Precise Deciphering of Brain Vasculatures and Microscopic Tumors with Dual NIR‐II Fluorescence and Photoacoustic Imaging

Abstract Diagnostics of cerebrovascular structures and microscopic tumors with intact blood–brain barrier (BBB) significantly contributes to timely treatment of patients bearing neurological diseases. Dual NIR‐II fluorescence and photoacoustic imaging (PAI) is expected to offer powerful strength, including good spatiotemporal resolution, deep penetration, and large signal‐to‐background ratio (SBR) for precise brain diagnostics. Herein, biocompatible and photostable conjugated polymer nanoparticles (CP NPs) are reported for dual‐modality brain imaging in the NIR‐II window. Uniform CP NPs with a size of 50 nm are fabricated from microfluidics devices, which show an emission peak at 1156 nm with a large absorptivity of 35.2 L g −1 cm −1 at 1000 nm. The NIR‐II fluorescence imaging resolves hemodynamics and cerebral vasculatures with a spatial resolution of 23 µm at a depth of 600 µm. The NIR‐II PAI enables successful noninvasive mapping of deep microscopic brain tumors (<2 mm at a depth of 2.4 mm beneath dense skull and scalp) with an SBR of 7.2 after focused ultrasound‐induced BBB opening. This study demonstrates that CP NPs are promising contrast agents for brain diagnostics.