Fluorescent Mn3O4 quantum dot as catechol oxidase nanozyme: A robust nano-platform for sensitive dopamine detection

• Published in: Applied surface science Vol. 675; p. 160949
• Main Authors: Jacob, Dhanya P., Thomas, Subin, Sanker S.S., Sree, Shanmughan, Prasanth, Madhusoodanan, K.N., Antony, Aldrin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.11.2024
• Subjects: Catechol oxidase enzyme; Dopamine; Fluorescence detection; Mn3O4 quantum dots; Nanozymes; Mn3O4 quantum dots; Dopamine; Nanozymes; Catechol oxidase enzyme; Fluorescence detection
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2024.160949

[Display omitted] •For the first time, a detailed study on fluorescent Mn3O4 Quantum dots synthesis and characterization is reported.•The material exhibits excellent Catechol-oxidase mimicking activity demonstrating excellent enzyme kinetic parameters.•Dopamine sensor is developed using Mn3O4 nanozymes with promising sensing parameters and LoD is obtained as 18 nM.•The quenching mechanism behind proposed Dopamine sensor has been studied and explained in detail. The development of multifunctional semi-conductor nano-enzymes has attained significant interest recently, due to their ease in fabrication, cost-effectiveness, and wide range of applications. In this work, we report the synthesis of ammine-functionalized Mn3O4 quantum dots (Mn3O4 QDs) with excellent luminescence properties. These QDs have been developed via the reduction of permanganate using L-cysteine through a simple, facile one-step bottom-up approach. The steady-state enzyme kinetic studies revealed the superior Catechol-Oxidase mimic activity of the Mn3O4 QDs with a Michaelis-Menten constant (Km) of 133.19 µM, and maximum reaction velocity (Vmax) of 69.40 µMs−1. Due to this superior enzymatic activity, dopamine (DA) gets easily oxidized into DA-quinone and eventually polymerized to form polydopamine. Schiff base/Michael addition reaction between nucleophilic ammine on the surface of QDs and the aromatic chain makes the probe and analyte come closer and leads to the formation of a charge transfer complex, resulting in fluorescence quenching of QDs. This fluorescence quenching has been quantified to develop a turn-off sensor for DA. The sensing characteristics are highly selective and sensitive towards DA with a detection limit of 18 nM. The synthesised Mn3O4 QDs with superior enzyme-mimicking properties have tremendous potential as fluorescent probes in imaging and health care applications.