NIR-Emitting Semiconducting Polymer Nanoparticles for In Vivo Two-Photon Vascular Imaging

Two-photon fluorescence (TPF) imaging holds great promise for real-time monitoring of cerebral ischemia-reperfusion injury, which is important for clinical diagonsis of stroke. However, biocompatible and photostable NIR-emitting probes for TPF imaging of ischemic stroke are lacking. Herein, we report the first NIR-emitting TPF probe (named as NESPN) prepared based on semiconducting polymer for TPF imaging of cerebral ischemia. By virtue of the excellent biocompatibility with nervous system and bright fluorescent NIR emission, NESPN enables real-time imaging of mouse brain vasculature with micrometer-scale spatial resolution, realizing clear visualization of ultrafine capillaries (~3.16 µm). Moreover, NESPN can be utilized in the dynamic monitoring of cerebral blood flow velocity. The microangiography based on NESPN was successfully used to indicate the openness of the penumbra area in the mouse brain stroke model. More importantly, this technique allows us to continousely monitor the whole process of ischemic stroke and subsequent reperfusion. This work provides a new and versatile tool for vascular research and diagnosis of vascular diseases.