Enzyme-immobilized nanoclay hydrogel simultaneously reduces inflammation and scar deposition to treat spinal cord injury

Spinal cord injury (SCI) is a severely disabling pathological condition and always results in sensory and motor functions loss. After SCI, inflammation-mediated secondary tissue damage and subsequent formation of neuroglial scar suppress neuron survival and regeneration, therefore resulting in severe neurofunctional dysfunction. Although nanoclay biomaterials demonstrated useful immunomodulation feature in non-neuronal tissue, it is unclear if they can inhibit inflammation in SCI lesions and promote neurofunctional recovery. In this study, we immobilized chondroitinase ABC enzyme (ChABC), which can degrade chondroitin sulfate proteoglycans (CSPGs) of neuroglial scar, inside nanoclay (Laponite®, Lap) hydrogel through electrostatic interaction. The presented ChABC-immobilized Lap hydrogel (ChABC@Lap) exhibited shear-thinning properties and excellent injectability, allowing to locally deliver it into injured area through a non-invasive manner. Cell biological experiments and SCI rat model research revealed that both pure Lap (without ChABC) and ChABC@Lap hydrogels significantly reduced pro-inflammatory macrophage marker (iNOS) intensity. Importantly, compared with Lap hydrogel, ChABC@Lap hydrogel significantly decreased GFAP and CS-56 marked scar deposition, increased Tuj-1+ neurons regeneration, and promoted NF200+ neurons survival, thereby improving SCI rat of electrophysiological characteristics and motor function. In summary, the designed enzyme-immobilized nanoclay hydrogel offers a promising strategy for SCI therapy through modulating simultaneously inflammation and glial scar deposition.