Amplification\nof Metalloregulatory Proteins in Macrophages\nby Bioactive ZnMn@SF Hydrogels for Spinal Cord Injury Repair

Macrophages\nare rapidly activated and polarized toward the M1 phenotype\nafter spinal cord injury (SCI), and inhibiting M1-like macrophages\nhas emerged as a promising SCI treatment approach. Metalloregulatory\nproteins, which sense specific metal ions with high affinity and specificity,\nplay a critical role in immune regulation. Here, we screened various\nbioactive metal ions associated with metalloregulatory proteins and\ndiscovered that Zn<sup>2+</sup> and Mn<sup>2+</sup> effectively suppressed\nM1 polarization. Based on these findings, mildly alkaline ZnMn-based\nlayered double hydroxides (ZnMn-LDHs) self-assembled from Zn<sup>2+</sup> coordinated with Mn<sup>2+</sup> were developed to inhibit M1-like\nmacrophages. ZnMn-LDHs effectively neutralized the acidic environment\nand promoted the expression of metalloregulatory proteins, including\nmetallothionein (MT), superoxide dismutase 1 (SOD1), and superoxide\ndismutase 2 (SOD2), thereby eliciting robust M1-like macrophage inhibition.\nMore importantly, nerve growth factor (NGF) released by macrophages\nfollowing the regulation by ZnMn-LDHs promoted the elongation and\nspreading of Schwann cells. By integrating ZnMn-LDHs with silk fibroin\n(SF), ZnMn@SF injectable hydrogels were constructed for SCI repair.\nAn in vivo animal model further revealed the excellent anti-inflammatory\neffects of the ZnMn@SF hydrogels in treating SCI, which promoted functional\nrecovery. Our findings underscore the importance of metalloregulatory\nproteins regulated by metal ions in inhibiting M1-like macrophages,\nproviding a promising therapeutic strategy for SCI treatment.