Ingenious Multifunctional MnO₂ Quantum Dot Nanozymes with Superior Catechol Oxidase-like Activity for Highly Selective Sensing of Redox-Active Dopamine Based on an Interfacial Passivation Strategy

Abstract

The single function and weak catalytic activity of nonprecious metal nanozymes distinctly hinder their practical applications, so it is intriguing to develop multifunctional nanozymes via a facile and green route. Here, for the first time, “bottom–up” strategies were used to realize the efficient synthesis of MnO2 quantum dots (QDs) with simple operation and mild reaction conditions based on proteins, avoiding the operation complexity of the traditional “up–down” approach. More interestingly, MnO2 QDs exhibit extraordinarily outstanding catechol oxidase-like activity. QD nanozymes can catalyze the oxidation of dopamine (DA) into DA quinone in just 2 min, and then DA quinone polymerizes to form PDA in more than 10 min at 37 °C over a broad pH range (above pH 7.4). Based on the catechol oxidase-like activity and the interaction between QDs with a DA quinone-induced passivation effect, a “turn-on” fluorescence sensor based on two sequential recognitions for DA with self-signal output is developed without using the commonly used chromogenic reactions. The dual recognition provides the sensor with extremely good selectivity, which removes the interference from common reducible substances and metal ions. The detection limit can reach 0.038 μM, and the sensor has good specificity and a short detection time (just 2 min) under mild conditions. This offers a flexible guide for rational design and fabrication of FL turn-on biosensors for redox-active dopamine and enriches our understanding of QD nanozymes in bioanalytical fields.

Porous NiCoP Nanowire Arrays on the Surface of Ti3C2Tx-Modified Carbon Cloth for Sensitive Determination of Dopamine

“…The x -coordinate is the linear range, and the y -coordinate is the detection limit. In recent literature studies, − the sensing performances of CC/Ti 3 C 2 T x /NiCoP for DA is at a relatively high level.…”

Molecular insights of nanozymes from design to catalytic mechanism

“…They play a crucial role in enzymatic browning by catalyzing the oxidation of catechol into corresponding o-quinones in the presence of oxygen to protect the damaged plant. Recently, a few nanozymes have been explored with ingenious catechol oxidase performance [64]. Among them, Dong's group [65] made an unprecedented work fabricating MOF-818 as catechol oxidase mimicking.…”

Copper Immobilized over 2D Hexagonal SBA-15 for Electrochemical and Colorimetric Sulfite Sensing

“…Since the report of Fe 3 O 4 NPs with peroxidase-like activity, several inorganic nanomaterials with enzyme-mimic activity have been explored. These include metal oxide nanomaterials, , mixed metal oxide nanomaterials, ,, graphene-based nanomaterials, , metal sulfides, , noble metals, , metal–organic frameworks, , and carbon nanotubes . These heterogeneous enzyme-mimic nanomaterials can compensate for deficiencies of natural enzymes and offer a wide range of applications, including biosensing, biocatalysis, medical diagnostics, and environmental cleanup.…”