Ischemic stroke is a refractory disease that endangers human health and safety owing to cerebral ischemia. Brain ischemia induces a series of inflammatory reactions. Neutrophils migrate from the circulatory system to the site of cerebral ischemia and accumulate in large numbers at the site of inflammation across the blood-brain barrier. Therefore, hitchhiking on neutrophils to deliver drugs to ischemic brain sites could be an optimal strategy. Since the surface of neutrophils has a formyl peptide receptor (FPR), this work modifies a nanoplatform surface by the peptide cinnamyl-F-(D)L-F-(D)L-F (CFLFLF), which can specifically bind to the FPR receptor. After intravenous injection, the fabricated nanoparticles effectively adhered to the surface of neutrophils in peripheral blood mediated by FPR, thereby hitchhiking with neutrophils to achieve higher accumulation at the inflammatory site of cerebral ischemia. In addition, the nanoparticle shell is composed of a polymer with reactive oxygen species (ROS)-responsive bond breaking and is encased in ligustrazine, a natural product with neuroprotective properties. In conclusion, the strategy of hitching the delivered drugs to neutrophils in this study could improve drug enrichment in the brain, thereby providing a general delivery platform for ischemic stroke or other inflammation-related diseases.

Due to the aggregation-caused quenching effect and near-infrared I poor penetration capabilities of common fluorescent molecules, their applications in visualized imaging and photoactivated treatment are limited. Therefore, new near-infrared II (NIR-II) molecule (named TST), which had the abilities of aggregation-induced emission (AIE) and photothermal therapy are synthesized. Moreover, in order to further improve its fluorescent yield and therapeutic effect, camptothecin prodrug (CPT-S-PEG) and novel immune checkpoint inhibitor AZD4635 are used to co-assemble with TST into nanoparticles for drug delivery. On account of the strong interaction of camptothecin and TST, the intramolecular rotation of TST is limited, thereby inhibiting non-radiation attenuation and promoting fluorescence generation when the nanoparticles are intact. As nanoparticles uptake by cancer cells, redox sensitive CPT-S-PEG is degraded and the nanoparticles disintegrate. The released TST enhances non-radiative attenuation and expedites photothermal conversion because of the removal of the constraint of camptothecin. Furthermore, photothermal therapy induces immunogenic cell death of cancer cells and releases abundant ATP into the tumor microenvironment to recruit immune cells. However, superfluous ATP is converted into immunosuppressive adenosine through the CD39-CD73-A2AR pathway. The AZD4635 released by photothermal disintegration of the nanoparticles just blocks this pathway timely, achieving favorable synergistic effect of photothermal therapy, chemotherapy, and immunotherapy.

Traumatic brain injury (TBI) is the main cause of death and disability in people of all ages worldwide. Neuroinflammation plays beneficial and harmful roles in secondary brain injury. Neutrophils play an important role in chemically mediated inflammatory responses through myeloperoxidase (MPO) and inflammation triggered by TBI. Herein, a nanodrug targeting neutrophils and MPO through chemical and biological functions after TBI is designed to enhance the retention and sustained release of drug cargos for improved TBI therapy. 5‐Hydroxytryptamide (5‐HT) is modified on nanoparticles (NPs) loaded with an anti‐inflammatory and antioxidant natural product, hesperetin, to obtain MPO‐ and neutrophil‐targeting NPs, denoted as T‐Hes. In a mouse TBI model, it is confirmed that neutrophil‐targeting NPs can quickly accumulate and remain in the brain tissue, reduce the secretion of inflammatory factors, and the level of microglia and astrocytes, subsequently inducing the transformation of microglia from pro‐inflammatory M1 to anti‐inflammatory M2 cells and promoting the infiltration of regulatory T cells (Tregs). T‐Hes significantly inhibits neuroinflammation and improves neurological deficits through the sustained release of hesperetin in the brain. The findings may open up new avenues for designing clinically translatable probes for TBI treatment.