MOF-On-MOF\nDual Enzyme-Mimic Nanozyme with Enhanced\nCascade Catalysis for Colorimetric/Chemiluminescent Dual-Mode Aptasensing

Abstract

A novel metal–organic framework (MOF)-on-MOF dual\nenzyme-mimic\nnanozyme was designed as enhanced cascade signal amplification for\nthe colorimetric and chemiluminescent (CL) dual-mode aptasensing.\nThe MOF-on-MOF hybrid is composed of MOF-818 with catechol oxidase-like\nactivity and iron porphyrin MOF [PMOF(Fe)] with peroxidase-like activity,\ncalled MOF-818@PMOF(Fe). MOF-818 can catalyze the 3,5-di-<i>tert</i>-butylcatechol substrate and produce H₂O₂ in\nsitu. Subsequently, PMOF(Fe) catalyzes H₂O₂ to\nproduce reactive oxygen species, which oxidize 3,3′,5,5′-tetramethylbenzidine\nor luminol to produce color or luminescence. Thanks to the nano-proximity\neffect and the confinement effect, the efficiency of the biomimetic\ncascade catalysis is greatly improved, which in turn generates enhanced\ncolorimetric and CL signals. Taking the detection of chlopyrifos as\nan example, the prepared dual enzyme-mimic MOF nanozyme is combined\nwith the aptamer with specific recognition ability to develop a colorimetric/CL\ndual-mode aptasensor for highly sensitive and selective detection\nof chlorpyrifos. The proposed MOF-on-MOF dual nanozyme-enhanced cascade\nsystem may provide a new pathway for the further development of a\nbiomimetic cascade sensing platform.