Redox-induced target-dependent ratiometric fluorescence sensing strategy and logic gate operation for detection of α-glucosidase activity and its inhibitor

A target-dependent ratiometric fluorescence sensing strategy was designed and fabricated based on a redox reaction for highly sensitive detection of α-glucosidase (α-Glu) activity and its inhibitor. In this study, silicon quantum dots (SiQDs) with excellent optical properties and two-dimensional (2D) cobalt oxyhydroxide (CoOOH) nanosheets were successfully prepared and exploited for the detection of analytes. The CoOOH nanosheets are able to oxidize o-phenylenediamine (OPD), and the product 2,3-diaminophenazine (oxOPD) not only quenches the blue fluorescence of SiQDs (440 nm) by the inner filter effect (IFE) but also emits orange fluorescence (565 nm). α-Glu can catalytically hydrolyze l-ascorbic acid-2-O-α-d-glucopyranosyl (AA2G) to produce ascorbic acid (AA). The redox between AA and CoOOH could lead to the damage of CoOOH nanosheets, thereby inhibiting the oxidization of OPD and effectively preserving the fluorescence of SiQDs. Thus, ratiometric detection of α-Glu activity was achieved according to the AA-dependent dual-fluorescence signal responses. Under the optimal conditions, good linearity was obtained in the range of 0.01-6 U mL-1 with a detection limit of 0.004 U mL-1. The IC50 of α-Glu inhibitor acarbose was estimated to be 0.216 μM. The method provides high sensitivity and selectivity for the determination of α-Glu activity and its inhibitor, which has great application potential in clinical diagnosis and anti-diabetic drug screening. Furthermore, a logic gate analytical device was successfully established based on double fluorescence signals, which makes it possible to monitor α-Glu activity by intelligence equipment.