Ultrasensitive determination of α-glucosidase activity using CoOOH nanozymes and its application to inhibitor screening.

In this work, a novel method for the colorimetric sensing of α-glucosidase (α-Glu) activity was developed based on CoOOH nanoflakes (NFs), which exhibit efficient oxidase-mimicking activity. Colorless 3,3',5,5'-tetramethylbenzidine (TMB) can be oxidized by CoOOH NFs into blue-colored oxidized TMB (oxTMB) in the absence of H2O2. L-Ascorbic acid-2-O-α-D-glucopyranose (AAG) can be hydrolysed by α-glucosidase to produce ascorbic acid, resulting in a significant decrease of catalytic activity of CoOOH NFs. Thus, a colorimetric α-glucosidase activity detection method was designed with a limit of detection of 0.0048 U mL-1. Furthermore, the designed sensing platform exhibits favorable applicability for the α-glucosidase (α-Glu) activity assay in real samples. Meanwhile, this method can be expanded to study the inhibitors of α-Glu. Finally, the as-proposed method combined with a smartphone would be a color recognizer, which was successfully applied for the determination of α-Glu activity in human serum samples.

MoS2 quantum dots as fluorescent probe for methotrexate detection.

Herein, we developed a unique fluorescence biosensor for methotrexate assay based on MoS2 quantum dots, which were synthesized in one step using sodium molybdate and cysteine as raw materials. The fluorescence of MoS2 QDs could be quenched when encountered with methotrexate, which was attributed to the inner filter effect (IFE). Furthermore, this present IFE-based method showed the linearity between the MoS2 QDs fluorescence intensity and the methotrexate concentration in the range of 0.05-1 µM with the LOD of 42 nM. The practical applicability of this strategy was successfully demonstrated by detecting methotrexate in real samples. Results indicated that the proposed method could be a promising sensing platform for methotrexate analysis.

A novel probe for tetracyclines detection and its applications in cell imaging based on fluorescent WS2 quantum dots.

In this study, a novel fluorescence sensor for tetracyclines (TCs) detection was designed using WS2 quantum dots (WS2 QDs). WS2 QDs could be quenched by TCs through the inner filter effect (IFE). The limit of detection of this proprosed method is 39 nM, 52 nM, and 28 nM for tetracycline (TC), doxycycline (DC), and oxytetracycline (OTC), respectively. The as-proposed strategy was successfully applied to detect TC in milk samples and human serum samples. The WS2 QDs were highly biocompatible and showed lower toxicity. Moreover, the WS2 QDs was successfully applied to imaging TC in HeLa cells owing to its excellent optical performance and great biocompatibility.