Discovery of a novel marine bacterial AIEgen that lights up specific G-quadruplexes

The emergence of aggregation-induced emission (AIE) phenomenon two decades ago marked a significant advancement in chemical science. It has fostered the development of versatile AIE luminogens (AIEgens) applicable in bioimaging, optoelectronics, and biochemical sensing. However, the application potential of synthetic AIEgens is limited owing to their constrained chemical space, environmental concerns, and uncertain biocompatibility. Consequently, the pursuit of naturally derived AIEgens (BioAIEgens) is considered a promising solution to developing next-generation AIEgens. Here, we report the discovery of 2-(2-hydroxy-6-methoxy-3-propionylphenyl)quinazolin-4(3H)-one (HMPQ) from marine bacterial metabolite as AIEgen for the first time. HMPQ shows its unique fluorescence mechanism through excited-state intramolecular proton transfer. Comprehensive photophysical assessments unveiled that HMPQ varied emissions in diverse solvents and solid-state polymorphic forms. Notably, HMPQ exhibited specific binding affinity to G-quadruplexes (G4s), illuminating these non-canonical nucleic acid structures without altering their conformation. Its remarkable safety profile and precise cellular visualization of G4 structures imply HMPQ's potential in biological applications, opening new avenues for utilizing BioAIEgens as G4 probes.