Dye-functionalized metal–organic frameworks with the uniform dispersion of MnO2 nanosheets for visualized fluorescence detection of alanine aminotransferase

The wide applications of metal-organic framework (MOF) luminescent materials in the field of optics have attracted the general attention of researchers. Therefore, the development of simple and multifunctional MOF light-emitting platforms have become a research hotspot. The composites (MnO2@ZIF-8-luminol) were prepared by an in situ synthesis method and room-temperature covalent reaction. The composites and o-phenylenediamine (OPD) constitute a dual emission sensor for detecting alanine aminotransferase (ALT). OPD can be oxidized by MnO2 to 2,3-diaminophenazine (DAP) with yellow fluorescence emission, which inhibits the blue emission of luminol through fluorescence resonance energy transfer (FRET). The presence of tiopronin (TP) will destroy the FRET process, extinguishing the yellow fluorescence emission and restoring the blue fluorescence emission. The special effect between ALT and TP will further reverse the changes in the two fluorescent signals. Moreover, in the detection process, when the blue and yellow fluorescence energies in the system are within a certain range, a new white light emission will be generated, which causes the sensing of ALT to present ternary visualization. In addition, a high-security anti-counterfeiting platform is constructed by using the prepared materials and agarose hydrogels. The anti-counterfeiting platform can encrypt information on demand according to the luminous characteristics of different materials. This study not only provides a typical case of ternary visualization sensing by MOF-based materials but also develops a possible method for the construction of a MOF-based hydrogel anti-counterfeiting platform.