Biocompatible nanoparticles with aggregation-induced emission characteristics as far-red/near-infrared fluorescent bioprobes for in vitro and in vivo imaging applications

Light emission of 2-(2,6-bis((E)-4-(diphenylamino)styryl)-4H-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) -4H-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 (H22)-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. Encapsulation of far-red/near-infrared luminogens with aggregation-induced emission (AIE) characteristics in a bovine serum albumin (BSA) matrix yields nanoparticles (NPs) with uniform size, high brightness, and low cytotoxicity. Applications of these AIE-active NPs for in vitro and in vivo fluorescence imaging are demonstrated using MCF-7 breast-cancer cells and a murine hepatic H22-tumor-bearing mouse model, respectively. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim