A smartphone-assisted dual-mode sensor based on GN-CDs for sensitive and portable detection of α-glucosidase.

The determination of the α-glucosidase (α-Glu) activity is crucial for the early screening of diabetes. However, traditional α-Glu detection methods mainly rely on a single-signal readout system, which is inevitably subjected to interference from a complicated detection environment. To address this practical issue, a fluorescence-colorimetric dual-mode sensor based on green-emitting nitrogen-doped carbon dots (GN-CDs) was designed for the sensitive and portable detection of α-Glu. The detection strategy of this sensor was based on the enzymatic reaction of α-Glu with the specific substrate p-nitrophenyl-α-D-glucopyranoside (PNPG) to generate p-nitrophenol (PNP), which not only displayed stronger absorbance at 400 nm but also could effectively quench the fluorescence of GN-CDs through the inner filter effect (IFE), thereby realizing the dual-mode detection of α-Glu. Through the mutual calibration of the double signals, the accuracy and anti-interference ability of α-Glu detection in complex environments were significantly improved, with the detection limits as low as 0.023 U/L in fluorescence mode and 0.045 U/L in colorimetric mode, respectively. Furthermore, portable α-Glu detection was successfully achieved by integrating GN-CDs loaded hydrogel microspheres and smartphone-based image analysis technology. Therefore, the developed dual-signal sensor provided an accurate and portable strategy for α-Glu detection, demonstrating great application potential in the sensing of diabetes-related biomarkers.