Tricyclic 2-Aminopyridinium Derivatives with Aggregation-Induced Emission for Concomitant Bacterial Discrimination and Inhibition

The development of new ionic compounds with aggregation-induced emission (AIE) has been widely noticed. They can not only effectively solve the problem of aggregation-caused quenching (ACQ) encountered in conventional fluorescent dyes, but also exhibit promising applications in biological imaging, diagnosis and therapy, etc. However, such AIE system should be further developed. In this work, a series of novel cationic AIE luminogens (AIEgens) of tricyclic 2-aminopyridinium derivatives with seven-membered rings were designed and synthesized via a simple multi-component reaction, which exhibit the ability to specifically stain gram-positive bacteria. Meanwhile, they also possess excellent bacteriostatic ability for S. aureus in liquid medium and solid agar plates, of which the minimum inhibitory concentration (MIC) value is between 4 and 8 µg/mL. In addition, these molecules showed mitochondria-targeting capability in hydrophilic AIEgens and specific staining lysosomes in lipophilic AIEgens by wash-free process in living cells. These AIEgens with bacteriostatic activity hold great promise for distinguishing bacteria and inhibiting bacterial infection in clinical trial.