NIAD-4 is a near-infrared (NIR) fluorescent label targeting amyloid-beta (Ki=10 nM) capable of crossing the blood-brain barrier. It serves as a fluorophore for optical imaging of Aβ in the central nervous system (CNS) for Alzheimer's disease, with absorption peaks at 475–480 nm.

NIAD-4 can enhance fluorescence quantum yield and fluorescence intensity by binding to amyloid aggregates and hindering their internal rotation, making it an effective tool for detecting amyloid proteins. Due to its charge neutrality and low molecular weight, NIAD-4 can penetrate the blood-brain barrier and can be used for imaging amyloid fibrils in the brain. The excitation wavelength of NIAD-4 is 475 nM, and the emission wavelength is 610 nM [2][3].