Spinal cord injury (SCI) is a severe central nervous system disorder that leads to long-term neurological dysfunction. Currently, there are no effective clinical treatments, making it imperative to develop novel therapeutic strategies that can simultaneously regulate immune responses and promote neural regeneration. Here, we designed and prepared an injectable self-healing multifunctional hydrogel composed of gelatin, quaternized chitosan, polydopamine, and curcumin. This hydrogel integrates immune microenvironment remodeling, spinal cord-matched mechanical properties, excellent biocompatibility, and sustained curcumin release for up to 14 days, effectively covering the critical acute-to-subacute phases of SCI repair. In vitro studies demonstrated that the hydrogel effectively scavenged reactive oxygen species (ROS) and induced macrophage polarization towards the anti-inflammatory M2 phenotype. In the rat model of SCI, treatment markedly alleviated oxidative stress and neuroinflammation during the acute phase, inhibited glial scar formation, promoted axonal and myelin regeneration, and ultimately improved motor function recovery. Collectively, this study presents a promising platform for SCI treatment and other central nervous system disorders by remodeling the immune microenvironment.

Atherosclerosis is an inflammatory disease that may cause severe heart disease and stroke. Current pharmacotherapy for atherosclerosis shows limited benefits. In the progression of atherosclerosis, monocyte adhesions and inflammatory macrophages play vital roles. However, precise regulations of inflammatory immune microenvironments in pathological tissues remain challenging. Here, we report an atherosclerotic plaque-targeted selenopeptide nanomedicine for inhibiting atherosclerosis progression by reducing monocyte adhesions and inflammation of macrophages. The targeted nanomedicine has 2.2-fold enhancement in atherosclerotic lesion accumulation. The oxidation-responsibility of selenopeptide enables eliminations of reactive oxygen species and specific release of anti-inflammatory drugs, thereby reducing inflammation responses of macrophages. Notably, we find the oxidative metabolite of selenopeptide, octadecyl selenite, can bind to P-selectin in a high affinity with a dissociation constant of 1.5 μM. This in situ generated active seleno-species further inhibit monocyte adhesions for anti-inflammation in synergy. With local regulations of monocyte adhesions and inflammations, the selenopeptide nanomedicine achieves 2.6-fold improvement in atherosclerotic plaque inhibition compared with simvastatin in the atherosclerosis mouse model. Meanwhile, the selenopeptide nanomedicine also displays excellent biological safety in both mice and rhesus monkeys. This study provides a safe and effective platform for regulating inflammatory immune microenvironments for inflammatory diseases such as atherosclerosis.

Carbon-based single-atom catalysts (SACs) have been widely studied in the field of biomedicine due to their excellent catalytic performance. However, carbon-based SACs usually aggregate during pyrolysis, which leads to the reduction of catalytic activity. Here, we describe a method to improve the monodispersion of SACs using silicon dioxide as a protective layer. The decoration of silicon dioxide serves as a buffer layer for individual nanoparticles, which is not destroyed during the pyrolysis process, ensuring the single-particle dispersion of the nanoparticles after etching. This approach increased the hydroxyl groups on the surface of Fe-SAC (Fe-SAC-SE) and improved its water solubility, resulting in a four times enhancement of the peroxidase (POD)-like activity of Fe-SAC-SE (58.4 U/mg) than that of non-protected SACs (13.9 U/mg). The SiO₂-protection approach could also improve the catalytic activities of SACs with other metals such as Mn, Co, Ni, and Cu, indicating its generality for SACs preparation. Taking advantage of the high POD-like activity, photothermal properties, and large specific surface area of Fe-SAC-SE, we constructed a synergistic therapeutic system (Fe-SAC-SE@DOX@PEG) for combining the photothermal therapy, catalytic therapy, and chemotherapy. It was verified that the photothermal properties of Fe-SAC-SE@DOX@PEG could effectively improve its POD-like activity, exhibiting excellent tumor-killing performance at the cellular level. This work may provide a general approach to improve the performances of SACs for disease therapy and diagnosis.

Oxidative stress and inflammation are central pathophysiological processes in a traumatic spinal cord injury (SCI). Antioxidant therapies that reduce the reactive oxygen and nitrogen species (RONS) overgeneration and inflammation are proved promising for improving the outcomes. However, efficient and long-lasting antioxidant therapy to eliminate multiple RONS with effective neuroprotection remains challenging. Here, a single-atom cobalt nanozyme (Co-SAzyme) with a hollow structure was reported to reduce the RONS and inflammation in the secondary injury of SCI. Among SAzymes featuring different single metal-N sites (e.g., Mn, Fe, Co, Ni, and Cu), this Co-SAzyme showed a versatile property to eliminate hydrogen peroxide (H₂O₂), superoxide anion (O₂^•−), hydroxyl radical (·OH), nitric oxide (·NO), and peroxynitrite (ONOO⁻) that overexpressed in the early stage of SCI. The porous hollow structure also allowed the encapsulation and sustained release of minocycline for neuroprotection in synergy. In vitro results showed that the Co-SAzyme reduced the apoptosis and pro-inflammatory cytokine levels of microglial cells under oxidative stress. In addition, the Co-SAzyme combined with minocycline achieved remarkable improved functional recovery and neural repairs in the SCI-rat model.