Terbium metal-organic framework/bovine serum albumin capped gold nanoclusters-based dual-emission reverse change ratio fluorescence nanoplatform for fluorimetric and colorimetric sensing of heparin and chondroitin sulfate

In this work, we designed a novel dual-emission reverse change ratio fluorescence nanoplatform for fluorimetric and colorimetric sensing of heparin (Hep) and chondroitin sulfate (CS) based on green emissive terbium metal-organic framework (Tb MOF) and red emissive bovine serum albumin capped gold nanoclusters ([email protected]). When excess Tb MOF was mixed with [email protected] NCs, the nanoaggregates of Tb MOF and [email protected] NCs could be precipitated by centrifugation due to the electrostatic interactions between them, and the supernatant displayed bright green color of Tb MOF under 254 nm UV lamp. However, the introduced Hep or CS caused the decomposition of Tb MOF since Tb3+ has stronger affinity with Hep and CS, which resulted in the release of [email protected] into the supernatant. As a result, the red fluorescence of [email protected] NCs turned on while the green fluorescence of Tb MOF turned off under the 254 nm UV illumination. The dual- emission reverse change ratio fluorescence nanoplatform possessed the variations of the emission intensity ratio at two different wavelength and the corresponding green-to-red fluorescent color changes, endowing a novel mechanism for fluorimetric and colorimetric analysis of Hep and CS using fluorescence spectrophotometer and smartphone, respectively. With the ratiometric fluorescence nanoprobe, simple and rapid sensing of Hep and CS with high sensitivity, selectivity and accuracy could be realized. Moreover, successful recoveries of the analytes in human serum samples were also validated, indicating promising application for Hep and CS analysis in biomedical diagnosis.