Amphiphilic quinoline-malononitrile AIE probes: From molecule design to bio-applications

Abstract

Traditional aggregation-induced emissions (AIE) probes are prone to aggregate in aqueous biosystem, leading to non-specific fluorescence signals prior to binding to specific receptors (targets), which hinders precise in situ detection of the target substances. To address this challenge, we propose a novel design strategy termed “amphiphilic AIEgens”, which ensures that the probes exhibit excellent dispersibility in both aqueous biological environments and lipophilic organelles, remaining in a fluorescence-off state to effectively mitigate false fluorescence signals. Upon binding to specific receptors (targets), the restriction of molecular motion activates AIE fluorescence, thereby selectively illuminating the targeted substances. This minireview summarizes recent advancements of amphiphilic AIEgens, particularly focusing on the innovative AIE building block quinoline-malononitrile (QM). These amphiphilic AIE probes are constructed by chemically grafting functional hydrophilic groups onto lipophilic QM, effectively addressing dilemmas of undesirable-aggregation and non-specific fluorescence activation typically associated with traditional AIE probes, thereby enabling high-fidelity and long-term imaging of target substances at cellular, tissue, and even in vivo levels. Herein, we delineate the molecular engineering design strategy that integrates various functional blocks for amphiphilic AIE-active probes, and elaborate their applications in biosensing, diagnosis, and photodynamic therapy. Finally, we delve into the challenges and opportunities for AIE biological probes in conclusion section.