Ce3+ and Fe2+ co-enhanced ratiometric fluorescence probe utilizing copper nanoclusters and coumarin for sensitive assay of hydrogen peroxide and glucose

Manganese dioxide nanosheet-modulated ratiometric fluoroprobe based on carbon quantum dots from okra for selective and sensitive dichlorvos detection in foods

Herein, we developed a ratiometric fluoroprobe by integrating okra-derived carbon quantum dots (CQDs) with amplex red (AR) using manganese dioxide nanosheets (MnO2 NSs) as a medium. Fluorescence intensities (FIs) of CQDs were sharply quenched by MnO2 NSs via an inner-filter effect processes, whereas the FIs of AR were significantly enhanced due to oxidation of AR to AR-ox by the oxidase-mimetic activity of MnO2 NSs. Acetyrylcholinesterase hydrolyzed acetylthiocholine to produce thiocholine, and the decomposition of MnO2 NSs to Mn2+ by thiocholine led to the FI recovery of CQDs, but decreased FIs of AR-ox. Based on the above phenomenon and the inhibitory effect of dichlorvos (DDVP) on acetyrylcholinesterase activity, a novel ratiometric fluoroprobe for DDVP quantification was pioneered. Under optimized conditions, this fluoroprobe gave a wide linear range (4-120 μg/L), low detection limit (1.2 μg/L), and satisfactory fortification recoveries (90.0-110.0%), thereby providing good prospects for routine DDVP monitoring in foods.

Fluorescence and colorimetric dual-mode multienzyme cascade nanoplatform based on CuNCs/FeMn-ZIF-8/PCN for detection of sarcosine

It is critical to develop a highly efficient and sensitive method for detecting the biomarker sarcosine (SA) of prostate cancer due to its importance for men's health. In our work, a fluorescence (FL) and colorimetric dual-mode multienzyme cascade nanoplatform for SA detection was designed and constructed. CuNCs/FeMn-ZIF-8/PCN nanocomposites with high FL properties and peroxidase-like activity were successfully prepared by encapsulating copper nanoclusters (CuNCs) into FeMn-ZIF-8 and then loaded onto P-doped graphitic carbon nitride (PCN). Furthermore, the nanocomposites served as carriers for the immobilization of sarcosine oxidase (SOX) to construct a high-efficiency dual-mode multienzyme cascade nanoplatform CuNCs/SOX@FeMn-ZIF-8/PCN for the detection of SA. The intermediate H2O2 generated in the cascade caused the FL quenching of nanocomposites and the discoloration of 3,3',5,5'-tetramethylbenzidin. The linear ranges for SA detection in the dual-mode system were 1-100 μM (FL) and 1-200 μM (colorimetric), with detection limits of 0.34 and 0.59 μM, respectively. This nanoplatform exhibited notable repeatability, specificity, and stability, making it suitable for detecting sarcosine in real human urine samples. Therefore, this dual-mode multienzyme cascade nanoplatform would have a potential applicative prospect for detecting SA and other biomarkers in real clinical samples.

Umbelliferone and Its Synthetic Derivatives as Suitable Molecules for the Development of Agents with Biological Activities: A Review of Their Pharmacological and Therapeutic Potential

Umbelliferone (UMB), known as 7-hydroxycoumarin, hydrangine, or skimmetine, is a naturally occurring coumarin in the plant kingdom, mainly from the Umbelliferae family that possesses a wide variety of pharmacological properties. In addition, the use of nanoparticles containing umbelliferone may improve anti-inflammatory or anticancer therapy. Also, its derivatives are endowed with great potential for therapeutic applications due to their broad spectrum of biological activities such as anti-inflammatory, antioxidant, neuroprotective, antipsychotic, antiepileptic, antidiabetic, antimicrobial, antiviral, and antiproliferative effects. Moreover, 7-hydroxycoumarin ligands have been implemented to develop 7-hydroxycoumarin-based metal complexes with improved pharmacological activity. Besides therapeutic applications, umbelliferone analogues have been designed as fluorescent probes for the detection of biologically important species, such as enzymes, lysosomes, and endosomes, or for monitoring cell processes and protein functions as well various diseases caused by an excess of hydrogen peroxide. Furthermore, 7-hydroxy-based chemosensors may serve as a highly selective tool for Al3+ and Hg2+ detection in biological systems. This review is devoted to a summary of the research on umbelliferone and its synthetic derivatives in terms of biological and pharmaceutical properties, especially those reported in the literature during the period of 2017-2023. Future potential applications of umbelliferone and its synthetic derivatives are presented.

A smartphone-based ratiometric fluoroprobe based on blue-red dual-emission signals of thiochrome and copper nanoclusters for sensitive assay of metam-sodium in cucumbers

It is of great importance to develop the highly efficient fluorescence strategy for rapid/sensitive detection of metam-sodium (MES) in evaluating its residual safety, especially in fresh vegetables. Herein, we prepared an organic fluorophore (thiochrome, TC) and glutathione-capped copper nanoclusters (GSH-CuNCs), and their combination (TC/GSH-CuNCs) was sucessfully employed as a ratiometric fluoroprobe by means of the blue-red dual emission. The fluorescence intensities (FIs) of TC decreased upon the addition of GSH-CuNCs via the fluorescence resonance energy transfer (FRET) process. When fortified at the constant levels of GSH-CuNCs and TC, MES substantially reduced the FIs of GSH-CuNCs, while this was not the case in the FIs of TC except for the prominent red-shift of ∼30 nm. Compared to the previous fluoroprobes, the TC/GSH-CuNCs based fluoroprobe supplied wider linear range of 0.2-500 μM, lower detection limit (60 nM), and satisfactory fortification recoveries (80-107%) for MES in the cucumber samples. Based on the fluorescence quenching phenomenon, a smartphone application was used to output RGB values of the captured images for the colored solution. The smartphone-based ratiometric sensor could be utilized for the visual fluorescent quantitation of MES by virtue of the R/B values in cucumbers, which gave linear range (1-200 μM) and LOD (0.3 μM). By means of blue-red dual-emission fluorescence, the smartphone-based fluoroprobe provides a cost-effective, portable and reliable avenue for the on-site, rapid and sensitive assay of MES's residues in complex vegetable samples.