Long-lasting chemiluminescence-based portable biosensor for POCT of food contaminant azodicarbonamide

Azodicarbonamide (ADA) in flour products is easily converted to semicarbazide which greatly threatens human health. Herein, a long-lasting chemiluminescence (CL)-based biosensor was developed for quantitative point-of-care testing (POCT) of ADA. The threonine (Thr)-functionalized Cu-hemin MOFs (Cu-hemin@Thr) could induce persistent CL of luminol with excellent stability. The CL intensity was related to the competition reaction among ADA and a composite of glutathione-silver ions (GSH-Ag⁺). In the presence of ADA, GSH is oxidized to glutathione disulfide (GSSG), which breaks the coordination between Ag⁺ and GSH. The CL of the sensing system is then decreased which is expected to be used for ADA detection. By combining a homemade portable device as a detector and a smartphone as an analyzer, quantitative POCT of ADA was successfully achieved. The limit of detection was 0.562 μM (0.065 ppm), which is much lower than the maximum permissible concentration of ADA (45 ppm) in flour extract. The developed strategy demonstrated quantitative POCT capabilities along with advantages of low cost, excellent selectivity, and repeatability, presenting great potential application in food safety and environment monitoring.