Carbon nitride nanoparticles as ultrasensitive fluorescent probes for the detection of α-glucosidase activity and inhibitor screening

In recent years, alpha-glucosidase inhibitors (AGIs) have played a significant role in the treatment of type II diabetes (T2D), so it is necessary to develop a reliable and sensitive method to find new AGIs. Herein, we establish a novel method based on fluorescent carbon nitride nanoparticles (CNNPs) for the sensitive detection of the activity of alpha-glucosidase (alpha-glu) and the screening of its inhibitors. A CNNP-based fluorescent probe is synthesized from green raw materials, urea and lysine, by a one-pot method. In the presence of alpha-glu, the substrate 4-nitrophenyl-alpha-d-glucopyranoside (pNPG) is hydrolyzed to generate 4-nitrophenol (pNP), leading to the fluorescence (FL) quenching of CNNPs due to the inner filter effect (IFE). On the other hand, the activity of alpha-glu is inhibited after the addition of AGIs, which turns on the FL of CNNPs. In this way, the detection of alpha-glu activity and the screening of AGIs are achieved. The linear range is 1.25-10.00 U L-1 with a limit of detection as low as 0.17 U L-1 and the IC50 values of two typical inhibitors (gallic acid and acarbose) are 813 mu M and 465 mu M, respectively. The CNNP probe is further applied for the determination of alpha-glu activity in human serum samples with satisfactory results.