Novel enzyme-linked immunoassay based on nanoceria as colorimetric substrate for foodborne pathogen detection

Rapid and reliable detection of foodborne pathogens is a key requirement for food safety. Traditional rapid ELISA methods assessed by the ability of horseradish peroxidase to oxidize a chromogenic substrate such as 3, 3′, 5, 5′-tetramethylbenzidine in the presence of H2O2 may result in the high rate of negative responses because of the instability of H2O2 and product. Here, we report the use of redox active nanoceria as colorimetric indicator in immunoassay taking Staphylococcus aureus as a model. The nanoceria is fully water-soluble and can be stored as least 90 days in the refrigerator while maintaining the same performance. Moreover, it does not require external H2O2, as glucose oxidase used in the immunoassay can catalyze the oxidation of glucose to produce H2O2 in situ, which is more robust in signal readout. Taken together, these results demonstrate that nanoceria are potentially suitable as colorimetric substrate in the development of novel enzyme immunoassays.