Cluster-bomb type magnetic biosensor for ultrasensitive detection of Vibrio parahaemolyticus based on low field nuclear magnetic resonance

Herein, a novel cluster-bomb type signal sensing and amplification strategy in low field nuclear magnetic resonance was proposed, and a magnetic biosensor for ultrasensitive homogeneous immunoassay of Vibrio parahaemolyticus (VP) was developed. The capture unit [email protected] was magnetic graphene oxide (MGO) immobilized by VP antibody (Ab) to capture VP. And, the signal unit [email protected]@Ab was polystyrene (PS) pellets covered by Ab to recognize VP and Gd-CQDs i.e. carbon quantum dots (CQDs) containing lots of magnetic signal labels Gd3+. In presence of VP, the immunocomplex signal unit-VP-capture unit could be formed and separated by magnetic force conveniently from the sample matrix. With the successive introduction of disulfide threitol and hydrochloric acid, signal units were cleaved and disintegrated, resulting in a homogeneous dispersion of Gd3+. Thus, cluster-bomb type dual signal amplification was achieved through increasing the amount and the dispersity of signal labels simultaneously. Under optimal experimental conditions, VP could be detected in the concentration range of 5–1.0 × 106 CFU/mL, with a limit of quantitation (LOQ) 4 CFU/mL. In addition, satisfactory selectivity, stability and reliability could be obtained. Therefore, this cluster-bomb type signal sensing and amplification strategy is powerful in designing magnetic biosensor and detecting pathogenic bacteria.