Emission enhancement of GFP chromophore in aggregated state via combination of self-restricted effect and supramolecular host–guest complexation

Abstract

The emission enhancement of GFP-like chromophores in the aggregated state is a great challenge due to its free conformational motions and aggregation-induced quenching (ACQ) features. Herein, the emission response of a GFP chromophore (GFPc) in its aggregated state has been greatly enhanced via combination of self-restricted effect and supramolecular host–guest complexation. Specifically, the benzene group of the GFP chromophore (HBHI) was tailored by 2,5-methoxy group to construct a self-restricted chromophore (MBHI), which shows enhanced emission response in both solutions and aggregated state compared to HBHI due to the formation of the self-restricted effect. After conjugated to adamantine (AD), the chromophore (MBIAD) exhibits aggregation-induced emission enhancement (AIEE) feature compared to MBHI in aggregated state. Moreover, the aggregated emission of MBIAD further enhances by complexation with proper β-cyclodextrin (β-CD), which reduces strong ACQ between chromophores. Furthermore, the aggregated emission can also be tuned by controlling the ratio of β-CD and AD. Under a ratio of 1 : 2, MBIAD and Me-β-CD can assemble into nanoparticle with a diameter of about 55 nm, which has been applied to cell imaging due to the relatively low cell cytotoxicity.