Redox-Induced Multisignal Sensing Based on Fluorescent Polydopamine Nanoparticles and MnO₂ Nanozyme for the Detection and Differentiation of Reducing Substances

Reducing substances play crucial roles in various physiological processes and serve as essential components in the antioxidant defense mechanisms within organisms. Nonetheless, accurately detecting and distinguishing between these substances present a notable challenge due to the presence of potential interferences in complex samples. In response to this challenge, a novel multisignal sensing platform and sensor array have been developed, leveraging fluorescent polydopamine nanoparticles (FPDA) and MnO 2 nanozyme. The MnO 2 /FPDA nanoplatform possesses exceptional catalytic activity and the ability to modulate ratiometric fluorescence in the presence of o -phenylenediamine (OPD), offering a platform with dual-channel output signals in ratiometric fluorescence and UV absorbance. Upon introduction of H 2 O 2, the MnO 2 undergoes transformation into Mn 2+, thereby reducing the oxidase-like activity of MnO 2 and reinstating the fluorescence of FPDA. Notably, this platform exhibits detection ranges for H 2 O 2 from 5 to 500 and 15 to 500 μM, with corresponding detection limits of 3.18 and 10.67 μM using fluorescence and colorimetric channels, respectively. This setup has been deployed for quantifying H 2 O 2 in milk and cell lysates, showcasing its versatility as a universal analysis tool for other reducing agents like ascorbic acid. Furthermore, a sensor array has been developed based on MnO 2 /FPDA/OPD, demonstrating a robust capacity to effectively differentiate and identify five reducing agents effectively. This sensor array also exhibits strong performance in discriminating reducing substances within intricate or authentic samples, such as oranges and cell lysates, underscores its practical utility. This study offers significant insights into the development of sensing platforms for the selectively detecting specific reducing species in real samples or deploying sensor arrays for distinguishing multiple components within authentic samples. Such advancements pave the way for enhanced analysis and screening of reducing substances in cellular and food samples.