Fluorescent Turn-On Detection and Assay of Protein Based on Lambda (Λ)-Shaped Pyridinium Salts with Aggregation-Induced Emission Characteristics

The lambda (Λ)-shaped pyridinium salts 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(p-ethenyl-N-methylpyridinium) ditosylate (DMDPS), 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(p-ethenyl-N-methylpyridinium) diiodide (DMDPI), and 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(p-ethenyl-N-methylpyridinium) dinitrate (DMDPN) based on Tröger’s base exhibit a typical aggregation-induced emission (AIE) behavior that it is virtually nonemissive in solution but highly luminescent in the aggregate state. The possibility of utilizing the AIE effect for protein detection and quantification is explored by using bovine serum albumin (BSA) as a model protein. These bioprobes undergo a large spectral change upon binding to BSA, which can be determined by fluorometry. Furthermore, the plots of photoluminescence intensity versus BSA concentration (0−70 μg/mL) display a good linear relationship, indicating quantitative fluorimetric protein detection may be achieved.