Bimetallic porous Mn/Co oxide nanosheets with efficient oxidase-mimicking activity for the sensitive colorimetric determination of resveratrol in different matrices.

BACKGROUND: Resveratrol, a natural polyphenol compound used as an ingredient in dietary supplements, and pharmaceuticals, has gained significant attention due to its potential health benefits. However, the accurate and sensitive determination of resveratrol in complex matrices remains a challenge. In this study, we propose the utilization of bimetallic porous Mn/Co oxide nanosheets (MnCoO-NSs) as catalysts for the colorimetric determination of resveratrol. RESULTS: The bimetallic porous MnCoO-NSs were prepared through a facile one-stone-two-birds strategy. These nanosheets exhibited superior oxidase-mimicking activity, as evidenced by the catalytic oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB), producing a blue-colored oxTMB species with a prominent absorbance peak at 655 nm. The catalytic activity was promoted through the production of superoxide anion (O2•-), which enhanced the affinity of MnCoO-NSs to the TMB molecules. Upon the addition of resveratrol, the oxidation process was inhibited, resulting in rapid fading of the blue color. This colorimetric sensing platform exhibited a linear response to resveratrol concentrations over the range of 2.2-87.6 µM, with a limit of detection of 0.210 µM. The method was further applied for the determination of resveratrol in different matrices including biological fluids, pharmaceuticals, and environmental water. SIGNIFICANCE: The utilization of these MnCoO-NSs offers a simple and cost-effective alternative to conventional analytical techniques for the determination of resveratrol. Their high sensitivity, selectivity, and stability enable accurate measurements of resveratrol in various complex matrices. This research has implications in areas such as pharmaceutical analysis, biomedical research, and environmental analysis, where the reliable determination of resveratrol is crucial for assessing its therapeutic potential and ensuring product quality.

Promoting the sensitive detection of ethamsylate via a colorimetric sensing platform based on the enhanced oxidase-mimicking activity of ultrathin MnO2 nanosheets.

In this work, we present a novel colorimetric sensing platform for the sensitive detection of ethamsylate (ETM) usingultrathin MnO2 nanosheets with enhancedoxidase-mimicking activity. A facile template-free hydrothermal process was applied to synthesize the MnO2 nanosheets under mild conditions. The nanosheets exhibited oxidase-mimicking activity, facilitating the conversion of TMB into the blue-colored oxTMB in the absence of H2O2. However, the presence of ETM inhibited this activity, resulting in the conversion of oxTMB back to colorless TMB and a substantial decrease in the blue color intensity. The colorimetric response exhibited a linear relationship with ETM concentration over the range of 0.5 to 10.0 µg/mL and a detection limit of 0.156 µg/mL. To further elucidate the underlying mechanism, we performed extensive characterization and kinetic experiments. The findings demonstrated that this unique property is attributed to the remarkable capacity of the MnO2 nanosheets to absorb oxygen, producing superoxide radicals (O2-). The oxidase-mimicking activity of the nanosheets was further confirmed by the reaction kinetics, following Michaelis-Menten's behavior. Moreover, the applicability of the sensing platform was assessed by determining ETM concentrations in various real samples (different pharmaceuticals, human plasma, and environmental water). The well-established platform demonstrates the prospective role that nanomaterials-based sensing platforms may play in clinical diagnostics, pharmaceutical analysis, and other relevant fields.