Immunomodulatory nanoparticles (IMPs) could provide an acute treatment for traumatic brain injury (TBI) that would help to preserve function and improve recovery, according to a recent mouse study published in Annals of Neurology. The biodegradable biopolymer nanoparticles, which are approved by the FDA, bind to monocytes and prevent them from migrating to sites of inflammation. In TBI, monocyte-derived macrophages infiltrate the brain after injury and are involved in mediating secondary damage — blocking this process with IMPs could, therefore, protect against this process. Sripadh Sharma and colleagues tested this theory by administering IMPs to two different mouse models of TBI. Treatment with IMPs reduced immune infiltration into the brain and led to preservation of tissue and neurological function. The findings provide a rationale for translating this approach into the clinic as an acute treatment for TBI.