Smartphone-assisted ratiometric fluorescence sensor for sensitive and portable α-glucosidase activity detection and inhibitor screening

α-Glucosidase (α-Glu) is an enzyme that plays an essential role in the digestion of carbohydrates, and its activity detection and inhibitor screening are crucial for the therapy of diseases and development of new drugs. In this study, α-Glu can catalyze the hydrolysis of α-arbutin to produce hydroquinone (HQ), and HQ can regulate the in-situ synthesis of polymer carbon dots (PCDs) with ethylenediamine (EDA). PCDs and tetraphenylporphyrin tetrasulphonic acid (TPPS) are separately designed as green and red fluorescent sensing units. With the increase of α-Glu concentration, the number of PCDs is gradually increased, resulting in enhancement of green fluorescence and quenching of red fluorescence. Conversely, when α-Glu inhibitors (AGIs) are present, the activity of α-Glu is inhibited, leading to weak green fluorescence and strong red fluorescence. Thus a ratiometric fluorescence sensor was designed for the determination of α-Glu activity and screening of AGIs. The developed ratiometric sensor exhibits a linear relationship between fluorescence intensity ratios and α-Glu concentrations (0.01 to 0.04 U/mL) with limit of detection of 0.184 mU/mL, which is much lower than the single fluorescence model. In addition, rapid and portable detection of α-Glu can be achieved using a smartphone with a color picking software installed as a signal detection device, which greatly reduces the cost and time of detection and provides a promising method for qualitative identification and quantitative analysis of α-Glu in the resource-limited areas. Moreover, the method is very promising for high-throughput screening AGIs from natural products.