Since the expected therapeutic results of ischemic stroke are strictly time dependent, early and accurate diagnosis as well as short intervals between diagnosis and treatment are key factors for the survival of stroke patients. In this study, we fabricated platelet (PLT) membrane-derived biomimetic nanobubbles (PNBs) for timely perfusion intervention and ultrasound imaging of acute ischemic stroke.Methods: The PNBs are fabricated by sonication-assisted reassembly of repeatedly freeze-thawed live platelet-derived PLT membrane vesicles (PMVs). The TEM, SEM, EDS and DLS were used to analyze the morphology and physicochemical properties of PNBs. The HPLC and LC-MS/MS were applied to confirm the lipid and protein compositions of PNBs. The in vitro macrophage uptake and platelet aggregation of PNBs were designed to examine the immune escape and thrombotic response characteristics. Furthermore, based on a photothrombotic ischemic stroke mouse model, the biodistribution, stroke microvascular network change, as well as cerebral blood flow of PNBs were studied by using near-infrared fluorescence imaging, multimodal optical imaging, and full-field laser perfusion imager. Finally, we assessed the brain ultrasound imaging of PNBs with a high-resolution micro-imaging system using both B-mode and contrast mode.Results: The natural lipid and protein components isolated from PLT membrane endow the PNBs with accurate lesion-targeting ability. The preferentially accumulated PNBs exhibit microvascular bio-remodeling ability of the stroke lesion, which is critical for recanalization of the obstructed vessels to protect the neural cells around the ischemic region of the stroke. Furthermore, with the increased accumulation of PNBs clusters in the lesion, PNBs in the lesion can be monitored by real-time contrast-enhanced ultrasound imaging to indicate the severity and dynamic development of the stroke.Conclusions: In summary, platelet membrane-based nanobubbles for targeting acute ischemic lesions were developed as microvascular recanalization nanoformulation for acute ischemic stroke lesion theranostics. This biomimetic PNBs theranostic strategy will be valuable for ischemic stroke patients in the future.

BackgroundIschemic stroke is a complex disease with multiple etiologies and clinical manifestations. Paired immunoglobulin‐like receptor B (PirB), which is originally thought to function exclusively in the immune system, is now also known to be expressed by neurons. A growing number of studies indicate that PirB can inhibit neurite outgrowth and restrict neuronal plasticity. The aim of the study is to investigate whether PirB can be an attractive theranostic target for ischemic stroke.Methods and ResultsFirst, we investigated the spatial‐temporal expression of PirB in multiple ischemic stroke models, including transient middle cerebral artery occlusion, photothrombotic cerebral cortex ischemia, and the neuronal oxygen glucose deprivation model. Then, anti‐PirB immunoliposome nanoprobe was developed by thin‐film hydration method and investigated its specific targeting in vitro and in vivo. Finally, soluble PirB ectodomain (sPirB) protein delivered by polyethylene glycol–modified nanoliposome was used as a therapeutic reagent for ischemic stroke by blocking PirB binding to its endogenous ligands. These results showed that PirB was significantly upregulated after cerebral ischemic injury in ischemic stroke models. Anti‐PirB immunoliposome nanoprobe was successfully developed and specifically bound to PirB in vitro. There was accumulation of anti‐PirB immunoliposome nanoprobe in the ischemic hemisphere in vivo. Soluble PirB ectodomains remarkably improved ischemic stroke model recovery by liposomal delivery system.ConclusionsThese data indicated that PirB was a significant element in the pathological process of cerebral ischemia. Therefore, PirB may act as a novel theranostic target for ischemic stroke.

Ischemic stroke is one of the leading causes of morbidity and mortality worldwide. The expression of major histocompatibility complex class I (MHC-I) molecules in the central nervous system, which are silenced under normal physiological conditions, have been reported to be induced by injury stimulation. The purpose of this study was to determine whether MHC-I molecules could serve as molecular targets for the acute phase of ischemic stroke and to assess whether a high-affinity peptide specific for MHC-I molecules could be applied in the near-infrared imaging of cerebral ischemic mice. Quantitative real-time PCR and Western blotting were used to detect the expression of MHC-I molecules in two mouse models of cerebral ischemic stroke and an in vitro model of ischemia. The NetMHC 4.0 server was used to screen a high-affinity peptide specific for mouse MHC-I molecules. The Rosetta program was used to identify the specificity and affinity of the screened peptide (histocompatibility-2 binding peptide, H2BP). The results demonstrated that MHC-I molecules could serve as molecular targets for the acute phase of ischemic stroke. Cy5.5-H2BP molecular probes could be applied in the near-infrared imaging of cerebral ischemic mice. Research on the expression of MHC-I molecules in the acute phase after ischemia and MHC-I-targeted imaging may not only be helpful for understanding the mechanism of ischemic and hypoxic brain injury and repair but also has potential application value in the imaging of ischemic stroke.