Broad-spectrum downregulation of inflammatory cytokines by polydopamine nanoparticles to protect the injured spinal cord

Acute neuroinflammation, which is notably characterized by a significant elevation in pro-inflammatory cytokines and chemokines, often rapidly develops following a traumatic spinal cord injury and exacerbates damage in the lesion area. This study addresses the limitations inherent in strategies that regulate only a single or a few cytokines, which are often insufficient to counteract the progression of secondary injuries. We explore the use of polydopamine nanoparticles as a broad-spectrum immunomodulator, capable of capturing by adsorption a wide range of cytokines and thereby effectively suppressing neuroinflammation. Leveraging their adhesive properties, these nanoparticles promptly reduce levels of various excessive cytokines, including IL-1α, IL-1β, IL-6, IL-10, IL-17A, IL-18, TNF-α, MCP-1, GRO/KC, M-CSF, MIP-3α, and IFN-γ, primarily through physical adsorption. This reduction in cytokine levels contributes to the subsequent inhibition of pro-inflammatory M1 microglia and A1 astrocyte activation, aiding in the recovery of motor functions in vivo. In summary, polydopamine nanoparticles represent a versatile and effective approach for modulating acute neuroinflammation in spinal cord injuries. By broadly down-regulating cytokines, polydopamine nanoparticles propose an innovative approach for treating spinal cord injuries. Statement of significance The current study demonstrated the immunomodulatory potential of polydopamine nanoparticles in mitigating neuroinflammation following spinal cord injury. Both in vitro and in vivo analyses revealed significant downregulation of several key cytokines among a panel of 23 cytokines and chemokines. The potential underlying mechanisms governing these interactions were elucidated through comprehensive molecular dynamics simulations for the first time. Consequently, the downregulation of these cytokines and chemokines led to the inhibition of pro-inflammatory M1 microglia and A1 astrocyte activation in both in vitro and in vivo models. This inhibition protected neurons within the microenvironment, resulting in improved locomotor functions. Overall, this study underscores the prominent therapeutic efficacy of polydopamine nanoparticles in alleviating neuroinflammation, highlighting their potential as broad-spectrum regulators in intricate microenvironments.