Rigidity-Dependent Emission: Inspired Selection of an ATP-Specific Polyvalent Hydrogen Binding-Lighted Fluorophore for Intracellular Amplified Imaging

ATP,a small molecule with high intracellular concentration (mMlevel), provides a fuel to power signal amplification, which is meaningfulfor biosensing. However, traditional ATP-powered amplification isbased on ATP/aptamer recognition, which is susceptible to the complexbiological microenvironment (e.g., nuclease). In this work, we communicatea signaling manner termed as ATP-specific polyvalent hydrogen binding(APHB), which is mimetic to ATP/aptamer binding but can avoid interferencefrom biomolecules. The key in APHB is a functional fluorophore thatcan selectively bind with ATP via polyvalent hydrogen, and the fluorescencewas lighted with the changes of the molecular structure from flexibilityto rigidity. By designing, synthesizing, and screening a series ofcompounds, we successfully obtained an ATP-specific binding-lightedfluorophore (ABF). Experimental verification and a complex analoguedemonstrated that two melamine brackets in the ABF dominate the polyvalenthydrogen binding between the ABF and ATP. Then, to achieve amplificationbiosensing, fibroblast activation protein (FAP) in activated hepaticstellate cells was taken as a model target, and a nanobeacon consistingof an ABF, a quencher, and an FAP-activated polymer shell was constructed.Benefiting from the ATP-powered amplification, the FAP was sensitivelydetected and imaged, and the potential relationship between differentiationof hepatocytes and FAP concentration was first revealed, highlightingthe great potential of APHB-mediated signaling for intracellular sensing.