Biocompatible Nanoparticles with Aggregation‐Induced Emission Characteristics as Far‐Red/Near‐Infrared Fluorescent Bioprobes for In Vitro and In Vivo Imaging Applications

Abstract Light emission of 2‐(2,6‐bis(( E )‐4‐(diphenylamino)styryl)‐4 H ‐pyran‐4‐ylidene)malononitrile (TPA‐DCM) is weakened by aggregate formation. Attaching tetraphenylethene (TPE) units as terminals to TPA‐DCM dramatically changes its emission behavior: the resulting fluorogen, 2‐(2,6‐bis(( E )‐4‐(phenyl(4′‐(1,2,2‐triphenylvinyl)‐[1,1′‐biphenyl]‐4‐yl)amino)styryl)‐4 H ‐pyran‐4‐ylidene)malononitrile (TPE‐TPA‐DCM), is more emissive in the aggregate state, showing the novel phenomenon of aggregation‐induced emission (AIE). Formulation of TPE‐TPA‐DCM using bovine serum albumin (BSA) as the polymer matrix yields uniformly sized protein nanoparticles (NPs) with high brightness and low cytotoxicity. Applications of the fluorogen‐loaded BSA NPs for in vitro and in vivo far‐red/near‐infrared (FR/NIR) bioimaging are successfully demonstrated using MCF‐7 breast‐cancer cells and a murine hepatoma‐22 (H 22 )‐tumor‐bearing mouse model, respectively. The AIE‐active fluorogen‐loaded BSA NPs show an excellent cancer cell uptake and a prominent tumor‐targeting ability in vivo due to the enhanced permeability and retention effect.