SCI, ND treatment significantly reduces neutrophil infiltration and reprograms the inflammatory and oxidative microenvironment in injured spinal cords. Importantly, ND treatment significantly improves neural regeneration and functional recovery in rats. Such a nano‐decoy platform opens up new approaches for efficiently treating SCI.