A Method for Improving the Optical Properties of a Fluoregenie Di-metal Chelator as a Zn~(2+)Ion Fluorescent Probe by Using a Bridging Substrate

摘要

Fluorescent probe based detection methods for metal ions are indispensable tools in many fields, including medical diagnostics, environmental monitoring, living cell studies, and electronics. These methods have multiple advantages over other methods, such as high sensitivity, low cost, ease of application, and versatility. Numerous fluorescent metal ion probes have been designed using many strategies, including fiuorogenic metal chelators, fluorescent dye tagged oligonucleotides, catalytic signal amplification, and chemodosi-metors. Fiuorogenic metal chelators, which consist of a fiuorogenic unit (signaling site) covalently linked to chelating moieties (receptor units) with an appropriate spacer, are a general type metal ion probe. The recognition of chelating moieties with metal ions induces a change in the photo-physical properties of the fluorescent probe. This is converted into an optical signal expressed as an enhancement or quenching of the fluorophore emission. The recognition can be enhanced to utilize additive reagents that provide additional binding sites for metal ions. For example, 8-amino-quinolino-p-cyclodextrin, developed by Liu et al., exhibited cooperative binding to Zn~(2+) ion with 1-adamatanoic acid. It also detected Zn~(2+) ions more efficiently than without 1-adamatanoic acid because 1-adamatanoic acid bound to β-cyclodextrin to provide additional binding site for Zn~(2+) ions. This strategy can easily expand to improve the optical properties of metal ion sensors with two metal binding sites. Di-metal complexes may include bridging substrates to complete the metal coordination sphere, and bridging substrates can modulate the properties of the resulting cascade complexes.4 In particular, bridging substrates provided additional metal ion binding sites and enhanced the binding properties of metal ions to metal ion ligands.