Nanoparticle based antigen detection of norovirus in human faecal samples: A proof-of-concept study

Immunocapture assays that are fast, affordable, and can be utilised as on-site sensors for detecting pathogens or their biomarkers hold great value for ensuring public health and food safety. As proof of concept, a magnetic immunocapture assay was developed to detect norovirus. Acommercially available monoclonal antibody capable of capturing both norovirus genogroup I and II (GI and GII) was conjugated to the magnetic nanoparticles (MNPs) for capture and sequestration of norovirus GI and GII under laboratory conditions. The capability of the functionalised MNPs to capture norovirus from the faecal extract was determined by reverse transcription-qPCR. The capture efficiency of MNPs was >90 % for both genogroups of noroviruses. To complement the magnetic capture and enable rapid detection and genogroup identification, two different monoclonal antibodies specific to genogroups GI and GII were conjugated onto a fluorescent nanoparticle surface, and then used to quantify captured norovirus in a ‘sandwich’ assay. Replicate faecal extract suspensions containing 10³ gene copies of norovirus GI and GII per µL were tested with the magnetic capture-fluorescence detection assay platform, with quantification of fluorescent intensity. The fluorescent particle assay for the detection of the biomarkers matched the sensitivity of qPCR. This method doesn’t require any sample preparation steps like nucleic acid extraction and can be easily converted into a rapid point of need detection system. This dual nanoparticle system holds promise as an inexpensive and reliable analytical tool for classical qualitative immunoassays that are prone to false positives.