Aggregation-induced emission nanoparticles for in vivo three-photon fluorescence microscopic rat brain angiography

Rodents are popular biological models for physiological and behavioral research in neuroscience and rats are better models than mice due to their higher genome similarity to human and more accessible surgical procedures. However, rat brain is larger than mice brain and it needs powerful imaging tools to implement better penetration against the scattering of the thicker brain tissue. Three-photon fluorescence microscopy (3PFM) combined with near-infrared (NIR) excitation has great potentials for brain circuits imaging because of its abilities of anti-scattering, deep-tissue imaging, and high signal-to-noise ratio (SNR). In this work, a type of AIE luminogen with red fluorescence was synthesized and encapsulated with Pluronic F-127 to make up form nanoparticles (NPs). Bright DCDPP-2TPA NPs were employed for in vivo three-photon fluorescent laser scanning microscopy of blood vessels in rats brain under 1550 nm femtosecond laser excitation. A fine three-dimensional (3D) reconstruction up to the deepness of 600 mu m was achieved and the blood flow velocity of a selected vessel was measured in vivo as well. Our 3PFM deep brain imaging method simultaneously recorded the morphology and function of the brain blood vessels in vivo in the rat model. Using this angiography combined with the arsenal of rodent's brain disease, models can accelerate the neuroscience research and clinical diagnosis of brain disease in the future.