Dual-signal viscosity flow paper sensor for ATP detection based on bio-recognition and nanozyme activity regulation of ZIF-90

Adenosine triphosphate (ATP) is an important biological biomarker, but its rapid extracellular decomposition poses challenges for on-site detection. We report a paper-based dual-readout viscosity flow sensor enabling rapid, equipment-free quantification of ATP. The assay integrates molybdenum disulfide nanozymes for signal amplification with zeolitic imidazolate framework-90 (ZIF-90) for selective ATP recognition and nanozyme regulation. In the presence of ATP, the intact chitosanase-encapsulated ZIF-90 structure was disintegrated to release chitosanase and thus hydrolyzed chitosan hydrogel, decreasing the viscosity of chitosan solution. Moreover, elimination of ZIF-90 inhibitory effect reactivated the catalytic activity of MoS2 nanozyme, resulting in the oxidation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) to produce obvious color change. The analytical signals, combining the distance- and colorimetric- readout, were directly displayed on filter paper without further processed. The proposed dual-readout viscosity flow sensor exhibited remarkable sensitivity for ATP detection with detection limits down to 0.038 nM with the distance-readout and 0.057 nM for the colorimetric-readout. Furthermore, we developed an integrated paper kit with a printed scale and color card for standardized on-site analysis without instrumentation. Successful application for ATP quantification in bacterial biofilms and blood samples demonstrates the sensor's strong performance and potential for decentralized testing.